[ r 58 ] 
objected, that tho’ the platina was dlfcoverable, when 
thus mingled fuperficially with the gold, it may r.e- 
verthelefs, when combined more intimately by fulion, 
elude this method of trial. 
1 . Mixtures of gold with fmall proportions of 
platina were therefore kept in fulion, by a very 
ftrong lire, for leveral hours, and afterwards diflblved 
in aqua-regis. The folutions being diluted with 
water, and a pure fixed alkaline fait gradually added, 
fo long as anv effervefcence or precipitation enfued, 
the liquors remained manifeftly coloured, tho’ ap- 
parently paler than when the two metals had been 
diffolved by themfelves. 
2 . A more convincing proof, that part of the 
platina remains fufpended, after the precipitation of 
the gold, was obtained, by putting into the filtered 
liquors fome plates of pure tin, which prefently 
contracted an olive hue, and threw down a large 
quantity of a browmifh precipitate, as from the com- 
mon folutions of the crude mineral. It was oblerv- 
able, that the tin plates were often fenfibly aCted on, 
even whilft the liquor was overcharged with alkali. 
3. It has been further fuggefted, and with great 
appearance of probability, that as a part of platina is 
precipitated as well as gold by alkaline falts, if only 
this part be mixed with gold, it will be thrown down 
by them again upon diffolving the compound. To 
determine this point, a precipitate of platina made 
by fixed alkali was melted with thrice its weight of 
fine gold, and kept in ftrong fufion for above an 
hour : they united more eafily than gold does with 
fo large a proportion of the crude mineral, and 
formed a fmooth neat bead, which hammered well 
into 
