Paragraph 7 PROCEDURE

Weigh to the nearest 0.001 g, 1 g of the prepared sample and transfer to the 500 ml graduated flask (5.2). Add 200 ml alkaline ammonium citrate solution (4.1). Stopper the flask and shake vigorously by hand to avoid the formation of lumps and to prevent any adherence of the sample to the sides.

• Place the flask in the water bath at 65°C and shake every 5 minutes during the first half an hour. After each shaking, raise the stopper to equilibrate the pressure. The level of water in the water bath should be above the level of solution in the flask. Allow the flask to remain in the water bath a further hour at 65°C and shake every ten minutes. Remove the flask, cool to a temperature of about 20°C, make up to volume of 500 ml with water. Mix and filter through a dry fluted filter paper, rejecting the first portion of filtrate.

Determine the phosphorus using Method 10 on an aliquot portion of the clear filtrate.