209 



.d^l -1 



/>,) X — 1 



in which y indicates the figure that is written as index at the con- 

 centrations h. WiJh the aid of tliis equation it is possible to draw 

 ca figure which indicate^ the progressive change of the concentrations 

 h at the semi-continuous lixiviation. 



III. Continuous liviviation nccorcUny to the counter-current principle. 



We pass from the semi continuous lixiviation to tiie continuous 

 one by taking n verv large and LI very small. 



In tlie same manner as in the continnous lixiviation we tind 

 here : ^) 



ih = KB Lh (b—a,) dt = BE'— dt {1\-h^) =- BD~dt («„— a,) . (12) 



dti dt(j 



in which 



dl dl 



— = — — and Lh = — LI,,. 



dt(, dta 



If now we replace generally h^ — a^ by /> — a, (/> and a beino- 

 variable quantities dependent on /) and write: 



dl> 



we get 



KO , (// (//> 



_(,,__„) = --_._ . (,3) 



KO dl da 



{h—a) = — . — C14) 



V ^ dt„ dl ^ ^ 



dt) da 



— dl=: .V — dl 

 dl dl 



') A deduction which agrees in principle with the one made here is given by 

 Van Loon v Tijdschrift der Algemeene Technis.he Vereeniging v. B. en R. 

 1911 — 1912 p. 231). In my opinion, however, the method used is not quite correct. 

 This does not prevent, however, that in the article cited there are mentioned many 

 very correct and original remarks on this subject. 



14 



Proceedings Royal Acad. Amsterdam. Vol. XVI. 



