86 



DIVERS AND H AU A. 



Di sodium or other bibasic imidoHulphonate does not precipitate 

 with lead nitrate and only feebly with normal lead acetate. It is 

 therefore necessary to take at least either the trisodium imidosul- 

 phonate, or else a basic lead acetate, to get an insoluble salt in suf- 

 ficient quantity. This salt is always a basic or hydroxy salt, so that 

 its separation renders its mother-licjuor much less basic than the 

 mixed solutions employed. Hence the common retention of lead salt 

 and imidosulphonate together in the mother-liquors, and also the fact 

 that either one or the other must Ije present in them. In fact, only 

 by the use of a basic lead salt is it possible to throw all imidosul- 

 phonate out of solution, and only by using the trisodium salt is it 

 possible to precipitate all lead. Oxy-lead acetate and lead nitrate or 

 normal acetate precipitate different salts with trisodium imidosul- 

 phonate, but all the metal of either salt precipitated is lead. One 

 other ])oint to l3e here noticed as affecting precipitation, is the solu- 

 bility in solution of normal lead acetate of the lead imidosulphonates 

 insoluble in water. The solution is alkaline and freely precipitable by 

 carbonic acid, and m;iy be regarded as containing basic lead acetate 

 and the soluble lead hydrogen imidosulphonate. Altliough a super- 

 ficial examination of the reactions of imidosulphonates with lead salts 

 may suggest the view of their being ill-defined, fuller investigation 

 proves them to be quite definite. 



The normal salt, Vh^l^.^C^O-^^^, appears not to exist. The first 

 addition of lead acetate or nitrate precipitates a basic salt with tri- 

 sodium imidosulphonate ; iind basic lead imidosulphonate treated 

 with small quantities of nitric acid dissolves as a whole to yield a 

 neutral or slightly acid solution, the undissolved part remaining 

 unchanged (p. 89). 



The lead Injcli-oycii salt, ]:\1^(Ü0-^.2V]), appears to exist in solution, 

 but the attempt to separate it leads to decomposition. Its solution can 



