f 
XV. Experiments to fiew the Nature of 
AurumMofaicum : By Mr. Peter Woulfe, 
F. R. S. 
Read, Feb. 14.^ | 5 H E Aurum mofaicum is known 
'JL by the names of Aurum mufivum, 
Aurum mulicum, and Purpurina. We can colledt 
but very imperfect ideas of this preparation, from the 
writings of antient and modern chemifts. It is true, 
that the method of making it has been defcribed 
by many; but no one hitherto has led us into the 
knowledge of its nature, by a fufficient number of 
experiments. It has been much ufed formerly as a 
pigment, but is now almoft laid afide, and the Bronzes 
fuhftitued in its place. It is fometimes ufed in medi- 
cine as a vermifuge, but how improper and uncer- 
tain it is for that purpofe, will appear by the follow- 
ing experiments. 
The beft preparation defcribed hitherto for making 
Aurum mofaicum, is fet down in the London Dif- 
penfatory, and is as follows. 
Take of tin twelve ounces, of flowers of fulphur 
feven ounces, of fal ammoniac fix ounces, and of 
purified mercury fix ounces ; melt the tin, and add 
the mercury to it ; and when cold, powder it, and 
mix with it the fal ammoniac and fulphur. Sublime 
the mixture in a matrafs. The Aurum mofaicum 
will 
