Colophony

COLOPHONY

Synonyms

Rosin, yellow resin; Abietic anhydride; colophony resin; amber resin; resin; coloponium.

Biological Source

Colophony is a solid residue left after distilling off the volatile oil from the oleoresin obtained from Pinus palustris (long leaf pine) and other species of Pinus such as P. pinaster, P. halepensis, P. massoniana, P. tabuliformis, P. carribacea var., belonging to family Pinaceae.

Geographical Source

The genus Pinus is widely found in United States, France, Italy, Portugal, Spain, Greece, New Zealand, China, India (Himalayan region), and Pakistan. Colophony is chiefly produced in the United States contributing about 80% of world supply. Other countries producing the resin are China, France, Spain, India, Greece, Morocco, Honduras, Poland, and Russia.

Collection

The collection of the oleoresin is very laborous procedure. Although Colophony is a normal (Physiological) resin of Pinus species, its amount is increased by injuring the plant. For its collection a few-feet long groove or blaze is made in the bark with the help of knife or some other instru-ment. A metal or earthenware cup is attached below the groove by nails. The cup is adjusted accordingly when the size of groove increases. The resin is taken out at different intervals and sent for further processing.

Cup and Gutter Method

This method is used in America, European countries, India, and Pakistan. The 60–100 cm long blaze or longitudinal groove is cut with a suitable instrument. It is enlarged at intervals and in about four years is about 4 m long. The metal or earthenware cups are attached to the trunk by nails and one or two strips of galvanized iron are placed above each to direct the flow of oleoresin. As the grooves are lengthened the cups are moved higher up the tree and new grooves are started when the old ones become exhausted or collection is difficult. The cups are emptied at intervals and the oleoresin sent to the distillery. Trees can be tapped by this method for about 40 years.

Preparation

The crude oleoresin arrives at the distillery in barrels. It is mixed with about 20% by weight of turpentine in a heated stainless steel vessel and allowed to stand to separate water and other impurities. The diluted oleoresin is then transferred to copper or stainless steel stills and the turpentine is removed by steam distillation. When distillation is complete the molten resin is run through wire strainers into barrels, in which it cools and is exported.

The resin obtained from trees during their first year of tapping is of a lighter colour than that obtained later on. The following grades of American rosin are recognized: B, FF (for wood rosin only), D, E, F, G, H, I, K, L, M, N, WG (window-glass), WW (water-white), and the extra-white X grades and American and Portuguese qualities (XA, XB. XC). A great deal of the American tall oil rosin is now paler than grade X. Grade B is almost black.

Characters

Colophony occurs as translucent, hard, shiny, sharp, pale yellow to amber fragments, fracture brittle at ordinary temperature, burns with smoky flame, slight turpentine-like odour and taste, melts readily on heating, density 1.07–1.09. Acid number is not less than 150. It is insoluble in water but freely soluble in alcohol, benzene, ether, glacial acetic acid, oils, carbon disulphide, and alkali solutions.

            Pinus palustris

Chemical Constituents

Colophony contains resin acids (about 90%), resenes, and fatty acid esters. Of the resin acids about 90% are isomeric α-, β-, and γ-abietic acids; the other 10% is a mixture of dihydroabietic acid and dehydroabietic acid. Before distillation, the resin contains excess amounts of (+) and (-) pimaric acids. During distillation the (-) pimaric acid is converted into abietic acid while (+) pimaric acid is stable. The other constituents of Colophony are sipinic acid and a hydrocarbon.

Chemical Tests

1.     To a solution of powdered resin (0.1 g) in acetic acid (10 ml) one drop of conc. Sulphuric acid is added in a dry test tube. A purple colour, readily changing to violet, is formed.

2.     To a petroleum ether solution of powdered Colophony twice its volume of dilute solution of copper acetate is shaken. The colour of the petroleum ether layer changes to emerald-green due to formation of copper salt of abietic acid.

3.     To alcoholic solution of Colophony sufficient water is added. It becomes milky white due to precipitation of chemical compounds.

4.       Alcoholic solution of Colophony turns blue litmus to red due to the presence of diterpenic acids.

Uses

Colophony is used as stiffening agent in ointments, adhesives, plasters and cerates and as a diuretic in veterinary medicine. Commercially it is used to manufacture varnishes, printing inks, cements, soap, sealing wax, wood polishes, floor coverings, paper, plastics, fireworks, tree wax, rosin oil, and for water proofing cardboard.

The abietic acids show antimicrobial, antiulcer and cardiovascular activity; some have filmogenic, surfactant, and antifeedant properties.