Limit Test for Calcium

All solutions used for this test should be prepared with distilled water R.

To 0.2ml of alcoholic calcium standard solution (100ppm Ca) R, add 1ml of  ammonium oxalate solution R. After 1min, add a mixture of 1ml of dilute acetic  acid  R and 15ml of a solution containing the prescribed quantity of the substance  to be examined and shake. Prepare a standard in the same manner using

a mixture  of 10ml of aqueous calcium standard solution (10ppm Ca) R, 1ml of dilute acetic acid  R and 5 ml of distilled water R.

 

 After 15 min, any opalescence in the test solution is not more intense than that in  the standard.

Reagent used

§  Ammonium Oxalate Solution: A 4% w/v solution of  ammonium oxalate.

§  Dilute Acetic Acid: Dilute 12g of glacial acetic acid  to  100ml with water . It contains not less than 11.5% and not  more than 12.5% w/v of C2H4O2 (2M)

§   Alcoholic Calcium Standard Solution (100 ppm Ca): Dissolve 2.50 g of dried  calcium carbonate in 12 ml of 5M acetic acid  and dilute to 1000.0 ml with distilled  water . Dilute 1 volume of this solution to 10 volumes with ethanol (96%) immediately  before use.