— 75 — 



the properties are nevertheless recorded here for the purpose of showing 

 f what low-grade products are placed upon the market as the result of the 

 present high price of bergamot oil: — 



d 15 o 0,8812 0,8802 0,8667 0,8710 0,8694 0,8629 



«„ 4-22° -f 19° 35' + 56° 30' -f 30° +30° 40' +53° 50 



Residue of evap 4,5°/o 4,4°/o 3,2% — — 1,7° o 



Solub. in 90% alcohol . 0,2 vols. 0,2 vols. 0,5 vols. 10 vols. 10 vols. 4,5 vols, 



a.m. a.m. a.m. insoluble insoluble a.m. 



Acid v 1,6 2,8 1,5 1,8 1,8 0,9 



Ester v 76,9 76,5 57,7 45,7 36,4 41,1 



Ester (calc. as linalyl 



acetate) 26,9% 26,8% 20,2% 16,0% 12,7 <>/o 14,4% 



Lemon Oil. In our Report of November 1908 (p. 61) we stated that 

 in the examination of a considerable number of samples of authentic lemon 

 oils we had estimated the citral-content by a method which had been 

 communicated to us from a friendly quarter (Dr. Kleber), but which so far 

 had not been published. Comparative tests with mixtures of known citral- 

 content, made at the time, demonstrated the satisfactory character of the 

 method. We ascertained the citral-content of the lemon oils in question 

 to be from 4,3 to 7,2 °/o. Afterwards (Report October 1911, p. 45) we made 

 it known that in its original form the method had given values which, in 

 part, were found to be too high, and that after having improved the method 

 it only showed a citral-content of from 4 to 5°/o. 



We are glad that, after a long interval, the publication of a paper by 

 Kleber 1 ) enables us to give further particulars of the method, and our 

 satisfaction is the greater because expressions of criticism of our prolonged 

 silence have already made themselves heard 2 ). As however, the method 

 was made known to us in confidence by Dr. Kleber at the time, we did 

 not regard ourselves entitled to publish it. The basis of Weber's method 

 is the observation that phenylhydrazine (when di-ethyl orange is used as an 

 indicator) gives a sensitive titration with mineral acids, and that with 

 aldehydes and ketones it forms hydrazones which give a neutral reaction 

 with di-ethyl orange. Kleber proceeds as follows: — 



About 10 g. lemon oil are exactly weighed into a flask, 20 cc. of 

 freshly-prepared 5°/o alcoholic phenylhydrazine solution are added, the 

 stoppered flask is allowed to stand about half an hour at about 35 °, 

 after which as much seminormal hydrochloric acid is added as is required 

 to neutralise the phenylhydrazine solution, the quantity having been 

 Ireviously estimated by a separate test. The mixture is poured into a 

 separator, the flask itself rinsed out with 20 cc. water and the whole 

 vigorously shaken. As soon as the two layers have separated, the lower 

 of the two is drawn off into an titration flask, the residue washed out with 



J ) Americ. Perfumer 6 (1912), 284. 



2 ) Umney, Perfum. and Essent. Oil Record 2 (1911), 260. 



