PIIUSS1C ACID. 3$ 



1 . That four parts of blood to one of carbonate of potafii are Beft proportion 

 too much, and that equal parts of blood and carbonate of potafli ^"^ ^^rkd 

 are rather good proportions for obtaining the moff. poffible blood, are i p. 

 quantity of pruffiated alkali. The latter proportions have f andab ' 

 moreover, the difadvantage, that the excefs of alkalis ads 



upon the oxide of iron of the blood as well as upon the cru- 

 cible, and therefore introduces new impurities. Two parts 

 of blood and one of carbonate of potafh, appear to be a 

 belter proportion for obtaining the greatefr. poffible quantity 

 of pruffiate of potafli, under like circumftances. 



2. Alcalies deprived of carbonic acid, are not better than It is no advan- 

 carbonated alkalies for the production of pruffiated a !k a ' ies p^VaUcalL* 

 by treatment with blood ; for they become reconverted into 

 carbonated alkalies during the procefs. 



3. No pure pruffiate of potafli can be obtained, except care The formation 

 be taken that the mixture of blood and alkali be neither too * P ure P' uffiate 



requires a gra- 



much nor too little ignited. The criterion which may fervedual heat ith- 



as a guide to the operator, is the ceflation of the flame, after ouC . fufion, 1 and 

 j ii . >..... . no longer than 



a gradually increafed ignition without fufion. For if the mafc till the flame 



be heated fuddenly fo as to effeft a partial fufion, or if it be ceafes * 



continued after the difappearance of the flame, it will be in 



vain to look for pure pruffiated alkali. 



4. The high colour of prufliated alkalis is not always owing When the high 



to the prefence of iron, but more frequently to a minute co .? ur ° p ' , * 

 r \ ^ J antes from char- 



quantity of charcoal. This impurity is not capable of yielding coal, it does not 

 refults that could miflead the chemical enquirer in the app!i-P roduce faliac y« 

 cation of this re-agent. 



5. The quantity of water employed for the lixiviation of Very little water 



pruffiated alkali from the ignited mafs, fhould be as fmall as ,h ° u | d be " k *» 

 -» . and " eat avoid- 



poffibfe, and heat fhould be avoided as much as poffible. For e d. 



if pruffiated alkalis be heated in contact with water, part of 

 the pruffic acid is liberated, ammonia is produced, and car- 

 bonate of potafli formed. 



6. Acetic acid cannot be employed for removing the ad- Acetic acid can- 

 mixture of carbonate of potafli from pruffiated alkalis; for the take cff ^ re _ 

 energy of the affinity of pruffic acid is lefs than the energy of dundant poufh. 

 the affinity of carbonic acid to potafli ; the union of the pruffic 



acid and potafh is therefore demoliftied, in preference to that 

 of the carbonate of potafli. 



Vol. X.— January, 1805. D On 



