188 Proceediugs of the Royal Irish Academy. 



This red or pui'ple combination appearing to be bnt little affected 

 by many of the metallic salts, seems to strengthen the view I haye 

 taken as to its nature, for had it been a peculiar cyanogen compound, 

 such as we have in the case of the ferro-, ferri-, and nitroferri-cyano- 

 gen, as well as in other compound salt radicals of that substance, we 

 should have expected that it would have produced very characteristic 

 effects with different metallic salts. 



I may further observe that the same compound is formed when the 

 ferricyanide of potassium (or as it is better known under the name of 

 red prussiate of potash), instead of the ferrocyanide of potassium (the 

 yellow prussiate), in aqueous solution is heated along with the fulmi- 

 nate of mercury, and that it, as well as the ferrocyanide, even without 

 the application of heat, give rise to, but more slowly, the formation of 

 the red or purple combination, the femcyanide acting, however, in 

 this respect more readily than the ferrocyanide. 



Lastly, I may add that I found that a similar purple compound 

 was produced when the fulminate of silver was substituted for the 

 mercurial salt in the reactions referred to, and it is probable that some, 

 at least, of the other fulminates would give rise to like effects. 



I regret that the results which I have brought before the Academy 

 are not, in some respects, of a more definite character ; but all who 

 have experimented on the fulminates have experienced the great diffi- 

 culties of such inquiries, arising from their instability and complexity 

 of constitution ; but I hope before long to be able to investigate more 

 fully the subjects of this communication, as well as other matters bearing 

 on them. I trust, however, that the results of the observations which 

 I have ali'eady made may not be considered as devoid of interest, as 

 any facts which may extend our knowledge of fulminic acid, a com- 

 pound regarding the true nature of which chemists are not yet agreed, 

 must possess more or less interest in a scientific point of view ; and it 

 is well known that many facts and observations which at first have 

 been regarded as mere matters of interest to men of science have after- 

 wards proved of much practical utility. 



