428 PROCEEDINGS OF THE AMERICAN ACADEMY. 



yielded results in close agreement and considerably higher than that of 

 Analysis 12. 



From an examination of this table two important deductions may be 

 drawn. First, there can be little doubt of the identity of the different 

 samples of iodine ; for the extreme averages of the results from the vari- 

 ous samples differ by only seven thousandths of a unit. The variation in 

 the values from the analysis of Sample II, Fraction 1, was undoubtedly 

 due in the case of Analysis 8 to lack of experience in manipulating silver 

 iodide, for this analysis was the first one to be completed in the final 

 series, and in the case of Analysis 9 to the small quantity of available 

 material. One may conclude without hesitation that, in the material 

 examined in this investigation at least, no new halogen existed. 



The second important deduction is that the atomic weight of iodine is 

 evidently very slightly greater than 126.973; for most of the experimen- 

 tal errors, such as loss of silver iodide, or loss of iodine by the silver 

 iodide, would have caused the result to be too low. 



PAKT II. 

 The Ratio of Silver to Iodine. 



The ratio of silver to iodine was next investigated. The problem of 

 obtaining iodine in a dry state presented most difficulties in this portion 

 of the research, and was finally solved as follows: Iodine which had been 

 prepared in the same way as Sample I, was first freed from the greater 

 part of the water which it contained by exposure to concentrated sul- 

 phuric acid, which had been boiled to remove every trace of hydrochloric 

 acid. It was then sublimed from a crystallizing dish to the bottom of a 

 glass dish half filled with water, which covered the crystallizing dish. 

 In this way the greater part of the " included " moisture must have been 

 eliminated. The sublimed crystals were finally again sublimed in a cur- 

 rent of pure dry air from a porcelain boat contained in a hard glass tube 

 into the weighing tube. This weighing tube was about ten centimeters 

 long and fifteen millimeters in diameter, and was drawn down to less than 

 half this diameter at both ends. Glass stoppers were ground into both 

 ends of the tube. The air was purified and dried by passing over beads 

 moistened with a solution of silver nitrate, then over sodic carbonate, and 

 finally over three feet of beads moistened with concentrated sulphuric acid, 

 all in an apparatus made entirely of glass and connected with the sublima- 

 tion tube by means of a ground glass joint. During the final sublimation 

 of the iodine, the end of the hard glass tube, which had been drawn down 



