2.2. Wash solution A
To 100 ml of water add 2 ml of HCl conc., one
drop of m-Nitrophenol solution and dropwise
ammonia solution till the indicator colors yellow.
2.3. Wash solution B
To 100 ml of water add 2 ml of buffer solution
and 1 ml of TDTC solution.
2.4. General procedure
Take 200 mg of the sample containing ]5% of
Sn, weighing to the nearest 0.1 mg. Transfer it to
a 250 ml conical flask and decompose with HCl
alone or together with a few drops of HNO3 (note
1). Cap the flask loosely and warm gently at
50–60°C till decomposition is complete (note 2).
Dilute to 30 ml with water, add TiCl3 solution in
excess, cap the flask as before and boil gently for
10 min (note 3). Add an appropriate amount of
tartaric acid (note 4), one or two drops of m-