HYDEOGENISED PALLADIUM. 331 



wire. In all cases, the thermoelectric current is from the pure 

 palladium to the charged palladium through the hot junction, is for 

 any given pair very nearly proportional to the difference of tempera- 

 ture of the junctions, and is greater for the greater charge of hydrogen 

 in the one wire. Thermoelectrically, fully saturated hydrogenium lies 

 hetween iron and copper at ordinai-y atmospheric temperatures. On 

 the thermoelectric diagram the hydrogenised palladiums of different 

 charge are represented (up to a temperature of 150° C.) by a series 

 of straight lines approximately parallel to palladium, an appreciable 

 deviation from parallelism occurring only for the bighly charged 

 specimens. The thermoelectric powers at 0° C. expressed in C. G. S. 

 units range roughly from — 600 (pure palladium) to + 1400 (saturated 

 palladium), the thermoelectric power f^r lead being zero.* In other 

 words, the electromotive force in a circuit of palladium and saturated 

 hydrogenium, when the temperature of the junctions are 0" C. and 

 100° C, is about 20 x 10' C. G. S. units or .002 volts. 



The deviation from parallelism between the lines iov pure pal- 

 ladium and saturated hydrogenium, referred to above, is of such a 

 nature as to produce intersection of the lines at a point corresponding 

 to —350° C. This of course is an unattainable temperature ; but the 

 existence of such a ' neutral point ' (as it were) must have some sig- 

 nificance. The data, upon which the estimation of this point was 

 made, are somewhat doubtful, the range of temperature employed in 

 the experiments being limited. With the object of testing this 

 supposed convergence of the palladium and hydrogenium lines, Messrs. 

 Saneyoshi and Hirayama undertook a series of experiments, in which 



* Compare Everett's " Uuit i and physical constants" page 151, whore, however, the signs 

 are reversed. It seems preferable to draw ths diagram as in Tait's classical memoir or as described 

 in Maxwell's F.leme.ntarij Treatise on Electricity and in Tait's Heat. The lines which have positive 

 inclination ac3ording to the usual convention are than the lines of metals, in which the Thomson 

 Effect is positire. [I notice that Professor Everett has, in the 2Dd edition lately published, altered 

 the signs so as to agree with this convention.] 



