t[ 152 ] 
In all thefe procefies, even where the proportion 
of platina was l'mall, the fufion was performed by a 
vehement fire, that the mineral might be the m '‘re 
intimately difi'olved, and equally diffufed thro’ tbc 
gold. The neceffity of this precaution appeared from 
an experiment formerly related; in which one of 
platina having been melted with four of gold, the 
button appeared not much paler than ftandard gold 
with filver alloy. On a fecond fufion it loft its yel- 
low colour, which had at firfl been only external, 
from an imperfect mixture, great part of the platina 
being concealed in the internal part of the mats, and 
covered as it were by a golden coat. 
The crucibles were rubbed on the infide with 
chalk, to prevent any particles of the metal from 
lodging in their cavities. A little borax was em- 
ployed in each as a flux ; with the addition of nitre, 
by which the colour of gold is fomewhat heightened. 
On remelting fome of the mixtures with fundry other 
additions, powdered charcoal feemed to improve the 
colour mod. 
Experiment II. 
The preceding compofitions, after being gently 
hammered and boiled, were weighed hydroftatically 
with great care, by a very tender balance, in diftilled 
water, wherein the gravity of ftandard gold turned 
out 17.788. 
All the mixtures proved heavier than ftandard 
gold. Their gravities were nearer to the medium 
of the gravities of the ingredients, than thole of the 
compofitions of platina with any of the other metals 
formerly 
