CA1340993C

CA1340993C - Method and device for producing pure elemental iodine

Info

Publication number: CA1340993C
Application number: CA 565290
Authority: CA
Inventors: Dennis Hardy O'dowd
Original assignee: Iomech Ltd
Current assignee: Iomech Ltd
Priority date: 1987-04-29
Filing date: 1988-04-27
Publication date: 2000-05-16
Anticipated expiration: 2017-05-16

Abstract

A method and a device for producing pure elemental iodine in which a substance containing thermodynamically free iodine is provided on one side of an iodine solving solid barrier and the iodine vapor generated by sublimation of the iodine through the barrier is collected on the other side of the barrier, creating stoichiometric balance between the two sides of the barrier and within the barrier.

Description

FIELD OF THE INVENTION
This invention relates to the production of pure elemental iodine.
BACKGROUND OF THE INVENTION
Iodine, in the form of Lugol's Solution (and tincture of iodine) has been recognized as an effective biocide by the U.S. Pharmacopia and other like publications in other countries since 1830, and iodophores have been given like status in these publications since 1960.
It h<is also been recognized that these iodines, and other sources of iodine and other forms of iodine are bio-active in man, animals, and bacteria of some types at some levels, and in plants and their seeds. A lack of this bio-active substan~~e has been recognized as the cause of many conditions in all life forms where iodine is seen to have a bio-active role, conditions which prevent the life form from achieving maximum health, growth, and reproductive success.
It has also been recognized recently by chemists, microbiologists and other concerned scientists that the active component in all biocidal iodines is in the form of thermo-dynamically free iodine, which includes the iodine species HIO (sometimes written as HOI) and I2 in the presence of H20 (which may be microli.thic), under certain conditions as described in United ~itates Patent No. 3,028,299 issued in the name of Winicov and Schmi.d~,and extended by others.
Thermodynamically free iodine (7:2 + HIO + H20), also known as aqueous iodine, is the only form of iodine which is biocidal.
Many other;~ have sought for ways to produce thermo-dynamically free iodine unknowingly from iodine crystals or other sources of iodine, but all such systems, whether by chemical means or by mechanical means, contain certain dis-I
advantages which limit their use functionality and commercial i success; such disadvantages being due to iodine's lack of solubility, it's reactivity, or the ease with which it is contam-inated in use or by dilutants, or the production of products which limit the presence of free iodine, i.e. poly-halides and iodides.
It i;~ shown in the above-mentioned patent to Winicov, and by others, that all of the desirable effects of iodine with reference to its microbioc:idal ability are limited to the effects of thermodynamically free iodine, but that the presence of thermodynamically free iodine in all iodine solutions, whether of alcohol/water, surfactant/water or other complexing agen.t/water or of water alone, ace limited to the water phase, and are further limited to amounts less than the titratable iodine by the agent used to complex the iodine at levels above that which is natural for iodine in water.
For example, in a Lu~;ol's Solution, where KI is used to in-crease the solubility of elemental iodine above its normal of about 0.03% to a t:itrateable level of 1%, the amount of free iodine detectable is only 180 p.p.m. by Winicov and Schmidt, N-Heptane test or other test for free iodine follow-ing the formula (LI2_I = KLI37/LI 7). Similar or lower results are obtained for tincture of iodine and all formulations of iodophore, where for various reasons there is as yet no mathematical formula available. It is to be noted, however, that the germicidal capacity of these products is dependent upon the continued release of thermodynamically free iodine (I2 + HIO + H20) from the reservoir of titratable iodine, as the level of thermodynamically free iodine drops in the product, either by dilution or contamination, or biocidal activity.

