106 NON-METALS AND THEIR COMBINATIONS. 



24; it is but sparingly soluble in water, more freely in 

 alcohol, abundantly in ether and bisulphide of carbon ; it is a 

 strong disinfectant, and its aqueous solution is also a bleaching 

 agent. 



Hydrobromic acid, Acidum hydrobromicum, HBr = 81, may be 



obtained by the formation of bromide of phosphorus, PBr 5 (the 

 two elements combine directly), and its decomposition by water: 



PBr- + 4H 2 = 5HBr + H 3 PO,. 



Hydrobromic acid is, like hydrochloric acid, a colorless gas, of 

 strong acid properties, easily soluble in water. A 10 per cent, 

 solution is the officinal acid. 



Hypobromic acid, HBrO, Bromic acid, HBr0 3 , and their salts, the 

 hypobromites and bromates, are analogous to the corresponding 

 chlorine compounds. 



Tests for bromides. 



1. Silver nitrate produces in solutions of bromides a slightly 

 yellowish-white precipitate of silver bromide, insoluble in nitric 

 acid, sparingly soluble in ammonium hydrate. 



2. Addition of chlorine water liberates bromine, which may 

 be dissolved by shaking with chloroform or ether. 



3. Mucilage of starch added to the liberated bromine is 

 colored yellow. 



4. Strong sulphuric acid added to a dry bromide liberates 

 yellowish-red vapors of bromine. 



Iodine, lodum, I = 127. Iodine is found in nature in combina- 

 tion with sodium and potassium, in some spring waters and in 

 sea-water, from which latter it is taken up by sea-plants and 

 many aquatic animals. Iodine is chiefly derived from the 

 vitrified ashes of sea-weeds, known as kelp. By washing this 

 kelp with water, the soluble constituents are dissolved the 

 larger quantities of sodium chloride, sodium and potassium 

 carbonate are removed by evaporation and crystallization, and 

 from the remaining mother-liquor iodine is obtained by treating 

 the liquor with manganese dioxide and hydrochloric (or 



