: ON THE PRIMARY, RED.
Bisulphide of arsenic combines with basic metallic sulphides forming a
class of sulphur-salts, called by Berzelius, hyposulpharsenites. The
hyposulpharsenite of manganese is a dark red precipitate, uninjured by
sulphuretted hydrogen, and so far applicable as a pigment. Containing
arsenic, it would of course be poisonous; and would probably be found to
fade on exposure to air and light.