— n6 — 



of ethylene bromide in water, the depressions obtained are too large 

 in consequence of the increased concentration. 



If waters containing alcohol are extracted with ethylene bromide, 

 the alcohol passes over in the latter, and would increase the depression. 

 This error can be corrected if the ethylene bromide containing alcohol 

 is once more shaken with 250 g. pure water. The ethylene bromide 

 thus remaining can now be used at once for the determination of the 

 freezing point. If the extraction is repeated again with 250 g. water, 

 the freezing point will fall by the correction-standard of 0,03°, as 

 soon as the ethylene bromide solution is completely freed from alcohol. 



In checking Vaubel's 1 ) method for the determination of the 

 bromine number in essential oils, G. Mossier 2 ) found that the 

 reaction does not proceed sufficiently rapidly to obtain reliable figures. 

 But in spite of the unsatisfactory results, he has occupied himself 

 further with the question of the action of bromine on essential oils, 

 and has worked out a method which renders it possible to determine 

 the whole quantity of the bromine which has reacted, and the portion 

 converted into hydrobromic acid. In order to determine the bromine 

 number (i. e. the quantity of bromine used up by an essential oil, 

 expressed in per cent), Mossier proceeds as follows: On the oil 

 dissolved in carbon tetrachloride he allows bromine to act which is 

 evolved from a solution of potassium bromide-bromate by acidification. 

 When the action has proceeded for six hours, he mixes the liquid 

 with solution of stannous chloride, until it is completely decolorised, 

 and determines the excess of stannous chloride with the help of 

 decinormal iodine solution. 



In order to determine the quantity of hydrogen bromide formed 

 during the action, Mossier also proposes to follow first the method 

 previously indicated. But when the time for reaction has elapsed, he 

 adds a solution of potassium bromate, shakes the mixture strongly, 

 and filters the aqueous layer in a separating funnel. From this solution 

 also the bromine is removed by extracting it three times with carbon 

 tetrachloride; to 100 cc. of the filtrate is now added potassium iodide, 

 and the iodine separated out is determined with solution of sodium 

 thiosulphate. With regard to the blind tests which should be made 

 at the same time, and also to the calculation, we would refer to the 

 original work. The quantity of bromine which is converted into 

 hydrogen bromide, expressed in per cent, of the oil, Mossier 

 designates as the hydrobromic acid number. It is claimed that from 

 the relation between the bromine number and the hydrobromic acid 

 number, the adulterations of the oils can be recognised. 



x ) Corap. Report April 1906, 66; October 1906, 77 '.' 



2 ) Zeitschr. d. allg. osterr. Apoth. Ver. 45 (1907), 223, 235, 251, 267, 283, 299. 



