AMIDOSULPHOXIC ACID. 253 



at 180° babbles begin to form in the liquid, and enlarge and 

 increase up to 190°, which are almost wholly reabsorbed on cooling 

 the liquid to 130°. If the temperature is very slowly and con- 

 tinuously raised, effervescence of ammonia goes on equably, but 

 if it is maintained constant, the escape of ammonia soon lessens. 

 Having reached 240° in two hours, the liquid cooled down again 

 begins to form tufts of silky fibres at 130°, which grow with fall of 

 temperature, and remain enclosed in a clear vitreous mass, unchanged 

 for days, whereas ammonium amidosulphonate cooled after having been 

 barely fused, forms an opaque homogeneous mass of small prisms. 

 The mass, thus cooled from 240 , weighs less than the salt taken, by 

 nearly half the weight of the difference in ammonia between normal 

 and two-thirds normal ammonium imidosulphonate. When heated 

 very gradually to 310°, it still evolves ammonia slowly at that point, 

 but other gases also, which form with the ammonia a slight pseudo- 

 sublimate. With loss of ammonia, the solidifying point of the liquid 

 rises, so that, on cooling slightly, solidification into a hard crystalline 

 mass of the two-thirds normal ammonium imidosulphonate occurs. 

 This mass is neutral, except where it has been more strongly heated in 

 contact with glass, treatment which decomposes it, renders it acid from 

 presence of acid sulphate, and causes it to attack the glass in a remark- 

 able manner, so as to strongly R&tumurise it and lessen its weight 

 considerably, without eroding it. The imidosulphonate can be tested 

 for and roughly estimated, by dissolving the mass in water containing 

 ammonia, cautiously concentrating the solution, and adding solid 

 potassium chloride. The sparingly soluble potassium salt can be thus 

 obtained, collected, and weighed. Another way is to precipitate the 

 ammoniacal solution by barium chloride, and determine the alkalinity 

 of the normal barium salt, as a measure of the imidosulphonic acid in 

 it. We have succeeded in converting the amidosulphonate into two- 



