— 153 — 



The phenol determinations also give different results for the com- 

 parative tests, but here Moerk used in one case a 10 per cent, and 

 in another a 5 per cent. (U. S. Ph.) liquor. This, of course, must 

 produce differences in the results. In the case of oils containing eugenol 

 a 10 per cent, solution is useless in any case, because it also dissolves 

 a portion of the non-phenols. Even a 5 per cent, liquor gives too high 

 results in the cases of pimento oil, terpeneless bay oil and clove oil 

 of high percentage, and for the same reason. Hence we have lately 

 used a 3 per cent, liquor for such determinations. On the other hand, 

 for thyme oils a 5 per cent, liquor is to be preferred. Some con- 

 siderable time ago we entered at length into this question, and we 

 may now refer to that publication 1 ). 



G. R. Pancoast and W. A. Pearson 2 ) write on preliminary tests for 

 the determination of the purity of essential oils. Among these they 

 class tests for odour, taste, colour, and solubility, giving further details 

 for the oils most in use. A reference to the paper will suffice here. 



The method of J. Walther for the determination of the citral-content 

 of oil of lemon by the aid of hydroxylamine, mentioned in our last 

 Report 3 ), which has been tried in a modified form with pure citral 

 and oils of lemon by A. H. Bennett, has been submitted by us to a 

 controlling test, Bennett's method is again described concisely below: 



A mixture of 20 cc. oil of lemon (in order to avoid a calcul- 

 ation in the determination of the percentage we used 20 g.), with 

 20 cc. alcoholic (80 per cent, alcohol) semi-normal hydroxyl amine- 

 hydrochloride solution is diluted with 8 cc. alcoholic normal potash 

 liquor and 20 per cent, of strong alcohol free from aldehyde, and 

 boiled half an hour with a reflux condenser. When cooled, it is diluted 

 with 250 cc. water and the hydrochloric acid which still remains in 

 the form of hydroxylamine hydrochloride is neutralised, phenolphthalein 

 being used as indicator. The hydroxylamine which is not combined 

 with citral is now estimated volumetrically with semi-normal sulphuric 

 acid by determining the final reaction by means of stipple - tests in 

 a highly- diluted solution of methylorange. A similar course is adopted 

 in a blank test without oil of lemon, in order to determine the 

 volume of the hydroxylamine solution. From the difference in the 

 cc. of semi-normal sulphuric acid used up in the two tests, the quantity 

 of hydroxylamine which has entered into the reaction is obtained 

 and thence, and by multiplying with 0,076, the citral-content. 





*) Report April 1907, 118. 



2 ) Amer. Perfumer 4t (1909), 65. 



3 ) Report April 1909, no. 



