OP ARTS AND SCIENCES. 255 



that the anhydride, although on account of its high melting-point some- 

 what less manageable than the non-substituted one, acts excellently on 

 all substnnces which can stand a high teniperature, and can usually be 

 made to act on those which cannot by heating with anhydrous benzol 

 in a sealed tube. As all the derivatives of parabrombenzoic acid 

 described in this paper, with the exception of the chloride, are new, 

 we give a full account of their properties, as a contribution to our 

 knowledge of this hitherto neglected acid. 



Preparation of Parahromhenzoic Acid. 



Although this method offers no new features, we think it best to 

 describe it as a matter of convenience for those who may wish to ob- 

 tain the acid in quantity. The first step is the preparation of crude 

 monobromtoluol by mixing toluol with ten per cent of its weight of 

 iodine and the calculated amount of bromine. After the mixture has 

 stood at the ordinary temperature for twelve hours, the product is 

 washed with sodic hydrate and water, the bromtoluol fractioned, and 

 the portion boiling from 180° to 190° oxidized by boiling 150 gr, of 

 it in a flask with a returu-condenser for twelve hours with 400 gr. of 

 potassic dichromate and 550 gv. of sulphuric acid diluted with twice its 

 bulk of water. The unoxidized oil, consisting of orthobromtoluol 

 with a little para, is distilled off with steam, and the acid purified 

 by washing with water and conversion into the sodic salt. The 

 product is free from the isomeric brombenzoic acids, as shown by 

 its melting point, 248-250° (uncorr.). The yield varied from 40 to 

 70 per cent of the weight of crude bromtoluol used, and a prepara- 

 tion can be carried through from toluol to the pure acid in less than 

 one week. 



Parabromhenzoylchloride, CeH^BrCOCl. — This substance has been 

 prepared by J. W. Raveill,* under the direction of Ilubuer ; but he 

 gives only the most meagre description of it, stating that it forms color- 

 less, easily fusible, volatile needles. It is prepared without difficulty 

 by heating a mixture of phosphoric pentachloride and the dry acid in 

 a flask to 100" until the reaction has ceased, when the temperature is 

 to be raised to 150°, and kept at this point until the greater part of 

 the phosphoric oxychloride formed has passed off. The chloride is 

 then extracted with ligroine and purified by distillation. The yield is 

 about 80 per cent. Its composition was determined by the following 

 analyses : — 



* Ann. Chem., ccxxii. 178, note. 



