ATOMIC WEIGHTS 



417 



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

 The results were as follows : 



1.5257 grm. Fe gave 2.1803 grm. Fe^Os. 



69.977 per cent. Fe. 



69.936 



69.928 



69.968 



69.960 



69.970 



69.935 



Mean, 69.9534, ± .0050 

 Hence Fe= 55.875. 



In the second series ferric oxide was reduced by ignition in a current 

 of hydrogen, yielding the subjoined percentages of metal : 



2.98353 grm. Fe^Oa gave 2.08915 grm 



2.41515 



2.99175 



3.5783 



4.1922 



3.1015 



2.6886 



1.6910 



2.09455 



2.505925 



2.9375 



2.17275 



1.88305 



Fe. 



70.025 per cent. 



70.015 



70.014 



70.030 



70.072 



70.056 



70.036 



Mean, 70.0354, ± .0055 



Hence Fe = 56.093. 



It is evident that one or both of these series must be vitiated by con- 

 stant errors, and that these probably arise from impurities in the mate- 

 rials employed. Impurities in the wire taken for the oxidation series 

 could hardly have been altogether avoided. 



In 1844 there was also published an important paper by Erdmann 

 and Marchand.^ These chemists prepared ferric oxide by the ignition 

 of pure ferrous oxalate, and submitted it to reduction in a stream of 

 hydrogen. Two sets of results were obtained with two different samples 

 of ferrous oxalate, prepared by two different methods. For present pur- 

 poses, however, it is not necessary to discuss these sets separately. The 

 percentages of iron in FcoOg are as follows : 



70.013- 



69.962 



69.979 



70.030 



69.977 



70.044 



70.015 



70.055 



Mean, 70.0094, ± .0080 



Hence Fe = 56.035. 



1 Journ. prakt. Chem., S3, 1. 



