152 
¢ = c, between « = A, and « = h 
é=0 between. 7 = Osand 7 = h,, 
and the limiting conditions : 
de 
— = 0 for == hand 
Ow 
e= 0 for 70 
the expression *): 
do, P= I (Qpt1)ah, . (2p+1)2e (PE. Vp 
== a COR 8 — e 
108 ——— sin — : 2h 
C — 5 zn 5 
JT p=0 2p + Qh 2h 
- (4) 
The quantity which has flowed through the upper section in a 
definite time f, is indicated according to Fick’s law by: 
A= | D be lt 
=") Coie 
0 
in which g represents the section of the vessel. 
From 4 we find for this value: 
pater (,_ CP} 
mu = (ap 1 
If we choose h,=+h, it is clear that in consequence of 
(2p +1) ar A, ; ; 
COC err es becoming zero for p= 1, the second term of the 
quickly converging series disappears; therefore the first term suffices 
for a great number of the determinations. This method of working 
had been applied by one of us before. *) 
In the determinations mentioned below we have taken h, = 0 
for experimental reasons; the filling of the diffusion cylinders up to 
?/, of their height for temperatures that differ from that of the 
surroundings is namely accompanied with great difficulties. 
For our case 4,=0, and the cosine disappears from all the 
terms; the series, however, remains complete, so that generally 
two or three terms must be used for the calculation of the expe- 
‘riments. If Q, represents the quantity of substance originally present, 
the value of the relative rest for a time ¢ becomes: 
nm Dt 9x? Dt 25x? Dt 
Qo — Q 8 ( ——- : eee 5 
ee) PN Oc ee a ae 
Qo n° 9 25 
1) SIMMLER and WILD, Pogg. Ann. 100. 217. (1857). 
2) J. D. R Screrrer. Ber. der Deutsch. Chem. Gesellsch. 15. 788 (1882) and 
16. 1903 (1883). 
