SU42981A1 - Method for determination of zinc by the gravimetric method in iron ores - Google Patents

Description

The subject of the present invention is a method for determining the content of a cycle in iron ores.

This method is as follows. A weighed ore s-10 g is treated first with hydrochloric acid beats. weight 1.19, then nitric acid beats. weight 1.40. After being freed of oxides of nitrogen and chlorine, the insoluble precipitate is filtered off and discarded.

From 0.7 to 1.5 g of citric acid is added to the filtrate for each gram of batch (depending on the amount of iron) and, after gentle heating, neutralized with ammonia to a slight odor (or neutral), then acidified with citric acid until the odor disappears and give an excess of citric acid from 1 to 1.5 g, after which the solution is heated to 70-80 °, 30-50 cm of 80% acetic acid are added and diluted with hot water to 300 cm. At an initial temperature of 60-70 ° Zinc and copper are precipitated with hydrogen sulfide until the solution darkens (usually does not change e 30 min.) If no browning occurs, attenuates the acidity of 2.5% aqueous solution of ammonia, hydrogen sulfide without interrupting the current, so as to gradually darkening occurred within 7 to 10 minutes. At the moment of darkening immediately stop the current of hydrogen sulfide, then tightly close the flask

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and left until the next day when the contents of the flask are filtered through a medium density filter. Wash the precipitate with a 0.5-l, OVo-HbiM solution of ammonium chloride saturated with hydrogen sulfide in the cold.

A filter with a precipitate containing zinc sulfide, copper sulfide and some ferrous sulfide (or only precipitate) is discharged into a flask, washed with 25 cm of cold water and 25 cm of cold 20% sulfuric acid, heated to 60 ° if you need to determine copper and until boiling, if copper is not to be determined, it is filtered and washed by decantation, first with 2% hot sulfuric acid and then with water. The filtrate contains zinc sulphate and ferrous sulphate. The precipitate contains copper sulfide and sulfur.

The filtrate is evaporated to a volume of 15-20 cm, after cooling, 1-2 drops of phenolphthalein are added and neutralized with 20% sodium hydroxide to a pink color. Then, an excess of 15 cm (3 g) of caustic soda is given, after which it is oxidized with 3 cm 3 / h of hydrogen peroxide, boiled, diluted with hot water to 90 ° C, and allowed to stand in a warm place of iron hydroxide, which filtered and washed with 0.5 / about-caustic soda.

Ferric hydroxide is dissolved in 20 / o-hot sulfuric acid and 3 g of excess caustic soda are precipitated again.

The total volume of alkaline filtrate is about 230 - 250 cm. The total excess of alkali is about 6-7 g.

The zinc in the solution is reduced by cold electrolysis to a platinum mesh cathode at 3.8-4 volts, with a current of from 1.5 to 3 amperes when the electrolyte is strongly stirred for 15-30 minutes (depending on the amount of zinc).

The precipitate obtained earlier, after dissolving zinc with sulfuric acid, containing copper sulfide and sulfur, is treated together with a filter with strong nitric acid (40-45 / o) under weak heating, then diluted with boiling water, filtered and washed. The filtrate is boiled, cooled, and copper is reduced by electrolysis to a platinum-mesh grid at 2.5–3.0 volts, amperage 1, 5 amperes for 20 minutes with strong stirring of the electrolyte.

The subject matter of the invention.

The method of determining zinc by the gravimetric method in iron ores containing zinc, characterized by the following sequence of methods: the sample is first dissolved in hydrochloric and then in nitric acid, citric acid is added to the solution and heated, neutralized with ammonia until the smell of the latter or neutral. reactions are acidified with citric acid, the solution is heated to 70-80 °, acetic acid is added, diluted with water and hydrogen sulfide is introduced, after which the precipitate containing sulphides of zinc, copper and partly iron is treated with sulfuric acid and a solution of zinc salts and iron is neutralized with alkali to pink color of phenolphthalein, is oxidized with hydrogen peroxide, filtered from the precipitated iron hydroxide, zinc and the filtrate is recovered by electrolysis.