Quinaldic acid or its sodium salt
precipitates cadmium quantitatively from acetic acid or neutral solutions. The
precipitate is collected on a sintered-glass crucible, and dried at 125 °C.
The solution (150 mL) should be neutral or weakly acid with acetic acid, and should contain 0.1-0.15 g of Cd. Heat the solution to boiling, and remove the source of heat. Add the reagent (a 3.3 per cent solution of quinaldic acid or of the sodium salt in water) dropwise with vigorous stirring until present in slight excess. Then neutralise carefully with dilute ammonia solution, and allow the white curdy precipitate to settle. When cold, wash with cold water by decantation, filter through a sintered-glass or porcelain filtering crucible, wash thoroughly with cold water, and dry at 125 °C to constant weight. Weigh as Cd(C10H6O2N)2.