Use
Mixtures of Mercurous oxide,black with barium oxide react vigorously with hydrogen sulfide in air. Explosions may result [Mellor 10:140. 1946-47]. Dissolves in nitric acid. Reacts with hydrochloric acid to give insoluble mercurous chloride (calomel). Contact of the metal oxide caused the explosive decomposition of hydrogen peroxide [Bretherick 5th ed., 1995]. Mixtures with phosphorus or sulfur explode by impact and friction respectively, [Mellor, 1940, Vol. 4, 77].