Notes on scientific research. 127 



the sublimate, when heated, develops an odour of benzaldehyde. In testing, regard is 

 to be had to the fact that the resins often contain benzoic acid in addition to cinnamic 

 acid. Where benzoic acid is present, it is found in the initial sublimates; the cinnamic 

 acid passing over at a later stage. Moreover, the benzoic acid crystals are very definite 

 in shape and under polarised light their complex is different from that of cinnamic 

 acid crystale. Among chemical differentiations Tunmann mentions the different behaviour 

 of the two acids towards silver nitrate and towards bromine vapours. When silver 

 nitrate solution is added, the greater part of the crystals of cinnamic acid enters in 

 solution, or they become insignificant and lose their magnificent colours under polarised 

 light. Benzoic acid, it is true, also dissolves, but it soon reappears in more pronounced, 

 vigorously polarising crystals of silver benzoate. The action of bromine vapour converts 

 cinnamic acid into dibromo cinnamic acid; upon benzoic acid it has no effect. 



Further examination is needed to ascertain to what extent the esters of cinnamic 

 acid are also found in the sublimates, and whether they occur in them in the crystalline 

 form. 



Some time ago {Report October 1910, 61; April 1911, 149) we described a method 

 for the quantitative estimation of glyceryl acetate in essential oils which consists in 

 shaking out 10 cc. of the oil under examination with 20 cc. of 5 p. c. alcohol and of 

 saponifying 10 cc. of the filtered alcoholic-aqueous liquid after the two layers had 

 separated, and after previously neutralising with 5 cc. seminormal potash liquor. If 

 glyceryl acetate is absent not more than 0,1 cc. seminormal potash liquor is used up. 

 M. S. Salamon and W. M. Seaber 1 ) have experimented with this method on bergamot 

 oil to which glyceryl acetate had been added and have found, in confirmation of our 

 previous results, that even 2 p. c. glyceryl acetate may thus be detected without diffi- 

 culty, although at the same time it was found that even after shaking out five times 

 with dilute alcohol the whole of the glyceryl ester had not been removed from 

 the oil. 



On the other hand another method 2 ) which has been recommended for the same 

 purpose proved to be entirely useless. This method is based upon the fact that 

 glyceryl acetate volatilises with difficulty, and draws the conclusion of an eventual 

 sophistication of the bergamot oil under examination from the saponification value of 

 the evaporation-residue. The limits of value for normal oil were given as 145 and 190. 

 By this method Salamon and Seaber were unable to detect even 5 p. c. of triacetin in 

 a sample of bergamot oil. Although, after the addition of the triacetin the sap. v. of 

 the evaporation-residue had risen from 161 to 191, yet the value was not high enough 

 to warrant the conclusion that the oil had been adulterated. The authors further point 

 out that in order to determine the evaporation-residue it is not enough to heat the 

 oil on the water-bath for two hours only, as is said to be done occasionally. In one 

 experiment constancy of weight was only reached after 97« hours with 5,82 p. c. residue, 

 while the evaporation-residue after 3 hours' heating was 6,61 p. c. 



We may add to the above that the second of the two methods referred to is useless 

 for the special estimation of glyceryl esters, if for no other reason, because other 

 sparingly volatilisable esters, such as triethyl citrate, would be left behind in the 

 evaporation-residue; hence the method could only give a general indication for sparingly- 

 volatile esters. With regard to the method devised by ourselves, we have shown in 



x ) Perfum. and Essent. Oil Record 3 (1912), 275. — 2 ) Salamon and Seaber do not state who is the 

 author of this method. 



