A gum resin from the base of the tufted trunk leaves of various species of Xanthorrhoea trees of Australia and Tasmania. It is also called gum accroides and yacca gum. Yellow acaroid from the X. tateana is relatively scarce, but a gum of the yellow class comes from the tree X. preissii of western Australia, and is in small hollow pieces yellow to reddish. It is known as black boy resin, the name coming from the appearance of the tree. Red acaroid, known also as red gum and grass tree gum, comes in small dusty pieces of reddish brown. This variety is from the X. australis and about 15 other species of the tree of southeastern Australia. The resins contain 80 to 85% resinotannol with coumaric acid, which is a hydroxycinnamic acid, and they also contain free cinnamic acid. They are thus closely related chemically to the balsams. Acaroid resin has the property unique among natural resins of capacity for thermosetting to a hard, insoluble, chemical-resistant film. By treatment with nitric acid it yields picric acid; by treatment with sulfuric acid it yields fast brown to black dyes. The resins are soluble in alcohols and in aniline, only slightly soluble in chlorinated compounds, and insoluble in coal-tar hydrocarbons. Acaroid has some of the physical characteristics of shellac, but is difficult to bleach. It is used for spirit varnishes and metal lacquers, in coatings, in paper sizing,...
TABLE OF CONTENTS 
