100 



SMITHSONIAN MISCELLANEOUS COLLECTIONS 



VOL. 5-1 



Dumas' figures might be rejected altogether without changing the final 

 mean. 



Silver iodide, heated in chlorine, is similarly converted into chloride. 

 This ratio has been repeatedly investigated, first by Berzelius.^ His 

 figures are subjoined, with the ratio AgCl : Agl : : 100 : x in the last 

 column : 



Agl. AgCl. Ratio. 



5.000 

 12.212 



3.062 

 7.4755 



163.292 

 163.360 



Mean, 163.326, ± .023 



There are also two early experiments by Dumas/ as follows : 



Ratio. 



Agl. 



3.520 

 7.011 



AgCl. 



2.149 

 4.281 



163.793 

 163.770 



Mean, 163.782, ± .008 



The modern work upon this ratio began with an investigation by 

 Ladenburg" in 1902, which showed that the previously accepted value 

 for the atomic weight of iodine was at least a tenth of a unit too low. 

 Ladenburg made two series of determinations, with vacuum weights; 

 one preliminary, the other conducted with greater care. His figures are 

 as follows : 



Preliminary Series. 



lAnn. Chim. Phys. (2), 40, 430. 1829. 



*Ann. Chem. Pharm., 113, 28. 1860. 



' Ber. Deutsch. chem. Ges., So, 2275. 1902. 



