374 Transactions. — Chemistry. 



2iid. The same experiment repeated, but vessel and contents not darkened. 

 Same results as before. 



3rd. Gold solution reduced to half its strength, and time of total deposition 

 extended to four months. Diffused sunlight admitted. 



4th. Soluble organic matter used in place of wood; sunlight excluded. 

 Time of total deposition of gold two months. 



No discernible difference in results upon point in question to those 

 obtained in experiment No. 1. 



So far, therefore, as is shown by these results gold reduced from solution 

 of its chloride by aid of such kinds of organic matter as cork or wood, 

 does not in the manner of its deposition exhibit such a notable selective power 

 for metallic gold as the description of Mr. Daintree's results would lead us to 

 suppose. It does not, indeed, show any such selective process at all, that is 

 to a greater extent than can be attributed to the action of surfaces generally 

 regardless of their nature ; and in sup^^ort of this, I believe I am correct in 

 stating that the whole sum of our experiences (omitting those of Mr. Daintree) 

 is directly against this theory, as to the rapid and marked deposition of gold 

 on gold in the manner stated ; indeed, so far as I am aware, we only produce 

 by these means fine incoherent powder — minute crystals or films of exceeding 

 thinness — nothing nuggetty. We get a certain size of grain or crystal or a 

 certain thickness of film, which our efforts have hitherto failed to enlarge. 



Our experience therefore on this point being in such opposition to that 

 of Mr. Daintree quoted above, and which he quiescently allows to be 

 imputed to him, and the subject itself being a most important one, it does 

 seem that the data upon which these apposite statements are founded should 

 be am]3le, of a definite character, and clearly stated ; but so far it does not 

 appear b}^ any means certain, from all I am able to gather on the subject, 

 whether there was in reality any notable deposition of gold on the undissolved 

 residue of gold, and if so, whether the reduction of this gold was solely effected 

 by agency of organic matter. Thus Mr.- Wilkinson states, " Accidentally some 

 extraneous substance, supposed to be a piece of cork, had fallen into the 

 solution, decomposing and precipitating the gold." Here then we are led to 

 suppose that the vessel containing the solution, etc., was not closed. What, 

 therefore, might not be reasonably supposed to have fallen in besides cork, or 

 any other kind of organic matter? Pyritous dust, or even a small nugget of this 

 substance, might have accidentally fallen in this solution, splintered off from 

 some specimen which perchance Mr. Daintree himself might have been 

 examining ; pyritous matters generally being able, as T have shown, to 

 reduce gold from such solutions, and to deposit it indefinitely upon gold or 

 other electric conductor. Unless precautions had been taken, therefore, to 

 prevent the introduction of reducing agents other than those coming under 



