LIQUIDS AND ALIBIED EXPERIMENTS. 



31 



23. Transpiration of Hydrogen into Air Through Water. — These experi- 

 ments, given in table 7 and fig. 10, are a sustained repetition of the work 

 in §11, using a much heavier swimmer, so that a decrease of the area of 

 diffusion due to loss of gas by transpiration may not occur. The curve, as 

 before, is remarkably regular and partakes of the qualities of the earlier 

 curve (fig. 5). The initial rate is — w = 7i X io~®g/day or 8.2X io~^%/sec., 

 which is of the same order as the datum of table 2, remembering that the 

 constants of the apparatus are slightly difi"erent. The coefficients of trans- 

 piration are, since <i= 11.5 cm.^ (inside area), 



h' 



1 1.5 cm. 



2h"' = g.o cm. 



/ = 20.5 cm. 



and, if the water heads be taken as a trial gradient for comparison, so that 



dp 



— = 549 dynes/cm. 



K = i6Xio 



-10 



somewhat larger than the above datum (^=1.1 X lo-'^), the difference, 

 however, being of the same order as the irregularities of the sectional areas 

 of the diffusion columns and referable, in part, to the values of h" and h'" 

 involved. There is, furthermore, a difference in the mean of the irregular 

 temperatures. Close agreement, therefore, was not to be looked for. 



Fig. 10. — Chart showing loss of mass of gas in diver in lapse of days. 

 Diffusion of hydrogen into air. 



The final coefficients are largely subject to the water heads under which 

 diffusion takes place. We may therefore write, since 



— ^ = 3.5Xio-^g/day or 4.oXio-"g/sec. ^ = 0.64X10"^* 



and from this 



K = 0.78X10-'° 



which approaches the coefficient for air (0.91X10"'°), as would be antici- 

 pated. One may note, however, that it is nevertheless still below it. 



