SU702300A1 - Method of detecting gypsum in soil - Google Patents

Description

The invention relates to agriculture and can be used in determining the content of gypsum in soils and gypsum crystals in various soil-forming clay rocks in the presence of highly soluble sulfates, for example sodium sulphate.

A known method for determining gypsum in soil involves treating it with water and then washing the sediment with water on the filter until the reaction disappears at 80. The content, total alkalinity are determined in the filtrate and the results of the gypsum are calculated as llr

However, this method is not accurate and fast (lasts several days).

A known method for the determination of gypsum carbonate and non-carbonate saline soils, including the processing of a sample of soil 0.2 n. hydrochloric acid, which converts gypsum into solution, soluble sulphates and destroys all forms of calcium and magnesium carbonates. In the filtrate, the total amount of sulphates is determined by weight. At the same time, a water extract (soil: water 1: 5 g) is prepared from a separate sample to determine the readily soluble sulfates. The difference in readings calculates the sulfate content in the form of gypsum 2. However, this does not take into account the solubility of gypsum in water, which reaches about 2-2.5 g / l. Therefore, the percentage of gypsum in the soils, with the simultaneous presence of soluble sulphates in it, is always underestimated. In addition, this method is very long and cumbersome.

A method for determining gypsum in the soil, including parallel tillage with water-acetone JBOpoM to determine soluble sulphates, and a chemical reagent for determining the total sulphate content, subsequent titration of the soil extract with barium chloride in the presence of a nitromaso indicator and calculating the sulphate content and calculating the sulphate content, and calculating the sulphate content, and calculating the sulphate content. the difference in readings in both extracts (31

As a chemical reagent in this method using 0.2 n. hydrochloric acid. However, when tillage 0.2 n. Hydrochloric acid, especially boiling, does not only completely solid carbonates and alkaline earth cations dissolve, but the alumina silicate of the soil (clay) is destroyed. A lot of impurities in the form of decomposition products, especially calcium chloride, accumulate in the qr filtrate of the suracid extract. The presence of these impurities interferes with the precise determination of sulfates. It is not always possible to purify the hydrochloric filtrate from calcium salts (ion-exchange-cationic HALS through the sorbent at g; r-large excess, and adding an aliquot to the fluoride solution of the total ammonium does not completely eliminate the negative effect of impurities on accurate determination. : The aim of the invention is to increase the accuracy of the method and the rate of onpef of the division of gypsum production. The goal is achieved as an chemical agent of a 20-40% aqueous solution of ammonium nitrate, mainly 20% .

Made CaCOe (% of sample)

Replacing the acid with salt makes it possible not to destroy the soil and its carbonates and, therefore, to avoid the appearance in the filtrate of numerous impurities that interfere with the determination of sul-. veils. In a medium of 20-40% aqueous solution of ammonium nitrate, soil gypsum is completely dissolved, the transition into the form of highly soluble ammonium sulfate. Ryo & ktsi proceeds both during settling-suspension in air, and during its short-term boiling. At the same time, the resulting calcium nitrate suppresses the solubility of CaCO in an aqueous medium. Therefore, when filtering the water-salt extraction, CaClO remains on the filter and does not go into solution. The presence of CASOD (1-50%) in the sample being analyzed cannot have any noticeable effect on the accuracy of gypsum determination by the proposed method (see Table 1). The solubility of gypsum depends on the concentration of NH4N03 in the aqueous solution (see Table 2X T a and c a 11. -,

4) in this soil sample, 0.194 () was found in the water-acetone extract.

The initial content of CaSO.- 2Н O in the soil sample is 15.625 (g "%).

As the concentration increases, the solubility of gypsum increases, reaching the maximum solubility state in a 20% aqueous solution of this salt. Above this concentration, the solubility does not change when the ratio of gypsum to water-salt (NH4NOg) solution is 1: 100. At the same time, in a 20% water-saline solution () gypsum, at H. Beat HaiBecKe 6, it dissolves completely within one hour.

When analyzing raw natural gypsum, gypsum concentrations, crystals and gypsum-bearing soil horizons, we should not take a sample of more than 1 g per 100 ml of water-salt () solution. If the soil contains a small amount of gypsum (1-5%), then the weight should be increased to 20-30 g, keeping the solution volume unchanged.

