This section is from the book "Chromatography; Or, A Treatise On Colours And Pigments, And Of Their Powers In Painting", by George Field. Also available from Amazon: Chromatography, or A Treatise on Colours and Pigments, and of Their Powers in Painting.
Orange Orpiment, or Realgar, improperly called also Red orpiment, since it is of a brilliant orange colour, inclining to yellow. There are two kinds of this pigment; the one native, the other factitious; the first of which is the sandarac of the antients, and is of rather a redder colour than the factitious. They are the same in qualities as pigments, and differ not otherwise than in colour from yellow orpiment, to which the old painters gave the orange hue by heat, and then called it alchymy, and burnt orpiment. See Yellow Orpiment.