226 PROCEEDINGS OF THE AMERICAN ACADEMY. 



and the appearauce under the microscope of crystals resembling ammonic 

 bromide ; but with these sources of error, we thought it necessary to 

 support our analysis with evidence of some other sort, and therefore 

 undertook the preparation of NH4BrIBr direct in order to compare its 

 properties with those of our compound. Upon treating ammonic bromide 

 with au ethereal solution of bromide of iodine, the salt dissolved, giving 

 a red solution, and on evaporation of the ether a residue was obtained 

 the properties of which were identical with those of the ammonic brom- 

 iodobromide described above. Further, upon exposing ammonic iodide 

 to the vapor of bromine an amount was absorbed corresponding very 

 neai'ly to that required by the formula. 



1.6487 grams of ammonic iodide absorbed 1.7804 grams of bromine. 



Calculated for Per cent of Bromine 



NHjBrlBr. in the Product. 



Bromine 52.46 51.92 



During the action of the bromine the ammonic iodide at first turned 

 black, but as the absorption went on it finally became scarlet, and this 

 product proved to be identical with the ammonic bromiodobromide. A 

 curve constructed from the increase of weight of the ammonic iodide 

 showed that there was a marked diminution in the speed of the absorption 

 after the first atom of bromine had been added. This decrease in the 

 speed of absorption is undoubtedly connected with the conversion of the 

 black substance into the red NH4BrIBr, but we are unable to decide 

 whether this black intermediate product is another compound NH4BrI, 

 or only a mixture of ammonic bromide and free iodine. It is a curious 

 fact, in view of the absorption of free bromine by ammonic iodide, that, 

 so far as we could find, an ethereal solution of bromine had no action on 

 this salt. We have not continued our experiments in this direction for 

 fear of intruding on the field of work occupied by Wheeler, who with 

 Pratt and Barnes has prepared the ammonic triiodide.* 



We have adopted provisionally the name ammonic bromiodobromide 

 and the formula NH^BrlBr for this substance, because it is made by the 

 action of bromide of iodine on ammonic bromide, and when it decomposes 

 bromide of iodine is given off and ammonic bromide left behind ; but we 

 do not feel that these observations settle its constitution finally, although 

 they certainly are strong arguments in favor of the formula adopted. If 

 this is correct, the formation from ammonic iodide and bromine must be 



* Am. Chem. Journ., XIX. 675 (1897). 



