AMIDOSULPHONIC ACID. 251 



5(NH 4 S0 3 ) 2 + 5NH 4 N(S0 2 ) 2 - 6NH 4 HS0 4 



+ 3HN(S0 3 NH 4 ) 2 + 2N 2 + NH S + 6S0 2 + 2S0 3 . 



This represents three-fifths of each of the pyro-salts as converted into 

 hydrated salt, and the imidosulphonate with double as much ammonia 

 as it had. When this change is about complete, the decomposition, at 

 still higher temperatures, goes on in such a way as to preserve a 

 residue nearly steady in composition as regards sulphur (29 per cent.) 

 but to cause it to become richer in water and poorer in ammonia and 

 imidosulphonate, until, quite at the Inst, the residue consists of am- 

 monium hydrogen sulphate alone. 



The result of heating 7.5 grams of the acid in an open crucible, in 

 the way described, for eight or ten minutes, was to leave a residue 

 crystallising in brilliant prismatic plates and weighing 4.879 grams. 

 The loss of weight included that due to ejection of a little of the liquid 

 as spray. The mass was analysed, and the results were calculated on 

 the, no doubt accurate, assumption that no amidosulphonic acid could 

 be present in it. Its composition is well represented as having three- 

 eighths of the sulphur as imidosulphonate and five-eighths as sulphate, 

 as follows : — 



Tmidosulphonates— 1NH 4 N(S0 2 ) 2 ; 2HN(S0 3 NH 4 ) 3 ; 



Sulphates— 8NH 4 HS0 4 ; 2(NH 4 ) 2 SO + : 

 as the following composition shows : — 



Total' Sulphate Imiclosulph. Ammonia 



Residue. sulphur. sulphur. sulphur. nitrogen. 



Calc. 65.6 28.73 17.96 10.78 13.36 



Found, 65.0 28.62 17.78 10.84 13.43 



These might have been derived from 28H 2 NS0 3 H by loss of 9S0 2 , 

 3S0 3 , 2NH 3 , 3N. 2 , and it must be near the truth to say that they were. 

 But the acid will have contained about one per cent, combined water, 

 which will have increased the sulphate, and also made the residue, 



