214 E. DIVERS AND T. HAGA : 



of nitrite be employed. Potassium nitrite, 30 grams ; potassium 

 liydroxide, 10 grams ; water, 50 to 100 grams are to receive a 

 current of sulphur dioxide freely until crystals begin to form, 

 the containing flask being all the time agitated in a cooling 

 bath of ice and brine. The sulphur dioxide is now to be entered 

 more slowly for some time longer and then stopped. After let- 

 tins: the flask stand for half an hour the solution should be full 

 of the desired salt which is then drained dry on the tile. Its 

 mother-liquor is alkaline to litmus but not to rosolic acid (pre- 

 sence of sulphite, absence of alkali) ; the well-drained salt itself 

 is only faintly alkaline to litmus, if at all so. The double salt 

 is also produced when to an ice-cold nearly saturated solution 

 of potassium nitrite a similar solution of potassium pyrosulphite 

 is very slowly added until crystallisation begins after which the 

 solution is allowed to stand for some time. Thus prepared, the 

 compound salt is liable to be contaminated with a little nitrilo- 

 sulphate and sulphite. The experiment just described was made 

 first by Raschig but he attached to it a significance unlike that 

 here presented. Discussion of his views will be found towards 

 the end of this paper. 



There is yet another way in which this potassium nitrito- 

 hydroximidosulphate can be produced which it is of interest to 

 mention because it illustrates the decomposibility of potassium 

 5/6 normal hydroximidosulphate into the normal and 2/3 normal 

 salts. AVhile the 2/3 normal salt dissolved in 16 per cent, or 

 richer solution of the nitrite crystallises out only in combination 

 with nitrite, the öjß normal salt can be dissolved in a nitrite 

 solution of even 50 per cent, and yet for the most part crystal- 

 lise out again uncombined. But generally with this strength of 

 nitrite solution a little fluffy or cotton-like lustreless matter also 



