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concentrations of the H-ions and OH-ions. The solutions 
are thus composed, that they form series. All solutions 
from one series contain the same hydrion concentration 
that means the same acidity or the same alkalinity, as 
the H-ions or the OH-ions are present in a greater 
number. The successive solutions from every series contain 
an increasing quantity of salt. The series succeed one 
another in such a way, that the hydrion-concentration of 
one of them is smaller than that of the next. 
We can also arrange tne solutions in such a way, that 
in each series the amount of salt is constant, whilst the 
hydrion-concentration of the following solution regularly 
changes. 
By the experiment we state from a series, in which 
the hydrion concentration is constant the limiting concen- 
trations of the salt. From the limiting concentrations we 
calculate the critical concentration for the salt with that 
definite hydrion concentration. In a similar way we can 
find the limiting concentrations and the critical concen- 
tration of the hydrions with the help of the series with 
a fixed amount of salt. Both proceedings must have the 
same results, for a solution, which contains the critical 
concentration for a salt by a fixed hydrion concentration 
can also be considered to contain the critical hydrion 
concentration by à constant concentration of salt. 
In most of our experiments we worked with series of 
constant hydrion concentration. The limiting concentrations 
which are fixed by that, represent the limiting concen- 
trations of the salt and must be used to calculate the 
critical salt concentration by a definite amount of hydrions. 
Occasionally this gave rise to difficulties. In those cases 
the limiting concentrations found for salt were used as 
limiting concentrations of hydrions and they were used to 
calculate the critical H-ion concentration. În a series with 
constant H-ion concentration we find one critical concen- 
