Arsenic, Disulphide of

As 2 S 2 . Syn. Arsenic bisulphide , Bisul′phide of a. , Red sul′phide of a. , ., Realgar ; Réalgal , Arsenic rouge sulfure , Orpin rouge , ., Fr.; Rothes schwefelarsenik , ., Ger. This substance is found native at Solfaterra, near Naples, and in several other volcanic districts; but that of commerce is often prepared by distilling arsenical pyrites, or a mixture of sulphur and white arsenic, ., in the proper proportions, as noticed under Reälgar and Red Pigments . Prop., . A fusible, volatile substance; scarlet or ruby-red in ma , but orange-red in powder, by which it is distinguished from cinnabar; crystals, oblique rhombic prisms. Sp. gr. 3·3 to 3·6. Its chief use is as a pigment and in pyrotechny to make white fire. The factitious sulphide has not the rich colour of the native mineral, whilst it is much more poisonous. It is improved by re-sublimation.