COLOPHONY 457 



The a- and /2-acids are removed from an ethereal solution of the 

 resin by shaking with solution of ammonium carbonate ; the -acid 

 by subsequent shaking with sodium carbonate solution, the resene 

 remaining in the ethereal liquid. The acid value 1 of colophony 

 varies from about 136 to 180 and the saponification value from 

 157 to 200. Although the saponification value is uniformly higher 

 than the acid value, the resin is nevertheless free from esters. 



Colophony may be identified by its high acid value and by the 

 following reactions : 0-1 gramme dissolved in 10 c.c. of acetic anhy- 

 dride and cooled assumes a bright wine-red colour on the cautious 

 addition of sulphuric acid ; 0*1 gramme warmed with 2 c.c. of methyl 

 sulphate gives a rose or violet coloration; a solution of 0-1 gramme 

 in petroleum spirit shaken with a 0-1 per cent, aqueous solution of 

 cupric acetate is coloured bright emerald green. 



Uses. Colophony has stimulant and diuretic properties. It is 

 used chiefly as an ingredient of ointments and plasters. 



Varieties, &C. Resin is obtainable in commerce in various grades 

 ranging from * water- white ' to nearly black. Opaque resin is made 

 by melting common resin with water. 



Bordeaux turpentine is obtained chiefly from P. maritima, Poiret, 

 in the south-western departments of Landes and Gironde. A vertical 

 incision is made through the bark and about 1 cm. deep into the wood 

 and an earthen pot is fixed at the bottom, in which the turpentine is 

 collected. The cut is gradually lengthened until it is about 3 metres 

 long, then the opposite side of the tree, and finally the edges of the 

 cicatrix of the first cut are incised, the tree remaining productive for 

 many years. A product similar to ' scrape ' is also obtained ; it is 

 termed ' galipot.' 



The resin consists of pimarinic, pimaric, and a- and /3-pimarolic acids. 

 The volatile oil is distinguished from American oil of turpentine by 

 being strongly Ia3vorotatory. 



Venice turpentine is obtained from the larch, Larix europcea, de 

 Candolle, in France and Southern Tyrol, by boring into the stem in 

 the spring, and collecting the oleo-resin that exudes. y It is a yellowish, 

 slightly turbid, viscid liquid, with bitter aromatic taste. The resinous 



1 The acid value is the number of milligrammes of potassium hydroxide 

 necessary to neutralise the acids present in one gramme of the resin. It is deter- 

 mined by dissolving a weighed quantity of the resin in alcohol and titrating with 

 alcoholic solution of potassium hydroxide, using phenolphthalein as indicator. 



The saponification value is the number of milligrammes of potassium hydroxide 

 necessary to neutralise the acids and also to saponify the esters present. It is deter- 

 mined by boiling a weighed quantity of the resin with an excess of alcoholic volumetric 

 solution of potassium hydroxide and titrating back with sulphuric acid. 



The ester value is the number of milligrammes of potassium hydroxide 

 necessary to saponify the esters present. It is obtained by deducting the acid value 

 from the saponification value. 



