254 EDWARD DIVERS AND TAMEMASA HAGA ; 



thirds of the full quantity of imidosulphonate. In heating- the salt, 

 access of moisture must be guarded against. 



Berglund observed the production of imidosulphonate by heating 

 ammonium, or potassium, or sodium amidosulphonate, but only in very 

 small quantity, even in the case of the ammonium salt, which gave 

 him much the best result. According to him, the ammonium salt 

 melts at 125°, without decomposition,' and begins to be decomposed at 

 150°, with escape of ammonia. Imidosulphonate is formed very slowly, 

 and is decomposed almost at the same rate. On account of the instability 

 of imidosulphonates, the temperature must not exceed 170°. Evident!)', 

 Berglund allowed access of moist air, for the true melting point of the 

 salt is much higher than 125°, and ammonium imidosulphonate is a 

 nearly stable salt, even at 357°, when it boils (This Journal, ß 55). 



The potassium salt. — In our paper on Imidosulphonates (6, 6'2) 

 we mentioned that potassium amidosulphonate becomes ammonia 

 and imidosulphonate when heated, and made reference to Berglund. 

 But, at that time, we had only seen abstract accounts of his work, and 

 have since found that, whereas we had observed a free production of the 

 imidosulphonate at 350°, he had got only a very small quantity 

 indeed of it, at the temperature he employed, 1 GO- 170°. 



The potassium salt melts at 212° (Jena thermometer, thread im- 

 mersed), but not without partial decomposition, the liquid beginning 

 to froth, through escape of ammonia, before its temperature reaches 

 220°. Berglund's observation that ammonia escapes at 160-170°, 

 though very slowly, may be set down as due to presence of the atmo- 

 sphere in his experiments, for the crystals do not change before fusion, 

 when air is shut out. The solidifying point rises as ammonia escapes, 

 so that at 260° the residue is solid, and remains so at 280°, potassium 

 imidosulphonate melting only at a red heat, as found by us (op. cit., p. 

 63). By far the greater part of the residue consists of the (neutral) 



