US1425185A - Separating process - Google Patents

Description

R. ELLIS.

SEPARATING PROCESS.

APPLICATION FILED APR. I5, I9Is.

Patented Aug. 8, 1922. l

III

II I IIIII incarica."

sanear', *otirice.f

Specification of Letters Patent.' Patqentdl Aung. 8, 11922.,

Application led April 15, 1918. 'Serial to. 228,623.

To allwlwmz't may concern: Y

Be it known that I, RIDSDALE ELLIS, a citizen of the United States, and a resident of Oak Park, in the countyof Cook and. State of Illinois, have invented certain new and useful Improvements in Separating* Processes, of which the following is a specification.

My invention relates to processes for concentrating parts of comminuted masses of composite character, such as metalliferous ore, by treating the cmminuted mass with a fiuid adapted to aid in the separation of certain of the comminuted particles from others having different qualities. v l This application is a continuation in part of my co-pending applications l Serial Number 7863, iiled Feb. 12, 1915, Serial Number 36,161, filed J une 24, 1915,

Serial Number 51,210, led Sept. 17, 1915,-

Serial Number 73,918, filed J an. 24, 1916. Broadly, my invention includes the use of means for producing certain changes in the'.

fluid and the particles of the mass whereby the separation of certain of the comminuted particles from others having dierent qualities is aided. Preferably such means include the" use of substances adapted when dissolved in fluid, preferably an ionizing Huid, to bring about certain electrical chanfres, and to this end to give polyvalent ione .'or aiding in the separation of certain vof the particles from others by means of a fluid having a preferential affinity for certain of the particles. v

More particularly, in its preferred form, my invention relates to processes 'for concentrating metalliferous ores by means of the combined action of gaseous bubbles and'oil, or other substances ysoluble or insoluble,

adapted to aid in the formation of a froth.

containing the .metalliferous constituents of the ore. L My invention is particularly adapted for the concentration'of sulphide ores, but is'- also applicableto the concentration'of other ores, such as 0Xides, carbonates or hydroxides either unchanged or after a sulphiding or other treatment, n tive or precipitated cop` per, gold, and for the j concentration of graphite and other similar materials.

The principal objects of my invention are in general to enhance the eiciency of concentrating processes as hitherto carried out; to increase the percentage extraction and rate of separation of the metalliferous constituents; to improve the grade of concentrate; and in particular to improve frothflotation processes for the concentration of. ores .and slmllar-comminuted materials of composite character. i

To this end my invention contemplates the use of electrolytes of various types and the modification of the otation processes as commonly carried out to enable the beneficial action of such electrolytes to be more fully obtained. V- A The eHe'cts produced by electrolytes may be convenientlyclassied according as they are clue to purely physical phenomenon or to chemical reactions in which the electrolyte added reacts chemically or electrochemically with the constituents of the ore.

' The physical action of electrolytes, more particularly inorganic electrolytes, appears to be dependent upon the valence (and to a lesser extent on the mobility) of the ions produced by the solution of the electrolyte in an ionizing fluid and is vconsequently electrical in its nature.

I have found that the results of such physical action may be modified by changing the time of addition ofl the electrolytes. Thus certain types of electrolytes give improved results when added prior to oiling and other types betterresults when added after oiling. There is also a very important relation b etween the physicalv action of such electro-v lytes and the size of the particles.

While effectsl produced by electrolytes ofgvarious types are readily demonstrable, the cause of these eects is far more complex. 7 i

In order, however,.that the invention may be-more fully understood T give `a statement of thegeneral principles underlying the-fon mationvofa froth and the action of electrolytes in aiding or hindering the separation of metalliferous matter by-froth flotation processes. 4

Practice carried out by me has shown that resultsl vobtained by thel use of electrolytes vary considerably according to the way in which the gaseous .bubblesare introduced to formla froth. Bubbles maybe introduced in twg-general Ways: In the first place, the bubbles may beforced in from without, and secondly, the bubbles of gas may be generated, or otherwise produced in the liquid itself. As examples of methods of introducin gas mechanically from the outside, the mep anit involve both methods of lntroduction in varying degrees. The vortex of -water produced by the rapidly v rotating propellers draws into the ore pulp infinitesimally thin films of air which break up into minute air bubbles. As these minute air bubbles have a much higher solution tension than larger air bubbles, the' water becomes supersaturated so far as bubble formation on a sulphide or oil surface is concerned and asv a result air comes out of solution on the surface of the oiled, sulphide particles. The

result of the violent mechanical agitation is therefore two-fold, first, the introduction of air bubbles bodily from the external air and second the generation of air bubbles abI initio on the surface of sul hide.

n the pneumatic agitation Vprocess the generationof bubbles in the pulp does not appear to take place to any great extent.

The formation of va froth in themechanical agitation' process and the effect of electrolytes thereon involves a large number ofl factors. In this process, asin all froth ilotation processes, the basic principleI is the vse- `of gaseous bubbles for metalliferous particles. Oil or a soluble frothing the oiled particles of agent is almost universally employed an there has been much eculation as to the function of4 such mo i ing agents. It seems to be settled that oi does not increase the' aiiinity of the gaseous bubbles.l for the sulphide or other particles and that 1ts princi al functions are to give increased stability to the bubbles and to the bond between the bubbles and the metalliferous particles.

It has been shown that a bubble of air gently lowered by suitable means into contact with a article'pf unoiled galena will lift a cube ofp the latter weighing as much as 40 milligrams. AIf the particle of galena is coated with oil the heaviest galena cube which can be lifted will not weigh more than about 30 milligrams. however, much heavier than those present in the ore pulp fed to a commercial fiotation apparatus. In ordinary flotation practice if the metalliferous particles weigh much in excess of 0.1 milligram, they cannot be iioated or only with great diiiculty.

This failure to lift large particles appears Such particles are,

to be due to the agitation of the pulp or to the shaking action resulting from the coales-` cence ofthe bubbles in the ore pulp or in the froth to form larger bubbles. Whether the particles can remain attached to the bubbles depends upon the relation between the intween the ertia ofthe particleA with respect to sudden movement and the inertia of the bond begarticle and the bubble with respect to su den disrupture.

lf two bubbles coalesce a larger bubble is formed very rapidly and with almost explosive violence, owing to the very high surface tension of water. This involves a sudden inward movement ofthe greater part of the air-water surface of thetwo air bubbles to the new position occupied by the air- -water surface of the larger air bubble formed by their union. If t esulphide particle is not to drop it must move in the same space of time from the position occupied by the air-water surface of one of the original bubbles to which it was attached to the position occupied by the air-water surface of the new ybubble formed therefrom. Whether it can do this vdepends on the ratio between the inertia of the particle and its strength of adherence to the bubble. For this purposethe strength of adherence would not appear'to'be so much its'static adherence vas 1ts inertia or resistance to sudden disrupture. In this respect the viscosity of the oil layer vwould appear to play a very important part since inA the Potter-Delpratt process, vin which no oil is used showering of sulphide particles, owing to coalescence of the bubbles'in thev froth is jectionable feature;

As Ithe inertia of the particles varies with the cube of vtheir diameter while the strength of adherence rou hly varies with the area or'the square oft e diameter by decreasing the size of the particles they can be made to adhere much more persistently to the air bubbles.

In ordinary flotation practice the finer the ore is ground the higher-the extraction and the lower. the grade of concentrate since the fine particles of gangue as well as the ne particles of sulphide float much more readily than large particles.

The oil by forming a very thin layer of oil over the air-water surface also greatly increases the viscosity ofthe latter and thus stabilizes the froth as well as providing -a viscousconnection or bond between that surface and the oiled metalliferous particle.

In processes where liquid oil is added to the pulp which is round or agitated with the oil prior to loation to coa-t -the metalliferous particles the great majority of the air bubb es appear to receive their oil coating from the oiled metalliferous particles instead of the coated air-bubbles.

Thus preferential flotation may be carried out by making the conditions such that the sulphide articles to be oated are oiled while the, ot er sulphide particles remain unoiled. Hence in the formation of a froth where a very marked and obllll particles lreceiving' oil from oil iframes In these cperations'electrolytes may act in four amongst other ways First in determining the readiness wlth which the oil can come into physiclal conitact with the particles of sulphide.

Second in changing the readiness with which the oil after contact with the particles of sulphide will spread over the surface of the latter and thetenacity with which the oil adheres to the sulphide surfaces.

Third in determining the readiness with which the gaseous bubbles can come into physical contact with theoiled particles of sulphide.

Fourth in changing the readiness with which the oil after contact with the gaseous bubbles will spread over the surface of the latter.

The changes produced by electrolytes in any one or more of the above ways may be the result of either (b) Chemlcal changes at the surface o the particles to Vbe floated;

(c) Changes in surface tension due to (a) Changes in the electrical conditions;

adsorption of the electrolyte at the oil-water, particle-water or air-water interfaces.

