of the Cyanide of Mercury. 12S 



ing the volume of cyanogen given off when it is decomposed 

 by heat. If two atoms of cyanogen he given off, then, from 

 100 grains of the pure dry salt, we should obtain 37.642 inches- 

 of pure gas. 



For 31.5 : Q.5 '. \ 100 : 20.603 grains = 37.642 inches. 



But though the volume of cyanogen given off is pretty 

 uniform, yet it falls very considerably short of this quantity. 



Thus 20 grains gave 6.3 inches — 31.5 from 100 grains. ' 

 23.2 7.08 = 30.5 

 30 9.3 31 

 21.15 Q.5 =: 30.7 

 Mean gas given off by 100 grains • 



cyanide =: 30.92 inches. * 



And 37.642 — 30.9'^ =6.722 inches of deficiency. That 

 is, more than a fifth part of the whole cyanogen remains in the 

 tube. Now, as the whole cyanide is decomposed, and there 

 remains in the tube only a charcoal looking substance, either 

 the salt is not a bi-cyanide, or the elements of the cyanogen 

 deficient must be contained in the black substance that re- 

 mains behind. To determine this, what remained in the tube 

 was detonated as above with chlorate of potash, and gave from 

 the first three 



In the two former of these results the azote is more than 

 half of the carbonic acid ; in the third it is exactly one-half, as 

 the results of many other experiments on this substance show 

 that it should be. 



Add the equivalent cyanogen in the third column to that 

 already obtained by heat in these three cases, and we have 



Cyanogen. Its elements. Sum. Atomic proportion. 

 20 grains gave 6-3 inches 1.6 7.9 6.93 



23.2 7.08 1.5 8.58 6.36 



SO 9.3 2.29 11.59 6.74 



Mean atomic proportion, 6.676 



