PHYSICAL CHARACTERISTICS AND CHEMICAL NATURE OF RESINS

Physical Characteristics: -

Resins are usually hard, transparent or translucent.

Upon heating resins are softened and finally melt.

They are insoluble in water and usually insoluble in petroleum, spirit but dissolve more or less completely in alcohol, ether and chloroform.

Chemical Nature: -

Chemically resins are complex mixtures of Resin acids, Resin alcohols (Resinols) Resin phenols (Resinotanols), Ester and Resens.

Resin acids: -

These contain a large proportion of OXYACIDS and combine the properties of CARBOLIC ACIDS and PHENOLS.

They occur both in Free State an as esters. They are soluble in aqueous solution of alkalies and usually form soap like solutions or colloidal suspensions.

Their metallic salts are known as RESINATES, some of these resinates are used extensively in the manufacturing of cheap soaps and varnishes.

Example of resin acid is

Abietic Acid in Rosin or Colophony.

Commiphoric Acid in Myrrh.

Resin Alcohols:-

These are complex alcohols of higher molecular weights. They occur in Free State and esters. Resin alcohols are classified into two types.

Resinotanols:- Give a tannin reaction with iron salts.

Resinols:- Do not give tannin reaction.

These are complex natural substances, devoid of characteristic chemical properties. They do not form salts or esters and insoluble in alkalies.