222 PROCEEDINGS OF THE AMERICAN ACADEMY. 



the original salt; this in all probability is an aniline addition product 

 analogous to the ammonia compound described later. Benzol, benzyl- 

 chloride, ether, phenol, or hydroquiuone gave no perceptible action with 

 ferrous iodide. 



Other Methods of Preparing Ferrous Iodide. 



In this section of the paper we shall describe a revision of the methods 

 used by our jiredecessors, and also some new methods of our own. 



The revision of the older methods was necessary, because in three 

 cases the ferrous iodide formed was described as gray or white ; and 

 although we have proved that the white samples formed from the red 

 salt owed their change of color to absorption of water, it did not follow 

 that those described by our predecessors were not anhydrous ferrous 

 iodide in a second isomeric form. De Luca,* who states that ferrous 

 iodide when pure is white, gives no method of preparation in any of the 

 journals to which we have access, so that it was impossible for us to 

 repeat his work. A. T. Thomson f prepared his gray ferrous iodide by 

 evaporating an aqueous solution in a flask containing some free iron. 

 On repeating this experiment we had so much difficulty from oxidation 

 that we carried on our later attempts in an atmosphere of carbonic diox- 

 ide. Under these conditions, when the water of crystallization began to 

 come off, the liquid became black and opaque-looking as if it contained 

 a suspended black precipitate. Later the surface of the boiling mass 

 became grayish white with a silvery lustre, but when all the water had 

 been driven off, the residue was brownish red like the ferrous iodide 

 prepared by our method. This experiment makes it probable that the 

 gray ferrous iodide of Thomson owed its color to the presence of water, 

 for in the absence of analyses he would undoubtedly have ascribed the 

 brownish red color of the final residue to the formation of a ferric salt by 

 oxidation. 



As the method of Carius and Wanklyn | consisted in heating iron 

 and iodine in a porcelain crucible, it seemed at first sight that the gray 

 color of the product could hardly be due to the presence of water, and 

 therefore we repeated their work, following their directions as carefully 

 as possible. One gram of rather coarse iron filiugs,§ mixed with a little 



* Coniptes-Rendus, LV. 615. 

 t Gmelin-Kraut, Handbuch, III. 350, 6th edition. 

 t Ann. Chem., CXX. 69. 



§ The success of the process depends on using filings of the right degree of 

 coarseness. With too fine or too coarse filings unsatisfactory results are obtained. 