Many attempts have been made to obtain a biocidally effective solution of thermodynamically free iodine from water, all of which rely upon a mechanical means of restrain-ing the elemental iodine and allowing the makeup water to have contact with the crystals of metallic elemental iodine as shown in U.S. Patent Nos. 3,408,295 and 4,384,960. Such means cannot restrict micro, and in some cases macro, particles of iodine from being entrained in the resulting thermody-namically free iodine, and none of these means can prevent the source of iodine used in the manufacture of thermody-namically free iodine from being contaminated by undesirable products, or releasing into the thermodynamically free iodine undesirable products originating at the source of iodine as primary or :secondary contaminates.
The <:hief fault of the chemical means of releasing thermodynamically free iodine such as iodophore, Lugol's Solution, or tincture of iodine i.s that a loss of solvent increases the total percentage of iodine in a volume, and decreases the availability of free iodine, while increasing ~ the toxic effect of tike remaining solution. Another fault of the chemical. means of releasing thermodynamically free iodine is that the maximum levels of free iodine are restricted to about 60% (i..e. as in Lugol's Solution) of the maximum strength of free iodine in water (maximum is about 0.03%) and usually much less (as in U.S. patent No. 3,650,965), an iodophore of 3.75% titratable iodine achieving a maximum strength only after dilution that is of less than 40 p.p.m.
Another fault c>f these chemical means of releasing thermody-namically free iodine is that in many applications where the effect of t:hermod;ynamically free iodine is desirable, (i.e. the irrigation of wounds or' incisions during surgery), the chemical means is an unwanted toxicant. This procedure was used with P.V.P.I. (p~rovidone iodine) for a time until it was realized the P.V.f. (povidone) macro molecule lodged in the lymph glands causing problems with the function of the gland. In this, and many other applications, the effects of iodine have been changed by the presence of chemical adjuvants, or the ;gdjuvants have produced undesirable side effects.
Another undesirable necessity of the use of chemical means of releasing thermodynamically free iodine is that the iodine used as source in the formulation must be as pure as is practically arnd economically obtainable to prevent inclusion of undesirable contaminants in the final product.
From the foregoing, it is evident that a method of reliably and practically producing thermodynamically free iodine (I2 + HIO + H~~O) in its purest state from any source of IZ is highly desirable and it is an object of the present invention to provide such a method and also to provide a device for carrying out the method.
SUMMARY OF THE INVENTION
According to an aspect of the present invention, there is provided a method for obtaining a desired amount of pure thermodynamically free iodine (TFI2~, comprising the steps of:
(a) providing a TFI2 solving solid barrier impervious to solvents and contaminants of TFI2;
(b) providing a source of TFIL which produces a predeterminable amount of TFIZ, the source of the TFI2 being located on one side of the solid barrier; and (c) providing <3 reservoir means on the other side of the solid barrier for receiving TFIZ which passes through the barrier to establish an equilibrium of TFI~, on both sides of the solid barrier, whereby there is a net flow of TFI2 between both sides of the solid barrier in response to a nonequilibrium condition of TFIZ on both sides of the solid barrier in order to re-establish the desired amount of TFIZ on either side of the solid barrier.
According to another aspect of the present invention the~~e is provided a device for producing a desired amount of pure thermodynamically free iodine (TFIZ), comprising:
(a) a T'rI2 solving solid barrier impervious to solvents and contaminants of TFIZ;
(b} a source of TFI2 which produces a predeterminable amount of TFI2, the source being located on one side of the solid barrier; and 20 (c} a reservoir means located on the other side of the solid barrier for collection TFI2 which passes through the solid barrier to establish an equi7.ibrium of TFIZ on both sides of the solid barrier, whereby is a net flow of TFI2 between both sides of the solid barrier in response to a nonequilibrium condition of TFI2 on both sides of the solid barrier to re-establish the desired amount of TFI2 on either side of the solid barrier.
:30 - 4a -According 1:o yet another aspect of the invention there is provided a device for producing pure thermodynamically free iodine (TFI2), comprising;
(a) a container;
(b) a cup opening from the container and defining a sealed cavity between the cup and the container;
(c) a source o:E TFI2 contained within the cavity; and (d) a TE'I2 solving solid barrier lining an outer wall of t:he cup located within the cavity, the cup 1Qi being perforated adjacent the barrier lining, and container and cup being formed of iodine impervious material.
BRIEF L)ESCRIPTION OF THE DRAWINGS
Example embodiments of the drawings are shown in the accompany drawings in which:
- 4b -Figure 1 is a schematic diagram showing a device for producing pure elemental iodine;
Figure 2 is a schematic diagram of an alternate embodiment of the device of Figure 1;
Figure 3 is another alternate embodiment of the device of Figure l; and Figure 4 is a cross-sectional view of another alternate device for producing pure elemental iodine.
DETA:fLED DESCRIPTION Of PREFERRED EMBODIMENT
Elemental 9_odine, that is the diatomic molecule I2~
is marginally solubl<5 (about 0.03%) in water, forming thermo-dynamically free iodine and in many other fluids forming two distinct types oi_' solution, which are differentiated by their colour, and as well it has been recognized that many substances normally considered solids are permeable to the iodine molecule. Many of these solids appear to act as liquids to iodine. When iodine permeates them, it exhibits a vaE>our pressure, has a solubility limit, and causes those solids of this class to change to one of the two colours observed when iodine dissolves in liquids (i.e.
in organic solvents such as carbon tetra chloride iodine produces a violet colour and in water it produces a clear amber colour) in the absence of polyhalides, complexing agents or other colourants. In the presence of polyhalides a black colour is exhibited and vapor pressure is reduced.
Considering those substances which are coloured throughout by exposure to thermodynamically free iodine as though they were liquids to iodine, has led to the unexpected discovery that such materials which are considered inert to substances, and inert and impermeable to water to such an extent that they have largely replaced glass as containers, and which have been considered as good containers of iodine as noted in U.S. Patent No. 4,384,960 are instead able to maintain stoichi_ometric balance in the equilibration of iodine in two fluids they are placed between, providing only that in both fluids iodine is soluble, and that in one fluid there is sufficient un-solved metallic crystal iodine, or other source of thermodynamically free iodine to satisfy the rnaximum demand in all fluids and the apparent 1« solid to saturation, or further. Since only the I2 molecule, not the solvent, moves freely back and forth to achieve and maintain equilibration, the inventor has adapted this discovery to a practical method for the production of thermo-dynamically free iodine with the use of these apparent solids which substances are hereinafter referred to as iodine solving solids.
Figure 1 of the drawings shows schematically an arrangement with a container 10 which is impregnable to iodine, a barrier 12 of an iodine solving solid, a source 2C~ ~ of iodine 14 in a chamber 16 containing a fluid and a second chanber 18 on the other side of barrier 12 containing water which is to be converted to thermodynamically free iodine.
Chamber 18 can lbe constructed as a vacuum chamber to produce crystals of elemental iodine.
One of the solid substances which is coloured by iodine and wlhich will maintain equilibration of iodine to saturation in two fluids between which it is placed and is a substance of this. class of solids, defined as iodine solving solids, is polyethylene, both high and low density.
30 Since it is preferable that the mass of the solid substance be low to reduce the volume of iodine needed to achieve s-~_ 1340993 saturation in the substance, which iodine is abstracted from the proce~;s, a film of 1 mm. thickness of low density polyethylene ir; preferred.
Figure 2 of the drawings shows schematically an alternate arrangement in which the iodine solving solid barrier is in t:he form of a capsule 20 which contains water and sufficient metallic crystalline elemental iodine or other source' of thermodynamically free iodine to satisfy the iodine demand to saturation i.n both the vblume of water and the volume of polyethylene. The capsule should be sealed in such fashion as to prevent water or other solvents from coming into direct physical contact with the amount of water and iodine within it, and may be sealed by heat sealing or the use of ;adhesives or closures which have in themselves or cause no additional iodine demand. This capsule may be formed as a ridged or non-ridl;ed pillow. If the capsule is placed in water 22, it will start to transfer of I2 molecules from capsule 20 (I2 has commenced transfer from the source of iodine to the water to the capsule already) to water 22 and will maintain that transfer until saturation in all three layers of material is~ achieved. This level (saturation) will be maintained, or re-attained even if water 22 is exposed to the air causing a loss of I2 to the air, or if the I2 in water 22 is reduced by biological action, or complexing, or chemical action as in titration, or by dilution from the addition of water or other solvent of iodine including an amount of any of the solids which is coloured by iodine, such as polyethylene which is an iodine solving solid.
Figure 3 shows an alternate construction in which 30 barrier 12 is spherical and flexible and carries within it a capsule 22 of frangible material holding iodine source 14. To use this embodiment barrier 12 is squeezed to break capsule 22 to bring the fluid in the barrier into contact with the iodine source 14 creating thermodynamically free iodine whereuFon the barrier is dropped into a fluid to obtain thermodynamically free iodine in the fluid.

