ON ELECTROLYSIS IN ITS PHYSICAL AND CHEMICAL BEARINGS. 351 



dipping with their open ends into two pairs of porous pots, each pair fidl of the 

 same liquid as is in its tube. The four pots, and also the two main (zinc) electrodes, 

 are contained in six separate glass vessels, all full of sulphate of zinc solution, 

 connected up by short stout siphon tubes, as shown in fig. 1. The tapping elec- 



FlG. 1. 



VxxV^Vxf'^^x g??'^'-^^^ 



trodes are zinc blocks, each in a Woulfie's bottle of sulphate of zinc, with a 

 projecting and recurved full tube able to dip into any part of the liquid in the glass 

 ■cells outside the porous pots, and so make connection (see fig. 2). 



Fio. 2. 



After taking readings for the two tubes filled with different liquids, they are both 

 filled with the same liquid and fresh readings taken, so as to compensate for 

 inequalities between the tubea. 



III. Conductivity of very dilute Neutral-salt Solutions. 



' When one takes a solution of a neutral salt, already pretty dilute, and doubles 

 the quantity of water it contains, the specific resistance is in general far from being 

 doubled, as one would a priori expect ; it is multiplied by a coefficient X, smaller 

 than 2, which increases progressively with dilution and tends towards the limit 2, 

 but only for excessive dilution. Here, for example, arejsome numbers furnished by 

 sulphate of zinc : — 