In the case of inorganic salts surface tension measurements indicate that (c) is negligible and this is confirmed by the fact that where the action of electrolytes does not follow certain laws based on the valency or number of electrical charges carried by the ions formed by the solution of the electrolytes the deviation from these laws may be attributed in most, if not all, instances, to chemical action between the electrolyte and the constituents of the ore.

With the majority of ores the most important function of electrolytes in aiding flotation appears lto be the production of favorable electrical conditions.

In this respect it is not the molecules of the electrolyte which are active but the ions produced by the dissociation of the electrolyte when dissolved in an ionizing fluid such as water.

All electrolytes, whether salts, acids or alkalies, when dissolved in an ionizing fluid produce ions to an extent depending upon the degree of dissociation of the electrolyte. The valence of these ions may range from one to six and possibly, though not probably, even seven or more.

The simplest combination of ions is M+R- where M represents the cation or positive ion and R represents the anion or negative acid radicle ion. Now the valence of the catlon or anlon may each be increased separately or the valence of both may be increased simultaneously. These three changes may be represented graphically as follows:

. MrR- I 7 l Examples.

Titanium Titanium Sodium chloride. pyrophosphate. pyrophosphate. 7 5

TCl4 N84P01 As the valence of the ions increases their effect on the contact and frictional electrification of the oil, sulphide and gangue particles and gaseous bubbles also increases, Whether the ions are positive or negative, and these changes in the sign and magnitude of the electrication of the constitu-ents of the ore pulp produce very marked results in the formation of a froth and the separation of the metalliferous matter by such means.

.Solid or liquid particles of all kinds acqulrea contact potential when suspended inpure water of from 0.03 to 0.06y volts, the partlclesy being almost invariably (with the exception of oxides, hydroxides and some carbonates) negative with respect to the water. YGases, onthe other hand, may be .electrified in at least two different ways which are essentially distinct First, frictional electrification, and second, contact electriication. If air is blown through vwater it becomes electrically charged by friction with the water, and electricity may 10@ be collected from the air and also from the water. The potential Yof the water may reach several volts. If a bubble of air is in stationary contact with water, it acquires a contact potential of the same magnitude as that acquired by solidor liquid drops suspended in water, namely, 0.03 to 0.06 volts.

In contact electriication the conversion of the original negative charge on a particle suspended in water (whether solid, liquid or gaseous) into a positive charge is brought about by means off polyvalent cations; the higher the valence of the cations, the smaller the concentration of the electrolyte required to bring about the reversal, and the greater the posltive charge which can be produced thereby. If a polyvalent anion is present, the concentration required to produce reversal is increased, and also the maximum positive charge which can be obtained is re- 12@ duced. This inhibiting action of the anion increases as the-valence increases. On the other hand, the original negative charge vmay be increased by polyvalent anions; the higher the valence of the anion the greater the 12E increase in the negative charge which can be produced. Catlons inhibit this increase in negative charge in proportion to their valence.

In -i'frictional. electrification the valence of 13@ the reversal, and the effect of cations in this respect increases as the valence increases.

The spreading of a drop of oil over a sulphide or similar surface is no doubt due to differences in surface tension at the oilwater, oil-particle and water-particle interl faces but before the oil can spread on such a surface it must be brought into actual physical contact with the Now it is the electrical factors which largely determine Whether or not such physical contact takes place readily or diflcultly.

In pure water an oil globule is strongly charged negatively, a sulphide particle very weakly negatively. Under these conditions there is a slight electrical repulsion, add a salt of the type of sodium pyrophosphate and the nega-tive charge on both oil globule and sulphide particle will be increased so that the electrical repulsion is also increased. On the other hand if a small amount of acid .is added the potential of the sulphide be- 'comes positive lwhile reducing but not reversing the negative potential on the oil, under these circumstances electrical attraction occurs.

In both cases if the oil lobule once comes in cont-act with the sulphlde particle it will probably spread substantially independently of the sign and magnitude of the electrical charges on the two materials, but in theI first case it is relatively difficult to get the initial contact of the oil and sulphide and so allow the surface tension forces tol come into play, in the other case it is relatively easy.

Consequently as sodium pyrophosphate tends to increase the negative char e of both oil and sulphide it will inhibit oi ing, just `as acid aids oiling by reversing the sign of. the charge-on the sulphide.

Although any ion, particularly a high Ivalent ion, tends to change the Contact potential of any solid. or liquid particles suspended in an ionizing fluid in the same direction there is a great difference in the natural tendencywof various substances to t acquire and retain a negative or positive charge. Thus oil is normally strongly negatively charged and a much higher concentration of acid is required to neutralize and reverse this char e than in the case of the much moreA weak y negatively charged sulphide particles.-

sulphide particle.

` during flotation Llamas Further with salts of the type of sodium pyrophosphate the negative contact potential of oil, sulphide and other substances increases to a maximum and then decreases and the position'of this maximum point depends on the chemical nature of the substance. With oil this point is reached with .a higher concentration of salt than with either sulphides or silica or silicates.

If a salt is used which Vis adapted to give anions and cations both having a relatively high valence, such as aluminum pyrophosphate it is possible to give the sulphides a positive charge Without reducing the negative potential of the oil to the same extent as when acid only is used to give the sulphides a positive charge. As oil acquires and retains a negative charge much more readily than do sulphides, a trivalent cation like aluminum has a much greater effec-t on the sulphides than on the oil, while at the same tune the quadrivalent pyrophosphate ion has a much greater effect on the oil than on the sulphides.

In general, the higher the valence of the ions, the greater the electrical changes which can be produced and the greater the differences which can be made between the electrical potentials or two substances in contact with the same solution.

As will appear later the type of salt, which will give the oil a maximum negative potential is i-n general the most eficient in aiding the adhesion ofthe bubbles of air to the metalliferous particles, on thev other hand it is not the most efiicient type for oiling. Such a salt may, however, be used in relatively high concentrations to take advantage of the difference .in the maximum potential points of oil and sulphide respectively. Further, a salt adapted to give both high valent cations and anions may be used 4to reverse the sign of the potential on the sulphides 'without lowering the negative potential on the oil to the same extent a'sacid alone. y Again, oiling may be caused ing, is in part at least, a reversible operaion, possessing therefore a position of` equllibrium. With mechanical agitation, therefore, the fact that the oil originally adhered to the sulphides is not suflcient and it is desirable, if possible, that conditions should be as favorable as possible for re-oiling.

The greater the afinity of oil for the mames metalliferous particles the more tenaciously 'will the oil adhere once it has been brought intocontact with the particles and the more irreversible will the operation become.

-The affinity of oil for sulphide' particles may be chan ed by salts, usually to reduce the adhesion employed in preferential flotation), but in seme cases to increase it. Such changes appear to be due to chemical rather than electrical causes.

The difference between the chemical andthe electrical action of salts is well illustrated by the action`of potassium ferrocyanide on the flotation of copper ores. In neutral solutions this salt acts as a power- 'ful poison owing to the ,forma-tion of insoluble copper ferrocyanide on the surfaces of the sulphide particles.V 0n the other hand with an alkaline solution of the same' salt very beneficial results are obtained since in the presence of alkali insoluble copper ferrocyanide is not produced so that the beneficial action of the quadrivalent anion is obtained.

Copper sulphate has a very marked chemical action. With zinc o-res its use is very beneficial, with pyrite ores it is deleterious.

With zinc ores it is more beneficial than the valency of the ions it forms would warrant-and while copper sulphate and acid under certain circumstances appears to be more efficient than either aluminum or sodium pyrophosphate' and acid, a combination of the latter salts with acid and copper sulphate gives better results than copper sulphate and acid alone.

The action of copper sulphate on zinc ores is probably due vto the formation of a very small amount of copper sulphide on the surface of the particles of blende owing to the fact that zinc being more electronegative than copper tends to replace the latter in solution. The electrochemical action of copper sulphate is further indicated by the fact that the same or similaryresults can be obtained by inserting a copper plate into the flotation cell.

The next factor to be considered is the air-sulphide adhesion. At the first moment of adhesion between the oiled sulphide particle and an air bubble there must be actual physical contact irrespective of the conditions which occur afterwards.

For efiicient flotation both air-bubble and particle must be oiled. This may be done in one of -three ways.

(l) Sulphides are oiled and air bubbles get their film of oil from the sulphides.

(2) Air bubbles are oiled (as in the case of oil vapor process) and the sulphides receive their oil from the air bubbles.

(3) Both sulphides and air bubbles are oiled independently. The first of these is the method used-in a circulating mechani- 4"cal agitation apparatus in which oil is* added in liquid form.

As already indicated, a salt. of the type of creased negative charge and the air a strong frictional positive charge (dependent upon the rate of movement of the air relatively to the Water) l'thereby producing anattracsodium pyrophosphate gives the oil an intion between the two oiled sulphide particles and the bubbles of air.

The effect is to bring the air and oiled sulphide particles into contact more rapidly and certainly, and thereby increase not only the lextraction but also the rate of separation, as is shown by actual practice to be the case.

