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EDWARD DIVERS AND TAMEMASA HAGA 



phonate and pyrosulphate, the hydrolysis of these would give 

 three-fourths of the sulphur and nitrogen as sulphuric acid and 

 ammonia. Partly one and partly the other change would give 

 proportions intermediate to one-half and three-quarters of the sulphur 

 and nitrogen. But, if any of the acid were to remain unchanged by the 

 heat, uncertainty, as to the relative extent of the two possible changes, 

 would be caused. The degree of acidity of the mass removes this 

 uncertainty, for, whereas this is less than that of the amidosnlphonic 

 acid to the extent that these changes have occurred and developed 

 ammonia (neutral imidosulphonates being the two-thirds normal salts), 

 the unchanged acid retains, of course, its full acidity. Any excess of 

 acidity of the mass over that equivalent to its ammonia is, therefore, a 

 measure of the quantity of the unchanged acid. Since, finally, the 

 amounts of ammonia and sulphuric acid prove to be the equivalents of 

 three-fourths of the nitrogen and sulphur of the changed part of the 

 acid, it becomes known that the change is wholly into the pyro-salts. 



There is another method of testing the vitreous mass, which is 

 not without importance from a qualitative point of view, and which is 

 one that may be used for a half direct estimation of the imidosul pho- 

 nate and sulphate. If to the cold, somewhat alkaline and unhydrolysed 

 solution, barium chloride is added so long as it precipitates anything, 

 the precipitate contains not only the original sulphate but almost all 

 the imidosulphonate. Much of the barium imidosul phonate could be 

 dissolved out by ammonium chloride, but to effect an approximate 

 determination of the composition of the precipitate, it is better to wash 

 it with warm water till it begins to pass the filter, then wash it off the 

 filter, boil it for a minute with very dilute hydrochloric acid, and filter 

 off again through the same filter, keeping the filtrates separate. The 

 precipitate is washed with hot water till it again begins to pass the 

 filter, then dried, ignited, and weighed as sulphate. The ainidosul- 



