280 0N PRUSSIC ACID. 



which are moft ftrongly heated always form lixivium faturatcd 

 with the carbonic acid ; this can only happen at the expence 

 of the oxigen of the water and the carbon of the carbonated 

 azote of potafh : The potafh, therefore, as I have already ob- 

 ferved, contributes in part, by a predifpofing attraction, to the 

 fucceffive developement of all thefe new combinations. 



After having proved that carbonated azote of potafli inftant- 

 ly decompofes water, and that water alfo fucceffively decom- 

 pofes the pruffire ; which is always by a diminution of its 

 quantity ; I (hall now (hew the means which mull: be ufed to, 

 prevent the deftruction of this fubflance, and (hew that they 

 perfectly agree with the theory I have here laid down. 

 Remedy againft The deftructibility of pruffire of potafh being highly preju- 



watertuh the" S d ' cial in ,ar S e °P erat5ons > l directed my refearches to the 

 pruflic calcined means of preventing that lofs. The refult of my obfervations 

 matter. j S) i\ )a [ ) J n order to (top this decompofition, it is an indifpen- 



fable condition, never to wet a pruflic calcination but with a 

 Sulphate of iron foI U Lion of fulphate of iron at the maximum of oxigenation ; 

 this method is intitled to the moil decided preference; for in 

 this cafe the pruffire, whichis formed at the moment of the 

 mixture, being in a (late favourable to the faturation of pota(h, 

 it becomes fixed at the expence of the oxigen of the oxide of 

 The pruffire can \ r0 n } and in this date it is pruflic acid. I mull obferve that 

 naced byTme- tms oxigenated combination of pruffire cannot lake place but 

 tallic oxide. by the concurrence of metallic fubllances already oxigenated ; 

 and that it is only then that an equilibrium of affinities is efta- 

 blifhed between the potafli, the pruffire, and the metallic 

 oxide ; which produces a complex and energetive combination, 

 that I propofe to call pruffiate of potafli by the oxide of iron; 

 which method of nomenclature I propofe to apply to each fe- 

 veral metallic oxide which enters into the compofition of pruf. 

 iiate of potafli. All thefe combinations cryftallize eafily by 

 evaporation, and by cooling the lixivium we may obtain very 

 regularly formed cryftals. 

 Inference. The confequences we fhould naturally draw from thefe latter 



obfervations (hew therefore irrevocably that the pruffire owes 

 its acid or neutralifing property to the oxigen of the oxide of 

 iron, and that as the quantity of water decompofed in this cafe 

 does not exceed what is neceflary to fupply the hydrogen in 

 the pruffire, we mud accordingly obtain more abundant pro» 

 ducts than in any other cafe. 



I may 



