ON A DIHYDRO-QUINOXALINE 1 25 



saturated benzene solution of the base is allowed to crystallize slowly, 

 the crystals obtained are large, well-defined monoclinic prisms; if, on 

 the other hand, a dilute benzene solution is allowed to evaporate, the 

 crystals obtained are large thin plates. Both melt at 124 , uncorrected. 



An elementary analysis of the substance corresponds to a compound 

 having a formula C I2 H l6 N 2 . A cryoscopic molecular weight deter- 

 mination gave 192, whereas, for the above, the calculated molecular 

 weight is 188. 



If a stream of dry hydrobromic acid gas is led through a cold solu- 

 tion of the base in benzene, a lemon-yellow crystalline powder is pre- 

 cipitated, which, on analysis, corresponds to a mono-hydrobromic acid 

 salt, C I2 H l6 N 2 ,HBr. If, however, the base is dissolved in aqueous 

 hydrobromic acid, and the solution evaporated over calcium chloride, 

 colorless needles separate out, which, on analysis, are shown to have 

 the composition C I2 H l6 N 2 ,2HBr. 



If dry hydrochloric acid gas is led into a cold benzene solution of 

 the base, at first a lemon-yellow crystalline powder, similar to that 

 obtained with hydrobromic acid, is precipitated. This, however, begins 

 almost immediately to turn white. Numerous attempts were made to 

 isolate the yellow powder from the solution before it could change, in 

 order to analyze it. Results nearer than i per cent, to the calculated 

 amount of hydrochloric acid required for a mono-hydrochloric acid 

 salt could not be obtained. Considering the speed with which the 

 yellow salt changes to the white one, this is not to be wondered at. 

 The white salt on being analyzed always gave too low a value (by 

 about 2 per cent.) of hydrochloric acid for a dihydrochloric acid salt. 

 If, however, the base is dissolved in aqueous hydrochloric acid and is 

 allowed to evaporate over sulphuric acid, long colorless crystals, similar 

 to those obtained with aqueous hydrobromic acid, are obtained. These, 

 on analysis, are shown to be the dihydrochloric acid salt, C I2 H l6 N 2 , 

 2HCI. 



These salts are extremely soluble in water. The solutions are color- 

 less when concentrated, but change to a bright yellow when diluted, 

 showing that the complex kation C I2 H I7 N 2 is yellow. The salts were 

 analyzed by titration with standard sodium hydroxide. They can act 



