INTERACTION BETWEEN SULPHITES AND NITRITES. 289 



never be enough, with ordinary care, to cause much less than 

 one-third of the sulphite to remain inactive. If excess of pyro- 

 sulphite is used the interaction appears to be — NaN02 + 2Na2S205= 

 NagNSgOc) + NaaSOa, but we have not made any quantitative deter- 

 mination of the sulphite remaining, the qualitative evidence being- 

 sufficient. 



The interaction between pyrosulphite and nitrite proceeds at 

 first very rapidly and with great elevation of temperature, but, 

 when the temperature is kept down by cooling, soon slows down, 

 so as to require many hours for its completion. The normal 

 sulphite seems here to inhibit the action of the pyrosulphite, just 

 as does the salt of a weak acid inhibit the action of that acid, 

 an effect now well recognised. This consideration points to the 

 propriety of looking upon the passage of pyrosulphite to normal 

 sulphite as its action as an acid upon the nitrite, and not as the 

 yielding up of half of its sulphurous acid for the sul phonation 

 of the nitrite, the interactions being 2 NaNOi + Na 38205 + 0112 = 

 2HN02 + 2Na2SO„ and then 2HN02 + 2jS'a2S205=2Na2HXS20; 

 (see section III ci). 



II. — b. Alkali not produced in the Sulphonation of 

 a Nitrite. 



One of the most remarkable things, according to Clans, is 

 the production of potassium hydroxide by the formation of Freray's 

 salts through the agency of a sulphite. He explained this pro- 

 duction by the equation~KN02+2[v,SO,-r 20H2=K2HNS20,+ 

 3KII0. Such an equation was also published by Berglund 



o 



(Lunds Univ. Arskr. 1875, 13, 14). Raschig gave the same 

 equation for results obtained by himself and, in order to express 



