1617.) On the Decomposition of the Earths. 201 
12. Alloy of Palladium and Nickel.—This beautiful alloy proved 
to be so far malleable that it admitted of being flattened by a 
common hammer upon an anvil. When filed and aes hata its 
surface became a perfect mirror; reflecting more light than any 
metallic substance with which I am acquainted. It would afford a 
useful and highly ornamental compound in the arts; perhaps sur- 
passing in lustre the most splendid metals known; and might be 
advantageously employed in making mirrors for telescopes. 
13. Alloy of Nicked with Iron.—The two metals were fused 
together in equal parts by bulk. _ Previously to their union there was 
a vivid combustion, but it ceased in the instant of their combina- 
tion. The fusion was afterwards more tranquil, with less of ebulli- 
tion; the residue being a globule of white and very splendid metal. 
Other Alloys obtained by Fusion before the ignited Gus, 
4. Alloy of Palladium and Copper-—The two metals were 
fused in equal parts, by lulk, and seemed to unite with an avidity 
as if they exercised a mutual attraction upon each other. After 
their union, the alloy was remarkably fusible; and its fusion was 
always attended with a partial combustion of the palladium. This 
alloy is of a pale colour, and easily acted upon by the file; but it 
is susceptible of a very high polish. 
15. Alloy of Platinum and Copper.—The metals were here 
combined in equal parts by weight. The alloy is remarkably 
fusible, and continued in a state of vehement ebullition after the 
extinction of the gas. It is soft; easily filed; malleable; and of 
a pale colour resembling that of pure gold. Indeed, it seems as if 
“. might be thus imitated, both with regard to weight and to 
colour. 
16. Alloy of Platinum and Iron in equal Parts by Weight.—To 
this alloy I alluded in the beginning of my letter. ‘The combustion 
of the two metals, when fused together in a charcoal crucible, ex- 
hibits a very brilliant firework. It is malleable ; but so hard that a 
file will scarcely touch it ; after being filed, the surface exhibits a 
very high degree of lustre. 
17. Alloy of Platinum and Iron in equal Parts by Bulk.—This 
alloy is always brittle. In cooling, a cavity is formed, in the 
centre of the mas, as in the cvoling of bismuth ; and it is studded 
with a minute but brilliant crystallization. 
With these alloys 1 must for the present conclude my observa- 
tions. The statement | have already made, in describing them, 
will show that the valuable work of Lewis,* although generally 
correct, is inaccurate upon some points. I might extend the detail 
A have now offered to 4 much greater length if 1 were to relate all 
the experiments which I have made, in forming metallic com- 
nds. Almost every combination mentioned by Lewis, with 
platinum, 1 have repeated, and many that he has not mentioned. 
* Philovophical Commerce of Arts, Lond, 1763, 