Further, it has been 'shown that after the electrical charge on )the air has been reversed from negative to positive increasing the,concentration of the electrolyte has no great effect on the magnitude of the charge so that the only electrical factor which will change appreciably with the concentration of sodium pyrophosphate is the charge on the oiled sulphides. V'.llhe .extraction of the oiled sulphides should, therefore, increase in proportion to the increase in the negative potential of the oil, and actual practice indicates that the cop-per, etc., left in the tails is roughly inversely proportional to the contact potential on the oil.

As the negative potential of silica and silicates is also increased by a salt of the type of sodium pyrophosphate, an increase in the amount of gangue floated would also be expected. Practice shows this to be the case. i

If frictional electriiication is an important. feature .then sodium pyrophosphate will give higher extractions with the mechanical than with the pneumatic agitation process, owin to the much more violent agitation in t e former than in the latter case. This is also confirmed by practice.

Again, as it has been shown that increasing the potential of the gangue increases the amount of the latter iioated in the pneumatic agitation process the greaterfrictional electrification of the air inthe mechanical agitation process should result in a further increase of the amount of ganguc floated. rlhis also has been found to be the case. f

rl`he relative movement of the bubbles of gas and water produces a positive or negative charge on the gas. according to the ions present in solution, and at the same time gives the water a charge of opposite sign. Now when polyvalent anions are present, the charge so produced on the water is of the same sign as that on the metalliferous particles which it is desired to unite to the bubbles of gas and consequently it is desirable to get rid of the charge on the water izo as it appears' to'have a repellent actionl on the similarly chargedh metalliferous. particles whichprevents the union of these particles with bubbles of gas. I have found that this charge may be. advantageously eliminated, preferably by grounding the flotation apparatus so as to connect the water electrically with the earth.

. The actionof electrolytes in changing the readiness with which the oil after contact with the gaseous bubbles will-spread over the surface of the latter is probably negligiblein the case-of inorganic salts. There can b e no chemical action at the air-waterinterface such as may occurat the sulphidel interface so that -ch face tension and the possible waterangesm 1n surproduction' of an adsorbed layer of yelectrolyte are the fac-- tors which may have to be considered. A soap solution decreases the surface tension and by adsorption forms a semi-solid layer at anv .air-water interface which interferes lwith the spreading of the oil. Ilrtheacas'e of inorganic salts the tension is normall ilicreased instead of decreased and there 1s no .appreciable adsorbed layer of salt at the air-water. interface. f I have also found that the action of electrolytes is greatly modified by the size ofthe' particles in the or'e pulo. coarse feed-say 80 to 100 mesh-' theaddition of sodium pyrophosphate even before oilinggrea'tly increases the extraction whereas wlth slimes the addition of this salt before oiling lmay even decrease the extraction. This clearly follows from the fact tha't the smaller` the particles the more important become the electrical factors 'in oiling. With particles of oil and sulphide 0.5 cm. in' diameter the electrical factors would have little or no effect on the readiness with which the particles come in contact. Reduce the diameterl of both sulphide and oil to say 0.0001 cm. when the Brownian movement becomes pronounced and the electrical factors will be all important.

I have found that actual contact between oil globules having electrical charges of the same size and a diameter of averaging about 70.0001 cm. is prevented .by the like charges on or -the electrical double layer surround-` ing the globules (according as the globules are considered as charged spheres or as spherical condensers) unless the kinetic energy of the collision of two particles is sufficient to enable the electrical repulsion to be overcome or the electrical double layer .to be. disrupted, and that the. greater the .electrical charge on the globule the less chance there will be that two globules c0lliding with one another will coalesce or adhere to 'each other.

The' electrical charge carried by a sphere charged toa given potential varies directly as the diameter. The charge carried by a With 'relatively spherical'c'ondenser varies as the s uare of the diameter. As suchcharged glo ules or particles migrate in an electric field they behave like charged spheres or imperfect spherical condensers so that the charge will vary with the diameter .at tween `1 and 2, say 1.5. c v On the other hand the inertia or kinetic energy of a sphere increases as the cubeof ythe diameter. As the electrical factor is proportional to (diameter) 1.5 While the kinetic energy is proportional to (diameter) 3 a decrease in the size of the particles greatly increases thel electrical factor as compared with the factors dependent-upon its inertia or kinetic enerl In the pneumatic agitation process, unlike the'mechanical agitation process, I have found that salts of the typesof thorium chloride or aluminum pyrophosphate are, under some conditions, distinctly deleterious, whereas a salt of the-type of sodium pyrophosphate is very useful though not\producing as advantageous results as in the mechanical agitation process.N Further, while 9o acid aids the action of salts in mechanical agitation alkali is preferably used in the pneumatic agitation process. There appear to be various reasons forthlp difference between the mechanical and pneu. matlc agitation processes. c l Thus areductlon of the negative potential of the oiled sulphides is particularly deleterious in the pneumatic'agitation process as much less frictional electricity is generated on the air than in the mechaniealagitation process, owing to the less violent agitation. This is due -to the fact that while the sign ofthe charge 0n the air depends upon the ions presentv in solution, its magnitude is largely dependent upon the speed at whicl the air bubbles `,are moved through the solutio i Y f? Then the production of conditions advantageous to ailing are more important in the mechanical than in t e pneumatic agitation process and such conditions are aided by acid or polyvalent cations.

Further, in the mechanical agitation process somevgeneration of gas-bubbles ab initio on the surface of the oiled sulphides occurs. The acquisition of a positive charge appears 4to favor the formation of a bubble ab initio in water since it has been shown that bubbles of gas are often, if not usually, positively charged when they have been generated from a solution which would not give a positive charge to a bubble of gas introduced bodily from an external source.

Apparently, therefore, hydrogen or high valent cations are useful as either directly or indirectly providing positivenuclei for bubble formation.

On the other hand, as a positive\charge favors and a negative charge inhibtsloubble 1o some power be- A formation, if a salt of the type of sodium pyrophosphate is-used whicli would tend to give the bubbles a strong negative contact potential, the bubbles may not come out of solution so readily, but when once. formed will adhere moretenaciously to the particles since by so adhering the area of the air-water Various forms of apparatus for carrying out the separation of metalliferous mattei` by otation are well known and, as showing examples of three types of such apparatus, United States atents to Hyde,

1,022,085; @allow 1,104,755; C5110w'1,125,

897; Callow 1,201,934 and lElmore 826,411 ma be referred to. 1

I* or carrying out my invention apparatusof well known types, such as those described in the above patents of Hyde and Callow, may be employed with such modifications in construction and arrangement as may be needed to enable my improvements to be employed to best advantage. As iiotation apparatus of the type proposed for use with my salts and other improvements are so well known to those skilled in the art detailed description will be unnecessary. Consequently in the accompanying drawing I have given only a diagrammatic.illustration of o'ne construction and arrangement adapted for carrying out my improvements.

In the drawings 1 represents a tube-mill to which ore js fed by means of a chute or launder 2. @il and such reagents as may be employed to aid flotation and in particular the oiling of the metalliferous particles, for example an ac'd solution containing such a quantity of lphuric acid and aluminum or titanium pyrophosphatethat the pulpv containing the slimes after separation from the sands will containV 1n the case of copper sulphide ores about 4 lbs.4

of acid per ton of dry slime ore' (for an ore which normally-requires 8 lbs. of acid when used without added salt) and about 0.25 lb. of aluminum lpyrophosphateor 0.10 lb of titanium pyrophosphate, are conveniently added to the ore as it enters the tube mill by means of pipes 3 and 4. y

The crushed and oiled ore passes from the tube lmill through piple 5 to a Dorr or other classifier 6. As the ore is ordinarily ground with a much smaller amount of water than is used for flotation the additional amount of water may conveniently be added to the pulp in the classifier. This classier is provided with an inclined bottom 7 up which the sands which settle out are moved by Vmeans of rakes (not shown) until they pass over the lip or weir 8 into the pipe 43. Atthe opposite end flow lip or Weir is provided at a lower classifier carrying the slime material in 'susf the classifier an over- .7.o level than the lip 8so that the Water in the' pension will all iow over the lip 9 while thel rakes in moving the sands over the lip 8 will lift them outof the water and deliver them to the pipe 9 very largely dewaterd. .By

this arrangement the electrolytes employed for aiding oiling, which are more especially useful in tlie flotation of slimes, are removed from the sands and retained in the slimes.

