1. HgS The black variety is a poisonous powder; insoluble in water, alcohol, and nitric acid, soluble in sodium sulfide solution; sublimes at 583_C; used as a pigment. Also known as black mercury sulfide; ethiops mineral. 2. The red variety is a poisonous powder; insoluble in water and alcohol; sublimes at 446_C; used as a medicine and pigment. Also known as Chinese vermilion; quicksilver vermilion; red mercury sulfide; vermilion.