946 EDWARD DIVERS AND TAMEMASA HAGA ; 



alternative, to the presence in the vitreous mass of these two pyro- 

 salts in molecular proportions, along with some unchanged amido- 

 sulphonic acid. The following equation expresses the formation of the 

 pyro-salts : — 



4 H 2 N S0 3 H = (NH 4 S0 3 ) 8 + NH 4 N(S0 2 ) 2 0. 



The formation of acid imidosulphonate,— 4H 2 N"S0 3 H = 2NH 4 N"(S0 3 H) 2 , 

 and that of pyrosulphate ,— 4H 2 ¥S0 3 rI = (NH 4 S0 3 ) 2 + (H 2 NS0 2 ) 2 0, 

 are not necessarily simultaneous ; but, within the limits of analytical 

 determination, appear to be so. In the case of some amidosulphonates, 

 however, the conversion to imidosulphonate partly precedes that into 

 sulphate. 



We now give such particulars of the analysis of the mass, and of 

 the calculation of the results, as seem to be necessary. Heating the 

 acid in a vessel only loosely covered is out of the question, because of its 

 avidity for moisture when fused or near its melting point. Heating 

 over the direct flame is also almost unmanageable. The operation 

 was found to become quite simple by using thin- walled tubes closed at 

 one end, about 5 mm. wide and 70 mm. long, closely plugged with 

 glass rod, but not air-tight. About a gram of acid served for an 

 experiment. Heat was imparted by a sulphuric acid bath, slowly raised 

 in temperature. The tube and vitreous mass were reweighed when 

 cold again, as a precaution. The mass dissolved in water and distilled 

 with alkali gave the quantity of ammonia in it. Dissolved in water 

 and left to stand for some hours, then heated almost to boiling, and 

 precipitated by barium chloride, the mass contained in another tube 

 gave the sulphuric acid compounded of that formed by heat alone and 

 that subsequently formed by dissolving the mass in water. Hydrolysis 

 at. 150° of the 61trate and addition of more barium chloride gave the 

 rest of the sulphur, and thus served as a measure of the quantity of 