The slimespass from the lip 9 into a pipe 10 which discharges into the agitation chamber 11 of a machine which may conveniently be of the mechanical agitation type. As-

the pulp flows into the pipe 10 further additional quantities of reagents, such \for)ex ample as a solution of aluminum or titanium pyrophosphate, may be added by means of pipe 12. In the agitation chamber 11 a ro-` tatable propellor 13 is provided driven by gearlng from a shaft 14. rl`he aerated o'e pulp passes through the aperture 15 into the spitzkasten 16 in which the bubbles of 'air carrying metalliferous particles form a layer of froth 17 while the sands fall to the bot'- tom and can be discharged through the pipe 18 to the tailing ond or another machine for re-treatment. 'lphe froth flows over a weir into a launder 19 from which the concentrates may be discharged. i

Frequently it is desirable to introduce frothing agent with the air or other gas eniployed for forming the froth either in addition to or in place of liquid oil or a soluble frothing agent. For this purpose the upper part of the agitation chamber 11 and spitzkasten 16 are enclosed by a cover 21 at opposite ends of which pipes 22 and 23 are provided for ingress and egress of air carryina frothing agent such as oil vapor.

referably the machine just described is employed merely as a roughing cell and the Iconcentrates discharged by pipe 20 are reerably of the Callow or pneumatic agitation.

type having a porous bottom 25 through which air may be blown from pipe 26. This air may, if desired, be charged with a frothing agent such as oil vapor. To allow the unutilized portions of the oil vapor to be conserved the upper part of the cell is enclosed at 27 so that the air liberated by the breaking of the bubbles in the froth may be led away by pipe 28 for re-introduction through the pipe 26 with such further additions of air and/ or oil vapor as may be required.

As the concentrates only contain a small percentage of Water additional water may be introduced into the cell 24 by,means of pi e 36.

he froth flows over weirs into laundersl out through the pipe 29.

The flow of the tails into the ipe 30 is controlled by a valve 31 operated in wellknown way by a float 32. These cleaner tails contain considerable quantities of metalliferous matter and so they are preferably' returned to the rougher cell by suitable means such as a centrifugal pump 33 and pipe 34:. The cells, particularly the rougher cell, are preferably electrically grounded in any suitable way as illustrated diagrammatically at 35., v

The sands may conveniently be treated by a similar arrangement of mechanical agitation rougher and pneumatic agitation cleanercells to those employed for treatin the slimes, and in the drawingv the same re erence letters are used for corresponding' parts in the two sets of cells.

However, the method of handling the circuit water'is referably somewhat different in the case ofp sands than of slimes for the reason that the sands are substantially dewatered by the classifier and further, the tails are readily dewatered as the sands -settle quickly. `These facts greatly facilitate the operation of the rougher and cleaner cells on a closed cycle so far as the circuit water is concerned. This is particularly advantageous with sand since for particlesof large size' relatively large quantities of a salt of the type of sodium pyrophosphate is employed for aiding in the production of a collective float of the values in the ore. In many cases it is desirable that oiling take place in acidified water and flotation in alkaline water and the dewatering of the sands by the classifier reduces the amount of alkali required to neutralize the acid in the water still adhering to the sands and to give the water the desirable alkalinity.

For copper sulphide ores a convenient concentration of sodium pyrophosphate is 6 lbs. pbr t0n of ore and if desired free alkali ma be employed in addition. The amount of7 alkali, suchas sodium hydroxides,

' may conveniently range' from 0.01 to 0.2 lb.

per ton of ore in excess of that required to neutralize any acid adhering to the particles of ore as they leave the classifier.

In the first place, instead of discharging the tails from the pipe 18 to the tailing pond they may to advantage be transferred to a settling cone 37 from which the circuit water may be drawn off and returned to the system by pipe 38, centrifugal pump 39 and pipe 40. A portion of the circult water passing through the pipe 40 ma convenlently be diverted by pipe 41 to t e cleaner cell 24. With this arrangement 4flotation takes place in the same solution in both rougher and'cleaner' cells.

Additional quantities of water, salt and/or alkali may be supplied as required by pipe 42.

For purposes of illustration I give in detail the results of 'practice with a process of the mechanical agitation froth type.

The amounts of electrolyte employed are given merely as examples of concentrations found suitable for certain ores, since, as is well known to those skilled in the art, the exact proportions of those substances which may be used in flotation processes vary somewhat according te the nature of the ore treated. V

As it is usually more convenient toA add the electrolyte used. prior to oiling the effect of electrolytes added prior to oiling will be considered first.

In the following examplesof practice car-y ried out by me the ore employed was a f cupriferous p rite ore which contained about 42% of sulp ide of iron and copper in a gangue of quartz and slate.

The ore was ground to pass 80 mesh and was therefore relatively coarse as compared with the slimes used in other practice which lwill be referred to later.

For emulsification or oiling prior toflotation separation the groun ore was mechanically agitated w1th three times its weight of water, 0.3%, to 0.4% of its weight of oil, and the desired quantity of electrolyte. The percentages of electrolytes used are based on the ore and not onthe water.

Using salts of a monovalent acid, i. e. hydrochloric'acid, I found that the highest recoveries were obtained with the following percentages of. sodium chloride, fcalcium chloride and aluminum chloride (each used alone without acid) respectively Sodium chloride, N aCl 0.40% Calcium chloride, CaCl2 0.27% Aluminum chloride, AlCl3 0.06%,

This table clearly shows that the higher the valence of the cation the smaller the quantity of salt re uired to give the best results for that particular salt. It was further found that not only did the amount of salt re uired decrease as-the valence of the cation lncreased, but also the amount of sul- A 'concentrations A maaien Aluminum chloride AlCl3 0.60% Aluminum phosphate AJP()4 (small amount acid added to make salts soluble) 0. 010% Aluminum pyrophosphate Al, (P207) 3 (small amount acid added to make salts soluble) 0.006470 Here again the efficiency of seperation improved as the valence increased.

IUsing (salts of a monovalent metal with acid radicles of different valence, the highest recoveries were obtained With the following concentrations Sodium chloride NaCl 0.40% Sodium phosphate NaaPOl4 above 0.064% Sodium pyrophosphate NaP2O, 0.016%

- With both sodium and aluminum salts increasing the valence of the anion not only decreases the amount of salts required to produce the best results, the. eiiciency of separation. lt will be observed that the smallest concentrations were obtained when the valence of both the cations and anions was the greatest, namely, when aluminum pyrophosphate was used.

In connection with sodium pyrophosphate l have found that there are two points of maximum extraction, one about 0.016% and the other above 0.3%. The contact potential of oil steadily rises to a maximum obtained with concentrations of sodium pyrophosphate above 0.3% of the first maximum o int is probably due to the fact that the di cult with which oiling of the sulphide partic es can occur increases to a maximum and then decreases as the concentration of sodium pyro hosphate is increased from lzero to 0.3%. f the two points of maximum extraction the higher concentration has been found by practice to be the most eficient, and this is probably due to the fact that not only is the contact potential on the oil much greater, which means that the oiled sulphide particles will have a more powerful attraction for the positively (frictionally) charged air, but also because Py at the higher concentration the difliculty of oiling appears to be lessthan at the lower concentration.

Using sul huric acid alone, the best results were obtained with a concentration of 1.2%. When, however,mixture of salts and acid lwere used it was found that the amount of acid which would give the best articular ore used, theV but also increases so that the existence results in conjunction with salts was lapproximately one-half'that required when acid alone was, used in the .caseof salts adapted to give trivalent ions, either' positive or negative, or both positiveand negative, as will be seen from the table given` bellow. ln the case of salts adapted to give qua'drivalentA ions, either negative or positive, it was found that the amount of acid could be advantageously increased beyond this amount (i.'e. 0.060%). For instance, vwith titanium sulphate, increasing the concentration of acid up to 0.74%,gave asteadily increasing yield, so that the best resultswould be obtained with the even higher conoentration of acid than that just referred to. Similarly with Sodium pyrophosphate, the best results were obtained with a concentration of acid in excess of 1%. v

When the valence of both cation and anion are increasedabove two the amount of acid which can be usefully employed falls off below 0.60%. The figures for the best concentrations of the salt and -acid,respec tively in each case are given in the following table:-

AlCL, 0.12% A1,(SO4)a 0.06% AIPO? 0.016% A1,(P207)3 0.010% Fe2(SO)3 1.16% "l`i(SO4)2 0.016% 'NMPZ7 0.016% H2S04 0.60% HZSO, 0.60% HZSO'. 0.53% ILS()4 (below) 0.33% 2 0,i 0.60% HZSO,L gabove) 0.74% l-IZSO4 above) 1.00%

.It will be seen that in each of the above acld and salt mixtures there is .a relatively much greater numberofhydrogen ions than polyvalent ions produced b the dissociation of the salt, whether suc ions are positlve ,or negative.

, In the above practice, both with and without acid, salts were used in the absence of heat and of material, such as bihromates adapted to inhibit flotation of certain sulphides.

I have further found that an acid solution of sodium pgrophosphate-0.3% Na4P2U., and.1.00% H2 O-gives better results than the above acid solution of sodium rosphosphate, namely :--0.016% Nia-P207 and 1.00% H504. A

llt was found that aluminum pyrophosphate gave higher' extractions than either aluminum chloride or titanium sulphate. With most ores neutral sodium pyrophosphate gave higher extractions than aluminum pyrophosphate and in practicallyvall cases a strongly acid solution of sodium py- ,rophotphate gave muchA better results than the liotation treatment and, especiallywhere low pulp densities have been used to permit larv amounts'f oil to be -used efficiently, ena les higher ulp densities to be employed.

The ore emp oyed in the foregoing prac-v tice was ground to pass 80 mesh but if the ore is ground to pass .2 00 mesh the results are markedly changed.

