OX1M]I)OSULPHOXATE8 OK SULPHAZOTATES. £7 



su]])hur dioxide are by calculation convertible into oximidosulphonate 

 and nothing el.se ; — 



XaXOo + XaOH + l>SO., = HUX(>S03Xa)2. 



It will therefore be seen that, with tliese proportions, were sulphite 

 used instead of hydroxide or carbonate to begin with, the use of 

 sulphur dioxide could still not be dispensed with. Cooling during 

 the preparation of the solution guards against premature hydrolvsis 

 and lessens the production of ni true. The quantity of water is limited 

 because it has to be evaporated afterwards in the cold. Much less 

 than the quantity jjrescribed will not be enough because then so much 

 acid-carbon.ate or normal sulphite, as the case may be, mav separate 

 ont in the middle of t lie process as to thicken the solution so that it 

 cannot be sufficiently rapidly agitated with the sulphur dioxide to 

 prevent the injiu'ious action of local excess of the latter. 



It is generally more convenient to work with sodiimi carbcjnate 

 than with the hydroxide ; and on a large scale especially or on a 

 moderately large scale, much more rapid working is possible with the 

 carbonate than with the hydroxide, because of the much greater heat 

 to be dealt with when the latter is used. 



Preparation of tlw neutral poiassuDn oxinudmiilplionate hij using 

 sulj>Jiur dioxide. — The ]^rocess just described foi' getting sodium 

 oximidosulphonate, but modified as to temperature, is eminently suc- 

 cessful, and even simpler than when used for thtit salt, when employed 

 for getting potassium oximidosulphonate from potassium nitrite and 

 either carbonate or hydroxide. Other j)rocesses, already published, 

 cannot approach it in certainty and in purity of the salt yielded. 0\er 

 the process described in this pa])er (p. 19), in which are mixed some- 

 what more than three molecules of potassium metasulphite with two 

 of nitrite, it lias the same advautau'e. althcjuiiii in a less deo:ree, and in 



