120 NON-METALS AND THEIR COMBINATIONS. 



Hydrochloric acid, Acidum hydrochloricum, HCl=36.4(CAfor- 

 hydric add, Muriatic acid. Hydrogen chloride). One volume of hydro- 

 gen combines with one volume of chlorine to form two volumes of 

 hydrochloric acid : 



Another method for obtaining it is the decomposition of a chloride 

 by sulphuric acid : 



NaCl + H 2 SO 4 = HC1 + NaHSO 4 ; 

 or 



H 2 SO 4 = 2HC1 + Na 2 SO 4 . 



Experiment 14. Use apparatus as in Fig. 8, page 86. Place about 20 grammes 

 of sodium chloride into the flask (which should be provided with a funnel-tube) 

 and add about 30 c.c. of concentrated sulphuric acid; mix well, apply heat, and 

 pass the gas into water for absorption. If a pure acid be desired, the gas has 

 to be passed through water contained in a wash-bottle ; apparatus shown in 

 Fig. 11, page 102, may then be used. Use the acid made for tests mentioned 

 below. How much of the U. S. P. 31.9 per cent, hydrochloric acid can be 

 made from 117 pounds of sodium chloride ? 



Hydrochloric acid is a colorless gas, has a sharp, penetrating odor, 

 and is very irritating when inhaled. It is neither combustible nor 

 a supporter of combustion, and has great affinity for water, which 

 property is the cause of the formation of white clouds whenever the gas 

 comes in contact with the vapors of water, or with moist air ; the white 

 clouds being formed of minute particles of liquid hydrochloric acid. 



Whilst hydrochloric acid is a gas, this name is used also for its 

 solution in water, one volume of which at ordinary temperature takes 

 up over 400 volumes of the gas. 



The hydrochloric acid of the U. S. P. is an acid containing 31.9 

 per cent, of HC1. It is a colorless, fuming liquid, having the odor 

 of the gas, strong acid properties, and a specific gravity of 1.163. 

 The official diluted hydrochloric acid is made by mixing 100 parts 

 by weight of the above acid with 219 parts of water. It contains 10 

 per cent, of HC1. 



The same antidotes may be used as for nitric acid. 



Tests for hydrochloric acid and chlorides. 



(Sodium chloride, NaCl, may be used.) 



1. To hydrochloric acid, or to solution of chlorides, add silver 

 nitrate : a white, curdy precipitate is produced, which is soluble in 

 ammonia water, but insoluble in nitric acid : 



A g N0 3 + NaCl = NaN0 3 + AgCl ; 

 AgN0 3 + HC1 = HN0 3 + AgCl. 



