580 Transactions . — Chemistry. 



and water are generally acidic, and all the reef quartz I have 

 yet tested also gives an acidic reaction. 



Short Notes on the Cyanodizing of Gold. 



I will now give you a few notes respecting the cyanodizing 

 of gold, &c., in anticipation of papers I am now preparing on 

 the subjects, and I do so merely to secure myself against being 

 forestalled. 



Note 1. 



Very finely granular gold, such as that in these papers, or 

 that prepared and described by Professor Faraday, requires 

 far more time (weight for weight) to dissolve in potassic 

 cyanide than solid gold such as gold leaf, the former taking 

 fully a hundred times longer than the latter, and this though 

 the extent of its superficies is comparatively very much greater. 

 This fact appears to me extraordinary, and leads me to suppose, 

 as the only explanation thereof, that the metal, as it exists in 

 the ruby form on the paper here, is in a different chemical 

 state from that of ordinary or massive gold — that is, this gold 

 is in an allotropic form ; and, after a most careful perusal of 

 Professor Faraday's celebrated Bakerian lecture on " Gold in 

 its Eelation to Light,"-'- I have come to the conclusion that 

 it so well supports this view of the case that I propose at 

 the next meeting of this Society to lay the whole matter (as 

 far as I know it) before you, in a paper to be entitled " Euby 

 Gold : an Allotropic State of the Metal." 



If this theory is incorrect, the only alternative appears to- 

 be one that supposes that solid gold allows of electrical cur- 

 rents being formed, which are helpful towards its dissolu- 

 tion, while tlie other gold is so finely granular as to afford no 

 room for the play of electrical currents localised in its own 

 separate particles. It cannot even conduct electricity. 



Note 2. 



Gold leaf placed upon the surface of a strong cyanide 

 solution is whitened throughout before being all dissolved 

 therein. The white film resulting is only very slowly soluble, 

 but if the solution of the cyanide is weakened a good deal the 

 film rapidly dissolves. This film is a cyanide of gold, and its 

 presence under these circumstances confirms the correctness 

 of a statement of mine that in the cyanide process the 

 cyanodizing of the gold is not always, if indeed it is ever, 

 simultaneous with dissolution — that, in fact, the latter process 

 often lags considerably behind the former process. 



Bakerian Lecture, delivered before the Eoyal Society, 1867. 



