422 On the Experimental Relations [1857. 



produce the change, but show no tendency to dissolve the gold. 

 Nitric acid acts in the same manner, but not so strongly : it 

 often causes re-solution of the gold after some time, because of 

 the hydrochloric acid which remains in the fluid. 



Amongst the alkalies, potash produces a similar action in a 

 weak degree. So also does soda. Lime-water produces a 

 change in the same direction, but the gold quickly precipitates 

 associated with the lime. 



Ammonia causes the ruby fluid to assume a violet tint; the 

 deposit is slow of formation and often ruby in colour ; the alkali 

 apparently retards the action of common salt. 



Chlorine or nitromuriatic acid turns the ruby fluid blue or 

 violet-blue before they dissolve the gold. 



Solution of sulphuretted hydrogen changes the ruby slowly 

 to purple, and finally to deep blue. Ether, alcohol, camphine, 

 sulphide of carbon, gum, sugar and glycerine cause little or no 

 change in the fluids ; but glycerine added to the dense deposits 

 causes serious condensation and alteration of them, so that it 

 could not be employed as a medium for the suspension of par- 

 ticles in the microscope. 



All endeavours to convert the violet gold back into ruby 

 were either failures, or very imperfect in their results. A violet 

 fluid will, upon long standing, yield a deposit and a supernatant 

 ruby fluid, but this I believe to be a partial separation of a 

 mixture of violet and ruby gold, by the settlement of the blue 

 or violet gold from ruby gold, which remains longer in suspen- 

 sion. Mucus, which often forms in portions of these fluids 

 that have been exposed to the air, appears sometimes to render 

 a fluid more ruby, but this it does by gathering up the larger 

 violet particles ; it often becomes dark blue or even black by 

 the particles of gold adhering to it, many of which maybe shaken 

 out by agitation in water ; but I never saw it become ruby- 

 coloured as a filter can, and I think that in these cases it is the 

 gathering out of the blue or violet particles which makes the 

 fluid left appear more ruby in tint. I have treated blue or violet 

 fluid with phosphorus in various ways, but saw no appearance 

 of a return in any degree towards ruby. Sometimes the fluids 

 possess a tendency to re-solution of the gold, a condition which 

 may often be given by addition of a very little nitric acid, but 

 in these cases the gold does not become ruby before solution. 



