12 



ELECTROMOTIVE FORCE OF IRON AND OCCLUDED HYDROGEN. 



A glance at the table shows that the beating had made considerable dif- 

 ference in the electromotive force of the iron in every sample which had 

 been beaten. It will be shown later, however, that this difference was due 

 not to the compression, but to another effect of the treatment. 



This effect was soon found to be closely connected with another relation 

 to be observed in the above figures ; namely, the fact that after immersion 

 the electromotive force of each piece of iron begins at a low point and rises, 

 attaining constancy at a maximum only after some time. In order to study 

 this phenomenon more closely, six other small pieces were immersed in the 

 solution and readings of the electromotive forces taken at short intervals. 

 The numerical results are given in table 2. 



Because it was evident that the electromotive force continued to rise slowly 

 for a very long time, four of these pieces were carefully sealed up with 

 paraffin immediately after immersion in order to prevent oxidation. This 

 was done in order to determine the electromotive force of the final equi- 

 librium. After three days No. 9 and No. 10 were opened and measured; 

 and after five days No. 11 and No. 12. 



Table 2.- 



-The increase of electromotive force with time Iron electrode 

 against decinormal electrode. 



This was later repeated with other samples, which gave similar results. 

 It should be noted that after several days a pale-green precipitate of ferrous 

 hydroxide was always found in the tube, but this seemed to exercise no 

 considerable effect on the potential until seven or eight days had passed and 

 the amount had become large. Even then by shaking the constant value of 

 the potential was usually regained. 



Thus it was obvious that spongy iron which has been exposed to the air 

 always gives at first an abnormally low electromotive effect, which slowly 

 rises. The only reasonable hypothesis capable of explaining the phe- 



