OF ARTS AND SCIENCES. 223 



Properties. — The substance sepai-ates from the oil at first obtained, 

 either in flat truncated octahedra with a marked basal cleavage belong- 

 ing either to the tetragonal or orthorhombic system, and having a very 

 strong resemblance to the crystals of ferrocyanide of potassium, or else 

 in flat twins imitating in a very beautiful manner the architectural 

 forms of the trefoil and quatrefoil. These crystals are yellowish 

 white, but the substance is rendered colorless by crystallization from 

 alcohol ; it has a disagreeable odor, does not attack the eyes, melts at 

 46*^, burns with a luminous green-bordered flame, and is insoluble in 

 water, moderately soluble in cold, freely in hot alcohol, soluble in 

 ether and glacial acetic acid, still more readily in carbonic disulphide 

 and benzole ; by boiling with alcoholic potassic hydrate or heating 

 in a sealed tube with hydrochloric acid it is easily converted into para- 

 bromalphatoluylic acid. It is to be remarked that the chlorbenzyl- 

 chloride, according to the observations of Neuhof,* gave when heated 

 as above with alcoholic potassic cyanide, the amide of chloralphatoluylic 

 acid, the cyanide being obtained only by heating the substances in a 

 sealed tube ; this difference in the behavior under like conditions of 

 two substances so nearly related as chlorbenzylchloride and parabrom- 

 benzylbromide is interesting. 



Parahromalphatoluylic Acid (^C^^H^Br.CH.-^COOH). This substance 

 was most easily obtained by heating the cyanide with crude fuming 

 hydrochloric acid to 100^ in a sealed tube. On cooling, the liquid 

 was found to be full of shining flattened needles of the acid, another 

 portion of which had fused on the side of the tube ; this method gave 

 better results more neatly than the saponification with potassic hydrate ;. 

 the acid was purified by recrystallization from boiling water, and its 

 composition established by analyses of its silver and copper salts. 

 (See bilow.) 



Properties. — It crystallizes in white glistening flattened needles 

 with but little odor, melts at 114.5", sublimes above its melting-point 

 m little plates, and burns with the usual luminous green-bordered 

 flame. It is but slightly soluble in cold, freely in boiling water, and in 

 alcohol, ether, benzole, carbonic disulphide, and glacial acetic acid. 

 Ammouic and sodic hydrates dissolve it at once, forming the corre- 

 sponding salts; it seems to decompose carbonates, but very slowly and 

 imperfectly : potassic dichromate and dilute sulphuric acid convert it 

 with some difficulty into parabrombenzoic acid melting in an impure 

 state near ■24C. 



* Zeitschr. Chem. 1866, p. 653. 



