RU2552914C1 - Thermionic method for quantitative determination of ammonia in concrete - Google Patents

Abstract

FIELD: construction.

SUBSTANCE: method comprises the preliminary moistening of concrete sample and its subsequent heating, in which the thermal emission is carried out in case of discharging of 700 mm Hg and temperature of 80-300°C.

EFFECT: increase of the efficiency and acceleration of analysis.

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Description

The invention relates to the field of construction technology and can be used to quantify ammonia in concrete structures used in residential construction.

When using concrete floors, additives such as acetic acid diamide, potash (waste from ammonia production), cement with fly ash, etc. are used. Subsequently, ammonia is released in residential premises due to the hydrolysis of ammonium-containing compounds, which creates uncomfortable conditions for housing. To choose a method of reducing ammonia in rooms, it is necessary to take into account the ammonia content in concrete.

A known method for the determination of ammonia from hermetically sealed thermostatic chambers with samples placed in them at a temperature of 23 ± 2 ° C and saturation, expressed as the ratio of the surface area of the sample to the volume of the chamber

In this case, chemical studies of the air of the chambers are carried out using a Crystal 5000-2 gas chromatograph (see Sanitary and Hygienic Assessment of Polymer and Polymer-Containing Building Materials and Structures Designed for Use in the Construction of Residential, Public and Industrial Buildings. Methodological Instructions. MU 2.1 .2.1829-04, approved by the Chief State Sanitary Doctor of the Russian Federation on 06.01.2004).

The disadvantage of this method is that the analysis is carried out for 5 days. In addition, at a temperature of 23 ± 2 ° C, hydrolysis is incomplete and thermal emission of ammonia is ineffective. The ammonia concentration determined in this way in mg / m of air does not allow us to estimate the mass ammonia content per ton of floor, which does not allow us to choose the optimal technology for reducing ammonia in the room volume.

The known Kjeldahl method, which consists in heating a nitrogen-containing substance to a boil with a sufficient amount of concentrated sulfuric acid (G. Meir / Analysis and determination of the structure of organic substances: trans. From it. / Ed. By Prof. V. Rodionov and Prof. A. Kipriyanov. - 5th ed. - Kharkov-Kiev: State Scientific-Technical Publishing House of Ukraine, 1936. - P. 129-130).

The disadvantage of this method is the duration of the boiling process and subsequent distillation. In this case, concentrated sulfuric acid at high temperature partially decomposes to SO ₃ , which leads to inaccurate determination of ammonia.

The technical problem solved by the claimed invention is to reduce the time for quantitative determination of the content of ammonia in concrete due to the rapid and complete extraction of ammonia from concrete.

The problem is solved in that the thermionic emission method for quantitative determination of ammonia in concrete consists in pre-wetting a concrete sample and its subsequent heating, in which thermionic emission is carried out with a discharge of 700 mm RT. Art. and a temperature of 80-300 ° C.

The essence of the proposed thermal emission method for the quantitative determination of ammonia in concrete is illustrated by the drawing, which schematically shows the installation of thermal emission analysis.

Installation of thermionic analysis contains a chamber 1 made of fluoroplastic and made in the form of a cylinder with two screw caps. One of the lids of chamber 1 is equipped with two nozzles, one of which is connected to Richter 2 absorbers made of glass. Richter 2 absorbers are filled with a solution of sulfuric acid with a concentration of 0.05 n and a volume of 5 cm ³ . Camera 1 is placed in an electric furnace 3 with a temperature controller 4.

The inventive method is as follows.

For a faster and more complete release of ammonia, the concrete sample is pre-moistened. A moistened concrete sample is placed in chamber 1 of the above-described thermionic analysis unit. To extract ammonia from chamber 1, a vacuum pump 3 is connected, which creates a vacuum of 700 mm RT. Art. to intensify the process of emission of ammonia from concrete. At a temperature of 150 ° C, heating is enough for 40 minutes, at 200 ° C - 20 minutes. Under these conditions, there is a rapid hydrolysis of ammonium-containing components of concrete. After thermal emission, the solution from the Richter 2 absorbers is transferred to a conical flask and titrated with a NaOH solution (sodium hydroxide) of 0.05 N concentration. The amount of ammonia C in the test sample of concrete is calculated by the following formula

C is the mass of ammonia in the test sample, μg / kg;

m is the mass of the sample, g;

1.225 - the amount of sulfuric acid in 5 ml of an absorption solution;

V is the volume of the NaOH solution, which went to the titration of the solution from Richter absorbers, ml;

n ₁ is the number of Richter absorbers;

n ₂ - correction factor determined by the formula

V ₁ - volume of NaOH solution (≈0,005 n) needed to titrate 5 ml (0.005 m) of sulfuric acid solution (single sample) ml.

Thus, the claimed invention allows to reduce the time of quantitative determination of the content of ammonia in concrete due to the rapid and complete extraction of ammonia from concrete.

Claims (1)

Thermionic emission method for the quantitative determination of ammonia in concrete, which consists in pre-wetting a concrete sample and its subsequent heating, in which thermal emission is carried out with a discharge of 700 mm RT. Art. and a temperature of 80-300 ° C.

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