350 
CHEMICAL PRINCIPLES. 
OxJdesofgold. the difference between these two muriates of gold 
might be caused by different degrees of oxidation, I examined 
the yellow muriate by decomposing it with mercury. It is the 
latter of the two foregoing analyses, from which it follows 
that the difference i& occasioned by the excess of the acid, and 
by the water, which are not contained in the red. 
2, Oxidum aurosum. If the neutral muriate of gold be 
exposed in a glass vessel to a heat a little above that of boiling 
water, it begins to give out oximuriatic gas. If left in the 
same temperature until it no longer continues to discharge the 
oximuriatic gas, the residue will consist of a saline straw- 
coloured mass, in which no traces of metallic gold can be 
discovered by means of the microscope. This salt is not soluble 
in water ; or, in case the red muriate has not been entirely 
decomposed, the water takes up that portion and becomes of a 
yellow colour, leaving the new-formed salt undissolved. In 
this latter case the mass is converted into powder by the action 
of the water, and the straw-coloured salt forms very small 
crystalline grains, which do not communicate to water any 
.appearance of dissolved gold. If, on the contrary, the water 
and the straw-coloured salt be left to macerate, the latter is 
decomposed and yields a considerable portion of metallic gold, 
' while a red muriate (rnurias auricus) is dissolved by the water. 
Boiling water occasions this decomposition almost instanta- 
neously. 
The explanation of this phenomenon is very easy. The 
muriatic acid which is extricated, together with a portion of 
oxigen before combined with the gold of the muriate, leaves 
behind a muriate of an inferior degree of oxidation- The same 
thing happens with the muriate ol the oxide of copper, and 
likewise (as w'e shall presently see) with the common muriate 
of platina. The rnurias aurosus is decomposed by the water, 
because this having a strong affinity with the rnurias auricus, 
it contributes to the formation of this latter, whereby the whole 
quantity of oxigen combined with the gold in the rnurias 
aurosus is concentrated in a part only of the metal. Thus the 
oxidum 
