RESINS

Resin

Resin, not to be confused with rosin, is a hydrocarbon secretion of many plants, particularly coniferous trees. It is valued for its chemical constituents and uses, such as varnishes and adhesives, as an important source of raw materials for organic synthesis, or for incense and perfume. Fossilized resins are the source of amber. All resins are practically insoluble in water. They dissolve more or less completely ill organic solvents, e.g. alcohol, oil of turpentine; those containing resin acids are usually proportionately soluble in alkalis. A solution of a resin in a volatile solvent, when painted on a smooth surface should rapidly and completely dry to form a hard transparent film; to be suitable for varnish the film should not darken with age or become impaired upon exposure to light or moisture.

Classification-
Various more or less unsatisfactory attempts have been made to classify resins according to principal components; the following classification is as follows.

1.Resins consisting principally of Resin and other Esters. Together with free Aromatic Acids.Resin, Resin or other Gum-Resin Esters Aromatic Acids or Oleo-Resin.

Benzoin (sumatra) {Benzoresinol and Sumaresinotannol}Cinnamic Acid 11 % combined with cinnamic and benzoic acids 60% Benzoic Acid 9%.

Asafetida. Asaresinotannol combined with ferulic acid.

Balsam of Peru. Peruresinotannol combined with cinnamic and benzoic acids 28%. Benzyl benzoate and cinnamate 58 - 70%.

Storax. Storesinol, free and combined with 35-40% Cinnamic Acid 16-24% Storax Cinnamates of ethyl phenylpropyl and 25% cinnamyl alcohols (average).

Balsam of Tolu.Toluresinotannol combined with cininamic and benzoic acids 80% Cinnamic Acid 12%.
Benzyl benzoate and cinnamate 7.5% Benzoic Acid 8%.

2. Resins consisting principally of Resin Acids. Resin, Oleo-Resin or Gum-Resin and Resin Acids : Colophony: Copaiba, Myrrh.

3. Glyco-Resins. This important and complex group comprises the glycosidal resins, which are so-called because when they are boiled with mineral acids hydrolysis takes place, with production of a sugar (usually dextrose) and a complex resin acid and simpler acids. Jalap resin and Ipomoea resin are examples of glyco-resins.