20 



E. DIVERS AND T. H AG A. 



molecules of nitrite, instead of one to one as when Rîischig's direc- 

 tions are followed. In the niother-liqnor remains much sul])hite but 

 only insignificant ([uantities, at most, of nitrite. In order to measure 

 with some degree of accuracy the qujintities of nitrite and metasulphite 

 taken, it is best to use good commercial nitrite, the real strength of 

 which in this salt is known from a previous assay ; and to prepare the 

 metasulphite, shortly before it is wanted, by passing-in sulphur dioxide 

 just to the point when the solution beromes neutral to methyl-orange or 

 to lacmoid paper. Some incimvenience in preparing the ice-cold 

 soUitions is caused by the sparing solubility of the metasulphite, 

 which entails the cooling of large volumes of solution. The yield of 

 washed crystals of the oximide is about 60 (63) per cent, of the 

 calculated quantity, and such therefore as seems not to have been even 

 remotely approached by previous vv(3rkers, although greatly surpassed 

 by that of the sulphur-dioxide method described on pj). '27 el seii. 

 By working at temperatures some degrees below 0° the pi'odnction of 

 nitriie seems to be further lessened and that of oximide somewhat 

 increased. 



It is besides almost certain that the formation of t lie nitriie in- 

 creases relatively to that of the oximide as the nitrite remaining 

 grows less, the sulphite having more and more already -formed oximide 

 to work u]3ou along with less and less nitrite. This view of the 

 matter is supp(jrted by experience. For when the metasulphite 

 is added to an excess of nitrite, the crystals of oximide produced 

 amount, wlien washed frtnn the little nitriie accompanying them, to 

 80 per cent, of the quantity theoretic^ally possible from the quantity of 

 metasulphite taken. 



Formation of tJie neutral sodiuni nxinudosulphonate from metasuU 

 fjhitc.-'Viy treating one molecule of sodium nitrite with two, or a 

 little less than two, of sodium metasulphite, the nitrite may be wholly 



