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concentrations which we used. Therefore we have not 
made the definition of the concentration of the salt-ions. 
To obtain solutions with different H-ion concentrations 
we can use various methods. The simplest way is to add 
to the solutions small quantities of acid or base. This 
manner of working is only suitable, when the solutions 
do not contain anything but neutral salt. [ used this means. 
However we must make allowance for all sorts of details. 
When, in this way, we will make a series of solutions 
with increasing amounts of hydrions, we have to make, 
for example, a solution of 0,001 normal acid. It must 
thus be preserved, that the strength of the acid can change 
as little as possible. Of this solution we must have enough 
to compose all solutions with the same salt. Solutions 
with different H-ion concentrations are now obtained by 
adding per 100 cM. fluid, 5, 10 etc. cM3. 0,001 normal 
acid. Thus we obtain solutions which contain f. i. 0,00005, 
0,00010 etc. normal acid. The distilled water, which is 
used, may not vary too much as regards the amount of 
carbonic acid. When working in the stated way, the 
method can be used. The drawbacks of the method are 
the following. The thus obtained solutions are not repro- 
ducable, that means, if we make the same solutions with 
another solution of 0,001 n. acid, the H-ion concentration 
can deviate a good deal from that of before-made. Small 
mistakes denote very great differences as regards the 
acidity. The H-ion concentration of these solutions cannot 
be reckoned out. Moreover it cannot be defined electro- 
metrically in this Only by means of indicators we can 
find here an amount for the acidity. However, I did not 
apply this method. 
The cause of the difficulties must be sought in the fact, 
that small quantities of acid or base enormously change 
the H-ion concentration. Moreover, small quantities of 
carbonic acid can also bring about a great change. For 
