211 



KG x—\ 



^=c=^^^l-Ll^ a//) 



b„ .t' — 1 



in wiiich for t„ mav also be wriltcn — {l„ = total length). 



■V, 



It is possible to deduce this expression for ^/(oontinuoiis) straight- 

 way from the expression for U (senii-oontiniions) and also from lliat 

 for U (discontinuons) by rearranging these expressions in a snilablc 

 manner and putting ?? == x. 



From (15) and (16^ we find the ecpiation ^) which indicates the relation 

 lietween the concentrations a and the length / (or the duration i) : 



1 1/ 1 ^_^,^± 

 a + -/>, = —/>„ + 7^>. '■ " "- %^ • . (17) 



,7! 1 ,V \ .V 1 J 



From (15) again follows : 



a, = -{f>o—h) (S) 



from which a„ can again be calculated if /;„, U, and .?■ are known. 



The i-elations deduced above furnish a means for calculating for 

 each method of working the results obtainable {U or b„ ; and a„ 



if the quantittes K, 0, v, T, /"„ I /„ and — , respectively J and ii are 



known or can be determined. 



K and (). As the quantity K {{he choice of the units being determiiiedl 

 accounts for all the specitic properties of the mass to be leached, 

 it will as a ride have to bo determined experimentally. Up to now 

 we have assumed sileutly ihat A" has no couuexiou with (), bul this 

 supposition will, in many cases, not be correct. In the lixivialiou of 

 masses where the bound liquid is not found at the sui-face ot 

 the solid substance, but must proceed a certain distance dependent 

 on the thickness of the solid particles, K will, as a rule, change 

 with '). As, however, as a rule O will also not be capable of 

 direct measurement, the product of the two quantities will, in such 

 cases, have to be introduced as a single constant. Of course, the 

 nature of the substance must be such that this quanlifi/ remains 

 really constant during the whole process. 



space at disposal for the lixiviating liquid is lakcji larger or smaller, hi practice 

 the opinion is often met with that such an influence is really present. 



1) We may, of course, deduce this equation also from (14) and (15) in the same 

 manner as (IG) was deduced from (13j and (15). 



2) Cf. VAN Loon I.e. 



14* 



