This inference seems theoretically sound, because
DDTC reacts with Sn(IV) in the same mole ratio
[11]. Hence, the conversion factor from SnL4
(L stands for the TDTC anion here) to Sn
should be 1:5.9280.1687. With a view to applying
this theoretical factor the reaction conditions
were optimized as follows.
Different temperatures for drying the precipitate
to constant mass were tested and their results
are shown in Table 1. Evidently 95°C
would be the optimum one, whereas low recovery
of Sn was found if dried at higher temperatures,
presumably owing to thermal
decomposition of the precipitate. Drying at B
95°C takes much more time.
The optimum volume of the analyte solution
for precipitating was found to be 80–100 ml.
The precipitate formed at room temperature is
difficult to filter. On the other hand, high precipitation
temperature favors its filtrability, but
accelerates the decomposition of the precipitant.
As a compromise, 70°C was specified and found
to be optimum. The precipitate should be aged
for 15 min at this temperature and filtered only
after cooling to room temperature. Otherwise
the results may be poorly reproducible.
Different amounts of the precipitant were
added for precipitating different amounts of
Sn(IV) and the results are shown in Table 2.
Obviously addition of a large excess of TDTC
does no harm. Its optimal amounts were specified
to be 1–3 g. One g of it suffices to precipitate
quantitatively 530 mg of Sn when present
alone.
Table 1
Effect of drying temperature on determination of 15 mg of Sn
Drying tempera- Mass of precipitate Sn found (mg)
ture (°C) (mg)
105 87.7 14.8
88.3 14.9
100 88.1 14.9
88.5 14.9
95 89.2 15.0
88.9 15.0
This inference seems theoretically sound, because
DDTC reacts with Sn(IV) in the same mole ratio
[11]. Hence, the conversion factor from SnL4
(L stands for the TDTC anion here) to Sn
should be 1:5.9280.1687. With a view to applying
this theoretical factor the reaction conditions
were optimized as follows.
Different temperatures for drying the precipitate
to constant mass were tested and their results
are shown in Table 1. Evidently 95°C
would be the optimum one, whereas low recovery
of Sn was found if dried at higher temperatures,
presumably owing to thermal
decomposition of the precipitate. Drying at B
95°C takes much more time.
The optimum volume of the analyte solution
for precipitating was found to be 80–100 ml.
The precipitate formed at room temperature is
difficult to filter. On the other hand, high precipitation
temperature favors its filtrability, but
accelerates the decomposition of the precipitant.
As a compromise, 70°C was specified and found
to be optimum. The precipitate should be aged
for 15 min at this temperature and filtered only
after cooling to room temperature. Otherwise
the results may be poorly reproducible.
Different amounts of the precipitant were
added for precipitating different amounts of
Sn(IV) and the results are shown in Table 2.
Obviously addition of a large excess of TDTC
does no harm. Its optimal amounts were specified
to be 1–3 g. One g of it suffices to precipitate
quantitatively 530 mg of Sn when present
alone.
Table 1
Effect of drying temperature on determination of 15 mg of Sn
Drying tempera- Mass of precipitate Sn found (mg)
ture (°C) (mg)
105 87.7 14.8
88.3 14.9
100 88.1 14.9
88.5 14.9
95 89.2 15.0
88.9 15.0
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