Skey. — On Cyanogen. 577 



paper referred to was read I learned that Mr. Park, late 

 Lecturer at the Thames School of Mines, had made a series 

 of valuable experiments on the subject, in which he used 

 the gravimetric method for determining whether there was 

 not a dissolution of gold by aqueous solution of this gas. 



The results of these experiments do not confirm the 

 correctness of this statement of mine (that cyanogen is unable 

 to dissolve gold), but, still, they clearly show that, at least, 

 solutions of this gas do not dissolve this metal at all readily. 

 Mr. Park informs us that he performed his experiments with 

 a button of pure "parted" gold gently hammered to a coherent 

 spongy mass of about lin. in diameter, and weighing 0-340 grain. 

 This button was placed in an aqueous solution of cyanogen 

 and the containing vessel loosely covered. Upon again weigh- 

 ing this button, at intervals of twenty-four hours, he found 

 there was generally a loss of about -g^^ of its weight at every 

 weighing— that, in fact, about i^Va§^- °^ g°^*^ dissolved per 

 diem. 



This does not appear to be a great loss ; still, it is very 

 much more than I should have anticipated, but, knowing that 

 the most recent works on chemistry to hand in the colony 

 decide that cyanogen in water alone does not decompose to 

 substances solvent of gold, this scientist could not support my 

 contention as he desired to do. 



It was this unsatisfactory state of the case that induced 

 me to make further researches in the matter. Now, as you 

 are aware, cyanogen is a substance that in the presence of 

 even minute traces of ammonia or potash is decomposed to 

 form alkahne cyanides which are solvent of gold, and when 

 once this action starts it proceeds with ever-increasing rapidity. 

 The atmosphere of a laboratory in full operation is frequently 

 alkaline ; the vessels used for receptacles in chemical work 

 are capable of yielding alkaline matter to cyanide solutions. 

 For these reasons any experimental results obtained in a 

 laboratory are likely to be misleading. 



It is evident, therefore, that any method which requires 

 considerable periods of time, such as the gravimetric method 

 does, is not well adapted for this kind of research ; one is 

 required that will speedily give reliable results. Eschewing, 

 therefore, the use of even the hypothetical just balance as an 

 abomination in this case, I adhered to my old method, which 

 is that of testing by sight alone whether any loss of gold does 

 occur by the action of free cyanogen. For this I merely 

 replaced the gold leaf of my former experiments by gold 

 paper, which is a Swedish filter-paper, in which gold has 

 been chemically precipitated in a very finely-divided state. 

 A sample of this test-paper is tabled here for exhibition, 

 and the red tint of its gold is easily perceptible in this paper, 

 37 



