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Method for Studying Mixed Hydroxo Complexes within the pH Range where the Ligand is not Protonated

H. Bilinski ; Institute »Ruder Boskovic«, Zagreb, Croatia, Yugoslavia

Sažetak

A general method is presented, which can be used for the
determination of the composition (j, p) of soluble mononuclear
mixed hydroxo complexes, [B(OH)iAP], formed in the presence of
an excess of the ligand and within the pH range in which the
ligand is not protonated. In order to find the value of j two titration
curves are compared: (1) the curve obtained when a solution of
pure alkali or ammonium salt of a polybasic acid, A = const., is
titrated with strong acid of total concentration a5
; (2) the curve
obtained when the same solution as above is titrated with addition
of a small amount of metal ions, B = const., the condition being
B « A. The difference (,1,) of pH between the two curves at
a0 = 0 is explained, exclusively as being an effect of the metal
ions. There are three possible cases that should be taken into
consideration:
1. /':,. = O; The mixed hydroxo complexes are either not formed,
or the initially hydrolyzed composite central group [B(OH)2]
is not further hydrolyzed; Bjerrum's method6 can be applied to
find the p value. A thorium oxalate complex• is given as an
example.2. /':,. > O; OH ions from the initially hydrolysed composite
central group, [B(OH)2] are replaced by the ligand. A zirconyl
oxalato complex11 is given as an example.
3. /':,. < O; Mixed hydroxo complexes are formed. Thorium
maleato3 and thorium phthalato2 complexes are given as examples.
In the cases 2. and 3., where Bjerrum's method can not be
applied, the solubility curve of metal hydroxide in an excess of
ligand, can be used to find the p value.

Ključne riječi

Hrčak ID:

197334

URI

https://hrcak.srce.hr/197334

Datum izdavanja:

20.4.1971.

Posjeta: 452 *