214 



space (dead space) '), battery work is in many cases to be preferred 

 to other methods of working. The fact that the apparatus which move 

 along the mass to be leached and therefore canse apparently a perfect 

 contimioiis process, often give results less favourable, is to a great 

 extent due to the mechanical motion disturbing the succession of 

 the concentrati(m hijers in the nuiss ; owing to this the process 

 becomes no longer continuous but changes into the most unfavourable 

 semi-continnous form. 



Finally, attention may be called to the following application of 

 the matter considered. We have assumed that the liquid used for 

 the lixiviation of the nuiss R-\-S(i(j consisted of pure water. If 

 now we suppose that the lixiviating liquid was contaminated, before 

 the leaching, with another dissolved substance Z, the question arises 

 what influence this will exert on the products obtained. 



We now readily perceive that in the lixiviation process the action 

 of the two liquids on each other is quite mutual and that we can 

 just as well "lixiviate" the lixiviating liquid with the comitincd 

 liquid as doing the reverse. If the process is conducted in a rational 

 manner this will benefit the one (real) as well as the other (secondary) 

 lixiviation. The bulk of the inq)urity Z does not then arrive in the 

 linal liquid, but in the exhausted mass. To the secondary lixiviation 

 we can apply iimtatis mutandis the same formula which applies to 

 the lixiviation proper. 



When carrying this out it appears that when a larger Fis taken, 

 the result of the lixiviation proper improves whilst that of the 

 secondary lixiviation gets w^orse. (Of course, the values of K are 

 not the same). 



This application alsc» has signiticance in practice. For it has 

 occurred that for the leaching water was used with considei-able 

 contamination, and yet the contamination of the liquid obtained 

 proved rather small. Such a method of working will, howevei-, 

 always be attended with the difficulty that a slight disturbance in 

 the continuity of the lixiviation (which distnrbance would otherwise 

 cause merely a dilution of the tinal liquid) will now cause a strong 

 contamination of the resulting liquid. 



The above study was carried out with a technical object. On the 

 practical application of the results obtained a connnunication will 

 be made in a trade journal. 



May 1913. 



1) VAN Loon 1. c. 



