AMMONIUM A3IID0SULPHITE. 191 



in the freezing-mixture. There was no other way of completely 

 drying the salt, and even this way was not sufficiently successful 

 when the salt had been allowed to cake together. The ammonia 

 could not be replaced by air or hydrogen for drying the salt, 

 nor could the flask be kept out of the freezing-mixture, so long- 

 as ether still moistened the salt, without the latter taking an 

 orange-colour. When dry and in an ammouical atinosi^here, 

 the salt is more stable, but cannot long l)e kept at the ordi- 

 nary temperature without getting discoloured through decom- 

 position. 



Analysis. — The stopper carrying the gas-tubes having been 

 replaced by a plain one, and air allowed to displace most of the 

 ammonia gas, the flask was at once weighed and left for a time 

 inverted with open mouth dipping into 100 c.c, or more, of 

 water in a beaker. When the salt in it had become damp, it 

 was washed into the water, and its very dilute solution distilled 

 with alkali for its ammonia. The residue was divided into two 

 measured portions, one of which was acidified and heated to 

 150° under pressure for some hours and then redistilled with 

 alkali for additional ammonia, of which only a trace was got 

 (0.001 per cent, of the salt). The other part of the solution was 

 treated with bromine, and next with hydrochloric acid and 

 chlorate, after which barium sulphate was precipitated with the 

 usual precautious. The results of the analysis were : — 



Found : 



S0,(NH3)o: 



The slight excess of ammonia indicated is safely attributable 

 to the means taken to preserve the salt till it was analysed. 



