350 



with the cineol in its diluted state, so that correctly speaking no general formula 

 can be given, as commercial phosphoric acid has not always the same concen- 

 tration. From the results of this work, which was carried out with the oils of 

 E. cinerea, E. Smithii, and E. Morrisii, it was found that the mean cineol content 

 in the perfectly dry powdery compound was 59-47 per cent., while the phosphoric 

 acid (H 3 PO 4 ) only represented 89-27 per cent., the difference being water. 

 The H 3 PO 4 in the acid employed was 89-4 per cent. The theoretical mean for 

 the cineol from the H,PO 4 found was 59-56 per cent., thus being in very fair 

 agreement. 



The results showed that 59-5 was approximately the amount of cineol in 

 100 parts of cineol-phosphate, and not 61-1 per cent., as was previously 

 supposed. 



QUANTITATIVE DETERMINATION OF CINEOL 

 IN EUCALYPTUS OILS. 



Although several methods for the quantitative determination of cineol 

 have been employed, chiefly based on the reactions and combinations it forms 

 with various reagents, yet, it must be admitted that none of them gives 

 results absolutely correct, so that a successful method for determining accurately 

 the amount of cineol in Eucalyptus oil, under all conditions, has yet to be 

 discovered. 



With present methods advantage is taken of the loose combinations cineol 

 forms with phosphoric acid or arsenic acid of certain strengths, or by absorption 

 with resorcinol. Difficulties, however, present themselves, particularly the 

 instability of the compounds with the acids under atmospheric conditions. 

 With resorcinol the trouble is that other substances present in Eucalyptus 

 oils besides the cineol are also absorbed. 



With the phosphoric acid or arsenic acid methods the result depends, to 

 a certain extent, on the manipulation, as well as the method of procedure 

 adopted, so that, for commercial purposes at any rate, some uniform method 

 should be recognised, such process being carried out always in a similar manner. 



To largely remedy this defect of the "personal equation" we have 

 devised a Rapid Phosphoric Acid Method, using petroleum ether, as in this 

 way both quantities and times are fixed and the results satisfactory. (In 

 connection with this problem see "' Perfumery and Essential Oil Record," 

 August, 1919, p. 211. Bennett and Salomon.) 



The quantitative determinations for cineol recorded in the first edition of 

 this work (published 1902) were all carried out with the phosphoric acid method 

 as employed at that time. It was then considered necessary for the cake of 

 cineol phosphate to be repeatedly pressed between fresh paper until grease spots 

 ceased to appear. This rigid method of procedure is now known to have given 

 too low results, more particularly in a hot climate like that of Sydney, and it 

 might therefore have been permissible to add a certain percentage to the 

 figures there given. We have, however, in this edition retained the results as 

 previously recorded, but have added the letters O.M. (meaning old method) to 

 denote the particular process employed. 



In other cases where the more recent application of the phosphoric acid 

 method has been used those letters are omitted, or the process employed is 

 noted. Recently the resorcinol method has been utilised to a considerable 

 extent, but in all cases where this has been done, it is so stated; with several 

 of the oils the necessary corrections have been made for the non-cineol substances 

 absorbed, or for the alcohols present, and with a very large number the results 

 obtained with the phosphoric acid method are also given for comparison. 