When a 20% saline solution is used, the gypsum sulphates and the readily soluble sulphates of the soil are extracted simultaneously. A water-acetone extract is used to determine the latter. In this case, the difference in the readings of sulfates in both extracts gives the exact amount of sulfates bound in the form of soil gypsum. For this purpose, two extracts from one sample are simultaneously prepared: salt () and water-acetone.

An average sample of the soil (or other gypsum-containing substance), passed through a sieve with a diameter of 0.25 mm, is ground in a mortar to the state of powder. The sample is placed in an Erlenmeyer flask with a volume of 150 ml. There is added 100 ml of pre-prepared 20% aqueous solution. Shake the contents of the flask on the rotator for one hour, then filter (the first portion of the filtrate is discarded). Take 5-10 ml from the filtrate (depending on the expected sulfate content), put it into a 250 ml volumetric flask and bring to tags. The diluted filtrate is passed through an H-cation exchanger until 40-50 ml of liquid have been collected (the first batch is filled with about 15 ml). From this cate-free filtrate, 5-10 ml of beet is placed in a flask with a volume of 100 ml, the same amount of acetone (or 96% ethyl alcohol) is added, 1-2 drops of a 0.1% solution of metal6-indium nitkhromaso and titrate 0.02 n. Yours until the indicator color changes from violet to blue. By. the amount of titrated barium chloride solution consumed is calculated by counting the total (total) sulfate content (in%) using the following formula

 A.K. 0.96066 S04. at . ten

0

where is the amount of 0.02 n. BaCt,

(in ml), more titration

K - amendment to the title of rast5 thief 0.02 n. 0,96066 a number indicating the number of SO (in mg),

equivalent to 1 ml

0.02 n. WAOKg;

0 V - weighed dry soil

(c) corresponding to a filter removed for analysis;

10 - number for recounting ko5

... quantity. SO in grams. And percent. For determination of readily soluble. 100 ml of an aqueous solution of acetone (volume 25:75 water) are poured into the sample of soil in the water-acetone extract. The suspension is agitated, filtered, and the content of sulphates is determined by the volumetric-nitrometric method in the purified filtrate.

five

From the obtained total amount of SO, the percentage of sulfates converted into the water-acetone extract is subtracted, and the resulting figure is multiplied by a factor of 1.792 to be converted to

0 percentage of gypsum (.) Soil.

If there is no gypsum in the soil, then. the content of sulfates in both extracts should be approximately equal. It follows that with the proposed method it is possible to determine a very small amount of gypsum, comparable to the level of water-soluble gypsum, which is less than half a percent of the weight of the Soil. This indicates high accuracy. the proposed method.

In tab. 3 shows examples of the determination of gypsum in various samples.

 if c 3

View- soil Serozem-arc ch. 40-45 saline Hunger Steppe Ch. 120-130 Mineral saline Ch. 10-20 Golodna Steppe Ch. 35-45, Gypsum horizon of ordinary chernozem Serozemna - gray-auger Karshinskaya steppe Uzb. SSR Gypsum crystalline39, 760 cue along the roots. Thin-plate gypsum 51,235 (Raw threshing gypsum from a concrete concrete 40.737 3 per unit - Table 4 compares the proposed and known methods.

Solonchak chloride-sulphate, containing gypsum. And 10.2% WITH carbonates

Soils not containing

gypsum + 15% CaSO4

+ 10% CaCO + 2% Na, SO4.

0.5 g CaS04-2H2 0 p.a.

0.5 g CaSO4-2H20 p.a.

+ 20%

Cover loam,

plaster free

, + 0.5 g CaSO4 2H, 2.O +

.. + 20% CaCO7, + 2%

  Of. This data subtracted the readings of soluble sulphates (where they were present), which had passed into the diano-acetone extract, which was common to both methods.

21.62 +3.15

+ 3.25 -1.10

+ 4.42

99.82

+ 5.82 30 39.540 70.837 26 51.009 91.392 05 40.432 72.454. Table data. 4 speak about the effect. the proposed method. T a b l and c a 4

Claims (3)

1. Methods of agrochemical soil analysis of Central Asia. Izd.4-e, the Allies, Tashkent, 1973, p. 128-131. 2. Arochemical methods of soil investigation. Ed. 5th, M.-, 1975, from 22-23. 3. Aydin and R.Kh. and others. Express method for the determination of gypsum in pochs (Instructions), M., 1968, ed. Soil Institute. Dokuchaeva. .