PltVSSIG ACID,' 2-79" 



1. Pruflic acid can only be formed during the carboniza- Pruffic acid is 

 tion of blood or animal matter, at a red heat: We, therefore, ^°J"jj*g^^°"^y ** 

 need not be afraid of heating the mixture of blood and alkali, 



in the preparation of pruffiated alkalies, to incandefcence, 



2. The affinity of pruffic acid with alkalies is greater at Its affinity whife 

 high temperatures, and in the dry way, than at low tempera- ^^.^J^^^^'® " 

 tures, and in the humid way. 



This obfervation diftinguiflies pruffic acid from the reft of All other vege^^j 

 the fo called animal and vegetable acids, and their co»bina- deitroyed by%- 

 tions with alkaline bafes ; for all of them are deftroyed at a nition. 

 red heat. Hence it is obvious, 



3. Tiiat in the preparation of pruffiated alkalies, the pre- Water fliould be 

 fence of water ihould be avoided as much as poffible. avoided. 



4. The dire<5l combination of pruffic acid with alkalies, can- P. acid and alk. 

 not be accompliffied. ^° ''^J^^^^ 



,5. Pure pruffiated alkalies are decompofable by the affufion P. pruffiated alk» 

 of water; part of the pruffic acid efcapes, and may eafily he d^<^om^hhk by" 

 recognifed by the odour of bitter almonds, and frequently alfo 

 by that of ammonia. 



6. The combination of pruffic acid with alkalies can only P. acid does not 

 ' be effected at all temperatures up to a red-heat, by the interpofi- <=o"™b»ne with 



tion of a portion of oxide of iron ; and the affinities confifting temp, but by 

 between the pruffic acid and alkali, are retained with a greater medium of irony 

 force in the humid way, in the ratio of the ponderable quan- 

 tity of iron prefent, 



7. All the precipitates obtained in chemical analyiis by Common pruf- 



means of pruffiated alkalies prepared m the ufual nian-^*^^^^*^®"*^""^^;, 

 . 1 r • • 1 . 1 "^"^^ metals with 



ner, contam more or iels iron, without exception; whereas iron j pure p, 



the fame precipitates, produced by the a6lion of abfolutely 8'^^ * different 



pure pruffiates, are free from that metal, and of a different 



colour than the former. 



8. The affinity of oxide of iron to charcoal, is more power- Moft of the 

 ful than the joint attradlion of pruffic acid and potafli to that ''■°'? prefent re- 

 metal; hence we always find that the greateft quantity of ^^"^ when*. ' 

 that metal remains behind with the charcoal, in the ufual alk, is made, 

 procefs for obtaining pruffiate of potafli. 



9. The precipitability of the oxides of metals by pruffiated Petals are pre- 

 alkalies, is in the ratio of their oxidability, or quantity of cip. by p. alk. in 

 oxigen they contain. ^^^ order of oxi- 



Such are the obfervations of this chemift. Other lefs in- 

 terefting fafls will be omitted in the prefent abftrad. 



Experimental 



