What is "potassium cobaltinitrite"

Potassium cobaltinitrite, IUPAC name potassium hexanitritocobaltate(III), is a coordination compound with the formula K[Co(NO)]. The anion of this yellow-coloured salt consists of a cobalt(III) center bound to six nitrito ligands. It is insoluble in water and is precipitated as yellow solids.

It was first made in 1848 by Nikolaus Wolfgang Fischer in Breslau, and it is used as a yellow pigment called Aureolin.