

1823.] Vegetable and Animal Substances. 355 



" In the first place, the prime equivalent of the crystallized 

 ferroprussiate of potash is 13-125, compared to oxide of lead 14, 

 and to nitrate of the same metal 20-75 ; that is, 13-125 of the 

 former salt neutralize 20*75 of the latter. In the second place, 

 14 parts of oxide of lead yield 21 parts of dry ferroprussiate of 

 lead ; or the atomic weight of dry ferroprussic acid is 7. 



" The mean of my analyses of ferroprussiate of lead gives the 

 relation of the constituents of the acid, as marked in the table. 

 These proportions, reduced to the atomic weight 7, afford 



Carbon 2-5774 



Azote 2-4703 



Ferreous matter 1-9523 



7-0000 



" Were we to suppose the prime equivalent of the ferroprussic 

 acid 7*5 instead of 7 ; and were we further to suppose that the 

 carbon in the above result should be 2-25 = 3 atoms, and the 

 azote = 3-5, or 2 atoms, then we might conceive an atom of dry 

 ferroprussic acid to be made up of 



Carbon 3 atoms 2-25 



Azote 2 3-50 



Iron 1 1-75 



7-50 



" But experiment does not permit me to adopt this theoretical 

 representation. 



" The best mode that has occurred to me for analyzing ferro- 

 prussiate of potash, is to convert it, by the equivalent quantity of 

 nitrate of lead, into the ferroprussiate of this metal ; then to 

 separate the nitrate of potash by filtration • and, after evapora- 

 tion, to determine its weight. In this way, 13-125 grains of 

 crystallized ferroprussiate of potash afford 12-33 grains of nitre, 

 which contain 5-8 of potash.* By heating nitric acid in excess 

 on 21 grains of ferroprussiate of lead, I obtained 2-625 grains of 

 peroxide of iron, equivalent to 1-8375 of the metal. Hence I 

 infer, that the iron in the ferroprussiate of lead is in the metallic 

 state ; for the joint weights of the carbon and azote contained in 

 7 grains of the dry acid is 5-0477 ; and the difference, 1*9523, 

 approaches too closely to the above quantity, 1-8375, for us to 

 suppose the metal to be in the state of protoxide. In fact, 2-625 

 parts of peroxide x 0-9 = 2-3625 of protoxide, is a quantity 

 much beyond what experiment shows to be present." 



* " By careful desiccation, 1 -69 grain of water may be separated from 13-125 grains 

 of the salt." 



2a2 



