Ammonium Osmyl Oxybromide, (NH₄)₂OsO₃Br₂

Ammonium Osmyl Oxybromide, (NH₄)₂OsO₃Br₂, is prepared in an analogous way to the chloride. Thus:

(NH₄)₂OsO₃(NO₂)₂ + 2HBr = (NH₄)₂OsO₃Br₂ + 2HNO₂.

The salt is obtained as a yellow, crystalline powder, but slightly soluble in water. With potassium hydroxide ammonia is evolved, potassium osmate remaining, thus indicating the hexavalent nature of the osmium.

No corresponding potassium salt is known.