Ordinarily the finer the ore is ground the more readily it iioats but when a salt of the type of sodium pyrophosphate is present during oiling poorer results may be obtained with slimes than with sands.

This difference is muchinore marked with zinc ores than with copper ores, doubtless due to the smaller aiinlty of oil for blende than for sulphides of copper.

-As an example the results obtained with a zinc ore assaying 16 to 18% zinc may be given. The ore in the one case was ground until 16% remained on 80 mesh, and in the other case the ore was ground until practically all would pass 200 mesh. The percentages of .zinc in the tails-were as follows:

Electrolyte. Zinc in tails.

Nature. Lbf" cxx-ds? Fine fed Withfa copper pre containing about 0.9 to 0.95% Cu similargthough less pronounced,

. results lwere obtained. Wlth coarse feed the use of about 10 lbs. per ton of'sodium pyrophosphate reduced the copper in the tails about In the case of fine feed, however, the copper in the tails was increased nearly 100% bythe same amount of salt.

If instead of a salt such as sodium pyrophosphate adapted to inhibit oiling a salt is used which aids oiling the reverse result is obtained. Thus using 4 lbs. H2SO4 and 0.24 lb. Al4 (P201), per ton with the above copper ore the tails with coarse feed contained 700% more copper than the tails with 8.8 lbs. HZSO, and 12 lbs. NaPO, per ton.

age belts or the like. hand, require much longer time to settle and treatment the ore is claified in order'that y the sands ior larger articles may be oiled and ioated in a di erent electrolyte than the slirnes or fine particles. F orthe sands the electrolyte may be of the type specially adapted to aid he flotation ofthe particles when oiled, e. gsdium pyrophosphate. In the case of the sli u es the electrolyte may be of the type specially adapted to aid the oilingof the particles, e. an acid solution of aluminum pyrophospate.

This .classification treatment'has the further advantage that it facilitates the recovery of the sodium pyrophosphate for further v use. It is comparatively easy to de-water sa-nds as they settle rapidly and can be readily separated from water by means of drain- Slimes, on the other more careful treatment to separate the water. The amount of aluminum pyrophosphate required is so much smaller than the quantity of sodium pyrophosphate needed -to give best results that the dewatering of the slimes is not nearly so important as the dewatering of theA sands. n

In addition to classifying. the ore according to size of particle I have found it useful with certain ores to employ mechanical agitation rougher cells in combination with pneumatic agitation cleaners. P

In practice using a low grade copper ore ground with oil and floated in the presence of 6 lbs. of sodium pyrophosphate by the mechanical agitation process an extraction of 97.5% was obtained with a concentrate weighing 25% of the original feed. 0n the other hand, using the pneumatic agitation vprocess and the same amount of such salt, the extraction was only 93%l in. stead of 97.5%, but the concentrate onlyA I weighed 16% of the original feed instead of 25%. Accordingly, I propose to employ the two processes inv conjunction in order to combine the good features of each. I have found that the above concentration of such salt gives very beneficial results in both forms of process so that the same solution` maybe used'in lboth rougher and cleaner.

cells.

Further, I may employ sodium pyrophosphate or other salt merely to improve the grade of concentrate. Thus in the case of zinc ores the beneficial -ei'ect of sodium or aluminum pyrophosphate on the grade of concentrate may be as important as the effect of these salts in increasing the extraction.

In practice with zinc ores I have found that a saltsuch as copper sulphate having tion should be employed in addition to acid- Mamet la beneficial chemical or electrochemical acand pyrophosphate, whether -sodium or aluminum. p ,I

The concentrations of sodium 'pyrbphosphate found most beneficial with zinc ores appear to be very considerably lower than in the case of copper and other ores.

Efiicient results with a zinc ore assaying 16.8% zinc have been obtained with the following mixtures and amounts of electro- 1ytes:-'

NaqPqOL.' 1.2 lbs. per ton mict" '22:11.'.:11111: 2:?

l 0.24lbs.perton 40 l( Il il in the flotation of a copperv ore assaying 1.00% Cu ground 16% on 80 mesh.

When the ore and voil were both ground and subsequently floated in the presence of 0.10%Na4P207 solution (on the water) the tails assayed 0.11% instead of 0.088% when ground with plain water and then floated 1n a solution of sodium pyrophosphate of that strength.' lThe same ore, both ground and floated in plain water, gave a tail containing 0.25% Cu. f

With smaller vconcentrations of salt the effect is more pronounced. For instance, with a 0.003% solution (on the water) of Na4l3'207 on a sample of ore assaying 1.92%

Cu, the tails assayed A0.55% Cu when the saltl was added prior to grinding and 0.42% Cu when the salt was added after grinding as compared with 0.47% Cu for plain water.

This is probably due to the maximum negative potential or the sulphides being reached in much lower concentrations than 0.10% sodium pyrophosphate. If this be the case, then-in a 0.10% solution, the negative potential of the sulphide will be brought to a value approaching zero.

The effect of changing the time of addition of the sodium pyrophosphate is much more marked in the case of slimes.

In the case of a copper ore slime assaying about 0.92% Cuusing acid alone (H2304 7 lbs. per ton) the ktails contained 0.07% Cu.

- Whenl sodium pyrophosphate (10 lbs. per

ton) was added with the acid prior to oiling the copper in the tails increased to 0.13% but when added after oiling (acid added before oiling) it decreased to 0.045%. This change in the time of addition also increased the grade of rougher concentrate from 8% Cu to 17 Cu as well as very materially hastening the rateofv separation.

As the addition of alkaliv toV a solution containing a salt of the type of sodium pyrophosphate greatly aids the latter in increasing the negatlve charge on the oil, I may, especially after oiling in acidiied solution, make the solution alkaline bythe addition of caustic alkalisimultaneously with the introduction of sodium pyrophosphate. Caustic alkali in very small concentrations (up to about 0.001 normal) itself increases the negative potential of oil as well as increasing the amount of high valent anions produced by the dissociation of the sodium pyrophosphate.

In practice carried out using the Elmore vacuum process I have foundthat advantageous results are obtainable by the use of high valent ions, both' positive and negative and that the addition of acid is normally advantageous. The concentrations suitable are substantially the same as those above given in the case of the mechanical agitation procafter oiling and before flotation.

. The use of polyvalent .ions particularly anions is applicable not only to the flotation of metallic sulphides but also to metallic carbonates or oxides either with or without sulphidization. Carbonates, oxides and basic sulphates tend to aggregate vat the interface between oil and water so that they are capable of acting as emulsifying agents. Sulphides on the other hand tend to leave the water entirely and enter the oil-bodily so as to become completely surrounded b v the oil. The alinity of carbonate, etc.,`particles for oil is therefore much less than it is for sulphide particles. For this reason the agitation should in general be as mild as possible the particles of carbonate for oil increases very rapidly as the size of the particles decreases. I-Ience preferably vthe ore should be ground until the carbonate particles are smaller Athan 200 mesh.' I have further found that the size of the particles of carbonate produced'by grinding the ore is de- Apendent not only upon the length of time occupied by the grinding but also upon the way in which carbonate occurs in the ore. If the ore is one in which carbonate has been deposited from solution, the carbonate will be present -in the form ofl extremely thin layers over the surface of the particles of gangue, so that frequently the ore has the Aappearance of being very rich when in reality it is very poor owing to the extreme thinness of the surface deposits. If such an ore is ground for even a short while this extremely thin surface layer will be. removed in the form of exceptionally small particles. On the other hand, when the carbonate occurs in separate masses of homogeneous carbonate, which may be larger than mesh, grinding the whole ore until it will pass through 200 mesh will not bring the carbonate particles into such a fine state of subdivision as is produced in a water-deposited ore after much shorter grinding.

For floating carbonates and other oxidized ores without sulphidization the electrolytes added should, in general, ,be ca pable of giving anions having a coagulating effect superior to that of monobaslc acids,

such as hydroxyl or polyvalent anions, and preferably anions having as high a valence as'possible. I have found that the addition of acid reduces the extraction and grade of concentrate obtained. I have further found that the use of a salt of the type of aluminum pyrophosphate is in general deleterious. Consequently I prefer to employ neutral or alkaline solutions of a salt ofthe type of sodium pyrophosphate adapted to give a monovalent cation and a high valent anion.

Practice carried out by me with. a New `Jersey carbonate of copper ore of the water' y deposited type using 0.016% sodium pyrophosphate 1n neutral solution gave an extraction of 81%, using the mechanical-agitation process.

The affinity of oxidized metalliferous material for oil may be increased by sulphidization, either of the peripheries of the particles or of the entire material of the particle.

If the particles are only filmed with sulphide vthe agitation. should be as mild 'as so that the film of sul hide was renewed whenever it was rubbe off, and oil was added in successive amounts, an extraction of 98.7% of copper was obtained.

