HYDROCHLORIC ACID. 



367 



sion, we shall find that it also destroys offensive and putrid matter, and 

 purifies the atmosphere very much. Most colouring matters include 

 hydrogen, and therefore they are destroyed by chlorine, which is a great 

 41 bleacher" as well as a purifier. If we dip any vegetable dyes into a jar of 

 chlorine, they will become white if the dyed substances are damp. 



Hydrochloric acid is known as muriatic acid and spirits of salt. It is 

 obtained when salt is treated with sulphuric acid and the gas comes off into 

 water. Equal parts of the acid and the salt are put into a flask as in the 

 cut (fig. 362), and diluted with water. The mixture is then heated. The 

 gas is condensed in the bottles half-full of water. The result gives sulphate 

 of soda and hydrochloric acid. This acid is procured in soda manufactories, 

 and with nitric acid is called "aqua regia," a solvent for gold. When 

 chlorine and hydrogen are mixed in equal proportions they explode in sun- 

 light. In the dark or by candle-light they are harmless. Dry chlorine 

 gas can be obtained by interposing a glass filled with some chloride of 



Fig. 362. Production cf hydrochloric acid. 



calcium. The gas being heavier than air (about 2| times), displaces it in 

 the flask, and when it is filled another can be placed in position. This 

 mode causes a little waste of gas, which should not be breathed. 



Chlorine possesses a great affinity for certain bodies. If the gas be 

 thrown upon phosphorus, the latter will burn brilliantly. Arsenic, tin, and 

 antimony when powdered and poured from a shoot into a vase of chlorine 

 will burst into brilliant sparks, and other metals will glow when introduced 

 to this gas. Chlorine forms many unstable combinations with oxygen. Its 

 combination with hydrogen has already been referred to. 



BROMINE is a rare element. (Symbol Br. Atomic weight 80.) 

 It is deep brownish red, very volatile, and of a peculiar odour. 

 Bromine unites with the elementary bodies, and forms some oxygen com- 

 pounds. It resembles chlorine in its properties, and is used in medicine 

 and in photography. It is found in saline springs and in salt water, com- 

 bined with soda and magnesium. The presence of bromine may easily be 



