288 THE ATOMIC WEIGHTS. 



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

 of hydrogen, yielding the subjoined percentages of metal : 



2.98353 grm. Fe 2 O 3 gave 2.08915 grm. Fe. 70.025 per cent. 



2.41515 i.6oro 70.015 " 



299175 " 2.09455 " 70.014 " 



3.5783 2.505925 70.030 " 



4.1922 2.9375 70.072 " 



3.1015 " 2.17275 " 70.056 " 



2.6886 " 1.88305 " 70.036 " 



Mean, 70.0354, .0055 



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, and in the reduction series 

 it is possible that weighable traces of hydrogen may have been retained 

 by the iron. At all events, it is probable that the errors of both series 

 are in contrary directions, and therefore in some measure compensatory. 



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 Fe 2 3 are as follows : 



70.013 ] 

 69.962 | 



69.979 }-A. 



70.030 I 



69.977 J 



70.044 1 



70.015 j-B. 



70.055 J 



Mean, 70.0094, =b .0080 



In 1850 Maumene'sf results appeared. He dissolved pure iron wire 

 in aqua regia, precipitated with ammonia, filtered off the precipitate, 

 washed thoroughly, ignited, and weighed, after the usual methods of 

 quantitative analysis. The percentages of Fe in Fe 2 3 are given in the 

 third column : 



1.482 grm. Fe gave 2.117 grm. Fe 2 O 3 . 70.005 per cent. 



1.452 2.074 " 70.010 " 



1.3585 " 1.941 " 69.990 



1.420 " 2.0285 " 70.002 " 



1.492 2.1315 " 69.998 " 



1-554 " 2.22O " 7O.OOO " 



Mean, 70.0008, =h .0019 



* Journ. fiir Prakt. Chem., 33, i. 1844. 

 tCompt. Rend., Oct. 17, 1850. 



