392 IODINE. 



discovered by Magnus and Ammermuller, is formed by trans- 

 mitting a current of chlorine through a solution of iodate of 

 soda, to which, at least, three times as much caustic soda has 

 been added as there is of soda in the iodate. Two salts are 

 formed, the chloride of sodium and a hyperiodate of soda with 

 excess of soda, which is sparingly soluble, and precipitated by 

 nitrate of silver, which throws down a sub-hyperiodate of silver. 

 This salt may be washed, and afterwards dissolved in nitric acid, 

 and the solution evaporated yields orange-yellow crystals of 

 neutral hyperiodate of silver. It is remarkable that when these 

 crystals are thrown into water they are decomposed, the whole 

 oxide of silver precipitating with half the hyperiodic acid, as the 

 former insoluble sub-hyperiodate, while half the acid is dissolved 

 by the water without a trace of silver, and obtained in a state 

 of purity. This solution when evaporated affords hyperiodic 

 acid in crystals, which are unalterable in the air, and of 

 which the solution in water is not changed by ebullition. The 

 solution, treated with hydrochloric acid, affords chlorine and 

 iodic acid, water being formed. Hyperiodic acid is resolved 

 into oxygen and iodine by a high temperature. 



Hyperiodates. Besides neutral salts of this acid, subsalts of 

 the potash family exist which contain two of base to one of acid. 

 If these are subsalts they are unique, as no true subsalts of the 

 potash family are known. But it is more probable that hyper- 

 iodic acid forms a second and bibasic class of salts, to which 

 they belong,* 



Iodide of nitrogen. Iodine has an action similar to that of 

 chlorine upon ammonia, and forms when digested in a solution of 

 that substance, an insoluble black powder, which is powerfully 

 detonating, and analogous to the chloride of nitrogen. The 

 iodide detonates more easily, but less violently than the chlo- 

 ride, always exploding spontaneously when it dries. Another 

 process is to mix a great excess of ammonia, with a saturated 

 solution of iodine in alcohol, and afterwards to add water so 

 long as iodide of nitrogen precipitates. The filter with the 

 humid precipitate should be divided into several pieces, other- 

 wise the whole may explode, at once, upon drying. The same 

 obscurity hangs over the composition and constitution of the 

 iodide as the chloride of nitrogen. 



* PoggendorfTs Annalcn, vol. 28, p. 514. 



