EOSEMAEY. 413 



Barenthin ... 185% 

 Davies ... 325%* 



Williams ... 161'7% (sp. gr. "894, probably foreign, judging 

 from sp. gr.)t 

 „ ... 142-4% (sp. gr. -912, probably English, judging 



from sp. gr.) 

 Sample ^N^o. 1. 



2 hours ... 98-8% mean 

 18 „ ... 117-3% 



Bromine ctbsorption. I greatly prefer this to the last test for 

 rosemary : in my hands it has given more concordant results, and 

 the short time of digestion (fifteen minutes) is a decided advantage. 

 In carrying it out I follow Allen :^ as employed for shale and 

 petroleum oils. "An approximately decinormal solution of 

 bromine is made by dissolving 2 c. c. of bromine in 750 c. c. of 

 recently distilled carbon disulphide. This solution is rendered 

 perfectly anhydrous by the addition of some lumps of dry calcium 

 chloride. An accurately weighed quantity of the dry oil, weighing 

 between '2 and '4 gram., or a measure of a solution in carbon 

 disulphide, containing a known weight of the oil, is placed in a 

 perfectly dry stoppered flask ; the solution diluted to about 25 c. c. 

 (I use 10 c. c.) with dry carbon disulphide, and then 25 c. c. of the 

 bromine solution added. The flask is then closed and the contents 

 agitated. If the liquid is distinctly red, sufficient bromine has been 

 added, but should it be nearly or quite decolorised, a further 

 addition of bromine should be made without delay. The flask is 

 then at once placed in the dark and kept there for exactly fifteen 

 minutes, when an excess of aqueous solution of iodide of potassium 

 is poured in, the whole agitated, the flask removed to a light place 

 and the solution titrated with decinormal solution of sodium thio- 

 sulphate." Violent agitation is necessary towards the end of the 

 titration, as the iodine remains dissolved in the carbon disulphide. 

 Twenty-five c. c. of the bromine solution is treated exactly 

 similarly in another dry flask ; when the difference between the 

 volume of standard thio-sulphate required in the two titrations 

 indicates the amount of thio-sulphate corresponding to the bromine 



* Pharm. Journ. [3], xix., p. 823. 



+ Chem. News., 1887, p. 175. 



X Commercial Organic Analysis, p. 331. 



