210 METALLOIDS. 



They are all gaseous, and are sometimes called hy- 

 dracids, from the hydrogen which enters into their com- 

 position. Their salts are described in Chap. III. 



HYDROCHLORIC ACID. 



518. DESCRIPTION. Hydrochloric acid 

 * s a c l r l ess g as j fuming, by contact with 

 add? What the air. It sometimes issues from volca- 



is said of its , . ,, . . ,, . , 



occurrence? noes, but is, tor the most part, an artificial 

 product. Its solution in water is known 

 as muriatic acid. 



519. PREPARATION. Gaseous hydro- 

 prepa'ratlon. chloric acid, may be produced, like water, 

 by the direct combination of its elements. 

 For this purpose, equal volumes of the two gases are 

 mixed by candle-light, or in carefully covered bottles, 

 and then exposed to the direct rays of the sun. The 

 action of the light is so intense, that on throwing a 

 bottle, thus filled, from shadow into sunlight, it imme- 

 diately explodes. The explosion is a consequence of 

 the energetic union of the two gases, under the influ- 

 ence of the chemical rays of the sun. The acid pro- 

 duced is at once dissipated in the air. Great caution 

 should be used in this experiment, for even the diffused 

 light of day has been known, in some instances, to 

 occasion explosion. 



520. ANOTHER METHOD. Hydrochloric 



Describe an- 



other mode of acid may also be made from common salt, 

 preparing it ? which f um i s h es the chlorine, and ordinary 

 hydrated sulphuric acid , which furnishes the hydrogen. 



