1821.] the Composition of Prussiates. 305 



We iind again here, as in the barytic salt, that half a propof^ 

 tion of water is wanting, that is to say, that the salt retains one 

 atom of water; and by comparing the loss from the substance* 

 destroyed by heat, with the capacity of saturation of the bases, 

 we also find in this case a surplus corresponding to the quan- 

 tity of water that has disappeared. 



(D.) Salt with Base of Oxide of Lead, 



Neutral nitrate of lead was poured into a solution of ferruginous 

 prussiate of potash, taking care that the latter should be in 

 excess, in order to prevent the precipitation of nitrate of lead, 

 which mixes with all the insoluble salts with base of oxide of 

 lead, if there be an excess of nitrate of lead in the liquid from 

 which they are deposited. The liquid remained perfectly neu- 

 tral. The precipitate was white, but viewed in a certain direc- 

 tion towards the hght, it appeared verging to yellow. I was 

 unable to determine, with the precision I could have wished, the 

 quantity of water contained in this salt, because its point of 

 perfect dryness approaches too near to that at which it begins 

 -to effloresce. However, the results I obtained led me to 

 .Relieve that in this salt, just as in the salt with base of potash, 

 .the water contains the same quantity of oxygen as the two bases 

 together. 



One hundred parts of the salt, dried on a very hot sand-bath, 

 were burned in an open porcelain capsule ; the mass was dis- 

 solved in nitric acid, neutralized with ammonia, and precipitated, 

 by sulphate of ammonia. The sulphate of lead, washed, and 

 <<jalcined at a red heat, weighed 96*5 parts. The filtered liquid 

 rwas precipitated by caustic ammonia, and gave 12*6 parts of 

 oxide of iron. Thus the analysis gave : 



Oxygen. 



Oxide of lead 70*0 containing 5-09 .... 2 



Protoxide of iron 11-9 2-57 .... 1 



Loss 17-7 



We find, therefore, also in thii case, the same relation betweea 

 the oxide of iron and that of lead, as well as between the bases 

 and the substance destroyed by combustion, as in the ferrugi- 

 nous prussiate of potash. 



I think these analyses, selected from the three classes of bases, 

 will suffice to prove that whatever be the state of the iron ia 

 these salts, it takes, in the state of protoxide, half as much oxygen 

 as the 7'adical of the other base, 



II. Experiments on tJie Acid of these Salts, 



The proofs on which Mr. Porrett has founded his opinion, 

 that the iron in the ferruginous hydrocyanic acid is in the metal- 

 Net^ Series, vol. i. u 