I have found that heat very materially aids the sulphidization of the particles so that the particles may not only be filmed, but practically wholly converted into sulphide by passing hydrogen sulphide into bolling hot wet ore pulp. By sulphiding hot before flotation when the amount of water in the pulp is'much less than it is during flotation loss of hydrogen sulphide by solution is' reduced to a negligible amount, particularli` since the gas is very diflicultly soluble in boiling hot water.

This method also facilitates removal of excess of lhydro en sulphide b boiling the pulp for a brie time to avoi deleterious effect of hydrogen sulphide on flotation, particularly if natural sulphides are also present in the ore.

One of the important factors in floating sulphidized material is to, collect the particles of sulphidized material b the oil, and as this is mort.'l difficult than 1n the case of natural sulphides the mixing of the oil and the ore should be much more thorough than is required for natural sulphides. This mixing may to advantage take place either after or during sulphidization in a ball or pebble mill as a more intimate mixing can lbe obtained in that way than bv the usual emulsifiers or Pachucas. In some cases it may be desirable to sulphide the ore in a silexlined pebble mill in the presence of oil.

Acid, either alone or with a salt such as aluminum pyrophosphat'e, may be added to the mixture prior to mixing with the oil in order to aid the collection of the particles of sulphide.

For natural sulphides salts adapted to give either polyvalent anions or cations can be used to great advantage in the mechanical-agitation process, and there is relatively little difference between the extractions obtained with quadrivalent anions and cations for example. In the case of artifically formed sulphides, however. there is a very marked difference as will be seen from the the possible following table Percenta e 0.15% Nalrfof 9s. 7% 51.6%

0. 30a Na P o 0. 309i Huso?. l 89' 2% 2li-6% 0.0157 ruso) o. 30%112510. .4f 66' 8% 1- 0% Small additions of oil were added at successive intervals. l

As in vthe case of natural sulphides the memes addition of the sodium pyro hosphate may to advantage be delayed pnti after the sul. nhided material has been mixed with oil.'

rlhe tails should. perferablv be drained not only to save the electrolytes used, but also to save the copper sulphide in^suspension. Further, the tails may often to advantage be washed after drainlng With a view to removing any fine particles of sulphide which may be adherin to the Aparticles of gangue.

l have also ound that the results with silicate of copper ores are in general much poorer than those obtained with other oxidized copper ores.-

The use of various salts adapted to give high valent ions has beenreferred to, and in particular, sodium and aluminum pyrophosphates. Other similar salts might be used although these two appear to be the most readily available.

As in general the anion appears to be more important than the cation the available salts capable of giving anions having a high valence Will be considered irst.

is examples of hexavalent anions the tetraphosphates such as NaePO, andhexametaphosphates such as Naflx()18 may be referred to. As instances of salts capable of giving quadrivalent anionsmay be mentioned the pyrophosphates such as NaJEZO?,

ferrocyanides such as K4Fe(CN)6, pyroarions of pyrophosphoric acid are respectively senates such as Na4As2O, and pyroantimonates such as K4Sb207. Similarl for trivalent anions phosphates such as a3Po, ferricyanides such as K3Fe(CN)6 or arsenates Nanas()4 might be used.

lf valence were the only factor Ito be considered the tetraphosphates and hexametaphosphates would be superior to salts which give quadrivalent or trivalent anions. However, another, almost equally important factor is the extent to Whichthe salt and its corresponding acid dissociates, as this determines' the 4number of high valentl anionsl furnished by a given amount of salt. Any polybasic acid or Salt of such acid dissociates in stages. ln other Words, cations are given od progressively with the formation of Ilegative ions of increasing valence. For instance yrophosphoric acid (H4P2O7) dissociates 't to form HallzO,- ions, a certain number of which then split up to form HZPZO," ions, a) certain number of whichl split up to form HPZOT" ions a number of which split up to form P20,

The dissociation constants of the fourth hydrogen ions. lirst, second, thlrd and 1.1)(10'2T, 2.9X107- and 3.6)(10'9. Consequently' the amount of quadrivalent PzOf" ion formed is much less than the amount of the trivalent ion, which in turn is very much less the divalent ion which inturn is less than the amount of the monovalent ion. The

than the amount ofi'found that rst and second dissociation constants aredivalent and as many divalent as the latter` gives trivalent ions. Consequently even though pyrophosphoric acid did not give a quadrivalent ion While phosphoric acid can only give a triva-lent ion pyrophosphoric acid Orthophosphoric acid on is a weak acid, the dissocia-` glVeS BLS many mOIlO- would be much superior to phosphoric acid on account of the much largerv number` of diand trivalent ions `it gives on dissociation. The dissociation of the acid corresponding to the saltradded is very importantfsince,

particularly when the electrolyte is added prior to oiling, acidiied solutions in eneral give better results than neutral so utions. Especially after-,oiling, and this, of course, includes the cleaning of rougher concen'- trates, the solution may' to advantage be made. slightly alkaline. Not only do hydroxyl ions tend to increase the negative charge on the oil but also the addition of alkali greatly increases the concentration of high valent anions.

This latter effect results from the fact that t-he product of the concentrations ofv the hydrogen and hydroxyl ions is always 1014:

In a solution containing only 0.05% of sulphuric acid the hydrogen ion concentration (assuming complete dissociation is 1X10'2. In a solutioncontaining 0.05% of sodium hydroxide lthe hydroxyl ion .concentration (assuming complete dissociation) is 1.2)(10'2 so that the hydrogen' ion concentration will be less than 10'12".4

The charge from acid to alkaline solution involves a change of hydrogen ion concentration from 1 10'2 to 1x10l2 which will result in 1greatly vincreasing the dissociation of the 2R07", HPZO, and similar ions.

In view of the importance of the hydrogen much greater in the case of inorganic acids than of organic acids.

Relatively little is knownof tetraphosphoric aci but the fact' that it has been over ten times the amount of sodium tetraphosphate is needed to produce the same edect on dotation as a given amount mation of insoluble ferrocyanides can be avoided. In view, however, of the fact that pyrophosphoric does not readily form injurlous insoluble compounds its use is ordinarily to be preferred.

So far as trivalent salts are concerned these would be superior to pyrophosphates only if they dissociated to an unheard ofV degree.' Phosphates have been shown to be far inferior to pyro hosphates and probably the same is true of t e arsenates.

The ferricyanides are in general open to the same objection as the ferrocyanides, namely the formation of insoluble compounds which oison flotation.

.It appears t erefore that the pyrophosphates are the most suitable source of high valent anions for flotation.. Sodium pyro-- phosphate, which appears to be the most gen-I erally usefull pyrophosphate can be very cheaply and easily prepared from the comhosphate of soda of commerce (NazI-l O4) by simply heating it to drive oil' water;

Since in connection with some ores and slime material in particular it may be found advisable to use a" salt adapted` to give cations and anions, both of high valence, the availability of suitable high valent cations will be considered.

' While in the. case of polyvalent anions vthe dissociation constants of the corresponding acid appears to be one of the most im ortant factors, in the case of polyvalent cation the mobility of the ions appears to be a very important factor. For instance, the aluminum ion has a greater mobility than the ferrie ion, and it is found that aluminum salts are much more effective in -flotation than are ferric salts. For linstance when ferrie sulphate was used in conjunction with' acid, the best results were obtained with a concentration of 0.16% of the salt as compared with 0.060% of aluminum sulphate. This difference between the mobility of the aluminum and ferrie ions i's in part if not entirely d ue to the smaller atomic 4weight of the aluminum ion, since according to the kinetic theory the velocity of movement of the ions in solution is inversely proportional to the square root of their mass, consequently since the atomic Weight of alumi-l num is 27 and vthat of iron is 56, we should expect a greater mobilityof the aluminum as compared with iron which is exactly the case'.

However, the atomic weight is not the only, and in some cases not even the principal factor which determines the mobility ofthe ion. Thi'sis due to the aa that practically all ions are hydrated toA a ,greater orless extent. For instance, the hydrogenion has two waters'of hydration, the potassium ion averages 9.6 waters of hydration, while. the lithium ionhas24 waters of hydration. This attached lwater has, of course, the effect of slowing upfth'e action of the ion in solution, so that whereas the hydro en ion with an atomic weight of lhasa mobi ity of 318, and the potassium ion with an atomic weight of 39 a mobility ofI 65.3, the lithium ion with an atomic weight of 7, has a mobility 'of only 33.4. Other things being equal therefore, ions having a high mobility should be selected in preference to those having a low mobility. u

Aluminum has an atomic weight smaller than any1 other tri-valent metal, and since with the exception of iron its salts are cheaper than those of other trivalent metals its salts are particularly suitable for use in flotation. f

There are anumber of metals which under certain conditions are quadrivalent, the most -be in erior to aluminum pyrophosphate and when titanium pyrophosphate was prepared it was found to be largel colloidal in character, so that, althoug theoretically it should be superior to aluminum pyrophosphate, the number of positive and negative quadrivalent ions produced was apparently not sufficient to enable it to give superior result to aluminum pyrophosphate. The

'pyrophosphates of other quadrivalent metals might possibly be used to advantage if their costis not prohibitive.