The device shown in Figure 4 of the drawings consists of a unit 30 comprising a cup 31 which fits into a container 32 in the manner known in cold cream jars, providing an annular cavity 34 between the cup and the container which is filled with iodine crystals 35. A removable screw cap (not shown) fits on cup 30 by engaging a thread 36. Cup 11 has an annular flange 37 which seals onto rim 38 of con-tamer 32.
The outer aurface of c:up 31 below flange 37 is coated with an iodine solving solid layer 39 of material which will pass iodine. A ring of apertures 42 in cup 31 exposes layer 39 and the bottom of the cup has burther apertures 44 which exposes layer 19 spaced from bottom 40 of container 23 within a ring flange 46 which has notches 48 spaced around its perimeter.
When it is desired to disinfect a quantity of water, some o:E that water is poured into cup 31 to the level of apertures ~+2. The cap is then placed on cup 31 and the unit is shaken. The cap is then removed and the water in the cup, now tinted with iodine, is poured into the quantity of water to be disinfected.
A dispenser of a rolled starched paper strip is provided (similar to a cellulose tape dispenser) for testing the quantity of water which may be disinfected by the cupful of tinted water. A piece of paper is torn from the rolled strip and inserted into the water in cup 31, causing the iodine to turn the starch blue. By comparing the shade of blue with a color chart on the side of the dispenser, the pints (or quarts or gallons) of water is indicated which may be disinfected b y the cup of tinted water. Cup 31 and container 32 are' made of any one of a group of iodine _ g _ ~3~+b993 resisting plast:Lcs such as F.E.P. (fluoroethylpolymer).
With this device 1500 imperial gallons of water may be treated with 42 grams of iodine and the device has an indefinite shelf life.
It w ill be seen that the described invention produces thermodynamically free iodine (I2 + HIO + H~0) or elemental iodine from another diatomic iodine source, such that (1) the source material of iodine cannot become contaminated from the source of water used for manufacture of the thermodynamically free iodine;
(2) l:he source of iodine will continue to maintain stoichiometric valance with the thermodynamically free iodine and the iodine ~oolving solid or any other reservoir of iodine.
(3) t:he source material of iodine will by equilibra-tion of the thermodynamically free iodine maintain~a high level of bio-active ef:Eect in the thermodynamically free iodine even after the thermodynamically free iodine is con-taminated by other matter;

