C)g ' HISTORY OF PRUSSIAETS, 



on which consequently we cannot rely, unless we join with 

 No prossiate thorn the counterproof proposed by Berthollet. I shall 

 Prnssi-m' 1 blue on! - y ad ^ because this should remain consigned to the his- 

 unless black tory of the science, that, when a chemist still employs with 

 tafhresent? 11 eflect a lixivium 5 or tcst liquor, purified by an acid, we may 

 be certain, he has not obtained a complete and entire sepa- 

 ration of the iron, as he flatters himself: for it is certain, 

 that every lixivium capable of affording blue with a solution 

 of red oxide contains black oxide, since without the assist- 

 ance of this oxide there would be no tingeing prussiate; in 

 other words, every prussiate of potash, not rendered, a tri- 

 ple salt by black oxide, is incapable of forming blue with a 

 solution of iron, the oxide of which is at a maximum, as 

 is most commonly the case with those produced in analyses. 

 Pnt^iatcsof no Xhis is a fact which Schcele perfectly developed. We may 

 to indicate the conclude therefore, that the alkaline or earthy triple prus- 

 presence of siates can no longer be considered as useful in analysis, any 

 farther than litmus, galls, and other reagents, which merely 

 indicate the presence of a certain principle, without being 

 capable of ascertaining its quantity. 

 Actios of sul- The aqueous sulphuric acid, applied to the triple prussv 

 ghaut .ici . a ^ a fl- or( j s |}, c same results as the muriatic. A hundred 

 parts of prussiate produce a hundred and fifteen or a hun- 

 dred and sixteen of sulphate of potash. If we knew ex- 

 actly how much alkali the sulphate contained, we might 

 thence deduce the quantity of the base of the prussiate. A 

 hundred parts of crystals of prussiate lose ten of water by 

 distillation. 

 Boiling neces- To complete its decomposition by the acids, itmust be kept 

 boiling at least half an hour, in order to dissipate the gas 

 entirely, and obtain the entire separation of the white 

 prussiate, which is formed during the operation, 

 or the assistance 'fhe prussiate of potash dissolves cold in the muriatic- 

 acid, without being decomposed. This mixture, as Ber- 

 thollet found, requires the assistance either of light, or of 

 heat. 

 Action of vine- Vinegar, assisted by boiling, decomposes it also : prussic 

 gas escapes, and white prussiate is formed, which does 

 not change blue so quickly as with the preceding acids; 

 finally, this prussiate, which does not appear till the mo, 



men,t 



