Hydrogen chloride is a gas, about 1.3 times heavier than air.It is without color, but with a sharp suffocating and characteristic odor.At a temperature of minus 84C, hydrogen chloride gas passes from the liquid state, and solidifies at minus 112C.Hydrogen chloride is dissolved in water.One liter of H2O is capable of absorbing up to 500 ml of gas.The solution is called hydrochloric his or hydrochloric acid.Concentrated hydrochloric acid at 20 ° C is characterized by the greatest possible mass of basic substance, equal to 38%.The solution - a strong monobasic acid (in the air, "smokes", and in the presence of moisture forms acid mist), it also has other names: hydrochloric, and on Ukrainian nomenclature - chloride acid.The chemical formula can be represented in this form: HCl.The molar mass is 36.5 g / mol.The density of concentrated hydrochloric acid at 20 ° C is equal to 1.19 g / cc.This is a harmful substance which belongs to the second class of hazard.
In "dry" form, hydrogen chloride can not communicate even with active metals, but in the presence of moisture the reaction proceeds quite vigorously.This strong hydrochloric acid is able to react with all the metals which are to the left of the hydrogen in the electrochemical series.In addition, it interacts with basic and amphoteric oxides, bases and salts:
- Fe + 2HCl → FeCl2 + H2 ↑;
- 2HCl + CuO → CuCl2 + H2O;
- 3HCl + Fe (OH) 3 → FeCl3 + 3H2O;
- 2HCl + Na2CO3 → 2NaCl + H2O + CO2 ↑;
- HCl + AgNO3 → AgCl ↓ + HNO3.
Besides general properties, characteristic for each of a strong acid, hydrochloric acid has reducing properties in a concentrated form is reacted with various oxidants, releasing free chlorine.Salts of this acid are called chlorides.Almost all of them are readily soluble in water and completely dissociate into ions.Slightly soluble are PbCl2 lead chloride, silver chloride AgCl, mercurous chloride Hg2Cl2 (calomel) and cuprous chloride CuCl.The hydrogen chloride can react accession unsaturated hydrocarbons with double or triple bond, wherein the formation of chlorinated organic compounds.
In the laboratory hydrogen chloride is obtained when exposed to dry sodium chloride, sulfuric acid, concentrated.Reaction in different conditions can occur with the formation of sodium salts (acidic or medium):
- H2SO4 + NaCl → NaHSO4 + HCl
- H2SO4 + 2NaCl → Na2SO4 + 2HCl.
first reaction is going to end with gentle heating, and the second - at higher temperatures.Therefore, in the laboratory of hydrogen chloride best to get the first method, for which the amount of sulfuric acid is recommended to take the rate of receipt of the acid salt NaHSO4.Then, by dissolving hydrogen chloride in water is obtained hydrochloric acid.In industry, it is obtained by burning in the atmosphere of hydrogen or chlorine affecting dry sodium chloride (only for the second equation of the reaction) of concentrated sulfuric acid.Also hydrogen chloride is obtained as a byproduct in the chlorination of saturated organic compounds.In industry, hydrogen chloride obtained by one of the above methods was dissolved in special tower in which liquid is passed from top to bottom, and the gas is fed from the bottom up, i.e. countercurrently.
Hydrochloric acid is transported in special rubberized tanks or containers as well as plastic barrels with a capacity of 50 liters or glass bottles with a capacity of 20 liters.The interaction of acid with metals there is a risk of explosive hydrogen-air mixtures.Therefore, it should be completely eliminated the contact formed by the reaction of hydrogen and air, and also (via anticorrosive coatings) contacting the acid with metals.Before the withdrawal of vessels and pipelines, where it is stored or transported in the repair, it is necessary to carry out a nitrogen purge, and monitor the status of the gas phase.
Hydrogen chloride is widely used in industrial production and in the laboratory.It is used for etching metal salts and obtain as a reagent in analytical studies.Hydrochloric acid is produced by technical GOST 857-95 (text identical to the international standard ISO 905-78), reagent - in accordance with GOST 3118-77.Concentration of the technical product depends on the quality and variety and may be 31.5%, 33% or 35%, and the product appearance is yellow in color due to the impurities of iron, chlorine and other chemical substances.Reactive acid must be colorless and transparent liquid with a mass fraction of from 35 to 38%.
