Osmium

Location:  Group 8, Period 6
Atomic Weight:  190.2
Coordination Number:  4, 5, 6, 8
Chemical Form in Solution:  OsCl₆^2-
(coordination numbers in green are observed less frequently)

Storage & Handling:  Keep tightly sealed when not in use. Store and use at 20 ± 4°C. Do not pipet from container. Do not return portions removed for pipetting to container.

Chemical Compatibility:  Stable in HCl. Stable with most metals and inorganic anions as the [OsCl₆]^2- in dilute HCl media. DO NOT EXPOSE TO NITRIC ACID - FORMATION OF THE VERY VOLATILE AND TOXIC OsO₄ WILL RESULT. Any oxidizing condition must be avoided.

Stability:  2-100 ppb levels are NOT stable in 1% HNO₃ / LDPE container. The stability of HCl solutions at ppb levels has not been determined by our laboratory. 1-10,000 ppm solutions are presumed chemically stable for years in 10% HCl / LDPE container, stability studies have not been performed.

Os Containing Samples (Preparation & Solution):  Oxides (fuse with KOH / KNO₃ in a Ag⁰ crucible and dissolve in water being sure to avoid addition of any acid); Ores (see Oxides); Organics (the OsO₄ is volatile and acidic oxidizing preparations should be used with caution. The preferred approach is the KOH / KNO₃ fusion and dissolution of the fuseate in water. Our laboratory has used APDC to help stabilize Os solutions, but more work is required to validate its effectiveness).

NOTE:  The presence of the OsO₄ will give false high results due to its enhanced nebulization efficiency (volatility). Only dilutions in HCl should be made. The use of nitric acid should be strictly avoided. Preparations from caustic nitrate fusions should be diluted in water.