SU322315A1 - METHOD FOR OBTAINING GREEN CHROMIUM OXIDE - •; - 'SIGN 5 •' - '' • '/: I; ^ - Г;, ^ - '^' ^ ПЛ - Google Patents

Description

A known method for producing green oxide with chromium nitrous oxide of chromium hydroxide compounds consists in suspending chromium hydroxide compounds in two stages from a solution of chromate and / or sodium bichromate in a lack of sulfur and sodium thiosulfate in the first stage and sulfuric acid in the second stage. The precipitate obtained after sprinkling is pulverized at 1300-1400 ° C. The resulting product contains a reduced amount of sulfur and non-ferrous metals, crystalline crystalline and is not suitable as a nigment.

In order to obtain a monodisperse pigment with high small-size properties, the sodium monochromate solution is mixed with sulfur and subjected to reduction, and the sodium monochromate solution is added to oxidize the nolysulfide. To the resulting suspension of chromium hydroxide in a solution of sodium thiosulfate, a solution of sodium monoiobromate is added during the casting and then concentrated sulfuric acid. After qlutration, the hydrated chromium chromate precipitate is washed with water, repulsed in sodium monochromate solution and separated from the mother liquor. The precipitate is calcined at a temperature not higher than 1000 ° C. The obtained chromium oxide is washed with water from soluble impurities and dried. The presence of Moiioxpomat sodium in the hydrated chromium chromate precipitate by thermal treatment to a content of 8–10% ensures monodisner production. Ryko-green pigment with good intensity. / A similar result on the quality of the final product is obtained in the case of using hydrated chromichromat prepared by other methods.

Example. 260 ml of a solution with a content of 260 g / l of Na2Cr04 and 15 g / l of NaOH are mixed with 22.3 g of flaked sulfur. The mixture was kept in an autoclave at 150 ° C for 1 hour (1 reduction step). 25 ml of sodium monochromate stock solution is added to the reaction products to oxidize the polysulfides, and the mixture is boiled for 30 minutes. To carry out stage II reduction to the suspension of chromium hydroxide in solution obtained

iatri thiosulfate at boiling slowly in

760 ml is added over 30 minutes

bichromate solution with concentration

225 g / l NaaCrsO / to RP 6.45.

Then 20 ml of concentrated sulfuric

Acids boil to pH 5.2. After boiling for 1 hour, the filter is zero, and the precipitate of hydrated chromium chromate is washed with water. The composition of the sediment contains,%: HvO 52, CsoOz 29, CrOz 4, complex insoluble

This precipitate is repulped in 620 ml of the initial monochromatic solution for 0.5 hour at 85 ° C to pH 7.8. The precipitate is then separated from the mother liquor and subjected to heat treatment at 900 ° C for 1 hour. After calcination, it is leached, washed of soluble impurities and dried. The product has a bright light green color and good intensity. Its hiding power is 8.2 g / W 2.

Subject invention

A method of producing green chromium oxide by calcining chromium hydroxide compounds, characterized in that, in order to obtain a monodisner pigment with high small properties, hydrated chromichromates are taken as hydroxide compounds and treated with sodium monochromate solution to contain 8-10% Na2CrO4 in the product.