Mercury(I) oxide

Mercury(I) oxide, also known as mercurous oxide, is an inorganic metal oxide with the chemical formula Hg₂O.

It is a brown/black powder, insoluble in water but soluble in nitric acid. With hydrochloric acid, it reacts to form calomel, Hg₂Cl₂. Mercury(I) oxide is toxic but without taste or smell. It is chemically unstable and converts to mercury(II) oxide and mercury metal.

References