IODINE. 61 



IODINE. 



Dumas determined the specific gravity of iodine vapor. 

 It answers to an atomic weii^bt of about 127. {Annal. de 

 Chim. et de Phys., 83, 1826, 33>.) 



L. J. Gay-Lussac : 123.9 (0 = 16). 



100 parts of iodine were found equivalent to 26.225 parts 

 of zinc. [If Zn = 65, these figures give the atomic weight 

 at 123.9.] {Poggend. Annal.., I4,, 1828, 559 ; Annal. de 

 Chimie, 91, 1814, 5.) 



W. Prout : W6 (0 = 16). 



Prout found 100 parts of iodine equivalent to 25.8 parts 

 of zinc. [If Zn = 65, this ^ives I = 125.97.] {Thomson's 

 Annals of Phil, 6, 1815, 323.') 



T. Thomson : I24. (0 = 16) ; 775 (0 = 100). 



Thomson found 20.5 potassic iodide = 19.75 zinc iodide, 

 = 20.75 plumbic nitrate. [If K = 39.1, and plumbic nitrate 

 = 331, the relation given leads to an atomic weight of 124.41.] 

 Thomson thinks that his iodine may have been somewhat 

 impure, as he purified it only by sublimation. ( Thomson's 

 System of Chem., 7th ed., 1, 1831, 81.) 



J. Dumas : 126.13 (0 = 16). 



Dumas determined the density of iodine vapor at 8.716 

 for air = 1. [Referred to the molecular weight of oxygen, 

 this density gives the above number for the atomic weight.] 

 Dumas thinks it probable that it can be more accurately 

 determined by analysis. [Annal. de Chim. et de Phys., 33, 

 1826, 337.) 



J. J. Berzelius : 126.26 (0 = 16) ; 789.14 (0 = 100). 



Determined by decomposing a known weight of argentic 

 iodide in a current of chlorine, melting the chloride and 

 expelling free chlorine by atmospheric air. The number is 

 the mean of two experiments; diflference, 0.01. Ag = 

 1351.607; CI = 442.653. The iodide was prepared by pre- 

 cipitation from a solution of potassic iodide with argentic 

 nitrate. The first portion of the precipitate was set aside 

 as possibly contaminated with chlorine. [Poggend. Ann., 

 U, 1828, 562.) 



