432 On the Experimental Relations [1857. 



exists in the ruby, amethystine, violet, and other coloured 

 fluids. 



The production by such different agents as phosphorus, 

 sulphide of carbon, ether, sugar, glycerine, gelatine, tartaric 

 acid, protosulphate of iron and protochloride of tin, of gold 

 fluids all more or less red or ruby at the commencement, and all 

 passing through the same order of changes, is again a proof 

 that only gold was separated ; no single one or common com- 

 pound of gold, as an oxide or a phosphide, could be expected 

 in all these cases. Many of the processes, very different as to 

 the substances employed to reduce the gold, left good ruby 

 films adhering to the glass vessels used, presenting all the 

 characters of the gold described already : this was the case 

 with phosphorus, sugar, tartaric acid, protosulphate of iron, 

 and some other bodies. 



Again, the high reflective power of these particles (unalter- 

 able by acids and salts), when illuminated by the sun's rays and 

 a lens, and the colour of the light reflected, is in favour of 

 their metallic character. So also is their aggregation, and 

 their refusal to return from blue, violet or amethystine to 

 ruby ; for the cohesive and adhering force of the gold particles 

 and their metallic nature and perfect cleanliness is against 

 such a reverse change. Particles transmitting blue light could 

 be obtained in such quantity as to admit of their being washed 

 and dried in a tube, and being so prepared they presented 

 every character of gold : when heated, no oxygen, water, phos- 

 phorus, acid of phosphorus, nor any other substance was 

 evolved from them : they changed a little, as the film when 

 heated changed, becoming more reflective and of a pale brown 

 colour, and contracted into aggregated porous masses of pure 

 ordinary gold. 



Gold is reduced from its solution by organic tissues ; and 

 stained gut has been quoted as a case. I have a very fine 

 specimen which by transmitted light is as pure a ruby as gold- 

 stained glass, and I believe that the gold has been simply re- 

 duced and diffused through the tissue. The preparation 

 stood all the trials that had been applied to the ruby films on 

 glass or the gold deposit on filtering-paper. Portions of it 

 remained soaking in water, solution of chloride of sodium and 

 dilute sulphuric acid for weeks, but these caused no change 



