PHYSICAL CONSTANTS OF HYDROGENIUM. 171 
cific heat of the palladium, or of the hydrogen individually or conjointly. The 
mere fact that we have only a very small weight of hydrogen relatively to the 
amount of palladium does not explain the anomaly, because a small amount of 
hydrogen by the second mode of comparison does not yield such high results. 
The observational errors, although much greater when we are dealing with 
small quantities, cannot be expected to fall always in the same direction, and 
thus we are forced to admit there is some regular sequential change taking 
place in the relations of the hydrogen and palladium. 
The palladium, after use, is not found to have increased in specific heat, but 
rather the reverse, so that the explanation can only rest on some altered con- 
dition of the bodies when united. So far as my experiments have led me, I am 
inclined to regard this alteration as a kind of molecular dissociation that 
increases with diminished charge of hydrogen. I am led to this conclusion from 
observing that the rate at which palladium loses hydrogen at constant tempera- 
ture is dependent on the amount present increasing with diminished charge. In 
conducting these specific heat experiments, a greater variation in the results has 
always been observed when small charges were under experiment, especially in 
the first two or three determinations. This increase of dissociation may be 
explained in part from the formation of regular cracks or channels in the mass 
of palladium, together with the effect of pressure resulting from the contraction 
of the external layers of palladium from the loss of hydrogen. It is, however, 
premature to discuss the cause of this increase of dissociation until a more 
extended series of experiments is made, and the behaviour of the alloy to pressure 
is investigated. 
TABLE IJ.—Sprciric HEAT. EXPERIMENTS WITH BAR PALLADIUM. 'THREE HYDRIDES. 
WEIGHT OF Bar, 31°802 GRAMMES. WATER AND CALORIMETER, 107 GRAMMES. 








ie TO III. IV. 
Weight of Hydrogen in Palladium, 0-1905 0:103 0:0415 N othing, 
2°426 2178 1:944 1°740 
Rise in Calorimeter for a fall of 2°430 2°175 1°958 1°780 
100° C., ; : ; 2:429 2:175 1:958 1°760 
2°435 2167 1:967 1:760 
Mean rise, : : ‘ 2°436* Doll Fes 1°956 1:760 
Rise due to Hydrogen, . : 0°676 0°413 0196 Nothing. 
Specific heat of Hydrogen, ; 3°79 4°29 5:05 
Rreatarogenin || aeaeCmaey | Septet fom ten, 
I. in excess of II. 0:0875 I, and II. 0:263 I. and II. 3°21 
II. in excess of III. 0°0615 II. and III. 0°217 Il. and III. 3°77 + 3°47 
I, in excess of III. 0°1490 I. and III. 0°480 T.and III, 3°44 
* Mean of eight experiments. 
VOL, XXVII. PART I. 2Y 
