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Description

This invention relates to methods for analyzing the physicochemical properties of soils.

Methods are known for determining the soil absorption capacity, based on the fact that all exchange cations are replaced by homogeneous cations, followed by their displacement into the solution by other homogeneous cations. The number of substituted cations can also be judged by the change in their concentration in the solution without first saturating the soil with any other exchange cation. However, the known methods are laborious and require a long time for their implementation. They are particularly inconvenient for the analysis of calcareous, saline and gypsum-bearing soils.

The aim of the invention is to reduce the time and increase the accuracy of determining the absorption capacity of the soil.

The proposed method, like the well-known method, includes saturating the absorbed complex with a solution of chloride bar, and and expelling barium ions from carbonate soils with a solution of sodium sulfate in the water-acetone mixture, and from non-carbonate soils with titrated sulfuric acid; in the presence of a nitchromaso metal indicator, the unreacted part of the sulfates is titrated with a solution of barium chloride, the difference between which determines the value of the absorption capacity; in carbonate soils, carbonates are preliminarily destroyed and soluble salts are removed with a solution of hydrochloric acid, and barium is displaced by exchange with hydrochloric acid, and the barium content in the filtrate is measured by means of sulfuric acid.

The course of the analysis. A portion of the soil 2.5 g, passed through a sieve (1 mm), is placed in a 50 ml beaker and 15-20 ml is poured with a non-buffer solution of 0.1 r. Barium chloride. After settling, the clear liquid is poured into a pre-weighted filter with a funnel. Decontamination is continued until about 350 ml of filtrate has been collected. After that, the entire soil is transferred to the filter 0.1 n. with a barium chloride buffer solution at pH 6.5 (raspberry OR borate buffer) and continue to rinse on the filter in small portions of 10-15 ml until about 150 ml of filtrate is collected.

In order to reduce the concentration of the mechanically delayed solution, the washing is continued as well with 0.01 n. nitrated: with a first solution of barium chloride with a pH of 6.5 to level out the concentration, which is achieved after collecting 120-150 ml of filtrate. Under such conditions of tillage with a solution of barium chloride, the absorbing complex is completely saturated with Ba2 +, binding and precipitation of barium carbonates and sulphate occurs and removal of easily soluble salts without residue.

After saturation and washing with a weak barium chloride solution, the contents of the filtrate with the funnel are weighed together with the mechanically retained solution. Then proceed to the displacement of the barium absorbed into the solution. If the soil is carbonate, saline or contains gypsum, the filter with wet soil is placed in a conical flask with a ground stopper (300 ml), in which 250 ml of 0.02 n is previously placed. titrated solution of Na2SO4 in an equal volume of a mixture of water and acetone. For non-carbonate and non-saline soils, the excluder is 0.02 n. aqueous solution of sulfuric acid. The contents of the flask are vigorously shaken and, after 7-10 minutes, filtered through a dense filter (funnel diameter 5 cm).

When filtering, the flasks should be closed with stoppers and the funnels with watch glasses. When about 30 ml of filtrate has been collected, a pipette of 5 ml per flask (per 50 ml) and one drop of a 0.1% aqueous solution of the nitchromaso metal indicator are taken from it. The contents of the flask are shaken and titrated from

microburettes (10 ml) 0.02 n. with a titrated solution of barium chloride before the color changes from violet to blue.

- Based on the amount of barium chloride consumed, the absorption capacity is calculated using the following formula

gV. (v.-...) N ,, ,, 1Ж

LVJ P

where g is the absorption capacity per 100 g dry

soil, mEq;

V - 0.02 N barium chloride consumed for titration, ml; Capacity for titration, test solution, ml; V2 - mechanically retained BaCla solution, welded to its weight, ml; & h-250 ml of 0.02 N Na2SO4 or H2SO4 + mechanically retained solution; normality of Na2SO4 solution or

H2SO4;

L 2-normality of a weak buffer VAC used at the end of saturation;

p is a sample of dry soil, in. The table shows the results of determining the absorption capacity of various carbonates and saline soils in two ways.