SU880974A1 - Method of decomposing phosphate rocks - Google Patents

Description

I

The invention relates to analytical chemistry, namely, methods for the decomposition of phosphate rocks, and can be used to determine the content of phosphorus, calcium, magnesium, iron, aluminum and manganese in a wide range of Concentrations in phosphate rocks.

There is a known method for the decomposition of phosphate rocks followed by the determination of only fishes and aluminum by treating rocks with mineral acids {nitric and hydrofluoric) with evaporation of the sample to dryness. The precipitate is treated with hydrofluoric and perchloric acid and evaporated to dryness on a stick. After cooling, the sample is moistened with water, treated with perchloric acid and again evaporated almost to dryness. Dilute hydrochloric acid is added to the cooled residue and heated in a water bath. If sediment is present, it is filtered off, calcined, and silica is removed.

by adding a small amount of sulfuric or hydrofluoric acid. After evaporation to dryness, the residue is calcined for one minute at 60080 (g), fused with a small amount of soda, and the cooled alloy is dissolved in the original acid solution | 1.

However, the known method is lengthy, and the presence of alkali metal salts in the solution after decomposition creates an additional salt background and interferes with the photocolorimetric determination of the components.

The closest technical

15 of the essence and the achieved result of the invention is a method of decomposing phosphate rocks by treating the starting material with mineral acids (concentrated

20 hydrochloric and nitrogenous when heated, after which they are boiled for 30 minutes then evaporated in a water bath to moist salts. 10 ml of concentrated hydrochloric acid is added to the sample, stirred, 2 ml of polyvinyl alcohol is added and stirred periodically for 10 minutes. Then dilute the solution with hot water to 60-80 ml and stir, after settling, filter out the insoluble residue through a benzene filter with a small amount of mass, thoroughly washing the precipitate with heated hydrochloric acid (1: 1) and then 2-3 times with water. The filtrate and washings are collected in a volumetric flask. 250 ml. The filter with an insoluble residue is placed in a platinum crucible, carefully salted and calcined to constant mass at 1000 Ci. Then cooled in a desiccator and weighed. The residue in the crucible is wetted with a few drops of water, 5-7 ml of hydrofluoric acid and 2-3 drops of concentrated sulfuric acid are added. The residue after the. Treatment with hydrofluoric and sulfuric acids is fused with 0.20, 3 g of the mixture for fusion (: Na2COi I :). The resulting alloy is leached with water and hydrochloric acid, heated until complete dissolution of j, and the solution is added to the main filtrate. The volume of the filtrate is made up to the mark with water (basic solution}. CaO, MgO,, L 3 are determined from the basic solution.

However, the known method takes a long time to dissolve one sample of phosphate 1 hour. In addition, the presence of polyvinyl alcohol in the solution, which interferes with the determination of phosphorus, is in the solution. fluorine ions interfering with the determination of aluminum, and chlorine ions interfering with the determination of manganese, requires the introduction of additional operations to remove interfering ions,. .

The aim of the invention is to accelerate the process and improve the accuracy of the analysis.

This goal is achieved by the fact that according to the method of decomposition of phosphate rocks by treating the starting material with mineral acids when heated, mainly for the subsequent analytical determination of individual components, the EXAMPLE sample is calcined at 750,850 ° C and subsequently processed with a mixture of chloric and hydrofluoric acids, and then with nitric acid.

The choice of conditions for the process of calcination due to the fact that

temperature does not occur less. Decarbonization of the rock and the complete burning of organic matter. It is not feasible to maintain a temperature of more than 850 ° C, since a sample may melt. The decomposition of the sample of the raw material of hydrofluoric and perchloric acids allows, at the very beginning of the process, to partially remove silicon and fluorine in the form of Sil, and, therefore,. rid of the fluorine components that interfere with the subsequent determination After treatment of phosphate raw materials with hydrofluoric and perchloric acids, the secondary decomposition of the sample is carried out. For this it is possible to use only nitric acid, since the use of other acids does not lead to the desired result. For example, hydrochloric acid does not destroy the organic impurities present in the sample. In addition, in combination with perchloric acid, it does not contribute to the complete removal of fluoride. With the subsequent two-time evaporation of the solution, to vapor of perchloric acid. Sulfuric acid, due to the presence of calcium and aluminum ions in the sample, forms insoluble salts, the subsequent dissolution of which requires additional operations. Only the introduction of nitric acid into the process accelerates the wet decomposition of the part of organic substances remaining during calcination and increases the accuracy of the determination of the components in the analyzed sample, since perchloric acid in the presence of nitric acid is a strong oxidizing agent.

Pr and m er. 0.5 g of the phosphate rock under study is crushed, kept in a muffle furnace for 10 minutes, then 5 ml of water are poured, mixed, the acid mixture consisting of 15 ml of hydrofluoric acid and 20 ml of perchloric acid is poured, and slightly evaporated to half of the original volume. heated hotplate. After that, 5 ml of nitric acid is poured into sample 5 and evaporated until copious evaporation, the dichloric acid is obtained, the edges of the cup are rinsed with water and again evaporated to

perchloric acid vapor. Water is then poured into the sample, the polynuenum solution is transferred to a volumetric flask, and the content of phosphorus, calcium, magnesium, iron, aluminum, and manganese is determined in it by known methods. Calcium and magnesium are determined by the complex method, and phosphorus, iron, aluminium and manganese are photocolorimetric.

Claims (1)

1. Groves A. Analysis of silicates. I., Foreign literature, 1953, with. 196. 2, Moizhes I. B. Handling according to analysis in the production of phosphorus, phosphoric acid and fertilizers. L., 1973, p. .