PRUSSIC ACID. 281j 



Being thus perfuaded that a lefs quantity of blood was not Blood and alkali, 

 more advantageous for forming pure pruffiate of potafli, I !^Jilnenr Lon*I 

 again mingled two ounces of dried blood with one of carbon- ly ignited for 

 ate of potafti : this mixture was treated as before, with the ^'^'Kr^"^ °^ 

 exception that the mafs, after the flame had entirely difap- 

 peared, was ftrongly ignited for three quarters of an hour. 

 The obtained mafs, after refrigeration, weighed nine drachms. 

 Digefted cold with four ounces of water, and filtered and 

 evaporated, it afforded a dark coloured fluid. On dropping The fluid of fo- 

 into a confiderable quantity of muriatic acid, no blue, but a ^"^^°" ^^.^ ^}^* 

 white precipitate fell down, which was infoluble in muriatic fome iron, 

 acid : Acetic acid occafioned no change in this dark-coloured '^oug^i very- 

 fluid ; and on mingling it with fulphuric acid, and evapo- 

 rating the mixture to drynefs, and re-diffolving the mafs in • - 

 water, it yielded a fmall quantity of pruflian blue ; a proof 

 that iron was prefent in this fluid. 



The quantity of iron being very fmall, but the colour of 

 the fluid very dark when compared with thofe of the former 

 procefl^es, it was natural to fuppofe, that the colouring- 

 malter could not be attributed to the minute quantity of iron 

 prefent, but that perhaps a portion of charcoal was diflTolved 

 in the fluid : to invefl:igate which the following experiments 

 were inftituted : 



A like quantity and like proportions of blood and carbonate Repetition of the 

 of potafli, asftatedlaft, were gradually heated to incandef-^XnT/thr'^ 

 cence, and the fire gradually augmented, until the mafs began la^k, 

 to fu/e on the fides of the crucible. The mafs, after having , 

 been diffiifed through water and filtered, yielded a much 

 darker-coloured fluid, which, when mingled with muriatic 

 acid, yielded a pearl-coloured precipitate. After being mixt 

 with muriatic or fulphuric acid, evaporated and rediflblved 

 in water, it afforded a confiderable quantity of oxide of iron; 

 a' proof that the union of the pruflic acid with potafli is perraa- The pruflic acid 



nent at very high temperatures, but that this combination, ''^."f^"f "'"^^<* 



n T n rt- 1 with alk. at very 



under fuch circumftances, exerciles a ftrong action upon the high temp, and 



oxide of iron contained in the blood. Jf^" '^on 



Thefe fads were proved by repeating this experiment,. but Lefs oxide taken 



taking care to expofe the mafs to a fomewhat lefs degree ofup by lefs heat. 



heat. The fluid now obtained was lefs coloured, and yielded 



lefs oxide of iron. 



This 



