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Copaiva Balsam Oil. The balsams which are used in the preparation 

 of Para copaiva balsam oil were occasionally very scarce, and the oil- 

 content of the imports in particular very often left much to be desired. 

 The price has undergone a corresponding increase and appears likely, 

 for the present, to be maintained at the advanced figure. Para copaiva 

 balsam oil has lately found a regular outlet as an artists* material for 

 painters' use, and appears to be found serviceable for that purpose. 



In our Report of October 1910, p. 40, we mentioned a method of testing 

 copaiba balsam recommended by Cocking, which is based, inter alia, upon 

 the feature that the optical rotation of the essential oil separated from 

 genuine balsam is invariably somewhat higher than that of the first 10°/o 

 distilled from the oil in vacuo. Cocking's method is intended to serve as 

 a means of detecting an addition of African copaiba balsam as well as 

 of Gurjun balsam, and has been recommended for adoption in the British 

 Pharmacopoeia. 



Parry 1 ), while examining several samples of Maracaibo balsam from 

 an undeniably reliable source has found that they did not correspond with 

 Cocking's requirements; on the contrary, in two samples the first 10% of 

 the oil, obtained by steam-distillation, showed a higher optical rotation 

 than that of the bulk of the sample, while in a third sample the two ro- 

 tations were exactly equal. The optical rotations of the separate fractions 

 of the oils compared with each other also deviated somewhat from the 

 values recorded by Cocking. Parry regards adulteration of the samples 

 examined by him as out of the question, the more so because the de- 

 viations were so slight that, if any adulteration were present, it could 

 only have been so small as not to be worth the trouble. 



Parry is of opinion that, in order to discover whether Cocking's me- 

 thod is really valuable, it would be necessary to examine a larger number 

 of samples of different origin. If this were done it would of course be 

 necessary also to lay down the conditions of distillation with great pre- 

 cision, and in all cases to carry out the separation of the oil from the 

 resin by steam-distillation, as any other distilling-method would give rise 

 to decomposition-products which would affect the rotation. Parry found 

 that the optical rotation of an oil distilled from the balsam in vacuo was 

 3,5° lower than that of an oil prepared from the same balsam by steam- 

 distillation. 



Cocking 2 ), in a rejoinder, denies the last-named assertion of Parry'*?. 

 Cocking has ascertained by experiment that it makes no difference whether 

 the oil is separated from the resin by distillation in steam or in vacuo, 

 and in proof of this contention he quotes the results of comparative ex- 



x ) Chemist and Druggist 80 (1912), 19. 

 2 ) Ibidem 128, 204. 



