30 



E. DIVERS AND T. HAGA. 



such as half or more oftliJit (|iiMiitify. It can l)e purified l)y recrystal- 

 lisatioM from water. It does not correspoFid in composition to 

 Fremv's basic aidjtliazotalf of potassium, heing more alkaline than that 



salt. 



Alkaline polüsahnii nxlinidosulphonatt's. — The alkaline potassium 

 salt, K^NSoO;. discovered Iw Raschig, was obtained by him by dis- 

 solving the neuti-al salt in hot alkalised water, cooling rapidly, adding 

 to the supersaturated solution cold concentrated potassimn-hydroxide 

 solution until it caused a troubling, and finally leaving the mixture 

 to de})Osit the new salt in crystals. lie also ])repared it by adding an 

 excess of very strong potassiuin-liydroxide solution to Fremy'x basic 

 salt alreadv dissoUed in a little warm water, and precipitating by 

 alcohol. 



Xot ordv is excess of alkali useful here, as when pre])aring the 

 sodivun salt, by diminishing the solubility of the salt in its aqueous 

 mother-liquor, it is also necessary, whicli is not the case with tlie 

 sodium salt, to preserve the salt from decomposition by water. But 

 when alcohol is to be used as the precipitating agent, tlie excess of alkali 

 used by Kaschig is uncalled for. equally as in the case of the sodiiun 

 salt, and only the calculated quantity of potassium hydroxide having 

 been added, a sufficiency of alci^hol precipitates the salt. Indeed the 

 best way to purify the salt from adhering alkali is to dissohe it 

 in water and precipitate by alcohol, repeating the process ont-e or 

 twice. 



The less alkaline polassiuni salt, KJi(NS20^).2, — Fremy found that the 

 neutral salt in the solid state combines at once with potassium hydrox- 

 ide when treated with an excess of it in solution, and that the product 

 dissolved u]) in hot water deposits his hasic sulpha :otate in crystals on 

 cooling. We have fully confirmed Freiny's ex])erience although from 

 the fact of both salts being very sparingly soluble, the change of the 



