SODIÜM NITROSOSULPHATE. 99 



sulphuric acid ; its sulphur by oxidation with bromine-water and 

 precipitation with barium chloride ; and its sulphite by titration with 

 iodine. These were all calculated as parts per cent, of the salt before 

 it was placed in the desiccator. The numbers found show a deficiency 

 of about 3 per cent, from those for the anhydrous salt, while sodium 

 nitrososulphate with one mol. of crystal -water would have lost 8*8 °/ 

 in becoming anhydrous. Here are the tabulated numbers : — 



Na,N,S0 5 . Found. with ^!eäient. 



Sodium 24-73 24-13 23*99 



Sulphur 17-20 16-64 16-68 



This deficiency includes moisture and any solid particles carried 

 away during the very rapid evolution of gas by the salt when decom- 

 posing. From the weight of the residue and that of the sulphite it 

 container], it can be calculated, approximately at least, that about 

 l-6°/ of the original salt, or l'2°/ of sulphate and sulphite, were 

 mechanically lost by the decomposition of the salt, and, therefore, 

 that, when placed in the desiccator, it had contained about l'4°/ of 

 moisture. Now, the amount of sulphite in the residue was 9'8°/ 

 of it, or 7*28°/ of the damp nitrososulphate. Therefore, to recompose 

 the salt, we have — 



Sodium sulphite 7'28 



Nitric oxide eqvt. to this 3'47 



Sodium sulphate 67*05 



Nitrous oxide eqvt. to this 20'78 



Moisture, by diff er ence l - 42 



100-00 

 Sodium nitrososulphate is, therefore, an anhydrous salt, like the 

 potassium salt. Like the potassium salt, also, though it continuously 

 decomposes into sulphate and nitrous oxide when in neutral solution, 



