234 PROCEEDINGS OF THE AMERICAN ACADEMY. 



I. 0.1508 gram of the substance gave by the method of Carius 0.1494 

 gram of argentic bromide. 

 II. 0.3041 gram of the substance gave 20.2 c.c. of nitrogen at a tem- 

 perature of 18°. 6 and a pressure of 760.4 mm. 



Calculated for Found. 



(C7U5Br)2NCN I. II. 



Bromine 42.11 42.18 



Nitrogen 7.37 7.64 



In view of the great tendency of cyanamides to polymerize, it was 

 thouglit safer to determine the molecular weight of the body * by the 

 metiiod of freezing a benzol solution, which gave the following results : —  



0.375 gram of the substance dissolved in 16.25 grams of benzol produced 

 a depression of 0°.28 in the freezing point. 



Calculated for (C7HeBr)3NCN. Found. 



Molecular weight 380 337 



There can be no doubt, therefore, that the substance is really 

 (C6H,BrCH2)oNCN. 



Properties of Diparabrombenzylcyanamide. 



The substance crystallizes from benzol in sheaves of white crystals 

 shaped like the blade of a lancet, sometimes united laterally into groups 

 wiih comb ends. It melts at 133°. It is freely soluble in benzol, chlo- 

 roform, acetone, or acetic ester ; soluble in toluol ; slightly soluble in cold 

 ethyl or methyl alcohol or glacial acetic acid, freely soluble in these 

 solvents when they are hot; slightly soluble in ether, carbonic disulphide, 

 or in hot or cold water ; essentially insoluble in ligroine. It is slowly 

 decomposed by cold strong sulphuric acid; apparently unaffected by 

 hydrochloric acid or nitric acid in the cold. The best solvent for it is 

 hot alcohol. 



In order to see if it could form a chloride, a portion of the dipara- 

 brombenzylcyanamide was dissolved in anhydrous benzol and saturated 

 with dry hydrochloric acid gas. No precipitate was formed even after 

 the mixture had stood for two weeks, and on evaporating off the benzol 

 the original substance was recovered unaltered. It would seem from 

 this experiment that the diparabrombenzylcyanamide cannot unite with 

 hydrochloric acid. 



* This work was done before the appearance of Wallach's statement that di- 

 substituted cyanamides show no tendency to pol^^merize. 



