26 



ELECTROMOTIVE FORCE OF IRON AND OCCLUDED HYDROGEN. 



apparatus or manipulation greatly bettered the result, which could have been 

 easily accomplished with larger quantities of material. Therefore another 

 method was tried, namely, the melting of the iron in a vacuum by means of 

 the heat generated by its own resistance to a great electric current. Be- 

 sides an apparatus suitable for exhaustion, the essentials for success were 

 iron electrodes, a suitable crucible, and a sufficiently high current. Bundles 

 of piano wire provided the electrodes, and a nest of powdered iron, sup- 

 ported on a crucible of lime made from the purest marble, was used to 

 contain the melted particles. In order to increase the resistance of the 

 metal it was powdered in the Hempel steel mortar, and the current was 

 passed through this powder. The arrangement of the apparatus and its 

 description are given in figure 5. 



The operation of the experiment was as follows : After everything was 

 arranged as shown in the figure, the Sprengel vacuum-pump was started 

 and the stoppers thus firmly forced in. This, however, disarranged the elec- 

 trodes and air was again admitted, so that they could be carefully placed at 

 the desired places in the lime boat. The apparatus was now evacuated a 

 second time and the current turned on. For some time nothing happened, 

 but finally the metal fused with the help of vigorous jarring. More and 

 more powder was added from above as the fusion progressed. There were 

 brilliant flashes of violet light with each addition of powder, followed by 

 bright-red glowing. By feeding powder into the open spaces left by the 

 fused material it was possible to maintain the fusion almost continually until 

 the supply was exhausted. The product consisted mainly of small pellets 

 about the size of the head of a pin or a little larger, resting in the nests of 

 pure powdered iron. Only one was large enough to use conveniently in a 

 cell. Nevertheless, this gave a result agreeing so well with that from the 

 commercial materials that a duplicate seemed unnecessary. The sample was 

 covered with soft paraffin on those parts which did not have a smooth fused 

 surface. 



Table 7. Pure iron fused in vacuum. (33). 



Thus this sample of exceedingly pure iron fused in vacuum gave essen- 

 tially the same potential as good quality commercial material (0.765). 



