187 
a minimum, if we add acid, the substance behaves like a 
base, when we add base like an acid. In many cases it 
can be stated that the isoëlectric point is reached, when 
the colloïdal particles do not move with cataphoresis or 
are driven partly to the anode partly to the cathode. 
The isoëlectric point can also be fixed indirectly. In the 
isoëlectric state, we often meet with flocculation, With the 
swelling of colloïdal substances the isoëlectric point often 
coïncides with the minimum of swelling. Of a colloïdal 
solution the inner friction would be a minimum in the 
isoëlectric point. 
In many cases the H-ions and the OH-ions are chiefly 
of influence on the electric state of the colloïdal particles. 
Then they fix the place of the isoëlectric point. However, 
if the ampholyte has suspensoïd properties, the ions of the 
salts have a great influence on the situation of the isoëlectric 
point. It was impossible to fix immediately the isoëlectric 
point of the plasm-colloïds of Chlamydomonas. The great 
tension between the electrodes, which would have been 
necessary, to submit the whole organism to cataphoresis, 
would have caused the death of the algae. An attempt to 
find out bij means of the galvanotactical reaction in 
solutions of various H-ion concentration, something about 
the situation of the isoëlectric point, miscarried, since 
Chlamydomonas did not react, to weak electric currents. 
Indirectly we can fix the place in the curves, by which 
the plasmcolloïds are isoëlectric. 
ÏJs our opinion on the symmetry of the middle most 
part of the curves right, then the isoëlectric point must 
undoubtedly be found in the place, where the axis of 
symmetry cuts the curve. For K,;SO, (fig. 2, page 51), 
with 0,00040 n. KOH, for KCI (fig. 4, page 56) with 
0,00045 n. KOH and for KNO, (fig. 5, page 57) with 
0,00030 n. KOHI. 
Even if we do not agree with the representation, which 
