430 On the Experimental Relations [1857. 



the result. Yet with gold thus proved to he metallic, colours 

 including grey, grey-violet, green, purple, ruby, especially by 

 heat, and green again by pressure, and by thinning of grey 

 films, may be obtained by transmitted light, almost all of them 

 at pleasure. 



It may be thought that the fluid preparations present more 

 difficulty to the admission, that they are simply cases of pure 

 gold in a divided state ; yet I have come to that conclusion, 

 and believe that the differently -coloured fluids and particles 

 are quite analogous to those that occur in the deflagrations 

 and the films. In the first place they are produced as the 

 films are, except that the particles are separated under the 

 surface and out of the contact of the air ; still, when produced 

 in sufficient quantity against the side of the containing vessel 

 to form an adhering film, that film has every character of lustre, 

 colour, &c. in the parts differing in thickness, that a film formed 

 at the surface has. Whilst the particles are diffused through 

 the fluid it is difficult to deal with them by tests and reagents ; 

 for their absolute quantity is very small, and their physical cha- 

 racters are very changeable, chiefly as I believe by aggregation ; 

 still there are some expedients which enable one to submit 

 even the finest of them to proof. In several cases particles 

 from ruby and amethystine fluids adhere to the sides of the 

 bottles or flasks in which the fluids had been preserved, and 

 the process of boiling seemed to favour such a result; the 

 adhesion was so strong, that when the fluid contents were re- 

 moved and the bottles well-washed, the glass remained tinged 

 of a ruby or of a violet colour. These films, in which the fine 

 particles were fixed mechanically apart and in place, were then 

 submitted to the action of various chemical agents. Drying 

 and access of air did not cause any marked alterations in them. 

 Strong nitric acid produced no change, nor hydrochloric acid, 

 nor sulphuric acid. Neither did a solution of chloride of so- 

 dium, even up to brine, cause any alteration in the colour or 

 any other character of the deposit. A little solution of chlo- 

 rine or of nitromuriatic acid dissolved them at once, producing 

 the ordinary solutions of gold. I can see no other mode of 

 accounting for these effects (which are in strong contrast with 

 what happens when ruby fluid is acted on by these agents), 

 than to suppose that the gold particles, being in a high state 



