| Chemical Formula: | OsO4 |
| CAS#: | 20816-12-0 |
| Formula Weight: | 254.21 |
| RTECS #: | RN1140000 |
| Apperance: | Not available |
| Color: | Not available |
| Odor: | Not available |
| Boiling Point: | 129.7° C / 265.46° F |
| Melting Point: | Not available |
| Specific Gravity (H2O = 1): | Not available |
| Vapor Pressure at 25°C: | 9.8 mm Hg |
| Solubilities: | 5.07% at 25°C, 6.5% at 90°C, unknown amounts in xylene, chloroform and heptane |
| FSC: | 6810 |
| Osmium Purity: | 99.99% |
Shipping Information
| UN #: | 2471 |
| Proper Shipping Name: | | Osmium tetroxide |
| Hazard Class: | 6.1 |
| Packing Group: | I |
Osmium tetroxide is a cornerstone fixative for transmission electron microscopy (TEM) and must be absolutely pure! The SPI-Chem™ brand of osmium tetroxide is EM grade and is available either as pure 99.995% crystals or, for convenience, as aqueous solutions. Both forms of the product are sealed under dry nitrogen in easy-to use, pre-scored safe, snap open ampoules for a one-time application and use. Osmium metal in many ways is unique among the elements and is even "heavier" than iridium, making it the heaviest of all the elements of the Periodic Table.
Osmium tetroxide is very hazardous and dangerous and strict safety procedures should be followed at all times. Toxicological information suggests that osmium tetroxide vapor is extremely hazardous and very low limits should be set for human exposure. As part of your "sharps" injury loss prevention program, always open ampoules with an SPI Supplies brand glass ampoule breaker.
Osmium tetroxide, as great as it is for electron microscopy, is not the only electron dense stain that can be used, so be sure to check out other possibilities. And while you are checking out other stains, think about what embedding resins or tweezers or grids you might be needing soon.
Much has been published in the literature about the osmium staining of different materials for TEM and even SEM, but the newest area has been for microwave assisted staining.
