100 Messrs. F. and E. Rodgers on certain Metallic Cyanarets. 



by adding a solution of persulphate of iron and sulphate of 

 potash to a solution of the cyanuret of barium. 



The double cyanuret of copper and barium may be formed 

 by adding a solution of sulphate of copper to cyanuret of 

 barium. The presence of copper in the solution cannot be 

 detected until it is digested with a little sulphuric acid; after 

 filtration, the copper may be precipitated by ferrocyanate of 

 potash. When a double cyanuret is prepared, by decom- 

 posing cyanuret of barium by a soluble sulphate, it is abso- 

 lutely necessary to add the solution of the sulphate to that of 

 the cyanuret. It appears that a metallic cyanuret and sulphate 

 of baryta are generated ; the former then unites with an ex- 

 cess of cyanuret of barium, and the latter is precipitated. On 

 the addition of a fresh portion of the sulphate, the hydracid 

 is precipitated in combination with the oxide, or the base of 

 the hydracid in combination with the metal. 



9. For experiment, the solutions of the double cyanurets 

 may be readily prepared by the following process, which is a 

 mere modification of that recommended in the work of Ber- 

 zelius, who recommends the cyanurets to be precipitated, 

 washed, and then dissolved in a solution of cyanuret of potas- 

 sium. During this process certain cyanurets — for example, 

 copper — appear to undergo some change. 



It is better, therefore, to precipitate sulphate of copper by 

 means of cyanuret of potassium, and immediately redissolve 

 the precipitate by an additional quantity of cyanuret of potas- 

 sium. The solution thus obtained has a yellow colour, simi- 

 lar to the solution described by Ittner: it is quite neutral. 



A double cyanuret of cobalt and potassium may be prepared 

 by precipitating the nitrate of cobalt by means of cyanuret of 

 potassium, and dissolving the precipitate as before. 



A double cyanuret of nickel and -potassium may be obtained 

 by decomposing sulphate of nickel in a similar way: the solu- 

 tion is yellow. 



If required, the double cyanurets may be separated from 

 the sulphate of potash by evaporation and crystallization. 



10. The experiments mentioned in this paper have as yet 

 entirely related to the alkaline and double cyanurets; but the 

 following facts seem to be worth recording, although they re- 

 fer to the pure cyanurets of the common metals, which are 

 much better known. 



The protocyanuret of lead may be readily thrown down as 

 a dense, white precipitate, from the solution of the acetate, by 

 means of hydrocyanic acid. It is soluble in nitric acid. Hot 

 water changes the white colour of the cyanuret to a faint 



