64 W. Gibbs on the Platinum Metals. 
The density of the osmiridium obtained from California varies ‘ 
greatly in different samples: in one specimen, composed of large — 
the separate scales or grains have probably very different com- 
positions. According to G. Rose, the density of the Siberian ore 
varies from 19°3 to 21:1. Dr. Torrey has found among the 
seales of the Californian ore some which could be flattened un- 
der the hammer; these were probably platin-iridium. In gene: — 
ral, however, the scales are not malleable; some of a lead gray — 
or bluish tint being with great difficulty cut by the emory Gus : 
employed by the gold pen racine In color the scales vary 
from nearly silver white to dark gra i 
§ 2. 
The resolution of the ores of iridium, osmium, ete., and the 
as is known always been considered as among the most di# 
ficult problems with which the chemist has todeal. Though the 
have thrown eck light on the rhage and though Claus, in — 
particlar, in his elaborate “ Beitriige zur Chemie der Platin-Me- — 
talle” has done much to free the chemical history of this group _ 
from ue errors of his predecessors, I yet found that much re- 
mained to be done, especially as the Californian ore differs from 
the Siberian in the greater relative proportion of Ruthenium — 
which it contains. This difference alone renders a different treat: _ 
cise | 
lieving that it will 1 . useful to others, who may hereafter take _ 
up the same subject. | 
States Assay Office, the proportion of osmiridium in the California gold, did n a 
ceed balf an aes to the million of dollars. Afterward, th proportion al ey in 
creased till the average was seven or eight ounces to the million of gold. Thenfor 
: hag or more the quantity diminished, but for the last year it ae enas large 38 
upon the mposition of the native ce 
ie the constant discovery of new ’ diggings. ve 
The grains of osmiridium, suitable for pens, — soundish and ble to 
exfoliate when ‘ eke or heated. They seem to have a direst ot com pesto from 
the compressed and tabular crystals, The proportion of pels <A a 
than a tenth of all the alloy, but it is sometimes as large as i 
The carefully selected grains used by the gold pen makers pane so gos he that from — 
10,000 to 15,000 of them are contained in a single ounce. The very best are worth — 
at least $250 an ounce, and a cubic inch, which would be equal to about eleven ounces, — 
is worth $2,7 750. eee 
