BS ISO 19747:2020 Fertilizers and soil conditioners — Determination of monosilicic acid concentrations in nonliquid fertilizer materials

BS ISO 19747:2020 Fertilizers and soil conditioners — Determination of monosilicic acid concentrations in nonliquid fertilizer materials. 7 Calibration standards 7.1 Blank: 0 mg/I Si — add 10 ml sodium carhonate—ammoniurn nitrate extractant solution (GA) to a II volumetric flask. Dilute to 11 with water. Stopper the flask and mix by inverting 10 times. 7.2 Standard 1: 0,25 mg/I Si — add 10 ml sodium carhonate—ammonium nitrate extractant solution (M) to a 1 L volumetric flask. Add 5 ml intermediate silicon standard solution (JO). Dilute to 1 1 with water. Stopper the flask and mix by inverting 10 times. 7.3 Standard 2: 0,50 mg/I Si — add 10 ml sodium carbonate—ammonium nitrate extractant solution (M) to a 1 1 volumetric flask. Add 10 ml intermediate silicon standard solution (J..Q). Dilute to 1 1 with water. Stopper the flask and mix well by inverting 10 times. 7.4 Standard 3: 1,0 mg/I Si — add 10 ml sodium carbonate-ammonium nitrate extractant solution (f.4) to a 1 1 volumetric flask. Add 20 ml intermediate silicon standard solution (610). Dilute to 11 with water. Stopper the flask and mix by inverting 10 times. 7.5 Standard 4: 2.0 mg/i Si — add 10 ml sodium carbonate-ammonium nitrate extractant solution (6A) to a 1 1 volumetric flask. Add 40 ml intermediate silicon standard solution (610). Dilute to 11 with water. Stopper the flask and mix by inverting 10 times. 7.6 Spike sample: Prepare a spiked talc sample by drying (9..L1) grinding (912) and weighing out (9Ja) a 0,2 g talc [Mg3Si4Olo(OH)21 test portion sample. Add 100 ml each of sodium carbonate (62) and ammonium nitrate () solutions using a plastic graduated cylinder. Before shaking (92) add 3 ml silicon spike solution (66) to the talc test sample. This talc-spiked test sample is processed and used for the matrix spike recovery test verifying that soluble (spike) rather than insoluble silicon (talc) is extracted and reported using this method. 8 Apparatus As silica (Si02) is a constituent of commonly used laboratory glassware, and detection limits are at 0,6 g/kg Si. it is important to adhere to strict glassware cleaning instructions. 8.1 Glassware, to be thoroughly acid cleaned prior to use in reagent and calibration standard preparation by soaking in a 40m1/l HNO3 solution (Ml) for 30 mm and rinsing three times with deionized water. Allow glassware to air dry prior to use. Glassware items needed include 100 ml...