356 
CIIEMICAL PRINCIPLES. 
O.videiofgold. 6on- The metallic button was of the colour of brass, and 
contained a large portion of tin. Moreover, the purple also, 
when melted with saltpetre, gives the same metallic alloy, 
the tin detaching itself from its oxigen and combining with 
the gold. I dissolved this alloy in some muriatic acid, 
mixed with a small portion of the nitric. The solution depo- 
sited a small quantity of the oxide of tin ; and, after having 
filtered, I evaporated it to dryness, increasing the heat suffi- 
ciently to convert the murias auricus into murias aurosus. 
This I was led to do by the opinion that the tin would 
evaporate in the form of spirit ofLibavius. I was, however, 
disappointed 5 for, on pouring water on the mass, which was 
of a dingy yellow colour, I obtained a solution of murius au- 
ricus, mixed with murias stannosus, the remainder consisting 
of a greenish powder undissolved. 1 washed this powder, 
^nd then macerated it with water. In its decomposition it 
deposited some metallic gold of a blackish colour, and pro- 
duced a yellow solution. This solution contained also tin in 
a large proportion. In these experiments the combination of 
the two metals was owing to their mutual affinity j (a) in 
the metallic alloy j in the purple; (c) in the muriate 
of the oxide ; and (d) in the muriate of the oxidule ; or, in 
short, in all the forms of combination common to the two 
metals. It therefore follows, that the mutual affinity of the 
two metals is the momentum primum for the production of the 
puiple. 
The momentum secundum consists in the partial reduction of 
the-oxidum auricum, which, in this case, should produce an 
oxide of a degree intermediate between the oxidule and the 
I oxide, where (as we have already seen) a member is wanting 
in the series. This oxide would be of a purple colour, and 
would constitute the oxidum auricum. It is evident, that 
the purple cannot contain any of the oxidum aurosum, because 
this is of a green colour, both in its solution witlr the caustic 
alkali, and in that with the double muriate of oxidum stan- 
nosum, "and oxidum aurosum, while the purple, in its solution 
with ammonia, is of a red colour. It also appears, that the 
purple 
r 
