530 Prof. Faraday on the Experimental Relations 
retted hydrogen, but no change occurred with any of them in 
two days. On the other hand, a very dilute solution of chlorine 
immediately turned the ruby to blue, and then gradually dis- 
solved the gold. A piece of the ruby paper immersed in a 
strong solution of cyanide. of potassium suffered a very slow 
action, if any, and remained unaltered in colour; being brought 
out into the air, the gold very gradually dissolved, becoming 
first blue. A portion of the ruby paper was dried and heated 
in oil until the oil and the paper began to change their hue; the 
gold had not altered in its colour or character. Another por- 
tion was heated in the vapour of alcohol and also of zther until 
the paper began to alter; the gold remained unaltered. A blue 
fluid being passed oftentimes through a filter gave a blue paper, 
which, being washed and tried in the same manner, was found 
to contain particles unchanged by the simple acids or alkalies, 
or by heat or vapours, but dissolving, as gold would do, in chlo- 
rine or nitromuriatic acid. These tests are, [ thik, sufficient 
to prove the metallic nature and permanence of the gold as it 
exists in the ruby, amethystine, violet, and other coloured fluids, 
The production by such different agents as phosphorus, sul- 
phide of carbon, «ther, sugar, glycerine, gelatine, tartaric acid, 
protosulphate of iron and protochloride of tin, of gold fluids all 
more or less red or ruby at the commencement, and all passing 
through the same order of changes, is again a proof that only 
gold was separated ; no single one or common compound of gold, 
as an oxide or a phosphide, could be expected in all these cases. 
Many of the processes, very different as to the substances em- 
ployed to reduce the gold, left good ruby films adhering to the 
glass vessels used, presenting all the characters of the gold 
described already ; this was the case with phosphorus, sugar, 
tartaric acid, protosulphate of iron, and some other bodies, 
Again, the high reflective power of these particles (unalter- 
able by acids and salts), when illuminated by the sun’s rays and 
a lens, and the colour of the light reflected, is im favour of their 
metallic character. So also is their aggregation, and their 
refusal to return from blue, violet or amethystine to ruby ; for 
the cohesive and adhering force of the gold particles and their 
metallic nature and perfect cleanliness is against such a reyerse 
change. Particles transmitting blue hight could be obtained in 
such quantity as to admit of their being washed and dried in a 
tube, and being so prepared they presented every character of 
gold: when heated, no oxygen, water, phosphorus, acid of phos- 
phorus, nor any other substance was evolved from them: they 
changed a little, as the film when heated changed, becoming 
more reflective and of a pale brown colour, and contracted into 
aggregated porous masses of pure ordinary gold, ; 
