J. W. Mallet on Osmious Acid, . 
* . . o 
reduction of a volatile metallic compou 
It seemed possible that the volatile yellow substance to which 
the present paper refers might have been an acid oxyd of ruthe- 
nium*—RuO,, RuO,, or RuO,—and reducible with extreme 
facility, Claus and others having already noticed the reducing 
effect of light upon salts of the platinum metals. A portion of 
the crust from the sides of the tube of yellow acid was carefully 
examined for ruthenium, the various tests given by Claus as 
well as that recently proposed by Dr. Gibbs being made use of, 
but no proof of the presence of this metal could be obtained. 
remarked an unmistakable blacking of the tallow, caused by the 
nd.” 
The properties of osmium and its compounds are very re- 
markable, and render it a matter of no little interest to trace the 
analogies of this rare substance and fix its place among the other 
elements. It is described in most chemical works along with 
Platinum nd its associated metals, mainly on the ground of com- 
munity of origin, for in many respects it is unlike the platinum, 
palladium, rhodium, &c., with which it always occurs in nature. 
All these metals are commonly thought of as very infusible, of 
great density, very slightly affected by reagents, and very easily 
reduced from their compounds to the metallic state; when more 
closely examined they are found to differ from each other in 
many of their other properties. The arrangement by Claus of 
the platinum metals in these groups, each containing one metal 
of high and one of low atomic weight, viz. 
Platinum, Tridium, Osmium, 
Palladium, Rhodium, Ruthenium, 
has been alluded to above; the two members of each group are 
More closely related to each other than to any of the rest. Os- 
mum and rathenium are clearly the most electro-negative of the 
Mes. Graham has inferred the isomorphism of platinum, pal- 
1am, iridium and osmium, from the fact that their potassio- 
chlorids atl crystallize in the form of the regular octahedron ; 
® corresponding compound of ruthenium has since been added 
to the list, while that of rhodium is still unknown. The occur- 
-Tence of two salts under the same form, in the regular system, of 
. r such a compound exist, an explanation may be found for the process by 
Frémy has obtained a wer oxyd of rithaphans<gretably the bin-oxyd—in 
crystals, He roasts * < s ; 
_ 9.4 porcelain tube at a bright red heat; osmic acid volatilizes, and is said to 
prt With it mechanically the oxyd of ruthenium, which deposits upon fragments 
re placed in the cooler part of the tube. But the oxyd sce distinct erys- 
can theref i rea 
ical way by a stream of vapor; and, moreover, there is no reason for oxyd 
“< ruthenium only being so ong, while other substances of no er 
sity remain behind. Is it not more likely that a volatile and very easily reducible 
chibe immediately afterwards decomposed, 
| ogue of osmi acid is formed, and almost imm 
depositing the bin-oxyd of ruthenium ? 
¥ 
