acidification
and preferentially oxidized. It was chosen
since it is very pure, harmless and can be readily
boiled off.
Attempts were made to eliminate interferences
from Mo and V, but failed. Thus, we can not help
taking another approach: to precipitate them altogether,
determine their co-precipitated amounts
and make corrections for them (Eq. (2)). Fortunately,
their presence or absence can be readily
detected by the naked eye: in their absence the
precipitate is pure white; while in their presence it
is colored (yellow if V is present and scarlet if Mo
present). Their determinations are also an easy
matter. Indeed, a clear-cut separation of Mo and
V from Sn seems very much difficult, if not impossible,
to incorporate conveniently in the proposed
method.
For anions, some alloys may contain 51% of
P which is tolerable. Effects of some ionic species
on the determination of Sn are shown in Table 3.
3.4. Applications
It should be noted that only Sn(IV) forms a
precipitate with TDTC in the highest mole ratio
of 1:4. Hence, its conversion factor is very small
Table 3
Effects of cations on the determination of 30.0 mg of Sn
Cation added Mass of precipitate Mass of Sn
(mg) found (mg) found (mg)