J. W. Mallet on Osmious Acid. 51 
- Itis easy however to imagine the cause of this change under- 
gone by the yellow acid if it be in fact the teroxyd of osmium 
(mixed with osmic acid). The teroxyd probably broke up into 
osinic acid and one of the lower oxyds of osmium or perhaps 
the metal itself We might have 
203s0,=O0s0,+0s0, 
5030, =30s0,+0s,0, 
30s 
3 4 
or, 4030 , =303s0, +Os. 
In order to ascertain, if possible, which of the above changes 
had taken place, the tube was opened two or three months fer 
it had been sealed, and the contents were examined. The fused 
stick of acid was found to be black and partially friable; on 
heating in another glass vessel most of it sublimed, leaving a 
little black powder behind, and condensed in needles, still 
slightly yellowish, bu 
mon osmic acid. The inner surface of the original tube was 
May replace nitrogen in nitrite of potash (KO, NO,)? From 
the relations of the two elements, to be noticed presently, this 
Would seem probable, and in fact Frémy has noticed the crystal- 
zation of osmite of potash from a solution in hot water of the 
e of nitre and iridosmium. A reason for osmic acid 
(0s0,) being usually obtained from the latter, instead of osmi- 
ous (OsO,,), might perhaps be found in the fact that the chemists 
; y be worked upon osmium recommend the 
t nitric or nitro-muriatic acid to neutralize the potash—sul- 
phuric acid, ‘to which Wollaston had recourse in his early ex- 
sUments, is now seldom employed. Thomson, in his “ Chem- 
thd of Inorganic Bodies,” published many years ago, observes 
“t osmic acid has sometimes a tint of yellow. ai 
e 
