168 
DE. EAEADAT OX THE EXPEEDIEXTAL EELATIOXS 
the gold converted into chloride, and compared by reduction on glass and otherwise with 
solutions of gold of known strengths. A portion of chloride of gold, containing O’ 7 of a 
grain of metal, was made up to 70 cubic inches by the addition of distilled water and con- 
verted into ruby fluid : on the sixth day it was compared with the ruby glass standard, 
and ndth a depth of 1’4 inch was found equal to it ; there was just one hundredth of a 
grain of gold difiiised through a cubic inch of fluid. In another compai-ison, some gold 
leaves were dissolved and converted into ruby fluid, and compared; the result was a 
fluid, of which 1’5 inch in depth equalled the standard, a leaf of gold being contained 
in 27 cubic inches of the fluid. Hence looking through a depth of 2 -7 inches, the quantity- 
of gold interposed between the hght and the eye would equal that contained in the 
thickness of a leaf of gold. Though the leaf is green and the fluid ruby, yet it is easy 
to perceive that more light is transmitted by the latter than the former ; but masmuch 
as it appears that ruby fluids may exist cont ainin g particles of very diff erent sizes (or 
that settle at least with very different degrees of rapidity), so it is probable that the 
degree of colour, and the quantity of gold present, may not be always in the same pro- 
portion. I need hardly say that mere dilution does not alter the tint sensibly, i. c. if a 
deep ruby fluid be put into a cylindrical vessel, and the eye look tlirough it along the 
axis of the vessel, dilution of the fluid to eight or ten times its volume does not sensibly 
alter the light transmitted. From these considerations, it would appear that one volume 
of gold is present in the ruby fluid in about 750,600 volumes of water; and that what- 
ever the state of division to which the gold may be reduced, still the proportion of the 
solid particles to the amount of space through which they are dispersed must be of that 
extreme proportion. This accords perfectly with theu’ mwsibihty in the microscope ; 
with the manner of their separation from the dissolved state ; Avith the length of time 
during which they can remain diffused ; and with their appearance when illummated by 
the cone of sun’s rays. 
The deposits, when not flxed upon glass or paper, are much changed by di’^ing ; they 
cannot be again Avetted to the same degree as before, or be again diffused ; and the hght 
reflected or refracted is as to colour much altered, as might be expected. "Siliilst dif- 
fused through water, they seem to be physical associations of metalhc centres with 
enveloping films of water, and as they sink together Avill lie for months at the bottom of 
the fluid without uniting or commg nearer to each other, or without being taken up by 
metallic mercury put into the same vessel. This is consistent AAith what Ave know of 
the manner in Avhich gold and platinum can be thoroughly Avetted if cleaned in Avater, 
and of the difference which occurs Avhen they are dried and become mvested AAith air. 
I endeavoured to transfer the gold particles unchanged into other media, for the pur- 
pose of noting any alteration in the action on light. By decanting the Avater very 
closely, and then carefully adding alcohol Avith agitation, I could difluse them through 
that fluid ; they still possessed a blue colour Avhen looked through in the dark tube, but 
seemed much condensed or aggregated, for the fluid AA’as obsciu’e, not clear, and the 
particles soon sirbsided. I could not transfer them from alcohol to camphme ; they 
