﻿124 Mr. T. Graham on the Relation of 



receded to its original length, but fell as much below that zero 

 as it had previously risen above it. The palladium wire first 

 measuring 609*144 millims., and which increased 977 millims., 

 was ultimately reduced to 599*444 millims., and contracted 9*7 

 millims. The wire is permanently shortened. The density of 

 the palladium did not increase, but fell slightly at the same time, 

 namely from 12*38 to 1 2*12 ; proving that this contraction of 

 the wire is in length only. The result is the converse of exten- 

 sion by wire-drawing. The retraction of the wire is possibly 

 due to an effect of wire-drawing in leaving the particles 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 pro- 

 portion as the hydrogen escapes; and the wire contracts in 

 length, expanding, as appears by its final density, in other di- 

 rections at the same time. 



A wire so charged with hydrogen, if rubbed with the powder 

 of magnesia (to make the flame luminous), burns like a waxed 

 thread when ignited in the flame of a lamp. 



Exp. 2. — Another portion of the same palladium wire was 

 charged with hydrogen in a similar manner. The results ob- 

 served were as follows : — 



Length of palladium wire 488*976 millims. 



The same with 867*15 volumes of occluded 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. c. 



Volume of occluded hydrogen gas ... 75*2 „ 



Weight of same 0*00684 grm. 



Volume of hydrogenium ...... 0*003601 cub.c. 



From these results is calculated 



Density of hydrogenium .... 1*898. 



Exp. 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. 



