Barium manganate

Barium manganate (chemical formula BaMnO4) is a type of manganates in which the manganese is in a +6 oxidation state. It is obtained by heating manganese dioxide with barium carbonate or nitrate, or by precipitating potassium manganate with barium chloride.¹ Barium manganate gives a green pigment, which was used to make manganese blue. Barium manganate can be used in the oxidation of a variety of functional groups efficiently and selectively: alcohols to carbonyls, alcohols to aldehydes, diols to lactones, thiols to disulfides, aromatic amines to azo-compounds, hydroquinone to p-benzoquinone, benzylamine to benzaldehyde, etc. ^2,3

1. N. Eastaugh, V. Walsh, T. Chaplin, R. Siddall, Pigment Compendium, 2008, ISBN: 978-0-7506-8980-9
2. https://en.wikipedia.org/wiki/Barium_manganate
3. http://reag.paperplane.io/00000118.htm

blue to dark blue-black fine crystalline powder

Useful for the selective oxidation of diols.

As pigment in fresco painting instead of Scheele's green because not so poisonous as latter. As mild oxidizing agent in organic synthesis.

Wash the salt with conductivity H2O by decantation until the supernatant gives a faint test for Ba2+ . Remove excess H2O in a vacuum (IMPORTANT), then heat at 100o and the last traces of H2O are removed in a vacuum desiccator over P2O5. Store it over KOH. It disproportionates in hot H2O or dilute acid into Ba(MnO2)2 and MnO2, and is a mild oxidant. [Schlezinger & Siems J Am Chem Soc 46 1965 1924, Nyholm & Woolliams Inorg Synth XI 56 1968.]