286 E. DIVERS AND T. HAGA : 



Sulphur dioxide 1st 10 cc. 2ncl 10 cc. 3rd 10 cc. 



as 



Sulphite .0662 grms. =96.6 o/o .r204grms. = 96..59^ .3996 grms. = 01.59^ 

 Snlphazot. .0023 „ = 3.4^ .0047 „ = 3..59^ .0365 „ = 8.5«^ 



It will be seen that all but 3.5 per cent, of the sulphur 

 dioxide entering the solution in the early stages of the experi- 

 ment remained in the form of sulphite, and that even up to the 

 time when the last of the hydroxide had been consumed, all but 

 8.e5 per cent, of the total sulphur dioxide was in the slate of sulphite. 

 That it must be impossible to prevent all temporary local excess of 

 sulphur dioxide wdll be at once admitted, as also that it must 

 be difficult in the later stages to keep down this local excess to 

 very narrow limits. Therefore it will seem in the highest degree 

 probable, if not certain, from this experiment that sulphur diox- 

 ide, equally with normal sulphite, does not act upon nitrite in 

 presence of alkali hydroxide. 



Now Freiuy believed that potassium hydroxide helps the 

 formation of sulphazotised salts and endeavoured, accordingly to 

 keep some of it always present when passing sulphur dioxide 

 into a solution of potassium nitrite. This he did by adding it 

 occasionally during the process, and to such an extent that at 

 the end of the operation the mother-liquor of his suits was al- 

 ways not merely alkaline but caustic and destructive to filter 

 paper. Clans did not go so far as to believe that the potash 

 exercised any specific influence upon the action between the sulphur 

 dioxide and the nitrite, but, agreeing wdth Fremy as to its 

 value in precipitating and preserving the sulphazotised salts, he 

 adopted the precaution to stop passing in sulphur dioxide when 

 the alumina contained in the potassium hydroxide began to pre- 

 cipitate, since this occurs while the solution is still strongly 

 alkaline to litmus. Kaschig, in attempting to prepare Fremy 's 



