IRON. 287 



not necessary. Their influence is imperceptible. Weeren's niarvelously 

 concordant data seem to receive undue weight, but they are abundantly 

 confirmed by the evidence of other experimenters. In short, the atomic 

 weight of manganese appears to be quite well determined. 



IRON. 



The atomic weight of iron has been mainly determined from the com- 

 position of ferric oxide, with some rather scanty data relative to other 

 com})Ounds. 



Most of the earlier data relative to the percentage of metal and oxj'gen 

 in ferric oxide we ma}' reject at once, as set aside by. later investigations. 

 Among this no longer valuable material there is a series of experiments 

 by Berzelius, another by Ddbereiner, and a third by Capitaine. The 

 work done by Stromeyer and by Wackenroder was probabl}^ 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 minimum of 30.01 to a maximum of 30.38 per 

 cent.* 



In 1844 Berzelius t published two determinations of the ratio in ques- 

 tion. 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 Fe^O^ : 



70.018 

 70.022 



Mean, 70.020, zh .0013 



About the same time Svanberg and Norlin X published two elaborate 

 series of experiments ; one relating to the synthesis of ferric oxide, the 

 other to its reduction. In the first set pure piano-forte wire was oxidized 

 by nitric acid, and the amount of oxide thus formed was determined. 

 The results were as follows : 



1.5257 grm. Fe gave 2.1803 g^m. I'e^O.^. 69.977 per cent. Fe. 



2.4051 " 3-439° " 69.936 



2.3212 " 3-3194 " 69.928 



2.32175 " 3-3'83 " 69.968 



2.2772 " 3.2550 " 69.960 " 



2.4782 " 3-5418 " 69.970 



2.3582 " 3-3720 " 69.935 



Mean, 69.9534, ± .0050 



* For additional details concerning these earlier papers I must refer to Oudemans' mono- 

 graph, pp. 140, 141. 

 t Ann. Cheni. Pharm., 30, 432. Berz. Jahresb., 25, 43. 

 X Berzelius' Jahresbericht, 25, 42. 



