462 Royal Society .— 



the latter while expanding retracts in length at the same time. The 

 expansion of both wires may he familiarly compared to the enlarge- 

 ment of the body of a leech on absorbing blood. The enlargement is 

 uniform in all dimensions with the palladium-platinum alloy ; the 

 leech becomes larger, but remains symmetrical. But the retraction 

 in the pure palladium wire has its analogy in a muscular contraction 

 of the leech, by which its body becomes shorter but thicker in a 

 corresponding measure. 



The same wire of palladium and platinum, charged a second time 

 with hydrogen, underwent an increase in length from 601*845 to 

 618 2, or sensibly the same as before. The gas measured 258*0 

 cub. centims., or 619*6 times the volume of the wire. The product 

 may be represented as consisting of 



By volume. 



Fixed metals 92-2/2 



Hydrogenium 7*728 



HKHJOO 



The density of hydrogenium deducible from this experiment is 

 0*7401. The mean of the two experiments is 0*7473. 



2. Palladium, Gold, and Hydrogenium. — Palladium fused with 

 gold formed a malleable alloy, consisting of 75*21 parts of the former 

 and 24*79 parts of the latter, of a white colour, which could be 

 drawn into wire. Its specific gravity was 13*1. Of this wire 601*85 

 millims. occluded 464*2 volumes of hydrogen with an increase in 

 length of 1 1*5 millims. This is a linear elongation of 1*91 on 100, 

 and a cubic expansion of 5*84 on 100. The resulting composition 

 was therefore as follows : — 



In volume. 

 Alloy of palladium and gold .... 100 or 94*48 

 Hydrogenium 5*84 or 5*52 



105*84 100*00 



The weight of the wire was 5*334 grms. 



The volume of the wire was 0*4071 cub. centim. 



The volume of hydrogen extracted, 189*0 cub. centims. 



The weight of the hydrogen, 0*01693 grm. 



The volume of the hydrogenium, 0*02378 cub. centim. 



Consequently the density of the hydrogenium is 0*711. 



The wire returned to its original length after the extraction of 

 the hydrogen, and there was no retraction. 



The results of a second experiment on the same wire were almost 

 identical with the preceding. 



The elongation on 601*85 millims. of wire was 11*45 millims., 

 with the occlusion of 463*7 volumes of hydrogen. This is a linear 

 expansion of 1*902 on 100, and a cubic expansion of 5*81 on 100. 

 The volume of hydrogen gas extracted was 188*8 cub. centims., of 

 which the weight is 0*016916 grm. The volume of the hydrogenium 

 was 0*02365 cub. centim., that of the palladium-gold alloy being 

 0*40/1 cub. centim. Hence the density of the hydrogenium is 0*715. 



In a third experiment made on a shorter length of the same 

 wire, namely 241*2 millims., the amount of gas occluded was very 



