170 CHEMISTEY. 



229. Properties. Iodine is a solid substance of a deep- 

 blue color, with a somewhat metallic lustre. By the ap- 

 plication of heat it may be made to rise in a beautiful vio- 

 let vapor or gas. This gives it its name, which comes from 

 a Greek word meaning violet-colored. The vapor of iodine 

 is nearly nine times as heavy as air, and is one of the heav- 

 iest of the gases. Iodine is not very soluble in water, but 

 is quite soluble in alcohol, and forms with it a tincture 

 much used in medicine. 



230. Iodine a Supporter of Combustion. Combustion in 



iodine is much the same as in chlorine. For 

 purposes of experiment in this respect you can 

 prepare the gas by placing a few grains of the 

 solid iodine in a jar, , Fig. 72, and heating the 

 jar by a sand-bath, b, and spirit-lamp, c. The 

 jar will become gradually filled with the violet- 

 colored gas, the air in the jar being pushed up 

 before it. If a lighted taper or candle be let 

 down into the jar it burns, but dimly, however. A piece 

 of phosphorus introduced into it takes fire spontaneously. 



231. Bromine. Bromine is contained in sea-water, where 

 it exists in small quantity, combined with magnesium. It 

 is the only elementary substance, save mercury, which is 

 liquid at ordinary temperatures. It is of a dark brown-red 

 color, and very heavy ; it has a powerful, irritating odor, 

 whence it receives its name, bromos being the Greek word 

 for bad odor. It is a corrosive and deadly poison. It is 

 used in medicine and in photography, chiefly as sodium bro- 

 mide. Iodine and bromine form hydrogen compounds and 

 oxygen compounds almost exactly the same as chlorine. 

 These three elements are always found associated, and seem 

 to be members of the same family. 



232. Fluorine. This element has never been prepared in 

 a free state, and is known to chemists only in combination. 



