AMMONIUM AMIDOSULPHITE. 189 



or Other of the gases is used in excess, unless the temperature is kept 

 very low. But the variation of the proportions and the apparent 

 condensation of additional sulphur dioxide by a sufficiently am- 

 moniated product, that may be observed, are results clearly due 

 to the secondary changes going on (p. 192). The simple union 

 of ammonia and sulphur dioxide, which can be secured by 

 keeping down the temperature by suitable means, especially with 

 the ammonia in excess, is that of two volnmes of the former to 

 one of the latter (p. 191). But since this union cannot be 

 made at the ordinary temperature without being immediately 

 followed by a decomposition, in which ammonia is evolved, the 

 union of the two gases can appear to take place in other pro- 

 portions than the above. It is pretty certain that, by proceeding 

 slowly enough and using strong cooling agencies, secondary ac- 

 tion could be almost entirely prevented and the statement just 

 made be verified, even when working with the gases alone. We 

 have not gone very near to getting such a result in this way, 

 but then we have, for good reasons, not striven much to over- 

 come the difficulties. Our experimental work, which will be 

 further on referred to (p. 195), has shown that two much more 

 nearly than one volume of ammonia can be made in this way 

 to unite with one volume of sulphur dioxide, the only propor- 

 tions which Rose met with in his experiments (p. 193), and that 

 the presence of much ammonium amidosulphite in the j^i'oduct 

 can be established with certainty. 



Preparation and analysis of ammonium amidosulphite. 



In order to get the primary product of the union of sul- 

 phur dioxide with ammonia in its unchanged state, ether was 



