THU ASH OF PLANTS. 133 



ill the free state as a greenish-yellow, suffocating gas, 

 which has a peculiar odoif, and the property of bleaching 

 vegetable colors. It is endowed with the most vigorous 

 affinities for many other elements, and hence is never met 

 with, naturally, in the free state. 



Exp. 55.— Chlorine may be prepared by heating a mixture of hydro* 

 chloric acid and black oxide of manganese or red-lead. The gas being 

 nearly five times as heavy as common air, may be collected in glass 

 bottles by passing the tube which delivers it to the bottom of the re- 

 ceiving vessel. Care must be taken not to inhale it, as it energetically 

 attacks the interior of the breathing passages, producing the disagree- 

 able symptoms of a cold. 



Chlorine dissolves in water, forming a yellow solution. 



In some form of combination chlorine is distributed 

 over the whole earth, and is never absent from the plant. 



The compounds of chlorine are termed chlorides, and 

 may be prepared, in most cases, by simply putting their 

 elements in contact, at ordinary or slightly elevated tem- 

 peratures. 



Htdkochlobic Acid, Sym. HCl, Tno. wt. 36.6.— WTien Chlorine and 

 Hydrogen gases are mingled together, they slowly combine if exposed 

 to diffused light ; but if placed in the sunshine, they unite ekplosively, 

 and hydrogen chloride or hydrochloric acid is formed. This compo\ind 

 is a gas that dissolves with great avidity in water, forming a liquid 

 which has a sharp, sour taste, and possesses all the characters of an 

 acid. 



The muriatic add of the apothecary Is water holding in solution 

 several hundred times its bulk of hydrochloric acid gas, and is pre- 

 pared from common salt, whence its ancient name, spirits of salt. 



Hydrochloric acid is the usual source of chlorine gas. The latter Is 

 evolved from a heated mixture of this acid with black oxide of manga- 

 nese. In this reaction hydrogen of the hydrochloric acid unites 

 with oxygen of the oxide of manganese, producing water, while 

 chloride of manganese and free chlorine are separated. 

 4 HCl -I- MnOa = MnClj + 2 H^ -|- 2 CI. 



When chlorine, dissolved in water, is exposed to the sunlight, there 

 ensues a change the reverse of that just noticed. Water is decom- 

 posed, its oxygen is set free, and hydrochloric acid is formed. 

 HjO -I- 2 Cl= 2 HCl -f- O. 



The two reactions just noticed are instructive examples of the differ- 

 ent play of affinities between several elements under unlike circum- 

 stances. 



This acid is a ready means of converting various metals or metallic 

 oxides into chlorides, and its solution in water is »• valuable solvent 

 and reagent for the purpose of the chemist. 



