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Chemistry. — "Economic Uxiviatlon" Bj Dr. P. J. H. v. Ginneken. 

 (Communicated by Prof. Ernst Cohen.) 



(Communicated in the meeting of June 28, 1913). 



An economic lixiviation requires tlie attainment of a sufficient 

 degree of leaching with as little solvent as possible, with the simplest 

 contrivances and in the shortest possible time. 



Let us lake a mass R -\- Saq, consisting of a substance R in- 

 soluble in water ^) and of a Wtiterj solution of the water-soluble 

 substance S. A definite quantity of this mass has to be lixiviated 

 with water in the most economical manner. 



We assume that the solution is combined with the solid substance 

 capillarily, by absorption, by inclusion in permeable walls or by 

 other means, but not chemically ; and also that during the lixiviation 

 the volume of the liquid combined with the solid substances in this 

 manner does not change. 



We equal this volume of the "combined liquid" in a definite 

 weight of the original mass to v. 



By V we represent: the volume of the water (or of the solution 

 respectively) which is added to a definite weight of the original 

 mass in each period of the lixiviation. In the following considera- 

 tions we assume that this volume also does not change during the 

 lixiviation by absorption of the substance S. The solution obtained 

 after each period has, therefore, also the volume V. This assumption 

 will (like that about v) be only roughly approximate in the case of 

 larger concentrations ; in each case, therefore, we shall have to 

 account for the extent of the deviation and of the influence thereof 



V 

 on the results obtained. We put — =: .v. 



V 



By Öq is represented the concentration "j (expressed in grams per 

 100 cc.) of the substance S in the combined liquid of the original 

 mass, by b^, b^,...bn the corresponding concentrations during or 

 after the lixiviation, respectively : 



By U:^ — : the degree of lixiviation indicating how many times 



bn 



the concentration in the combined liquid has been reduced owing 

 to the lixivianon ; 



by üq : the concentration of the solution resulting from the whole 

 process ; 



1) All this applies mutatis mutandis to an arbitrary solvent. 



2) Unless stated otherwise, the concentration will in future mean gram per cc 



