952 EDWARD DIVERS AND TAMEMASA HAGA ; 



calculated with this correction, materially greater (quite 5 per cent.) ; 

 on the other hand, the heating of the acid had to be brisk, and the 

 crucible open, or volatilised products would have been returned 

 condensed, and this mode of working entails much more loss as spray 

 than the number above calculated allows for. The sulphate, from this 

 cause, being found in marked excess and the last stage of the decom- 

 position having no doubt commenced, the results obtained are plainly 

 in accordance with the assertion that the pyro-salts become hydrated 

 at about the same rate, until hydration of the residue is complete. 



In an experiment, where the heating was stopped when a little 

 more than half of the acid had been rapidly driven off, the residue 

 gave, on analysis, 29 per cent, sulphur and 14.4 nitrogen, a 

 result which nearly corresponds to 4NH 4 HS0 4 , 1HN"(S0 3 NH 4 ) 2 , and 

 1H 2 NS0 3 H (in form of the two pyro-salts). In another case, when only 

 a fourth of the acid had been expelled, the liquid residue was at once 

 decanted into a second crucible, except for a sixth of it, which had crys- 

 tallised. The two portions showed a somewhat different composition ; 

 that left behind contained 28.83 per cent, sulphur, the decanted part con- 

 tained 29.44 per cent, sulphur and 16.8 per cent, nitrogen as ammonia. 



The ammonium salt. — The melting point of the thoroughly dry am- 

 monium salt is 135°, as determined in a capillary tube, by a Jena 

 thermometer with stem all immersed in the sulphuric-acid bath. The 

 melted salt, when in some quantity, remains in fusion at temperatures 

 as low even as 70°. Heated much above its melting point, the salt, in 

 part, becomes imidosulphonate, at first, apparently, the isomeric normal 

 ammonium salt, 2H 2 NS0 3 NH 4 =NH 4 N(S0 3 NH 4 ) 2 (' sulphatammon '), 

 which then, with rising temperature, changes into ammonia and the 

 two-thirds normal salt, HN(S0 3 NH 4 ) 2 (' parasulphatammon '), but 

 yet not fully before the latter salt begins to decompose into sulphate, 

 sulphur dioxide, and nitrogen. The phenomena observed are that 



