8 6 The Naturalists^ Companion. 
of copper, and a specific gravity varv- 
ing from 16, impure grains, to 21-15, 
cast platinum. It is, therefore, the 
heaviest metal in the world, unless it 
be osmium. Like gold it is obtained 
by washing away the earth and sand 
wdth which it is associated. It is found 
in combination with the rare metals, 
iridium, rhodium, palladium and os¬ 
mium, besides copper and iron, which 
increases its hardness and gives it a 
darker color. An analysis of a Russian 
specimen afforded, platinum, 78.9; iri¬ 
dium, 5.0; osmium and iridium, 1.9; 
rhodium, 0.9; palladium, 0.3; copper, 
0.7; iron, 11.0, 98.75, 
Platinum is distinguished by the 
following characteristics: Its high 
specific gravity, its malleability, its in¬ 
solubility in any single acid, and its 
extreme infusibility, being wholly un¬ 
altered before the blowpipe. The fol 
lowing is an accurate chemical test; 
Dissolve the crude metal, as far as pos¬ 
sible, in nitro-muriatic acid containing 
an excess ot h 3 ^drochloric acid, slight- 
h" diluted with water, in order to dis¬ 
solve as small a quantity^ of iridium as 
possible; to this deep yellowish-red so¬ 
lution add chloride of ammonium, when 
an orange precipitate is thrown down, 
in the state of ammonium plantino- 
chloride. This substance, if washed 
with a little cold water, dried and 
heated to a redness, leaves metallic 
platinum in a black powder, or, as it is 
called, ‘‘spongy platinum,’* It can be 
formed in a compact mass by making 
the spongy platinum into a thin uni¬ 
form paste in a brass or steel mold, 
and then subjecting it to gradual pres¬ 
sure b}" which the water is squeezed 
out and the mass finality rendered suf¬ 
ficiently solid to bear handling. It is 
then dried and carefully heated to 
whiteness, when it can at last be forged 
into a bar. 
Since the discoy’^ery of platinum in 
the alluvial workings of the Pinto river 
it has been found in the Ural Mount¬ 
ains in Russia; on the island of Borneo, 
in the sands of the river Rhine; in St. 
Domingo; and in the United States in 
North Carolina, California, Oregon 
and Arizona. The most? important 
sources of platinum are the hydraulic 
mines of Nizhne-Tagihlsk, in the Ural 
Mountains, where it is found with 
chromite in serpentine. Nearly^ eighty 
per cent, of the world’s production of 
the metal is derived from this source. 
Platinum in considerable quantity is 
found with t^e gold washecl from the 
Atral river in the United States of 
Columbia, from where it is sent to 
Paris. In Brazil platinum is obtain¬ 
ed in the province of Minas Geraes 
near sy enite. It has also been discov¬ 
ered in Ha^’ti, Peru, India, County of 
Wicklow in Ireland, Australia, and in 
the Chaudiere river in Quebec. 
Though commonly found in small 
grains, masses of platinum have occas- 
ionall}^ been discoy ered. The largest 
nugget yet found yveighed tyventy. one 
pounds, and is in the Demidoff cabinet 
in Russia. Humboldt brought from 
South America a mass weighing 1088 
grains, which he deposited in the Berlin 
Museum. In the Madrid Museum is 
a mass yveighing 11,640 grains, found 
in Condoto in 1822. In 1827 a speci¬ 
men was discovered in the Ural Mount¬ 
ains, near the Demidoff mines, which 
weighed 11.57 pounds trov. 
Until recently, platinum has ahvays 
been found in placer or alluvial depos¬ 
its; but a few vears since a discovery 
yvas made of great interest to mineral¬ 
ogists and geologists. In deepening the 
