560 J. READ AND M. M. WILLIAMS. 



lated quantity of bromine is sufficient to produce a per- 

 manent yellow tinge in the liquid. 



When the absorption is complete the undissolved cinnamic 

 acid dibromide is separated by filtration from the aqueous 

 liquid, which contains the phenyl-a-bromolactic acid in 

 solution. This substance is readily isolated by extraction 

 with ether, in which it is extremely soluble. The extracted 

 aqueous liquid upon evaporation yields nothing beyond a 

 further small quantity of cinnamic acid dibromide. No 

 bromostyrolene appears to be formed in the reaction. 



The purification of phenyl-a-bromolactic acid appears to 

 have been effected in many cases by crystallisation from 

 chloroform, notwithstanding its ready solubility in the cold 

 solvent. The best results are obtained by crystallisation 

 from hot water or from hot benzene or toluene; the acid 

 may also be crystallised from hot ligroin, in which, how- 

 ever, it is only sparingly soluble. The pure acid dissolves 

 to a clear solution in warm water. A slight admixture of 

 cinnamic acid dibromide is sufficient to cause turbidity in 

 such solutions, due to the formation of bromostyrolene; the 

 latter substance may easily be removed by shaking the 

 liquid with light petroleum. It may also be noted that 

 phenyl-a-bromolactic acid separates readily from aqueous 

 solution, in the form of a crystalline precipitate, upon the 

 addition of dilute sulphuric acid. 



After one recrystallisation from hot toluene, the acid 

 prepared in the manner described above melted at 120° — 

 122°. Upon adding an equivalent amount of silver nitrate 

 solution to an aqueous solution of the acid, a rapid separa- 

 tion of the crystalline silver salt occurred; titration of the 

 washed and air-dried salt with standard ammonium thio- 

 cyanate solution indicated a silver content of 30*28 per 

 cent., the formula 9 H 8 3 BrAg corresponding to 30*68 per 

 cent. 



