﻿212 Prof. W. Ramsay on the Passage of 



patience failed me to make more than one determination. It 

 was begun on May 4th. On May 10th pressure was still 

 rising, but very slowly. On May 11th it had reached 501*7 

 millim. ; on the 13th it was 525*2 millim., and on the 14th 

 531*2 millim. Taking the figure actually read, the fractional 

 pressure (barometer = 766*3 millim.) was 0*6932. Judging 

 from this experiment, the pressure would appear to depend on 

 the temperature of the palladium and of the hydrogen. Still, 

 it is possible that had the experiment been carried on sufficiently 

 far, the pressure might have risen much higher. 



Experiment 12. — The next set of experiments was made at 

 a higher temperature — that of the boiling-point of dibenzyl- 

 ketone (335°). The pressure registered at a barometric 

 height of 758*7 millim. was 681*6 millim. The ratio is 

 0*8984, practically identical with that obtained at the boiling- 

 point of bromonaphthalene. 



Experiments 13, 14, and 15. — The hydrogen in these experi- 

 ments was mixed with 50 per cent, of nitrogen, so that the 

 exterior of the palladium tube was exposed to a partial 

 pressure of hydrogen. The first of this set gave a pressure 

 of hydrogen of 367*9 millim., the barometer standing at 

 770*9 millim. ; the second, 352*9 millim., barometer at 771*8 

 millim. ; and the third 362*7 millim. at the same pressure. 



Experiment 16 was made with a mixture of one volume of 

 hydrogen to three of nitrogen ; the read pressure was 176*7 

 millim., the barometric height being 756*5 millim. 



The ratios are : — 



Experiment. 13 14 15 



Eatio .... 0*4771 0*4573 0*4700. Mean 0*4681. 



Experiment 16 : Ratio 0*2336. 



Multiplying the first mean ratio by 2, and the second by 

 4, the products are comparable with that from pure hydrogen. 

 The figures are : — 



Pure hydrogen 0*9053 



Hydrogen + 50 p. c. nitrogen . . . 0*9362 

 Hydrogen + 75 p. c. nitrogen . . . 0*9344 



The pressure, as might have been anticipated, is propor- 

 tional to the partial pressure of the external hydrogen. 



It is obviously possible to test the percentage of hydrogen 

 in coal-gas by this means, provided the other constituents of 

 coal-gas are unable to pass through palladium. Axi experiment 

 with marsh-gas showed that it is not capable of permeating 

 palladium ; and the vapour of ether is also unable to pass. 



