150 PROCEEDINGS OF THE AMERICAN ACADEMY. 



The substance can be obtained more expeditiously in a pure state by 

 avoiding the preparation of solid phenylene diacetaniide as follows. 

 A strono- ethereal solution of phenylene diamine is treated with acetic 

 anhydride until a portion gives a white or slightly yellow precipitate 

 with bromine (if unaltered phenylene diamine is present, the precipitate 

 will be brown). When this is the case, an excess of bromine water 

 is added to the solution, and the mixture stirred vigorously until 

 the precipitation is complete. The product is essentially pure without 

 recrystallization. 



Properties. The dibrommetaphenylene diacetamide crystallizes by 

 slow evaporation from an alcoholic solution in very small, rather 

 short prisms. If on the other hand the crystallization takes place by 

 cooling, obscurely crystalline masses are obtained in which it is hard 

 to make out any definite form ; they seem to be prisms coated with 

 needles. Its color is white, and it melts at 259° to 260° with decom- 

 position, as is shown by the fact that the melted mass turns black and 

 puffs up to many times its original volume. On account of this de- 

 composition it is necessary to keep the melting tube in the oil bath as 

 little as possible in determining the melting point. If the substance is 

 allowed to remain in the bath while its temperature is raised, a melting 

 point as low as 250° may be obtained. It is very slightly soluble in 

 cold alcohol, and only a little more soluble in hot ; very slightly sol- 

 uble in benzol, chloroform, or carbonic disulphide ; somewhat more 

 soluble in acetone, or glacial acetic acid ; essentially insoluble in ether 

 or ligroine. The best solvent for it is glacial acetic acid or alcohol, 

 although it is soluble in the latter only sparingly and with great diffi- 

 culty. It is very slightly soluble in boiling water, insoluble in cold. 

 Strong hydrochloric acid saponifies it quickly when the two are gently 

 heated together ; strong sulphuric acid dissolves it in the cold, but 

 without decomposition, as the unaltered substance is obtained by dilut- 

 inor and neutralizing the acid, it decomposes the substance when hot; 

 if dilute it has no apparent effect when cold, but when heated 

 saponifies and afterward decomposes it; strong nitric acid dissolves it 

 quickly when cold, but the substance is recovered unaltered on neu- 

 tralization ; when hot it decomposes it. A strong solution of potassic 

 hydrate saponifies it when hot. 



Dibrommetaphenylene diamine, C,;H2Bro(NH2)2. — This substance 

 was obtained by removing the acetyl groups from the preceding com- 

 pound as follows : 10 grams of the dibrom phenylene diacetamide were 

 heated with from 30 to 40 c.c. of commercial strong hydrochloric acid 

 for half an hour in a flask with a return-condenser ; at the end of this 



