IRON. 131 



complete analysis of silver permanganate, i:)utting Ag =^ 108 

 and ^ 16, they find in three estimations Mn = 55.51, 

 54.04, and 54.45. From the analysis of pure MnOa, made 

 from the nitrate, Mn = 53.3 to 53.G. Up to the date of 

 writing a detailed account of the methods employed has 

 not been published. 



IRON. 



The atomic weight of iron has been determined almost 

 exclusively from the composition of ferric oxide. Beyond 

 this there are only a few comparatively unimportant ex- 

 periments by Dumas relative to ferrous and ferric chlorides. 



Most of the earlier data relative to the percentage of metal 

 and oxygen in ferric oxide we may reject at once, as set 

 aside by later investigations. Among this no longer valua- 

 ble material there is a series of experiments by Berzelius, 

 another by Dobereiner, and a third by Capitaine. The 

 work done by Stromeyer and by Wackenroder was probably 

 good, but I am unable to find its details. The former found 

 30.15 per cent, of oxygen in the oxide under consideration, 

 while Wackenroder obtained figures ranging from a mini- 

 mum of 30.01 to a maximum of 30.38 per cent.* 



In 1844 Berzelius t published two determinations of the 

 ratio in question. He oxidized iron by means of nitric acid, 

 and weighed the oxide thus formed. He thus found that 

 when = 100 Fe =: 350.27 and 350.369. 



Hence the following percentages of Fe in FeoOg. 



70.018 

 70.022 



Mean, 70.020, =b .0013 



About the same time Svanberg and NorlinJ published 



* For additional details concerning these earlier papers I must refer to Oude- 

 mans' monograph, pp. 140, 141. 



f Ann. Chem. Pharm., 50, 432. Berz. Jahresb., 25, 43. 

 \ Berzelius' Jahresbericht, 25, 42. 



