IMÎDOSULPHOXA'Jl^S. 77 



ohtaiiied whirh arc nnhydrous and stable in the air. They cannot be 

 washed, and must be freed from their mother-liquor bv pressure in 

 paper. The new ;>alt i« of a composition which may l)e represented as 

 being that of one molecule of diammonium imido.>ul[>lionate with one 

 of sodium nitrate. Prepared from a good excess of ammonium nitrate 

 the crystals pr()\'ed to be almost pure, but holding a little water (a); 

 with the use of less ammonium nitrate, the salt showed on analysis the 

 presence of a very slight excess of clisodium imidosulphonate. The 

 yield of salt was three-f(xu-ths of the possible quantity. The mother- 

 liquor on eva[)oration gave crystals of sodium nitrate and some more 

 of the salt. Tlic double salt cannot be recrystallised, its solution 

 yielding, first, good crystals of a salt which inay he described as (anhv- 

 dioiis) diammonium imidosulphonate contaiiiing o per cent, of sodium, 

 ;ind. af'er this salt, crystals of the double salt. Since the mother-li<pior 

 of the double salt yields sodium nitrate, it would seem that double 

 decomposition occurs between sodium imidosulphonate and ammonium 

 nitrate. 



The presence of nitrate in the d(juble salt cannot be directly 

 indicated in the ordinary way, Ijut may be ar once detected by a new 

 reaction of delicacy and of some general interest. The salt freely 

 effervesces when immersed in strong sulphuric acid, the gas being- 

 nitrous oxide with a little nitrogen. iS'o nitrosyl sulphate is jiroduced. 

 Quite a minute quantity of nitrate mixed or combined with an 

 imidosulphonate is shown by dropping the dry solid into a little of 

 tlie acid, and not mixing tliem up t<jo much. The reaction needs 

 careful study. V\e ventured to determine the nitric acid in the salt 

 by means of this reaction, taking the gas as nitrous oxide only, and 

 got a good result, l)ut do not ieel justified in entering it in the tabular 

 statement below 



In one preparation we determined the nitric acid; in the other it 



