158 Intelligence and Miscellaneous Articles. 



Auro-cyanogen. Auro-cyanide of Potassium. — This salt is obtained 

 by adding a perfectly neutral and saturated solution of chloride of 

 gold to cyanide of potassium. On evaporation and on the cooling of 

 the solution, the salt crystallizes in very white scales, of a pearly 

 lustre ; the chloride of potassium and the excess of cyanide of potas- 

 sium remain in solution. This salt gilds much better than those 

 now employed in the arts. 



Platino-cyanogen. Platino-cyunide of Potassium. — Dcebereiner, 

 who discovered this body, prepares it by heating to redness a mixture 

 of equal parts of spongy platina and ferrocyanide of potassium. 

 The residual mass is to be washed, and the undecomposed ferro- 

 cyanide is to be obtained first by crystallization, and afterwards the 

 platino-cyanide remaining in the solution, crystallizes when that is 

 concentrated. This process is a long one, and it is difficult to pro- 

 cure a pure salt. M. Meillet prepares it by adding concentrated 

 chloride of platina to a saturated solution of cyanide of potassium ; 

 there is immediately formed a precipitate of chloride of platina and 

 potassium mixed with cyanide ; it is to be heated to ebullition, and 

 then it redissolves with strong effervescence and disengagement of 

 carbonate of ammonia. It may be supposed that, in this case, the 

 cyanide of platina which is formed reacts like an acid on the atom of 

 cyanate of potash (always contained in this cyanide of potassium), 

 and sets free cyanic acid, which, by absorbing three atoms of water, is 

 converted into bicarbonate of ammonia. Cyanic acid being C 2 Az q O, 

 with three atoms of water H 6 3 , there will be formed an atom of 

 bicarbonate of ammonia, C 2 O 4 , Az 2 H 6 . 



After the complete solution of the precipitate, the platino-cyanide 

 of potassium crystallizes in blue needles, which are variegated by re- 

 flected and yellow by transmitted light. 



Cupro -cyanogen. Cuprocyanide of Potassium. — This is prepared 

 by dissolving either cyanide of copper, or carbonate of copper with 

 heat in cyanide of potassium and evaporation ; on cooling the salt 

 crystallizes in fine white needles. When, after having poured very 

 concentrated hydrocyanic acid on hydrate of barytes, carbonate of 

 copper is added, it dissolves with strong effervescence, and the 

 liquor assumes a carmine-red tint of extraordinary intensity. On 

 rapidly evaporating the solution, it is gradually decolorated, so per- 

 fectly indeed, that on treating the residue with cold water, cupro- 

 cyanide of barium is obtained entirely colourless ; the cause of this 

 colour was found to be derived from the formation of a considerable 

 quantity of murexide or purpurate of ammonia; M. Meillet endea- 

 voured, but unsuccessfully, to explain the reaction to which its 

 formation was owing, seeing that this body contains a large quantity 

 of hydrogen. Once or twice he found some rudiments of crystals 

 spontaneously formed, which had the colour of cantharides wings, 

 a tint which sufficiently characterizes it. This solution of cupro- 

 cyanide of barium, evaporated to dryness, moderately heated, and 

 then treated with water, leaves a residue of carbonate of barytes. 

 On adding a dilute acid, as the hydrochloric, to the cupro-hydrocya- 

 nate and purpurate of barytes, purpurate of copper is precipitated, 

 hydrocyanic acid is evolved, and hydrochlorate of barytes only re- 



