Definition
The brownish black precipitate
formed when mercury is treated with cold
concentrated sulfuric acid for a long time is
thought to be mercury(I) sulfide. Alternatively
it may be prepared by the action of
hydrogen sulfide or an alkaline sulfide on a
mercury(I) salt solution. As soon as the
mercury(I) sulfide has been formed it disproportionates
to give mercury(II) sulfide
and mercury.
