1821.] Prof, Berzeliuson the Composition of Prussiates. 433 



ing silver-plated goods, that it is generally Ksed for that purpose 

 in those silver manufactories where it is introduced. 



I hope this explanation will convince your readers that my 

 first statement was not so incorrect as Mr. R. wished to make it 

 appear. I remain, yours respectfully, 



A Subscriber. 



AUTICLE VII. 



Researches on the Composition of the Prussiates^ or ferruginous 

 Hydrocyanates. By J. Berzehus. 



{Continued from 2^' 308.) 



In order to examine whether, in these experiments, the 

 remaining bases be in the state of common carbonate, I heated a 

 mixture of carbonate of potash with six times its weight of oxide^ 

 of copper in a proper apparatus for receiving tlie gas that might 

 be disengaged. As soon as the mixture had acquired a red heat, 

 carbonic acid gas began to be given oif, and continued for more 

 than half an hour. Thus the oxide of copper has the property of 

 expelhng the carbonic acid at a high temperature, and of forming 

 a kind of double salt, in which it is to be presumed that one-fourth 

 of the potash is combined with the oxide of copper, and three- 

 fourths with the carbonic acid. This salt is decomposed in the 

 humid way, the water seizes a mixture of caustic potash, and 

 carbonate of potash, and the oxide of copper remains undissolved. 

 This last phenomenon also ensues when oxide of copper is dis- 

 solved in hydrate of potash by igneous fusion. The compound, 

 which in the liquid state is transparent, and of a yellow colour, 

 is decomposed by water, which takes the potash, without, at the 

 same time, dissolving the oxide of copper, with which it was 

 combined. 



It was necessary, therefore, in order to obtain a more decisive 

 result, to analyze a ferruginous prussiate whose base is incapable 

 of retaining the carbonic acid, and 1 chose for this purpose that 

 oflead. 



12*35 grains of prussiate oflead were mixed with 308*8 grains 

 of oxide of copper obtained by calcining copper in a cupel- 

 ling furnace. The gas was collected aver mercury in a 

 fraduated receiver, in which it could be accurately measured, 

 o determine with the greatest" possible accuracy the relative 

 volume of carbonic acid gas to that of the azote, a portion of the 

 gas collected towards the end of the operation, and consequently 

 free from atmospheric air, was examined separately ; 13U mea- 



New Series, vol. i. 2 e 



