lMIDO«ULPHONATEÖ. g7 



be prepared by treating' either basic salt with somewhat less than 

 enough dilute sulphuric acid, and decanting the clear solution from 

 the sulphate and undecomposed basic salt. The solution can be 

 preserved unchanged in absence of acetates for a very short time only. 

 It has a slight acid reaction with litmus. Left in a desiccator it 

 suffers decomposition into amidosulphonic acid and lead sulphate, 

 slowly at first, more rapidly as the .solution grows concentrated. 

 Heating the solution effects the same change. Alcohol gives a volu- 

 minous precipitate gradually giving place to a crystalline de{josit 

 ]>artly adhering to the sides of the vessel, nearly insolul)le in \v:!ter, 

 and p.pparently sulphate. 



Hemihiidroxji-lcad iiiiidosulplionate, HOPb]S[(80;.Pb()H)o — Lead 

 nitrate and trisodium imidosidphonafe in solution brought together 

 in widely varying proportions yield this salt as a precipitate, volumi- 

 nous at first, but soon becoming dense and granular. Disodium 

 imidosulphoiiate and s(jdium nitrate are the otlier pr(^ducts of the 

 reaction : — 



3Pb(NO,)2 + 3OÎI2+ 4Na3N(S03)2 = (HOPb)sN(S03)o + 3HNaoN(S03)2 



+ 6NaN0;, 

 The precipitation is closely quantitative. With the trisodium salt not 

 used in excess the mother-li([uors ai-e neutral in reaction with metliyl 

 orange. 



ISTormal lead acetate may be used in place of the nitrate, hut only 

 with less perfect results. The best way to proceed is to mix the 

 solutions rapidly together in soinething approaching the right propor- 

 tions ; or the two salts may be ru))bed together in the solid state and 

 only then treated Avith water. In either of these ways, when the 

 proportion of either salt is not very many times greater than it should 

 be, a product of constant composition is obtained, which differs 

 however from the pure lead salt in having about one-seven ty-third of 



