226 PROCEEDINGS oh THE AMERICAN ACADEMY. 



and the appearance under the microscope of crystals resembling amnionic 

 bromide; bnt with these sources of error, we thought it neoessary to 



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

 undertook the preparation of NH«BrIBr direct in order to compare its 

 properties with tlio.se of our compound. Dpon treating amnionic bromide 

 with :m ethereal Bolution of bromide of iodine, the salt dissolved, iri \ imz 



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

 tin- propertied of which were identical with those of the amnionic l.r..m- 

 iodobromide described above. Further, upon exposing amnionic iodide 

 to the vapor of bromine an amount was absorbed corresponding very 

 nearly to that required by the formula. 



1.0487 grams of ammonie iodide absorbed 1.7804 grams of bromine. 



Calculated for Pit cent of Bromine 



Nll 4 Hrll(r. In the Product 



Bromine 52.46 51.92 



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

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

 product proved to be identical with the amnionic bromiodobromide. A 

 curve constructed from the increase of weight of the amnionic 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 NH^BrlBr, but we are enable to decide 

 whether this black intermediate product is another compound NH 4 BrI, 

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

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

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

 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 ammonie triiodide.* 



We have adopted provisionally the name amnionic bromiodobromide 

 and the formula NH 4 BrIBr for this substance, because it is made by the 

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

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

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

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

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



* Am. Clicm. Joum., XIX. G75 (1897). 



