Zirconium may be precipitated from a hydrochloric acid solution with mandelic acid (C6H5-CH(OH)-COOH) as zirconium mandelate, Zr(C8H7O3)4, which is ignited to and weighed as the dioxide. Quantitative separation is thus made from titanium, iron, vanadium, aluminium, chromium, thorium, cerium, tin, barium, calcium, copper, bismuth, antimony, and cadmium. If sulphuric acid is employed, the concentration should not exceed 5 per cent: higher concentrations give low results.
The solution (20-30 mL) may contain 0.05-0.2 g Zr, and should possess a hydrochloric acid content of about 20 per cent by volume. Add 50 mL of 16 per cent aqueous manclelic acid solution and dilute to lOOmL. Raise the temperature slowly to 85 °C and maintain this temperature for 20 minutes. Filter off the resulting precipitate through a quantitative filter paper, wash it with a hot solution containing 2 per cent hydrochloric acid and 5 per cent mandelic acid. Ignite the filter and precipitate to the oxide in the usual manner: a temperature of 900-1000 °C is satisfactory. Weigh as ZrO2.
Note. Bromomandelic acid is a superior reagent for this determination, but is more expensive. A similar procedure to that above is employed.
Stir for 1 hour and then allow the precipitate to settle. Filter by decantation. wash the precipitate until free from excess reagent, dry at 105 °C and weigh as Pb(C7H5O2N)