DIN ISO 5544:2020 pdf download.Caseins — Determination of “fixed ash” (Reference method)
5.1 Magnesium acetate tetrahydrate, [Mg(CH 3 CO 2 ) 2 ⋅4H 2 O], 120 g/l solution.
6 Apparatus
Usual laboratory apparatus, and in particular the following.
6.1 Analytical balance, capable of weighing to the nearest 0,000 1 g.
6.2 One-mark pipette, of capacity 5 ml, complying with the requirements of ISO 648, class A.
6.3 Silica or platinum dishes, of diameter about 70 mm and depth 25 mm to 50 mm.
6.4 Drying oven, capable of being controlled at (102 ± 2) °C.
6.5 Electrical furnace, with air circulation, capable of being controlled at (825 ± 25) °C.
6.6 Water bath, capable of being maintained at boiling point.
6.7 Desiccator, containing an effective desiccant.
6.8 Grinding device, for grinding the laboratory sample, if necessary (see 8.1.4), without development of undue heat and without loss or absorption of moisture. A hammer-mill shall not be used.
6.9 Test sieve, wire cloth, of diameter 200 mm, of nominal size of aperture 500 µm, with receiver,complying with ISO 3310-1.
7 Sampling
A representative sample should have been sent to the laboratory. It should not have been damaged or changed during transport or storage.
Sampling is not part of the method specified in this International Standard. A recommended sampling method is given in ISO 707|IDF 50 [1] .
8 Procedure
8.1 Preparation of the test sample
8.1.1 Thoroughly mix the laboratory sample by repeatedly shaking and inverting the container (if necessary,after having transferred all of the laboratory sample to an airtight container of sufficient capacity to allow this operation to be carried out).
8.1.2 Transfer about 50 g of the thoroughly mixed laboratory sample to the test sieve (6.9).
8.1.3 If the 50 g portion directly passes or almost completely passes the sieve, use for the determination the sample as prepared in 8.1.1.
8.1.4 Otherwise, grind the 50 g portion, using the grinding device (6.8), until it passes the sieve.
Immediately transfer all of the sieved sample to an airtight container of sufficient capacity and mix thoroughly by repeatedly shaking and inverting. During these operations, take precautions to avoid any change in the water content of the product.
8.1.5 After the test sample has been prepared, the determination (8.4) should proceed as soon as possible.
Clean the device after grinding each sample.
8.2 Preparation of the dishes
Heat two dishes (6.3) in the electrical furnace (6.5), maintained at (825 ± 25) °C, for 30 min. Allow the dishes to cool in the desiccator (6.7) to the temperature of the balance room and weigh to the nearest 0,1 mg.
8.3 Test portion
Weigh, to the nearest 0,1 mg, directly in or by difference approximately 3,000 0 g of the test sample (8.1) into one of the prepared dishes, designated dish A.
8.4 Determination
Using the pipette (6.2), add 5 ml of the magnesium acetate solution (5.1) to dish A so as to wet all of the test portion, and allow to stand for 20 min.
Using the pipette (6.2), add 5 ml of the magnesium acetate solution (5.1) to the other prepared dish,designated dish B.
Evaporate the contents of dish A and dish B to dryness on the water bath (6.6).
Place dish A and dish B in the oven (6.4), maintained at 102 °C, for 30 min.
Heat dish A with its contents on a low flame until the test portion is completely charred, taking care that it does not burst into flame.
Transfer dish A and dish B to the electrical furnace (6.5), maintained at 825 °C, and heat for at least 1 h until all carbon has disappeared from dish A. Allow dish A and dish B to cool in the desiccator (6.7) to the temperature of the balance room and weigh to the nearest 0,1 mg.
Repeat the operations of heating in the electrical furnace (6.5), cooling and weighing, until the mass remains constant to within 1 mg or begins to increase. Record the minimum mass.
9 Expression of results
9.1 Calculation
9.1.1 The “fixed ash” of the sample, including phosphorus, w fa , as a percentage by mass, is given by Equation (1):
Calculate the “fixed ash” to the nearest 0,01 % by mass and report the final result to the nearest 0,1 % by mass.DIN ISO 5544 pdf download.DIN ISO 5544 pdf download
