364 



CHLORINE. 



when allowed to escape, by condensing the moisture in the air. 

 By a pressure of 40 atmospheres at 50 it is condensed into a 

 liquid, ofsp. gr. 1.27- It is quite irrespirable but much less 

 irritating than chlorine ; it is not decomposed by heat alone, 

 nor when heated in contact with charcoal. Hydrochloric acid 

 extinguishes combustion, and is not made to unite with oxygen 

 by heat ; but when electric sparks are passed through a mixture 

 of this gas and oxygen, decomposition takes place to a small 

 extent, water being formed and chlorine liberated. It is com- 

 posed by volume, of one combining measure or 2 volumes 

 of each of its constituents, united without condensation; so 

 that its combining measure is 4 volumes, and its theoretical 

 density 1269.5. It may be formed directly by the union of its 

 elements. 



If a few drops of water or a fragment of ice be thrown up 

 into a jar of hydrochloric acid over mercury, the gas is com- 

 pletely absorbed in a few seconds ; or if a stout bottle filled 

 with this gas be closed with the thumb and opened under water, 

 an instantaneous condensation of the gas takes place, water 

 rushing into the bottle as into a vacuum. Dr. Thomson finds 

 that 1 cubic inch of water absorbs 418 cubic inches of gas, at 

 69, arid becomes 1 .34 cubic inch. He has constructed the 

 following table, from experiment, of the specific gravity of hy- 

 drochloric acid of determinate strengths.* 



HYDROCHLORIC ACID. 



To this may be added the following useful table, for which 

 we are indebted to Mr. E. Davy : 



First Principles of Chemistry. 



