214 



Mr. Graham on the Relation 



[Jan. 14, 



ladium did not increase, but fell slightly at the same time, namely from 

 12*38 to 12*12, proving that this contraction of the wire is in length only. 

 The result is the converse of extension by wire- drawing. The retraction 

 of the wire is possibly due to an effect of wire-drawing in leaving the par- 

 ticles of metal in a state of unequal tension, a tension which is excessive 

 in the direction of the length of the wire. The metallic particles would 

 seem to become mobile, and to right themselves in proportion as the 

 hydrogen escapes ; and the wire contracts in length, expanding, as appears 

 by its final density, in other directions at the same time. 



A wire so charged with hydrogen, if rubbed with the powder of mag- 

 nesia (to make the flame luminous), burns like a waxed thread when ig- 

 nited in the flame of a lamp. 



Expt. 2. — Another portion of the same palladium wire was charged 

 with hydrogen in a similar manner. The results observed were as fol- 

 lows : — 



Length of palladium wire 488-976 millims. 



Thesame with 867' 15 volumes ofoccluded gas 495*656 „ 



Linear elongation 6' 68 ,, 



Linear elongation on 100 1*3663 



Cubic expansion on 100 4-154 „ 



Weight of palladium wire , 1*0667 grm. 



Volume of palladium wire 0-08072 cub.centim. 



Volume of occluded hydrogen gas 75 -2 „ 



Weight of same 0-00684 grm. 



Volume of hydrogenium 0*003601 cub.centim. 



From these results is calculated 

 Density of hydrogenium 1*898. 



Expt. 3. — The palladium wire was new, and on this occasion was well 

 annealed before being charged with hydrogen. The wire was exposed at 

 the negative pole for two hours, when it had ceased to elongate. 



Length of palladium wire 556' 185 millims. 



Same with 888-303 volumes hydrogen . . 563-652 „ 



Linear elongation 7*467 „ 



Linear elongation on 100 1-324 ,, 



Cubic expansion on 100 4 '025 „ 



Weight of palladium wire 1*1675 grm. 



Volume of palladium wire 0-0949 cub. centim. 



Volume of occluded hydrogen gas 84*3 cub. centim s. 



Weight of same 0*007553 grm. 



Volume of hydrogenium 0*003820 cub. centim. 



These results give by calculation 



Density of hydrogenium 1 * 9 77. 



It was necessary to assume in this discussion that the two metals do not 



