420 On the Experimental Relations [1857. 



fluid ; in a few moments the fluid will become blue or violet- 

 blue, and sometimes almost colourless : by mingling up the 

 neighbouring parts of the fluid, it will be seen how large a 

 portion of it can be affected by a small quantity of the salt. 

 By leaving the whole quiet, it will be found that the changed 

 gold tends to deposit far more readily than when in the ruby 

 state. If the experiment be made with a body of fluid in a 

 glass, twelve or twenty-four hours will suffice to separate gold, 

 which in the ruby state has remained suspended for six months. 



The fluid changed by common salt or otherwise, when most 

 altered, is of a violet-blue, or deep blue. Any tint, however, 

 between this and the ruby may be obtained, and, as it appears 

 to me, in either of two ways ; for the intermediate fluid may 

 be a mixture of ruby and violet fluids, or, as is often the case, 

 all the gold in the fluid may be in the state producing the 

 intermediate colour ; but as the fluid may in all cases be carried 

 on to the final violet-blue state, I will, for brevity sake, describe 

 that only in a particular manner. The violet or blue fluid, 

 when examined by the sun's rays and a lens, always gives evi- 

 dence showing that the gold has not been redissolved, but is 

 still in solid separate particles ; and this is confirmed by the 

 non-action of protochloride of tin, which, in properly prepared 

 fluids, gives no indication of dissolved gold. When a ruby 

 solution is rendered blue by common salt, the separation of the 

 gold as a precipitate is greatly hastened ; thus when a glass 

 jar containing about half a pint of the ruby fluid had a few 

 drops of brine added and stirred into the lower part, the lower 

 half of the fluid became blue whilst the upper remained ruby ; 

 in that state the cone of sun's rays was beautifully developed 

 in both parts. On standing for four hours the lower part 

 became paler, a dark deposit of gold fell, and then the cone 

 was feebly luminous there, though as bright as ever in the ruby 

 above. In three days no cone was visible in the lower fluid ; 

 a fine cone appeared in the upper. After many days, the salt 

 diffused gradually through the whole, first turning the gold it 

 came in contact with blue, and then causing its precipitation. 



Such results would seem to show that this blue gold is aggre- 

 gated gold, i. e. gold in larger particles than before, since 

 they precipitate through the fluid in a time which is as nothing 

 to that required by the particles of the ruby fluid from which 



