6.5.Calculate the organic matter extracted (7.1). If the result is greater than 1 mg/l, carry out a blank test on the reagents and recalculate the weight of organic matter extracted.U.K.
The blank test should be carried out by repeating sections 6.3 and 6.4 but using two litres of the extracting solvent, to give weights m3 and m4 in sections 6.3 and 6.4 respectively.