- 46 - 



Both methods have the drawback that the addition - products 

 of eucalyptol with hydrobromic acid and with phosphoric acid decom- 

 pose very readily, which renders a quantitative separation very diffic- 

 ult. In consequence of this, the results obtained by the one or the 

 other of the two methods are mostly too low, and in any case not 

 absolutely reliable, as will be seen from the annexed table. This 

 applies above all to the phosphoric acid determination, with which 

 the results are almost without exception incorrect. If the undiluted 

 oil is employed, the product separated off is so viscid, that it 

 becomes most difficult to remove by pressure the portions of the 

 oil which have not entered into reaction, whilst at the same time 

 losses of cineol, owing to decomposition of the compound, cannot 

 possibly be prevented. The separation of the compound succeeds 

 better, if the oil is previously diluted with petroleum ether, as already 

 mentioned in the description of the method given above; but in this 

 case also the cineol is not removed quantitatively, as, according to 

 Mossler's 1 ) observations, a portion of the cineol is again abstracted 

 from the reaction product by the petroleum ether (or does not enter 

 into reaction at all). This is also found in washing the product with 

 petroleum ether, when we observed partly also direct losses of cineol. 

 It is, moreover, necessary to exercise great care in adding the phos- 

 phoric acid, as a slight excess already renders the originally crystalline 

 product sticky; there is consequently added the risk that owing to 

 an insufficient addition of phosphoric acid, not the entire cineol 

 is combined. A really correct result is here more a matter of 

 chance. According to these experiences we consider the 

 phosphoric acid method totally unreliable and useless, 

 and must decidedly caution against its adoption. 



With the aid of hydrobromic acid we obtained results which 

 were partly correct, but without being able to obviate in some cases 

 quite considerable losses. The development takes place best from a 

 saturated solution of hydrobromic in glacial acetic acid, but if the in- 

 troduction of hydrogen bromide is prolonged, it is, even when using an 

 intermediate vessel containing sulphuric acid, impossible to avoid that 

 small quantities of acetic acid also pass over, and then exert a decom- 

 posing action on the cineol hydrobromide. This may of course 

 occassionally give rise to considerable errors. Attempts to effect the 

 development of the hydrobromic acid in a different manner gave no 

 better results, and were for that reason again abandoned. A further 

 difficulty in the quantitative separation of cineol hydrobromide is this, 

 that the compound is extremely hygroscopic, and the absorption of 

 water also takes place with decomposition. As it is impossible to 



*) Zeitscbr. d. allg. osterr. Apoth. Ver. 45 (1907), 299. 