There are also a number of metals which form l entavalent salts, the principal of these eing tungsten. This metal is also hexavalent under certain conditions. However, many of these `salts do not appear to exist in the presence of Water, at least to any appreciable extent. For instance tungsten pentachloride on treatment with large quantities of water is at once decompose almost entirely into blue oxide 'WZO and hydrochloric acid with the evolution of heat. f

While I have referred to the 'employment of oil as a frothing agent, I may use a soluble organic frothmg agent such as amyl alohol either alone or in conjunction with o1 v Further, although oleic acid and similar Mamet other practice carried out by me other gases.

have been employed and in particular air -with additions of readily condensible gases.

As a general rule, the readiness with which a gas will condense upon a surface depends on the ease with which the gas can be liquelied. For instance, carbon dioxide condenses to a greater extent on a sulphide surface than does air for theereason that the critical temperature of carbon dioxide is +310 C., whereas that of oxy en and nitro en are, respectively, 118 and 146 In some cases I may therefore employ air or other gases containing as a frothing agent a readily condensible vapor such asthe vapor of a hydrocarbon oil, gasoline for example, or a more volatile member of the same series. Further, in place of oilvapor, I may use the vapor of a soluble organic compound such as amyl alcohol.

Such oil or other vapor may be employed either in substitution for or 1n addition to the use of oil in the liquid state or the introduction of a soluble organic frothing agent independently of the a1r`or other gas reriired to operate the process..

lectrolytes are preferably added to the ore pulp to aid the separation of the metalliferous constituents when such frothing vapor is used.

I claim:

1. The process of concentrating ores which includes mixing the comminuted ore with water and an oily liquid to oil the metalliferous particles, then aerating the mixture to form a froth and separating the froth from the remainder by flotation, and which further includes the addition, intermediate the oilingand aeration treatments, of material adapted to give anions having a greater valence than two for aiding the formation of a froth.

2. The process o f concentrating vores which includes agitating the comminuted ore with water and an oily liquid to oil the metalliferous particles, then disseminating bubbles of gas through the ore pulp by the action of moving' agitators to form a froth and separating the froth from the remainder by flotation and which further includes the addition, intermediate the oiling and aeration treatments, of material adapted to give anions having a greater valence than two for aiding in the formatlon of a froth.

3. The process of concentratingv ores which includes,I mixing the comminuted ore with water and an oily liquid inthe presence of an electrolyteadapted to aid in the oiling of the metalliferous. articles, then adding an electrolyte adapte to aid in the flotation of the particles so oiled, subsequently aerating the mixture to form a froth and separating the froth from the remainder lby flotation.

4. The process of concentrating comminuted masses of composite character which includes the treatment of the mass with a fluid adapted to aid in the movement of certain of thel comminuted particles relatively to lothers having dierent qualities,

and Which further includes the use of a so lution containing anions formed from nonmetallic oxides having aV valence greater 4than three for increasing theselective action of the fiuid.

5. The process of concentrating ores which includes mixing the comminuted/ore with water, aerating the mixture t0.` form a froth and separating the froth from the remainder by flotation and which further includes the use of anions having a greater valence than three for aiding in the formation of the froth.

6. The process of concentrating ores which includes mixing the comminuted ,ore with water, disseminating bubbles -of gas through the mixture -by the action of moving agitators to form a froth and separating the froth yfrom the remainder by flotation and which further includes the use of anions having a greater valence than three for aiding in the formation of the froth.

7. The process of concentrating. ores which includes mixing the comminuted ore with water, disseminating bubbles of gas through the mixture by the action of mov- -ing agitators to form a froth and separating tions having a greater valence than three forl aiding -in the formation of the froth.

8. 'Ihe process of concentrating ores which includes mixing the comminuted ore with water, disse'minatinobubbles of gas through the mixture by the action of moving agitators to form a froth and separating. the froth from the remainder by flotation and which further includes the use of anions having a greater valence than two and cations having a greater v'alence than one'for aidin in the formation of the froth.

9. fgfhe process of concentrating ores which includes mixing the comminuted ore with water, disseminating bubbles of gas through the mixture by the action of moving agitators to form a froth and separating the froth from the rem'ainder byflotation and which further includes the simultaneous use of acid and a salt adapted to Igive anions having a greater valence than two for aiding "in the formation of the froth. 1,

10. The process of concentrating" ores which includes classifying the comminuted ore into sands and slimes, subjectin the sands to flotation treatment in a so ution containing an added salt adapted to give anions of greater valence than that of the cations and the slimes to flotation treatment in acid solution.

11. The process of concentrating ores which includes classifying the comminuted ore into sands and slimes, subjecting the sands to flotation treatment in a solution containing anions of greater valence than that of the cations and the slimes to flotation treatment in acid solution of a salt of a polyvalent metal.

12. The process of separating composite comminuted masses which includes a preliminary flotation treatment by mechanical agitation, separation of the froth produced by such agitation, and a secondary recleaning flotation treatment of such froth by fluid-pressure agitation, and which further includes the use in each agitation treatment of a solution containing ions having a greater valence than two.

13. The process of separating composite comminuted masses which includes a pre` liminary flotation treatment by mechanical agitation, separation of the frothproduced by such agitation, and a secondary recleaning flotation treatment of such froth by fluid-'pressure agitation, and which further includes the use in each agitation treatment of a solution containing anions having a greater valence than cations.

14. The process of concentrating ores which consists in mixingthe powdered ore with water to form a pulp, adding a small proportion of a liquid frothing agent as such to the pulp, introducing into the pulp bubbles of a non-frothing gas carrying a frothing agent, allowing the bubbles to rise to the .surface ofthe pulp to form a froth and separating the mineral carried by the froth from the remainder of the ore.

15. The process of concentrating ores' which consists in mixing the powdered ore with water to form a pulp, adding a small proportion of a liquid oily frothing agent as such to the pulp, introducing into the pulp bubbles of a non-frothing gas carrying a frothing agent, allowing the bubbles to rise to the surface of the pulp to form a froth and separating the mineral carried by the froth'from the remainder ofthe ore.

16. The process of concentrating ores which consists in mixing the powdered ore with water to form a pulp, adding a small proportion of a liquid frothingl agent as.

such to the pulp, introducing into the pulp bubbles of a non-frothing gas carrying a frothing agent in gaseous form, allowing the bubbles to rise to the surface of the pulp to form a frothiand separating the mineral carried by the froth from` the remainder of theore. i s

17. The process of concentrating ores which consists in mixing the oWdered ore with water to form a pulp, a ding a small proportion ofa liquid oily frothing agent as such to the pulp, introducing into the pulp bubbles of a non-frothing gas carrying a frothing agent in gaseous form, allowing the bubbles to risev to the surface of the pulp to form a froth and separating the mineral carried by the froth from the remainder of the ore.

18. The process of concentrating composite comminuted masses of composite character .which includes the treatment of the mass with a fluid adapted to aid in the movement of certain of the comminuted particles relatively to others having different qualities, and which further includes the use of a solution containing positive ions having more than one electrical charge and negative ions having more than two electrical charges for increasing the selective action of the fluid.

19. The process of concentrating composite, comminuted masses of composite character which includes the treatment of the mass with a fluid adapted y'to aid in the movement of certain of the comminuted particles relatively to others having different qualities, and which further includes the use of a solutionv containing positive ions having more than one electrical charge and negative ions having more than three electrical charges for increasing the selective action of the fluid.

20. The process of concentrating compos.ite,com1ninuted masses of composite character which includes the-treatment of the masses with a fluid adapted to aid in the movement of certain of the comminutedO particles relatively to others having different qualities, and which further includes the use of a solution containing negative and positive ions both having more than two electrical charges for increasing the selective action of the fluid.

21. The process` of concentrating composite, comminuted masses of composite character which includesv the treatment of the mass withv a fluid adapted to aid in the movement of certain of the comminuted particlesl relatively to others havin different qualities, and which further includes the use of a solution containing positive ions having more than two electrical charges and negative ions having more than three electrical charges for increasing the selective action of the fluid.

22. The process of concentrating composite, comminuted masses of composite character whichL includes the treatment of the mass with af fluid adapted to aid in the -movement of certain of the comminuted particles relatively to others having different qualities, 4and which further includes the use of a solution containing positive ions having more than `three electrical charges for increasing the selective action of the fluid.

23. The process ot concentrating composite,' comminuted masses of composite characterivhichA includes the treatment of the mass with a fluid adapted to aid in the movement of certain of the comminuted particles relatively to others having di'erent qualities, and which further includes the use of a solution containing positive ions having more than vthree electrical charges and negative ions having more than one electrical .charge for increasing the selective action of the fluid.

24. The process of concentrating com-v posite, comminuted masses of composite character which includes the treatment of the mass with a fluid adapted to aid in the movement of certain ot' the comminuted particles relatively to others having different qualities, and which further includes the use of a solution containing positive ions" having more than three electrical charges and ne ative ions having more than two electrical c iarges for increasing the selective action of the fluid.

