"iSoith Cyanide of Mercury. 129 



23*5 grains corresponding to 58*75 per cent, containing 50*13 

 mercury, equivalent to 63*05 of cyanide. 



The liquor from which the mercury had been thus sepa- 

 rated, was evaporated carefully to dryness, and the salt ob- 

 tained was deprived of all water of crystallization by exposure 

 to a temperature of 300°, until it ceased to lose weight. It 

 then weighed 31*32. It was pure dry ferrocyanide of potas- 

 sium. 



A quantity of the new salt equal to 50*4< grains was ig- 

 nited and icinerated; the residue then treated by muriatic 

 acid, and the iron thrown down by ammonia added in excess. 

 The oxide of iron weighed contained 2*23 of metallic iron, 

 corresponding to 4*47 per cent. 



The liquor after the separation of the iron was evaporated 

 to dryness, and ignited ; there remained chloride of potassium, 

 equal to 12*3, containing 6*51 potassium or 12*91 per cent. 



This new salt, therefore, contained 



Mercury 50*13 



Iron 4*4!7 



Potassium 12*91 



Water 5*78 



Loss and cyanogen 26*71 



100*00 



The relation is exactly such that the mercury employs 

 half of the cyanogen to form cyanide of mercury, and the re- 

 maining half forms with the potassium and the iron common 

 ferrocyanide of potassium : the result as calculated should be 



3 atoms mercury 304*2 50*26 



2 potassium 79*4 13*11 



1 ■ iron 28*0 4*62 



6 cyanogen 157*8 26*07 



4 water 36*0 5*94 



605-4 100*00 



The existence of this salt is of considerable practical im- 

 portance, as it shows the necessity of avoiding any excess of 

 ferrocyanide of potassium in preparing cyanide of mercury; 

 an error into which, from motives of ceconomy, the manu- 

 facturing operator would be peculiarly liable to fall. 



23, Gloucester Street, Dublin, Dec. 23, 1839, 



Phil. Mag. S. 3. Vol. 16. No, 101. Feb. 1840. K 



