pH metric curves of metallic ions in presence of alkali fluorides.

In the following process the possibility of measuring the metalic ions such as Th4+, Zr4+V4+, Ce4+ and so on in the acid solutions by meane of two pH metry curves has been investigated.
We believe that the method is simple and fast, the results are consistent and the accuracy is about 0,5%.
The procedure will include the following steps:
1-Total acidity measurement: 'The solution containing the metallic ion is titrated with N/2 sodium hydroxyde.
Metallic hydroxide wille be precipiteted at pH of 1•6 according to the acidity of the cation.
In this case the sum of H+ concentrations is measured according to reactions:
H+ +OH- H20
Mn+nOH- M(OH)n
2- Free acidity measurement: In another sample solution an excess of alkali fluoride is added, as a result of which the metallic ionis changed to a complex ion or precipitated. The metallic hydroxide is not precipitated at pH below7and addition of sodium hydroxide solution will neutralize the hydrogen ion.
The stability of the fluorine complex depends on the pH and the amount of the fluoride added.
By this method we can only determine the free acidity of the solution.
The difference between the two measurements will give the concentration of the metallic ion.