25. The process of concentrating composite, comminuted masses of composite character which includes the treatment of the mass with a fluid adapted to aid in the movement ofi certain of the comminuted particles relatively to others having diHerent qualities, and which further includes the use of a solution `containing negative ions having more than two electrical charges and a relatively much greater amount of hydrogen ions for increasing the selective action of the fluid.

26. rlhe process of concentrating composite, comminuted masses of composite character which includes the treatment of the mass with a fluid adapted to aid in the movement of certain of the comminuted particles relatively to othersliavin different qualities, and which further includes the use of a solution containing negative Aions having more than three electrical `charges and 'a relatively inuch greater amount of hydrogen ions for increasing the selective action of the fluid.

27. rThe process of 'concentrating coinposite, comminuted masses of composite character, which includes the treatment of the mass with a fluid adapted to aid in the movement of certain of the comminuted particles relative to others having dierent qualities. and which further includes the use of a solution containing positive ions having more than one electrical charge, a relatively larger number of hydrogen ions and negative ions having more than two electrical charges for increasing the selective action of the fluid.

2t?. The process of concentrating coinposite, comminuted masses of composite character which includes the treatment of the masswith a fluid adapted to aid in the movement of' certain of the comminuted particles relatively to others having different qualities, and which further includes the use of a solution containing positive ions having more than one electrical charge, a relatively larger number of hydrogen ions and negative ions having more than three electricalJ charges for increasing the selective action of the fluid,

29. The process of concentrating composite, comminuted masses of composite character which includes the treatment of the mass with a fluid adapted to aid in the movement of certain of the comminuted particles relatively to others having different qualities, and which further includes the use of a solution containing negative and positive ions both having more than two electrical charges and a relatively larger number of hydrogen ions for increasing the selective action ofthe fluid.

30. The process of concentrating composite, comminuted masses of composite character which include the treatment of the mass with a fluid adapted to aid in the movement of certain of the' comminuted particles relatively to others having'dierent qualities, and which further includes the use of a solution containing positive ions having more than two electrical charges, a relatively larger number of hydrogen ions and negative ions having more than three electrical charges for increasing the selective action of the fluid.

31. The process of concentrating composite, comminuted masses of composite character which includes the treatment of the saine with a fluid adapted to aid in the movement of certain of the comminuted particles relatively :to others having differentl qualities, and which further includes the use of a solution containing positive ions having more than three electrical charges and a relatively larger number of hydrogen ions t', for increasing the selective action of thev fluid., 7

32. rllhe process of concentrating composite, comminuted masses ofcomposite character which includes the treatment of the mass with a fluid .adapted to aid in the movement of certain of the comminuted particles relatively .to others having dierent qualities, and which further includes 'the use of "a solution containing positive ions atA lll@

lill@ MIB y the having more than three electrical charges, a relatively larger-number of hydrogen ions and negative ions having more than one electr'ical charge for increasing the selective action of the fluid.

The process of concentrating composite, comminuted masses of' composite character which includes the treatmentof the mass with a fluid adapted to aid in the movement ot' certain of the comminuted particles relatively to others having different qualities, and which further includes the use of a solution containing positive ions having more than three electrical charges,v a relatively largernumber of hydrogen ions and negative ions having more than two electrical charges for increasing the selective action of the fluid. Y

34. The process of concentrating sulphide ores which includes the treatment of the comminuted ore with a fluid adapted to aid in the movement of sulphide particles relatively to other particles of the ore, and which further includes the use of a solution containing negative ions havingmore than three electrical charges for increasing the selective action of the fluid.

35. The process of concentrating sulphide ores which includesl the treatment of' the com'- minuted ore with a fluid adapted to aid in movement of sulphide particles relatively to lother particles of the ore, and which further includes the use of a solution containing positive ions having more than one electrical charge and negatlve ions having more than two electrical charges for increasing the selective action of the fluid.

36. The process of concentrating sulphide oreswhich includes the treatment of' the comminuted ore with a fluid adapted to aid in 'the movement of sulphide particles relatively to other particles of the ore, and which further includes the use of a solution containing positive ions having more than one electrical charge and negative ions having more than three electrical charges for increasing the selective action of the fluid.

37. rlhe yprocess of concentrating sulphide ores which includes the treatment of the comminuted ore, with a fluid adapted to aid in the movement of sulphide particles relatively to other particles of the ore, and which -further includes the use of a solution containing positive ions having more than two electrical charges, negative ions havin more than one electrical charge and a re atively much larger number of hydrogen ions than said positive ions for increasing the selective action of the fluid.

38. The process of concentrating sulphide ores which includes the treatment of the comminuted ore with a fluid adapted to aid in the movement of sulphide particles relatively to other particles of the lore, and whichfurther includes the use of a solution containing negative and positive ions both having more Athan two electrical charges for increasing the selective action of the Huid.

39. The process of concentrating sulphide ores which includes the treatment of the com'- Ininuted ore with a fluid adapted to aid in the movement of sulphide particles relatively to other particles of the ore, and which -further includes the use of a solution con taining positive ions having more than two electrical charges and negative ions havlng more than three electrical charges for increasing the selective action of the fluid.

40. The process of concentrating sulphide ores which includes the treatment of the comminuted ore with a fluid adapted to aid in the movement of sulphide particles relatively to other particles of the ore, and which further includes the use of a solution conf taining positive ions having more than three electrical charges for increasing the selective action of the fluid.

4l. The process of concentrating sulphide ores which includes the treatment olf/the comminuted ore with a fluid adapted to aid in the movement of sulphide particles relatively to other particles of the ore, and which further includes the use of a solution. containing positive ions having more than three electrical charges and negative ions having more than one electrical 4charge for increasing the selective action of the fluid.

42. The process of concentrating sulphide ores which includes the treatment ofv the comminuted ore with a fluid adapted to aid in the movement of sulphide particles relatively to other particles ofthe ore, and which further includes the use of a solution containing positive ions having more than three electrical charges and negative ions having more than two electrical charges lfor increasing the selective action of the fluid.

43. The process of concentrating sulphide ores which consists in agitating the comminuted ore with a solution containing positive ions havingmore thanone electrical charge and negative ions having more than two electrical charges and a frothing agent until a froth is formed which contains sulphide particles, and separating the froth from the remainder by flotation.

44. The process of concentrating sulphide ores which consists in agitating the commi-4 nuted ore with-a solution containing positive ions having more than one electrical charge and negative ions having more than three electrical charges and a frothing agent until a froth is formed which contains sulphide particles, and separating the froth from the remainder hy flotation.

45. The process of concentrating sulphide ores which consists in agitating the comminuted ore with a solution -containing posi` tive ions -having more than two electrical charges, negat1ve ions having more than one -one electrical charge and a frothin electrical charge and a relatively much larger number of hydro en ions than said positive ions and a frot` ling agent until a iiroth is formed which contains sulphide particles, and separating the froth from the remainder by iiotation.

46. The process of concentrating sulphide ores Which consists in agitating the comminuted ore with a solution containing negative and positive ions both havingmore than two electrical charges and a frothing agent until a froth is formed which contalns sulphidev particles, and separating the froth from the remainder by otation.

47. The process of concentrating sulphide ores which consists in agitating the comminuted ore With a solution containing positive ions having more than two electrical charges and negatlve lons having more than threeelectrical charges and a frothing agent until a froth is formed Which contains sulphide particles, and separating the froth from the remainder by flotation.

48. The process of concentrating sulphide ores which consists in agitating the comminuted ore With a solution containing positive ions having more than three electrical 'charges and a frothing agent until a froth is formed which contains sulphide particles, and separating the froth from the remainder by flotation.

49. The process of concentrating sulphide ores which consists in agitating the comminuted ore With a solution containing positive ions having more than three electrical charges and negative ions having more than agent until a froth is formed which contalns sulphide particles, and separating the froth from the remainder by flotation.

50. The process of concentrating comminuted masses of composite character which includes the treatment of the mass with anionizing liquid and a) gas, and

`Which further includes the movement of the produced on,l the liquid by such movement.

51. The process of concentrating comminuted masses of composite character which includes the treatment of the mass with an ionizing Huid and a gas, and which further includes the relatively rapid movement of the gas relatively to the liquid, and the substantial elimination of the electric charge produced on the liquid by such movement.

52. The process ofv concentrating comminuted masses of composite character which consists in mixing the comminuted mass with Water 'containing in solution negative ions having a valance greater than three,.agtating the mixture to form a froth and separating the froth.

53. The process of concentrating composite, comminuted masses of composite character which includes the treatment of the mass with a gaseous fluid adapted to, aid in the movement of certain of the comminuted particles relatively to others having different qualities, and which further includes the use of a solution containing a pyrophosphate for increasing the selective action of the fluid.

54. The process of concentrating comminuted masses of composite character which includes the treatment of the mass with a fluid adapted to aid inthe movement of certain of the comminuted particles relative to others having different qualities, and which further includes the use of a solution containing anions comprising phosphorus, and having a greater valance than three for increasing the ,selective yaction of the fluid.

RIDSDALE ELLIS.

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