Cyanides of the Metals. 59 



cyanogen, and chromo-cyanogen, and afterwards the hydro- 

 genated acids analogous to ferro-hydrocyanic acid, and seve- 

 ral other metallic salts." Here again we have more evidence 

 of the singular confusion with which this subject has become 

 invested. If we are to accept these names for what they ex- 

 press, and as yet we have no reason to do otherwise, we must 

 infer that these metallo-cyanogens are analogous to the ferro- 

 cyanogen ; but this is not the case, for we have just shown 

 that platino-cyanide of potassium is not similar in constitution 

 to the ferro-cyanide of potassium. Meillet then proceeds to 

 say, " that the processes employed by these chemists were 

 somewhat complicated, and they had not continued their ex- 

 periments ;" the method which he employed, he says, "is 

 simple, and there may be procured by it a great number of 

 perfectly definite compounds." The remaintler of the paper 

 is taken up with a brief description of the characteristics of 

 these salts; among others he mentions the auro-, the argento- 

 and the cupro-cyanides of potassium, classifying these under 

 their supposed salt radicles, as auro-cyanogen, argento-cya- 

 nogen, and cupro-cyanogen. It is in the consideration of these 

 various metallic combinations with cyanogen, that we have 

 made the following investigations. Before commencing the 

 detail of these, we must offer a few observations upon the 

 cyanide of potassium as usually prepared, and as employed by 

 Meillet in his experiments. 



5. The cyanide of potassium which is employed by us in 

 our daily operations is prepared according to the process first 

 pointed out by Messrs. F. and E. Rodgers, now generally 

 known by the appellation " Liebig's Process;" from what 

 particular cause it came to be so named we know not, unless 

 it may have been that the publication of this process by Pro- 

 fessor Liebig occurred at a time when the attention of prac- 

 tical and scientific men were more particularly drawn towards 

 an attentive consideration of this compound, from its important 

 applications in chemical analyses, and its extensive employ- 

 ment in the new art of electro-metallurgy. To show, how- 

 ever, that this process was known long before this illustrious 

 chemist pointed it out, we may be allowed to quote the fol- 

 lowing passage from the memoir of Messrs. Rodgers, already 

 mentioned as having been published in the Philosophical Ma- 

 gazine for February 1834. After detailing the various pro- 

 cesses then known, and others which they had discovered, they 

 describe this pi-ocess as follows: — " Cyanuret of potassium 

 may be prepared by exposing a mixture of anhydrous car- 

 bonate of potash and anhydrous ferro-cyanuret of potassium 

 to a moderate red heat, in a covered porcelain crucible, for 

 about twenty minutes." " The proportions employed should 