(4) the source material of iodine will prevent , or ameliorate the effects of loss of solute in thermodynamically free iodine;

(5) the method will prevent the inclusion of micro or macro particles of iodine (I2) or other undesirable products which may be present at the source of iodine from becoming entrained or dissolved in the thermodynamically free iodine; and (6) the method will balance, through stoichionetic pressure from the source of iodine,any loss of iodine in the solventto other reservoirs.

The material used as the iodine solving solid (barrier 12) must have the characteristic that it be able to solve iodine and that iodine chemical reaction be able to take place in it. Examples rnaterials which have been shown to be e:Efective in this regard are linear polyethylene, isotactic polyethylene, polyoxymethylene and polybutylene terephthalate.
An example material used as the iodine source (14) in the embodiment of Figure 3 is potassium iodide and an example of a product chemical which would convert it to thermodynamically free iodine would be chloramine. For instance in the embodiment of Figure 3 the potassium iodide would be included in source 14 <ind the chloramine would be included between capsule 22 and barrier 12. On bursting capsule 22 the potassium iodide and the chloramine would come into contact creating potassium chloride and thermody-namically free iodine (together with some free amines).
In the embodiment of Figures 1 and 2 source 14 may be techni-cal grade iodine which contains some thermodynamically free iodine.
The term fluid used in this disclosure includes a gas. Where a vacuum is present (in chamber 18 in the embodiment of Figure 1) instead of a fluid iodine gas would fill the vacuum and commence precipitation and recrystaliza-tion at the coolest point in the vacuum chamber until such time as a stoichiometric balance would be achieved on either side of the iodine solving solid.

