Estimation of aluminium by gravimetry
8-hydroxyquinoline (oxine reagent) can be used to quantitatively
precipitate
several metal ions. Control of pH is necessary.
Calculate
the amount of your
prepared crystals that will contain 25 mg of aluminium
- use the formula of the
anhydrous complex (since you do
not know the amount of water
of hydration present in the
crystals).
Take
the crystals approximately equal in
weight to
the calculated quantity
and deterimine its weight accurately. Transfer it
quantitatively into
a beaker, dissolve in water
and proceed to precipitate as described in Vogel. What will happen
if the pH is too high (above 9) during your precipitation?
Calculate
the percentage by
weight of Al present in the crystals.