352 
CHEMICAL PRINCIPLES. 
Oxidcsofgold. the whole quantity of green oxide was converted into a blackish 
brown powder, being evidently a mixture of gold and oxidum 
auricum. The latter of these was separated by means of the 
muriatic acid which received from it a yellow colour. 
The gilded phial, in the foregoing experiment, when held 
agflinst the light, appeared to be covered with a semi-transpa- 
rent pellicle of a green colour. In another phial, gilded by 
the spontaneous decomposition of the oxidum auricum, the 
colour of the metallic pellicle, when held against the light, 
was purple ; and in a third phial, where the rays of the sun 
had dissolved a portion of the muriate of gold, and gilded the 
surface of the phial, the metallic pellicle was, under the same 
circumstances, void of colour. The different shades of colour 
in the metallic pellicle seem therefore to depend on a small 
portion of the reduced oxide contained in the metal; For if 
the gilded phial be heated to a red heat, the colour of the pel- 
licle disappears. 
Ey the foregoing experiments, it is proved that the oxidum 
aurosum may exist without being combined with the acids j 
and that in this state it has the form of a powder whose colour 
is a bright green ; but that it suffers a still quicker decompo- 
sition than the oxidum auricum. I have reason, however, to 
believe, that the oxidum aurosum is, in a small degree, more 
durable than the foregoing experiment seems to indicate. For 
in some little time after I had finished this series of experi- 
ments, I found that the caustic lixivium I had employed, con- 
tained a small quantify of alcohol, by means of which it had 
been rendered pure. The College of Medicine of Stockholm, 
ordered me, towards the autumn of 1811 , to procure for it 
the preparations of gold employed by M. Christien for the cure 
of the venereal disease. One of these preparations was the 
submuriate of the oxide of gold; which preparation, until M» 
Oberkampf shewed the contrary, had been considered as a pure 
oxide. I obtained it by precipitating some neutral muriate with 
a portion of the forementioned caustic lixivium, which I still 
had left. Having left the glass containing the mixture during 
five or six hours in a heated room, I found the precipitation 
entirely 
