Elements · ← Re Rhenium · Ir Iridium →
Osmium tetroxide is a classic fixative and stain for electron microscopy.
| Symbol | Os |
|---|---|
| Atomic number | 76 |
| Standard atomic weight | 190.2 |
| Group | 8 |
| Period | 6 |
| Block | d-block |
| Category | Transition metal |
| Standard state | Solid |
| Discovered | 1803 |
Source: PubChem, Osmium (periodic table data, retrieved 2026-10-19). Group and period follow the standard 18-column periodic table.
Palade showed that acidification during osmium tetroxide fixation distorts cells seen by electron microscopy, and that buffering the fixative near neutral pH greatly improved preservation.
As reported in: Palade (1952). A STUDY OF FIXATION FOR ELECTRON MICROSCOPY. Journal of Experimental Medicine. doi:10.1084/jem.95.3.285
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