specific Gravity , and comparative Wear of Gold. 83 
fine, being completely melted, one pennyweight and fourteen 
grains of purified platina were added, and, when well mixed, 
the whole was poured into a mould. 
This metal was of a yellowish white, like tarnished silver, 
and was extremely ductile.* 
The specific gravity of it was 19,013. 
Experiment 11. 
The ounce of standard gold formed by the foregoing experi- 
ment, was again alloyed with one pennyweight and fourteen 
grains of copper, so that the standard proportion of alloy was 
doubled. 
This metal was of a pale dull yellow; it was not quite so 
ductile as the former; and the specific gravity was 16,816; 
It was not thought necessary to extend these experiments, as 
the properties and effects of platina upon gold are now so ge- 
nerally known, as well as the means usually employed to 
detect it.-f 
* The platina had been purified by precipitation with muriate of ammonia, and 
was therefore in the state of a fine metallic powder, which probably contributed 
much to facilitate the union of it with the gold. I must observe, however, that it was 
not absolutely pure, for it still contained a small portion of iron. 
The specific gravity of this platina was 18,717. 
Gold made standard by platina, is not only very ductile, but also (when hammered) 
tolerably elastic. Perhaps it might be advantageously employed for the springs of. 
watches, &c. 
f Quand le platine ne surpasse pas les 30 a 40 milliemes de son alliage avec l’or, ce 
dernier n’en garde point, si le depart est fait avec les precautions necessaires ; et, lorsque 
ce metal est au-dessus de ce terme, la fraude devient trop sensible et trop evidente, 
pour qu’on ne s’en apper^ive pas; imo, par la plus grande chaleur que l’essai de- 
mande pour passer et prendre une forme arrondie ; 2do, par l’absence de l’eclair ; 3010, 
par la surface crystallisee, et la couleur blanche et matte du bouton ; 4010, par la 
couleur jaune de paille, plus ou moins foncee, qu’il communique a l’eau-forte pendant 
M 2 
