92 Messrs. F. and E. Rodgers on certain Metallic Cyanurets. 



of the cyanurets of potassium, sodium and barium, is to cal- 

 cine the anhydrous lerrocyanurets in covered porcelain cru- 

 cibles. He gives no process for the preparation of the cya- 

 nuret of strontium ; but he mentions that the cyanurets of 

 calcium and magnesium may be prepared by dissolving the 

 hydrates of lime and magnesia in dilute hydrocyanic acid. 



Thenard mentions two general processes for the prepara- 

 tion of the alkaline cyanurets. He prepares them by saturat- 

 ing the bases with hydrocyanic acid, or by heating the an- 

 hydrous ferrocyanurets to redness in close vessels. 



It is also necessary to state that Dr. Nimmo, in his process 

 for the preparation of hydrocyanic acid, recommends that the 

 cyan met of barium should be prepared by decomposing the 

 solution of the sulphuret of barium by the bicyanuret of mer- 

 cury. 



However, even the cyanuret of potassium was not obtained 

 in a pure form until recently ; for, according to Mr. Laming, 

 the cyanuret obtained by heating the anhydrous ferrocya- 

 nuret of potassium to redness in earthen vessels is always more 

 or less impure. Although this statement does not agree with 

 the experiments of other chemists, it must be admitted that 

 the cyanuret obtained by this process is frequently of a yellow 

 colour, and consequently very impure. In consequence of 

 Mr. Laming's observations, we endeavoured to obtain the 

 cyanuret of potassium by some other process; the results of 

 our experiments on this subject, together with those on some 

 other cyanurets, are contained in the following paper. In all 

 probability these processes cannot be employed to prepare 

 these compounds for commercial purposes, but it may prove 

 useful to state the new modes by which they may be ob- 

 tained. 



1. It is stated in most chemical works that the solution of 

 the sulphuret of potassium is decomposed by the bicyanuret 

 of mercury, cyanuret of potassium remaining in solution, and 

 the cyanuret of barium was obtained by Dr. Nimmo by the 

 analogous process ; but no other protocyanuret has hitherto 

 been obtained by such a process. The following experi- 

 ments show that other cyanurets may be prepared by a similar 

 mode. 



On the addition of the solution of the bicyanuret of mer- 

 cury to a solution of the protosulphuret of potassium, sodium, 

 barium, strontium, calcium, or magnesium, the bisulphuret of 

 mercury is precipitated, and the pure protocyanuret remains 

 in solution. One equivalent of the bisulphuret of mercury, 

 and two equivalents of the protocyanuret, result from the 

 decomposition of two equivalents of the protosulphuret and 



