Heated rather below 300° C. amber suffers decomposition, yielding an "oil of amber," and leaving a black residue which is known as "amber colophony," or "amber pitch"; this forms, when dissolved in oil of turpentine or in linseed oil, "amber varnish" or "amber lac."
The raw materials used in the manufacture are: (I) iron-free kaolin, or some other kind of pure clay, which should contain its silica and alumina as nearly as possible in the proportion of 2SiO 2: Al203 demanded by the formula assigned to ideal kaolin (a deficit of silica, however, it appears can be made up for by addition of the calculated weight of finely divided silica); (2) anhydrous sulphate of soda; (3) anhydrous carbonate of soda; (4) sulphur (in the state of powder); and (5) powdered charcoal or relatively ash-free coal, or colophony in lumps.
Examples of resin acids are abietic (sylvic) acid, C19H2802, occurring in colophony, and pimaric acid, C20H3002, a constituent of gallipo resin.
Abietic acid can be extracted from colophony by means of hot alcohol; it crystallizes in leaflets, and on oxidation yields trimellitic, isophthalic and terebic acid.
ROSIN (a later variant of "resin," q.v.) or Colophony (Colophonia resina, resin from Colophon in Lydia), the resinous constituent of the oleo-resin exuded by various species of pine, known in commerce as crude turpentine.