Fig. 1. Fig. 2. : 
It will now be evident without any further comment that the 
limit value is not (or but very faintly so) a function of the 
concentration when a is small in regard to y and when consequently 
vy =y. In the case of monovalent cations with their relatively high 
limit value this will have to be the case. In the di-, and still in a 
higher degree in the trivalent cations, the limit value will have to 
increase with the concentration. 
8. Concentrated sols of As,S, were made according to a method 
devised by ScHurze *). After in a nearly saturated solution of As,O, 
this had been converted into As,S,, a fresh quantity of As,O, was 
dissolved and H,S again passed through. This treatment was then 
repeated a few times’). The determination of the limit value for 
such concentrated sols must be modified somewhat. A mere shaking 
of the glasses is not sufficient as after the congulation, they may be 
placed upside down without anything running out. Hence, before 
and after the two hours required, stirring rods were used. In the 
case of monovalent cations the precipitate obstinately adheres to the 
glass walls thus rendering the observation much more difficult. 
In the first five columns of the subjoined table 1 are communicated 
the results of a series of measurements. The determinations have 
been carried out with the same measuring instruments, standard 
solutions, working arrangements, in fact as much as possible under 
the same conditions. For each concentration a separate sol was prepared. 
The concentration was determined by precipitating the As,S, with 
HCI, drying on a Gooca filter at 50° and weighing. 
In Table 1 all concentrations are end concentrations, that is they 
relate to the volume after addition of the electrolyte solution. 
In Fig. 3 these results are represented in such a manner that the 
limit value of experiment 1 is put for each electrolyte each time as 
1) Journ. f. prakt, Chem. N. F. 25, 431 (1882). 
2) Full experimental details will be published elsewhere. 
