175 
OF GOLD (AND OTHEE METALS) TO LIGHT. 
In such ruby jelly the reduced particles of gold preserve their state and relative place, 
and the tint does not pass to blue, even though a considerable proportion of salt be 
present. Such jelly will remain in the air for Aveeks before it decays, and has every 
character, in colour and appearance, of gold ruby glass. It is hardly possible to examine 
the series of ruby glass, ruby membrane, ruby jelly cold and gelatinous, ruby jelly warnr 
and fluid, and the ruby fluids, to consider their production, and then to conclude that 
the cause of their common ruby colour is not the same in all. 
"When the warm ruby jelly is poured into a capsule or on to a plate, alloAved to gelati- 
nize and then left in the air, it gradually becomes dry. When dry, some of these jellies 
remain ruby ; others Avill probably be of an amethystine violet colour, or perhaps almost 
blue. When one of the latter is moistened with water, and has absorbed that fluid, it 
becomes gelatinous, and whilst in that state resumes its first ruby colour ; but on being 
sufiered to dry again it returns to its amethystine or blue colour. This change will 
occur for any number of times, as often as the jelly is Avetted and dried. Here the gold 
remains in the same metallic state through this great change of colour, the association 
or the absence of Avater being the cause: and the efiect strengthens in my mind the 
thought before expressed, that in the ruby fluids the deposited particles are frequently 
associates of water and gold. It is a striking case of the joint efiect of the media and 
the gold in their action on the rays of light, and the most striking case amongst those 
Avhere the medium may be changed to and fro. 
AWien a ruby jelly is prepared Avith salt, and being warm is poured out in thin layers 
on to glass or porcelain, it first gelatinizes and then dries up ; in Avhich case the salt is 
excluded and crystallizes. When the dry jelly is put into cold Avater, the salt dissolves 
and can be removed. The jelly then SAvells to a certain amount, after Avhich it can be 
left soaking in water for a Aveek or longer, until everything soluble is separated. No 
change takes place in the ruby tint, no gold is removed. When the last Avater is poured 
ofl" and the remaining jelly Avarmed, it melts, forming a fine ruby fluid, Avhich can either 
be dissolved in more Avater, or regelatinized, or be dried and preserved for any length of 
time. It is perfectly neutral ; gives no signs of dissolved gold by any of the tests of the 
metal; is not changed by sulphm’etted hydi’ogen, gallic acid, p}a'ogallic acid, dilute 
caustic alkahes, or carbonated alkalies or lime-Avater ; or by dilute sulphuric, hydrochlo- 
ric or nitric acids, the actions being continued for fourteen days : — being boiled Avith zinc- 
filings it does not change ; and even Avhen dilute sulphuric or hydrochloric acid is added 
to evolve nascent hydrogen, still the ruby character undergoes no alteration. Strong 
sulphuric, or nitric, or hydrochloric acid do not alter it Avhilst cold ; but when warmed, 
the first causes the gold to separate as dark aggregated metallic particles, and the two 
latter gradually cause the change to amethyst and blue formerly described. Chlorine, 
or a mixture of hydrochloric and nitric acids, dissolves the gold, the ruby colour disap- 
pears, and the ordinary solution of gold is produced. In all these cases the ruby gold 
behaves exactly as metallic gold Avould do Avith the same agents, and quite unlike what 
would be expected from any possible combination of oxygen and gold. 
