Commercial notes and scientific information. 25 



In view of the fact that Sadtler's method also determines only the free benzalde- 

 hyde which is present in the bitter almond oil, Dodge calls attention to the illo- 

 gicality of the requirements of the U. S. A. Pharmacopoeia in insisting upon a hydro- 

 cyanic acid content of from 2 to 4 p.c, together with a minimum of 85 p.c. benzaldehyde, 

 inasmuch as the hydrocyanic acid percentage demanded represents a proportion of 

 free benzaldehyde varying from 80,3 to 90,1 p. c. 



Dodge has worked out yet another method for the quantitative estimation of 

 benzaldehyde. This is based upon Cannizzaro's reaction (reaction of benzaldehyde 

 with potassium hydroxide): — 



2 C 6 H 5 CHO + KOH = C 6 H 5 COOK + C 6 H 5 CH 2 OH. 



He made tests with alcoholic potash liquor, which showed that the reaction does 

 not proceed quantitatively when the liquor is of less than twice the normal strength. 

 Good results were obtained with a 2,5-normal liquor. With this, 10 cc. is allowed to 

 stand for 24 hours at room-temperature with an exactly-weighed quantity (1 to 2 grams) 

 benzaldehyde (a shorter period of reaction with warming had proved ineffective), after 

 which the unattacked alkali is titrated back with seminormal hydrochloric acid. This 

 blank test makes it possible to ascertain at the same time the exact strength of the 

 potash-liquor. The difference shows how much of the alkali has entered into reaction, 

 expressed in cc. of seminormal potash-liquor. By multiplying the number of cc. with 

 the molecular weight of benzaldehyde (106) and dividing by the quantity of oil employed 

 in the test, the aldehyde-content is obtained. 



In the case of pure artificial products, Dodge found this content to be from 99,03 

 to 100,3 p. c. He rightly lays stress upon the fact that in measuring off the 2,5-normal 

 potash liquor it is necessary to proceed with great care, because so small a difference 

 as 0,05 cc. represents an error of not less than 1 to 2,5 p. c. benzaldehyde. In our 

 opinion this fact alone makes the usefulness of the method somewhat problematical. 



In the case of natural bitter almond oil the method gave no useful results, presumably 

 because the saponification of the benzaldehyde-cyanohydrin into mandelic acid was 

 incomplete. Moreover, in this case it is probable that owing to the presence of ammonia 

 when phenolphthaleine is used as an indicator, the terminal point of the reaction is 

 not easily distinguished. 



As the odour and taste of the benzaldehyde which is prepared from bitter almond 

 oil are generally regarded as superior to those of even the best artificial product, it 

 is to be presumed that the natural article contains a hitherto unknown constituent. 

 Dodge has attempted to solve this problem by dissolving 60 grams of a bitter almond 

 oil which had been freed from hydrocyanic acid in 100 cc. ether, and diluting the 

 solution with 200 grams concentrated bisulphite solution. The resulting bisulphite 

 compound was filtered off after 18 hours, and washed with ether, the ethereal extract 

 being evaporated in a vacuum-desiccator after being shaken with a little soda-solution. 

 This left a residue of about 0,2 p. c. of a yellow oil, heavier than water, and possessing 

 a pleasant, characteristic odour. So far Dodge has not succeeded in identifying it. 

 Artificial benzaldehyde, when similarly treated, yielded traces of an oil without any 

 clearly-expressed odour. 



Almond Oil, Pressed. See Chemical Preparations and Drugs, p. 113. 



Ambrette Seed Oil. Ambrette seed of good quality remains extraordinarily 

 scarce, hence the elevated values have been maintained. The demand for ambrette 



