M. W. Feddersen on Thermo diffusion of Gases. 



Time. 



Cold side. 



Hot side. 



Observed. 



Calculated for 

 10 minutes. 



Observed. 



Calculated for 

 10 minutes. 



h m h m 

 12 Oto 12 10 

 12 10 „ 12 15 



11 15 „ 12 25 



12 25 „ 12 30 

 12 30 ,, 12 35 



millims. 



225 



94 



tube wanting 



105 



110 



millims. 

 225 



188 



210 

 220 



millims. 



tube wanting 



95 



241 



95 



tube wanting 



millims. 

 190 

 241 

 190 



Accessory tubes removed, and, after an hour and a half, replaced. 



2 Oto 2 5 



73 



146 



49 



98 



2 5 „ 2 20 



205 



137 



153 



102 



2 20 „ 2 30 



151 



151 



112 



112 



2 30 „ 2 35 



76 



152 



58 



116 



After the last observation the bent end of the tube on the cold 

 side was immersed in sulphuric acid. The displacements ceased 

 as soon as the acid had risen about 6 millims. in the -tube, in 

 which position it remained until, at the end of an hour and a 

 half, I dismounted the apparatus. The capillary rising of the 

 acid in the tube did not amount to one millimetre ; so that the 

 difference of pressure produced by the difference of temperature 

 on the two sides of the plug corresponded to a column of sul- 

 phuric hydrate of at least 5 millims. height. 



Spongy palladium. — In most of my experiments with this 1 

 introduced it into an atmosphere of oxygen ; but the results ob- 

 tained were the least regular of any. I had contrived a special 

 arrangement of straight and T-tubes to bring oxygen into the 

 plug- tube as well as into the accessory pieces. In the experi- 

 ments a movement always showed itself in the expected direc- 

 tion, but with extraordinary variability. The singular irregu- 

 larities appeared to be provoked chiefly by the variability of the 

 absorption by the palladium with oscillations of temperature ; 

 but probably the aqueous vapour, which always formed when 

 the atmospheric air was expelled from the tube by oxygen, was 

 a further cause of the irregularities. Nevertheless the direction 

 of the phenomenon was by all this not reversed. 



As an example of the movement the following numbers of one 

 observation may serve : the tubes had from 3| to 4 millims. 

 internal diameter, and on both sides were stopped by a drop of oil. 



h m 

 9 5 

 9 25 

 9 45 



Time, 

 h 

 to 9 



Cold side. Hot side, 



m millims. millims. 



25 130 



35 155 190 



50 45 Aperture touching oil sur- 



face raises slight bubbles. 



