5s6 Mr. PoRRETT on the nature of the Salts 
grains of ferruretted chyazate of potash to a solution of iron ; 
now by my analysis of this salt, it appears that the quantity 
of acid in these 1 12 grains is 53.38 grains, the whole of which 
acid enters into the composition of the 100 grains of blue pre- 
cipitate. 
B. 124 grains of crystallized green sulphate of iron being 
dissolved in water, there was required to precipitate all the 
oxide of iron from it, a solution containing 112 grains of crys- 
tallized ferruretted chyazate of potash ; now 124 grains of 
crystallized green sulphate contain, according to Berzelius, 
31.44 grains of protoxide of iron, but as this iron is in the 
state of per-oxide in Prussian blue, it must- be reckoned as 35 
grains. 
C. Proust has stated that the quantity of per-oxide of iron 
procured by calcining 100 grains of Prussian blue is 55 grains, 
I have repeated this experiment and obtained the same result; 
of these 55 grains, 2 1.53 grains must have been derived from 
the 53.38 grains of acid in the Prussian blue (see Exp. A), 
in which they existed as black oxide, weighing only 19.33 
grains. 
D. I attempted to obtain by distillation the water that is 
contained in Prussian blue, that had been dried as much as 
possible at 212° by heating 100 grains of it at the temperature 
of melting tin in a small retort adapted to a receiver contain- 
ing fused muriate of lime, the retort and the receiver with 
their contents being separately weighed, both before and aher 
the experiment ; but I found that only an approximation to 
the truth could be gained by this method, as the water that 
came over held prussiate of ammcnia in solution, and as some 
of the same prussiate escaped as gas : after the experiment 
