JACKSON AND CALVERT. DERIVATIVES OF BENZOL. 133 



small amount of white needles was obtained, which melted at 119°, 

 the melting point of symmetrical tribrombenzol. The residue which 

 had not sublimed at the very low temperature used made up the prin- 

 cipal bulk of the product, and was chiefly unaltered tetrabrombenzol. 

 This method of fractional sublimation has also yielded us excellent re- 

 sults in aoother similar case, which will be described later in this 

 paper. The sodic ethylate therefore acts on the tetrabrombenzol in 

 the same way that it does on the tribromiodbenzol, replacing by hy- 

 drogen the bromine atom occupying the same position as the atom 

 of iodine, but the action takes place with more difficulty, and is less 

 complete. 



Behavior of Unsymmetrical Tribromchlorbenzol. 



The tribromchlorbenzol was prepared by a method similar to that 

 used for the tetrabrombenzol. Upon adding the hydrochloric acid to 

 the solution of tribromaniliue in glacial acetic acid a precipitate of the 

 chloride was formed, but this went into solution as the amido was con- 

 verted into the diazo compound. Twenty grams of tribromaniliue 

 yielded 15 grams of tribromchlorbenzol melting at 82°. Two grams 

 of this substance were heated for four hours with an alcoholic solution 

 of sodic ethylate, prepared from half a gram of metallic sodium ; when 

 upon evaporation to dryness and washing with water only a very 

 faint test for halogens could be obtained from the wash water, and the 

 residue, which consisted of unaltered tribromchlorbenzol, weighed 

 nearly 2 grams. A similar experiment with the tetrabrombenzol, in 

 which the mixture was boiled for only three hours, gave a strong test 

 for sodic bromide and a small amount of tribrombenzol. The chlor- 

 tribrombenzol, therefore, if affected at all by sodic ethylate, is much 

 less susceptible to its action than either the corresponding iod or brom 

 compound. 



Behavior of Symmetrical Tetrahromhenzol. 



Tetrabrombenzol, melting at 174°-175°, which has been proved by 

 work done in this Laboratory to have the symmetrical constitution (1, 

 2, 4, 5), was boiled for over twelve hours with an alcoholic solution of 

 sodic ethylate ; tlie brown liquid thus obtained, with some long rather 

 dark colored crystals, which were deposited as it cooled, was evapo- 

 rated to dryness, and the residue washed with water. The wash 

 waters gave a good test for sodic bromide. The residue insoluble in 

 water was then extracted, with a mixture of alcohol and benzol, 

 filtered to remove a brown insoluble substance, and the filtrate concen- 



