of the Cyanide of Mercury. 'VSHX 



with chlorate of potash, they detonate by heat, by friction, and 

 in some cases by percussion. The sulpho-cyanide of potas- 

 sium rubbed in a mortar in this way detonates with a purple 

 flash, and with much greater ease and violence than sulphur 

 in the same circumstances. The same salt, the crystallized 

 ferro-cyanic acid, and the acid of the red ferro-cyanides mixed 

 with chlorate, detonate under the hammer, while all the salts 

 of cyanogen, excepting the oxy-cyanides of Wohler, explode 

 by a very gentle heat, or by merely scraping together the parts 

 of the powder in a glass mortar with the broken end of a glass 

 rod. The exception of the oxy-cyanates shows that it is the 

 affinity of the carbon for oxygen which determines these rapid 

 decompositions. If the parts of the powder be separated by 

 a sufficient admixture of pounded glass, the decomposition 

 may be so regulated as to admit of the gaseous products being 

 collected with pej-fect precision. In the following experiments 

 the mixture was introduced into a glass tube of from three to 

 five-tenths of an inch in diameter, connected by a small bent 

 tube with the mercurial trough. The flame of a spirit lamp 

 was then applied for a short time to the extremity of the pow- 

 der nearest the open end of the tube. It speedily ignited, 

 when, the lamp being removed, the ignition and decomposition 

 proceeded gradually along the tube till it reached the sealed 

 end, when gas ceased to be given off". The flame of the lamp 

 was now passed along the tube to insure the entire decompo- 

 sition of the whole substance operated upon. 



This mode of analysis is peculiarly elegant, and, from the 

 little heat required and the very short time necessary to per- 

 form an experiment, is admirably adapted for public exhibition. 

 The following results show that it admits also of nearly as 

 much accuracy as the other methods. 



Mixed with an equal weight of chlorate of potash and 50 

 grains of pounded glass, five grains of cyanide in four experi- 

 ments gave 



considered them to be chloro ferro-cyanides, and as such have described 

 some of their properties in a short paper inserted in the last Fasciculus of 

 the Edinburgh Transactions* 