Claims

1. A method for obtaining a desired amount of pure thermodynamically free iodine (TFI2), comprising the steps of:
(a) providing a TFI2 solving solid barrier impervious to solvents and contaminants of TFI2;
(b) providing a source of TFI2 which produces a predeterminable amount of TFI2, the source of the TFI2 being located on one side of the solid barrier; and (c) providing a reservoir means on the other side of the solid barrier for receiving TFI2 which passes through the barrier to establish an equilibrium of TFI2 on both sides of the solid barrier, whereby there is a net flow of TFI2 between both sides of the solid barrier in response to a nonequilibrium condition of TFI2 on both sides of the solid barrier in order to re-establish the desired amount of TFI2 on either side of the solid barrier.

2. A method as claimed in claim 1. in which the source of TFI2 is encapsulated by the iodine solving solid barrier.

3. A method as claimed in claim 1 in which the thermodynamically free iodine is collected in a liquid.

4. A method as claimed an claim 3 in which said liquid is water.

5. A method as claimed in claim 1 in which the thermodynamically free iodine is collected in a gas.

6. A method as claimed in claim 1 in which said reservoir is a vacuum.

7. A method as claimed in claim 1 in which the thermodynamically free iodine is collected in an iodine solving solid.

8. A method as claimed in claim 1 in which the thermodynamically free iodine is collected on the surface of a solid in which iodine is not soluble.

9. A method as claimed in claim 1 in which the thermodynamically free iodine is collected in an iodine complexing compound.

10. A method as claimed in claim 1 in which the iodine source comprises an iodine/iodine complexing compound mixture.

11. A method as claimed in claim 1 in which the iodine solving barrier is a plastic.

12. A method as claimed in claim 11 in which the plastic is selected from the class consisting of linear polyethylene, isotactic polyethylene, polyoxymethylene and polybutylene terephthalate.

13. A device for producing a desired amount of pure thermodynamically free iodine (TFI2), comprising:

(a) a TFI2 solving solid barrier impervious to solvents and contaminants of TFI2;
(b) a source of TFI2 which produces a predeterminable amount of TFI2, the source being located on one side of the solid barrier; and (c) a reservoir means located on the other side of the solid barrier for collection TFI2 which passes through the solid barrier to establish an equilibrium of TFI2 on both sides of the solid barrier, whereby is a net flow of TFI2 between moth sides of the solid barrier in response to a nonequilibrium condition of TFI2 on both sides of the solid barrier to re-establish the desired amount of TFI2 on either side of the solid barrier.

14. A device as claimed in claim 13 in which the iodine source is encapsulated within the iodine solving solid barrier, and in which the means for collecting the thermodynamically free iodine is a container.

15. A device as claimed in claim 13 in which the means to collect the thermodynamically free iodine is a liquid.

16. A device as claimed in claim 15 in which said liquid is water.

17. A device as claimed in claim 13 in which the means for collecting the thermodynamically free iodine is a gas.

18. A device as claimed in claim 13 in which the product side of the iodine solving solid barrier consists of a vacuum.

19. A device as claimed in claim 13 in which the means to collect the thermodynamically free iodine as an iodine solving solid.

20. A device as claimed in claim 13 in which the thermodynamically free iodine is collected on the surface of a solid in which iodine is not soluble.

21. A device as claimed in claim 13 in which the thermodynamically free iodine is collected in an iodine complexing compound.

22. A device as claimed in claim 13 in which the iodine source consists of an iodine/iodine complexing compound mixture.

23. A device as claimed in claim 13 in which the iodine solving solid material is a plastic.

24. A device as claimed an claim 23 in which the iodine solving solid material is selected from a class consisting of linear polyethylene, isotactic polyethylene, polyoxymethylene and polybutylene terephthalate.

25. A device for producing pure thermodynamically free iodine (TFI2), comprising:
(a) a container;

(b) a cup opening from the container and defining a sealed cavity between the cup and the container;
(c) a source of TFI2 contained within the cavity; and (d) a TFI2 solving solid barrier lining an outer wall of the cup located within the cavity, the cup being perforated adjacent the barrier lining, and container and cup being formed of iodine impervious material.

26. A device as claimed in claim 25 in which the iodine source comprises an iodine/iodine complexing compound mixture.

27. A device as claimed in claim 25 in which the iodine solving solid material is a plastic.

28. A device as claimed in claim 27 in which the iodine solving solid material is selected from a class consisting of linear polyethylene, isotactic polyethylene, polyoxymethylene and polybutylene terephthalate.