INTERACTION BETWEEN öULPHITES AND NITRITES. 291 



which potassium hydroxide can be generated from potassium 

 sulphite and that is one made known by us, namely, treatment 

 of the sulphite first with nitric oxide and then with alcohol and 

 water (this Journal, 9, 106). 



III. — a. A Pyrosulphite all active upon Nitrous Acid. 



As remarked at the end of section II. a., a pyrosulphite 

 appears to act as an acid upon the nitrite and then sulphonates 

 the nitrous acid itself, only indirectly, therefore, sulphonating 

 the nitrite of a metal or of ammonium. One third of the pyro- 

 sulj^hite should, accordingly, be replaceable by some other acid, 

 and so it proves to be (section III. d). It is not new to formuhite 

 the sulphonation of HNO2, and to speak of ' nitrous acid' as the 

 reacting substance, for (passing over Fremy) Raschig has already 

 done so. But, whereas we would be understood to confine the 

 activity to nitrous acid itself, or its acidic equivalents (sect. III. d), 

 such was not the thought of Raschig, who only wrote H as a 

 general symbol, and ' acid ' as a general term, while representing 

 metal nitrites as active by generating alkali hydroxide. 



Nor is it new to learn that nitrous acid can be sulphonated. 

 By treating a dissolved sulphite with nitrous acid (nitrous fumes) 

 Fremy did succeed in obtaining sulphazotised salts, but the dif- 

 ficulty of moderating the flow of the gas, and the presence in it 

 of nitrogen peroxide and nitric acid made the operation so in- 

 convenient, he said, that he did not use it in preparing any of 

 the salts he examined, and gave no further attention to it. We 

 have taken up the matter, since untouched and unmentioned, 

 where Fremy left it half a century ago. Our work has been 

 very simple but very eflective, and has consisted in f^^ubjecting a 



