496 OLEO-RESINS 



crystals embedded in a transparent mass and accompanied by a little 

 vegetable debris. 



It is easily soluble in alcohol, acetone, and chloroform, but only 

 partially soluble in carbon disulphide, yielding to the latter princi- 

 pally cinnamic acid. The solution obtained by gently warming the 

 balsam with carbon disulphide leaves when evaporated about 25 per 

 cent, of crystalline residue consisting chiefly of cinnamic and benzoic 

 acids. The British Pharmacopoeia requires that the balsam should 

 contain at least 25 per cent, of free aromatic acids, but it has been 

 shown that 20 per cent would be a more reasonable requirement. 

 Cocking and Kettle (1918) found an average of about 36 per cent, 

 of total aromatic acids, free and combined, of which about 8 per 

 cent, was free benzoic and 12*8 free cinnamic acid, 7 per cent, 

 combined benzoic, and 8 per cent, combined cinnamic acid. 



Constituents. Tolu balsam was examined by Oberlander (1894), 

 who found it to contain the following constituents : about 7*5 per 

 cent, of an oily liquid (consisting of benzyl benzoate with a little 

 benzyl cinnamate), traces of vanillin, free aromatic acids, principally 

 cinnamic, and resin. The resin, amounting to about 80 per cent, of 

 the drug, yielded by saponification an alcohol (toluresinotannol), and 

 cinnamic acid, with which was associated a little benzoic acid. 



Distilled with water good fresh balsam of Tolu yields from 1*5 to 

 3'0 per cent, of a very aromatic volatile oil containing tolene, styrol, 

 and free benzoic and cinnamic acids. 



Uses. Tolu balsam is used chiefly as a pleasant ingredient in cough 

 mixtures. It possesses antiseptic properties due to the cinnamic and 

 benzoic acids contained in it. 



Adulterants. The chief adulterants of balsam of Tolu are colo- 

 phony and balsam that has previously been used in making syrup 

 of Tolu and hence deprived of most of its free cinnamic acid and 

 aromatic constituents. 



The acid value of genuine balsam ranges from 107*4 to 147*2, and 

 the saponification value from 170 to 202. 



Colophony may be detected by exhausting the balsam with carbon 

 disulphide and evaporating the filtered solution. Pure balsam gives 

 about 25 per cent, of crystalline residue ; if colophony is present the 

 residue is resinous and gives with concentrated sulphuric acid a green 

 colour ; a petroleum spirit extract of the residue shaken with an 

 equal volume of a 0*1 per cent, solution of cupric acetate assumes 

 a bright green colour if colophony is present. - 



Exhausted balsam may be detected by the deficient amount of 

 substances soluble in carbon disulphide and of aromatic acids. 



