'20 NON-METALLIC SIMPLE SUBSTANCES. ?ART I. 



muriatic acid. A mixture of these two gases remains 

 inactive in the dark, but explodes in sunshine. 



By chemical means chlorine is made to combine with 

 oxygen so as to produce four substances, two of which 

 are gases of such unstable equilibrium and weak affinity 

 that the slightest cause makes them detonate violently ; 

 the other two are more stable, though they contain a 

 greater quantity of oxygen. The only combination of 

 chlorine with nitrogen is the most powerful and dan- 

 gerous explosive compound known. Chlorine combines 

 naturally with sulphur, and with the metals so as to 

 form ores. 



Common salt affords a remarkable instance of change 

 of volume by chemical combination. Twenty-four parts 

 in bulk of salt contain 20' 7 parts of sodium and 23-3 

 parts of liquid chlorine ; hence by chemical combination a 

 bulk of 44 is compressed into a bulk of 24, yet that 

 great compression is consistent with perfect transpa- 

 rency, crystallized salt being perfectly transparent to 

 light, and more so as regards radiant heat than any 

 other substance. Thus chemical affinity does what no 

 mechanical power could accomplish. 



At an ordinary temperature and barometric pressure, 

 bromine is an orange red, extremely volatile fluid, which 

 congeals and becomes brittle at a temperature a little 

 below the zero of Fahrenheit's thermometer, and if 

 combined with water at that degree of cold it crystallizes 

 in octohedral crystals which are permanent even at 50 

 Fahr. Bromine is very poisonous, corrodes the skin, 

 has a disagreeable taste, and a smell similar to that of 

 chlorine, but more pungent and hurtful. It possesses 

 a powerful bleaching property, does not conduct electri- 

 city, and like chlorine a taper will not burn in its gas, 

 though it spontaneously sets fire to phosphorus, and 

 some of the metals. Reasoning from analogy Professor 

 Schonbein believes that chlorine and bromine are not 



