osmium
(ˈɒsmɪəm, ˈɒz-)
[f. Gr. ὀσµή odour (see quot. 1804) + -ium.]
a. One of the metals of the platinum group, generally found, associated with platinum, in the alloy iridosmine or osmiridium. Chem. symbol Os; atomic wt. 199·6 (Frémy).
| 1804 Tennant in Phil. Trans. XCIV. 416 A pungent and peculiar smell... This smell..arises from the extrication of a very volatile metallic oxide; and, as this smell is one of its most distinguishing characters, I should on that account incline to call the metal Osmium. 1805 Ibid. XCV. 317 Metals that were found by Mr. Tennant in the black powder which is extricated by solution from the grains of platina, and which he has called Iridium and Osmium. 1853 W. Gregory Inorg. Chem. (ed. 3) 260 Osmium..is chiefly remarkable for forming with oxygen a volatile acid, which has a pungent smell, like that of chlorine, and is very poisonous. 1892 Spectator 19 Mar. 396 Aluminium cannot be obtained without osmium also. |
b. Special comb.:
osmium lamp, a filament lamp in which the filament is made of osmium;
osmium tetroxide, OsO
4, a poisonous, pale yellow solid that has a distinctive pungent and harmful vapour and is used in solution as a biological stain,
esp. for lipids, and a fixative; also called
osmic acid.
| 1907 Westm. Gaz. 16 Feb. 14/2 The osmium lamp..was expensive to start with, and could be used only in the pendent position. 1952 H. Hewitt Mod. Lighting Technique iv. 34 Whilst further developments such as the Nernst lamp, the osmium lamp and the tantalum lamp were all of technical interest, it was not until the adoption of the tungsten filament by Coolidge in 1909 that there was any considerable advance towards more efficient electric lamps. |
| 1876 Encycl. Brit. V. 537/2 Osmium tetroxide is reduced at red heat. 1920 Jrnl. R. Microsc. Soc. 133 The Golgi apparatus has the following reactions:..2. Black in Kopsch's or Mann-Kopsch's osmium tetroxide methods. 1954 H. W. Deane in R. O. Greep Histol. iii. 43 Many lipid substances will also blacken with osmic acid (osmium tetroxide). In most instances..this blackening apparently depends on the fact that unsaturated fatty acids reduce the colorless osmic acid to black osmium dioxide. However, many nonfatty protoplasmic constituents..may also be blackened with osmic acid. 1968 J. March Adv. Org. Chem. xv. 616 There are many reagents which add two OH groups to a double bond. OsO4 and alkaline KMnO4 give cis addition, from the less hindered side of the double bond. Osmium tetroxide adds rather slowly, but almost quantitatively. 1974 Nature 18 Jan. 145/1 White Leghorn chicken embryos..were fixed in glutaraldehyde and osmium tetroxide. |