INTERACTTOX BETWEEN SULPHITES AND NITRITES. oOo 



late in the process, the amount of salt separating is small, and 

 generally depends then for its existence npon its ])Ower to resist 

 the action of acid sulphite in ice-cold solutions. The solution 

 when, potentially at least, it is richest in acid carbonate, was 

 found by us to crystallise soon, if left to stand in closed vessel, 

 although sulphonation which is destructive of acid carbonate was 

 slowly going on in it. 



III. — ;/. Primary Action of Sulphur Dioxide upon a Nitrite. 



Solution of sulphur dioxide added to that of potassium or 

 sodium nitrite produces a sulphate and either nitric or nitrous 

 oxide, according as one or other of the interacting substances is 

 in excess. That is the ordinary well-known result, but there are 

 two ways of limiting the extent of the action so as to get either 

 hydroximidosulphate and nitrous acid or the undoubted products 

 of their transformation. By these ways, the interaction of sul- 

 phur dioxide and a nitrite is shown to be — 



2KNO2 + 2S0, + OH, = K.HNS A + HNO,. 



The more important way to thus limit the action is by an 

 experiment first tried by Glaus {Ber., 1871, 4, 508 ; see preceding- 

 paper) which consists in adding an alcoholic solution of sulphur 

 dioxide to excess of potassium nitrite in strong aqueous solution. 

 For this experiment gives, as we have ascertained, potassium 

 nitrito-hydroximidosulphate which precipitates and ethyl nitrite 

 which boils off' by the heat of the reaction : — 



3KNO2 + 2SOo + CoHoO = KN02,K,HNS,0, + CM, NO,. 

 By becoming ethyl nitrite the nitrous acid is rendered inactive 

 on the hydroximidosulphate, which is thus saved from oxidation. 



The other way of tracing the earlier action of sulphur dioxide 



