Commercial notes and scientific information. 63 



By this method, which he has put in practice for several years, Dodge has obtained 

 satisfactory results with mixtures of eucalyptol, terpenes, and terpineol. In applying 

 it, he has found the eucalyptol-content of eucalyptus oils to be from 52 to 85 p c. and 

 that of cajuput oils from 50 to 61 p. c. Oils rich in terpenes require about 400 cc. 

 and oils which are poor in terpenes about 100 cc. of the potassium permanganate 

 solution. 



C. T. Bennett 1 ) has experimented with Dodge's method, by making simultaneous 

 control-tests with phosphoric acid and with resorcinol. His conclusion is that although 

 with eucalyptol and eucalyptus oils of high cineol-content approximate results may 

 be obtained, the method is not to be relied upon for cajuput oil and for eucalyptus 

 oils of low cineol-content, as the results obtained were much too high, the reason 

 obviously being that the last-named oils contain constituents which are not entirely 

 oxidised by potassium permanganate in the cold. Bennett carried out his experiments 

 with 5 cc. oil in a cassia flask, whereby he obviated pouring over the non-oxidised 

 portion of the oil. 



We have also experimented with the method on artificial mixtures, and have also 

 failed to obtain satisfactory results. It is true that we found that pure eucalyptol 

 almost failed to react with potassium permanganate, but on the other hand it is partly 

 attacked in mixtures containing readily oxidisable substances, as for instance terpineol. 

 Terpineol, we may add, readily reacts with 5 p. c. permanganate solution, giving rise 

 to soluble oxidation-products. 



The conditions are different with pinene. Here, if the mixture is at once cooled 

 down at the beginning of the oxidising process, barely-one half of the pinene is 

 oxidised, but if cooling down is delayed until a faint self-heating has set in, and if 

 it is only carried out carefully when the temperature exceeds room-temperature, it is 

 possible to oxidise completely say 5 cc. pure pinene with 200 cc. of the solution. The 

 stability of the terpene towards permanganate is still more markedly shown in the 

 presence of eucalyptol. When the mixture consists of 25 p. c. eucalyptol and 75 p. c. 

 pinene, scarcely any pinene is oxidised during cooling, and even at room-temperature 

 the oxidation is very imperfect and unequal, with the result that far too much eucalyptol 

 is found. Only in the case of a great excess of permanganate, as for instance 1,5 cc. 

 pinene -f- 0,5 cc. eucalyptol (25 p. c.) to 200 cc. of the solution, all the pinene is oxidised 

 at room-temperature, but at the same time a portion of the eucalyptol is oxidised. In 

 any case it would seem that in oils rich in terpene, the terpenes can only be oxidised 

 with great difficulty, nor does an excess of permanganate mean that the oxidation 

 process is actually terminated. On the other hand, in the case of oils which are 

 poor in terpene, too little eucalyptol is found as a rule, because in such oils part of 

 the eucalyptol is also attacked. 



In our estimations we also used cassia-flasks, of course of sufficient size to allow 

 for the addition of enough potassium permanganate, that is to say at least 200 cc. of 

 5 p. c. permanganate solution for 5 cc. oil. 



The results obtained by us are summarised in the following table: — 



25 p. c. Cineol -f 75 p. c. Pinene: Cineol-content (est. by Dodge's method) 95 p.c. ; 90 p.c. ; 93,7 p. c. 



50 p. c. „ -j- 50 p.c. „ „ „ „ „ „ „ 95 p.c; 62,5 p.c; o5 p.c. ; °2,5 p.c. 



75 p.c. „ -f 25 p.c „ „ „ „ „ „ „ 62,5 p.c; 70 p.c; 72,5 p.c. ; o5 p.c. 



25 p.c „ +75 p.c. terpineol „ „ „ „ „ „ 7,5 p.c 



50 p.c „ + 50 p.c. „ „ 30 p.c. 



75 p.c. „ -f 25 p.c „ „ „ „ „ „ „ 60 p.c. 



') Per/, and Essent. Oil Record 3 (1912), 295. 



