[ i6 ° ] 
on folutions of platina. This experiment affords not 
only a criterion for diftinguifhing with certainty whe- 
ther gold has been debafed by platina, but likewife an 
infallible means of recovering it perfectly pure from 
any admixture of that mineral. If the compound 
be diffolved in aqua-regis, the folution mingled with 
twice its quantity or more of the fpirit, and the mix- 
ture fuffered to hand for fome days in a glafs flightly 
covered ; the whole of the gold ariles to the furface, 
leaving the whole of the platina diffolved. The 
golden pellicles may be collected, by pouring the 
matter into a filter juft large enough to contain it. 
The diffolved platina paffes thro’, leaving the gold 
upon the paper, which is to be wafhed with frefh 
parcels of water till the liquor runs colourlefs. The 
paper is then to be carefully fqueezed together, and 
burnt in a crucible previoufly lined with vitrefied 
borax : when fully funk down, a little frefh borax is 
to be. injected, and the fire railed to melt the gold. 
The ufe of lining the crucible with borax is to pre- 
vent any molecular of the gold from lodging in its 
cavities. — This procefs is attended with one inconve- 
nience, the flownefs of the feparation of the gold from 
the folution : this may be in fome meafure expedited 
by employing a fpirit, which has been diftilled from 
vegetables, that give over an effential oil. 
i. As effential oils take up gold from aqua-regis, 
and keep it diffolved for a time upon the furface of 
the acid ; a pure colourlefs oil, that of rofemary, was 
poured into about half its quantity of a folution of 
platina, the mixture well fhaken, and fuffered to reft : 
the oil quickly arofe, without taking up any thing 
from the platina, or receiving any colour : the acid 
liquor 
