OF ARTS AND SCIENCES. 243 



■white needles, often one to two centimeters long, which appear under 

 the microscope as tolerably thick prisms frequently tapering owing 

 to modification by the planes of a pyramid with a very acute angle, 

 but almost always, even in addition to this tapering, terminated bluntly 

 by the planes of another very obtuse pyramid. Occasionally the ter- 

 mination is a single plane at a moderately acute angle to the sides, but 

 this looked as if it were due to cleavage. The crystals are generally 

 very well developed, but if they are small, a tendency to twin longi- 

 tudinally is observed. If the substance is crystallized from alcohol, 

 the forms like feathers, or half-feathers, described in our previous 

 paper, and groups of branching needles looking like certain feathery 

 seaweeds, appear ; but as the alcohol decomposes the substance, these 

 forms can hardly be ascribed to the substituted acetic acid itself. It 

 melts at 177° ; and is essentially insoluble in ligroine or carbonic 

 disulphide ; very slightly soluble in chloroform, slightly in benzol, 

 more soluble in both of these solvents when hot ; tolerably soluble in 

 ether, separating from the solution in a liquid form, which solidifies 

 on stirring ; easily soluble in acetone or glacial acetic acid ; soluble 

 in cold alcohol, more freely in hot, but the alcohol, decomposes it, as 

 is indicated by the change in the appearance of the crystals, the long 

 yellowish prisms of unaltered bromdinitrophenylacetic acid becoming 

 roughly studded with fine needles of another substance, and by the 

 lowering of the melting point, when the substance is crystallized from 

 alcohol ; evaporation to dryness of the alcoholic solution, if repeated 

 three times, reducing the melting point from 177° to 147° ; while after 

 two more evaporations, making five in all, the melting point had sunk 

 to 103°-104°, at which point it remained constant after repeated 

 crystallization. The substance obtained in this way crystallized in 

 rectangular prisms, or plates, was not acted on by alkalies, and was 

 recognized as Grete's metabromdinitrotoluol.* For greater certainty 

 it was analyzed, with the following results : — 



I. 0.1690 gr. of the substance gave by the method of Carius 

 0.1210 gr. of aro-entic bromide. 

 II. 0.2185 gr. of the substance gave 20.3 c.c. of nitrogen at a 

 temperature of 22°. 5 and a pressure of 773.3 mm. 



* Ann. Chem., clxxvii. 258. 



