Messrs. F. and E^ Rodgers on certain Metallic Cyanurets. 97 



usually red, but m one experiment, it was quite colotirless. 

 Another solution, prepared by precipitating the acetate of 

 copper by means of cyanuret of potassium, and redissolving 

 the precipitate in an excess of the latter salt, was of a beauti- 

 ful purple tint, similar to the salts of permanganic acid; but 

 this solution was instantly changed to yellow, and finally de- 

 colourized by the application of heat. 



The double cyanuret of copper and potassium, like the c\ r - 

 anuret of potassium, throws down a yellow precipitate from 

 the solution of the protosulphate of copper ; but it is easily di- 

 stinguished by its neutrality, and by causing a white precipi- 

 tate in the solution of the protosulphate of iron, whilst the cy- 

 anuret of potassium throws down an orange precipitate from 

 the same salt. 



Berzelius describes the double cyanuret of copper and lead, 

 on the authority of Ittner, as a green precipitate; but the red 

 solution throws down a French white precipitate from the so- 

 lutions of the acetate and nitrate of lead. From nitrate of 

 silver a white flocculent precipitate, with a slight tinge of pink, 

 is thrown down, which soon changes to lead colour. 



Cuprocyanic acid cannot be prepared by means of tartaric 

 acid, for this acid produces a pink precipitate in the solutions 

 of the double cyanuret of copper and potassium. In that pe- 

 culiar variety of the double cyanuret which forms a colourless 

 solution, tartaric acid produces a white flocculent precipitate. 

 Probably cuprocyanic acid may be prepared by decomposing 

 the double cyanuret of copper and lead by a current of sul- 

 phuretted hydrogen, or the solution of the double cyanuret of 

 copper and barium by dilute sulphuric acid; but the elements 

 of the hydracid do not appear to have much affinity for each 

 other, for although the double cyanuret of copper and barium 

 is not precipitated by ferrocyanuret of potassium, the copper 

 is immediately precipitated if the baryta is thrown down pre- 

 viously by dilute sulphuric acid. The double cyanuret of 

 copper and potassium cannot be generated by fusing metallic 

 copper with carbonate of potash and isinglass. When the 

 heat rises sufficiently high, the copper fuses, but suffers no 

 other change. 



A double cyanuret of zinc and potassium may be prepared 

 by dissolving the hydrated oxide of zinc in a solution of cy- 

 anuret of potassium, and neutralizing the solution by means 

 of hydrocyanic acid. The solution is colourless. It appears 

 that zincocyanic acid may be prepared by adding tartaric acid 

 to the concentrated solution of this salt, for bitartrale of 

 potash is then precipitated. 



A double cyanuret of nickel and potassium may be formed 

 by digesting the hydrated oxide of nickel in a solution of 



Third Scries. Vol. 4. No. 20. Feb. 1834. O 



