Appendix to Lecture of Jan. 22, 1915 8ia 



Records of Experhiexts omitted from the 

 Lecture ox "Proble3is of Hydrogex axd the Rare Gases." 



Friday, January 22, 1915. 



The behaviour of hydrogen and the Rare Gases in their passage 

 through metals and other permeable materials have stimulated 

 further investigation, since Graham published his classical researches 

 in 18G6. Some of the problems of gaseous transmission at high tem- 

 perature through quartz, platinum and various metals were discussed 

 in the Discourse of last year.* 



TRAXsmssiox through Ixdiarubber. 



In the method adopted by Graham " a thin film of rubber from 

 a small balloon " was stretched over " a thin plate of stucco " closings 

 the upper end of a glass tube 1 metre in length, filled and inverted 

 in mercury to give a Torricellian vacuum. Over this tube he fixed a 

 " hood of vulcanised rubber, provided with a small entrance and exit 

 tube " whereby different gases were introduced over the rubber, and 

 their rate of transference into the vacuous space was determined.. 

 The values of the relative rates determined by Graham were as 

 follows : — 



The absolute rate of air at three different temperatures, through 

 a thin coat of indiarubber on silk, were also given. Expressed in. 

 c.c. per day through each square cm. of membrane surface, the 

 values are : 



Tempr. 0^ C. 4 14 60 



Rate 0-07 0-28 0-83 



Wroblewskif in 1876 examined the diffusion of gases through 

 absorptive substances. In the use of caoutchouc he found that a 

 membrane * 031: mm. thick was almost completely impervious to air. 

 Carbonic acid diffused through at a rate proportional to its pressure 

 on the membrane, and independently of the pressure of air on the 

 other side when this was free from carbonic acid. The connection 

 between this result and Henry's Law of Absorption was pointed out. 

 Hydrogen he found took 3*6 times as long to diffuse as an equal 

 volume of carbonic acid ; and in a mixture of the two, each diffused 

 independently at a rate proportional to its partial pressure. 



* Problems of Hydrogen and the Rare Gases. Proc. Roy. Inst., XXI., p. 543. 

 t Ann. Phys. Chem. 158, 1876, pp. 539-568 ; Rep. der. Pbysik. 12, 1876, 

 pp. 423-453. 



