Messrs. F. and E. Rodgers on certain Metallic Cyanurets. 93 



one of the bicyanuret of mercury. The sulphurets of potas- 

 sium, sodium, barium and strontium should be prepared for 

 this experiment by heating the anhydrous sulphates to red- 

 ness with half their weight of charcoal ; and the sulphuret of 

 calcium by transmitting a current of sulphuretted hydrogen 

 gas through lime, suspended in recently boiled distilled water 

 previously allowed to cool in close vessels. As the protosul- 

 phuret of magnesium cannot be prepared by heating sulphate 

 of magnesia with charcoal, it must be prepared by transmit- 

 ting sulphuretted hydrogen gas through magnesia suspended in 

 water, or by decomposing the solution of the sulphate of mag- 

 nesia by means of sulphuret of barium. In order to obtain a 

 pure protocyanuret by this process, great care must be taken, 

 otherwise an excess of the alkaline sulphuret will redissolve 

 some of the precipitated bisulphuret of mercury, and an ex- 

 cess of the bicyanuret of mercury would also cause serious 

 mistakes. The proportion of one equivalent of the bicya- 

 nuret to two equivalents of the protosulphuret must be rigidly 

 adopted, and before filtration the solution should be tested 

 to ascertain that it is pure. 



It is not advisable to attempt to crystallize the protocyanu- 

 rets obtained by this process in the open air, owing to the 

 rapid decomposition produced by the carbonic acid existing 

 in the atmosphere, and to the tendency which the cyanurets 

 have to resolve themselves into new compounds. 



All the solutions have an alkaline reaction and evolve the 

 odour of hydrocyanic acid. 



2. The cyanurets of potassium, sodium and magnesium may 

 be readily obtained by decomposing the solution of the cy- 

 anuret of barium by a solution of the sulphates of potash, 

 soda, or magnesia ; for sulphate of baryta is immediately pre- 

 cipitated, and a very pure cyanuret of potassium, sodium, or 

 magnesium remains in solution. Should an easy mode of pre- 

 paring the cyanuret of barium be discovered, this process will 

 probably afford the most easy mode of preparing a solution of 

 the cyanuret of magnesium ; but the solution cannot be eva- 

 porated by the aid of heat without decomposition. 



3. The following process is not applicable to the formation 

 of large quantities of the cyanurets of potassium and sodium ; 

 but it is interesting in a theoretical point of view, being ana- 

 logous to the reduction of chloride of silver by fused earbo- 

 nate of soda. 



On projecting powdered bicyanuret of mercury (dried by 

 a water-bath,) by small portions upon carbonate of potash, 

 heated to a temperature just approaching low redness, the 

 carbonate of potash turns black and enters into a state ol semi- 



