Dosage du calcium dans le lait

Abstract - The International Dairy Federation has standardized an official method for the determination of calcium in milk on the following basis:
1) Defecation of a test portion of 20 g with trichloracetic acid. This treatment of the test portion was preferred to dry ashing and to wet mineralization. The reasons for that are given.
2) Precipitation of calcium, on an aliquot part of the filtrate, as oxalate; separation of the oxalate by centrifugation and washing of the precipitate.
3) After dissolution of this calcium oxalate in diluted sulfuric acid, titration of the oxalate with a solution of potassium permanganate. This treatment was preferred to complexometric titration for the given reasons.
The repeatibility of this method is excellent (less than 0,002 g of calcium for 100 g of milk)