Mr. Kemp's new Process for preparing Cyanogen. 1 79 



very generally, for I would not trust to my recollection, and 

 would have you, if you wish for perfect accuracy, to refer to 

 the India House for a detailed account of what passed be- 

 tween you and the Government of India on the subject of 

 lightning-conductors. 



" I am however certain that there was no question or order 

 on the * removal' of lightning rods. The proposition dis- 

 cussed was one for erection of lightning-conductors for the 

 safety of all powder magazines ; such magazines having 

 hitherto been thought secure from accident without them. 

 And upon this questions arose, — 1st, as to the necessity of 

 such erections ; and 2ndly, if erected, as to what should be 

 the form and size and distance from each other, and from the 

 magazine, of the conductors. I think that your reasonings 

 upon the danger of small conductors placed very near to a 

 hazardous building was very generally admitted to be con- 

 vincing. In the end, as it were necessary that the rods, if con- 

 structed, should be made in England, it was thought best to 

 refer the whole question to the authorities at home. 



"Very faithfully yours, 

 (Signed) " Auckland." 



« To Dr. W. B. O'Shaughnessy." 



O 



XXIII. A new Process for preparing Cyanogen. 

 By Alexander Kemp, Esq.* 



N mixing together cyanide of potassium and bichloride of 

 mercury, both in powder, and leaving them for a few 

 days, I observed that the mixture became of a greenish colour, 

 which at first led me to suspect the presence of iron in the 

 bichloride of mercury ; but as I failed in detecting it, I next 

 proceeded to make a few experiments with the substances, the 

 result of which was, that I found that cyanogen might be 

 more easily and ceconomically obtained by the following me- 

 thod, than by any of the usual processes. 



Take six parts perfectly dry ferrocyanide of potassium, and 

 nine parts bichloride of mercury, both in fine powder, and 

 mix them intimately together, then apply heat to the mixture, 

 in a glass retort, when cyanogen gas will be disengaged, mer- 

 cury at the same time distils over, and a dark-coloured matter 

 is left in the retort, being a mixture of chloride of potassium 

 and cyanide of iron. 



University of Edinburgh, Aug. 11, 1843. ALEX. Kemp. 



* Communicated by the Author. 



N2 



