IPT10 POTASSIUM IN FERTILISERS Last Revised: Mary 2015
1. PURPOSE This exercise determines the levels of K in fertilisers by flame photometry, using an internal standard. 2. REAGENTS & EQUIPMENT 2.1 Soluble fertiliser 2.2 1000 mg/L K 2.3 1000 mg/L Li 2.4 0.01 M EDTA 3. PROCEDURE 3A. Sample preparation 3.1 Weigh accurately about 1 g of sample, in triplicate, and transfer to 250 mL volumetric flasks, labelled S1, S2 & RC. 3.2 To the RC flask, pipette 50 mL of 1000 mg/L K as a recovery check. 3.3 Make up to mark with water. Mix until dissolved. 3.4 Pipette 5 mL of Sample 1, 5 mL of 1000 mg/L Li and 5 mL of 0.01 M EDTA (measuring cylinder) to a 100 mL volumetric flask and make up to the mark. Label as S1D. 3.5 Repeat for Sample 2 & the recovery check. 3.6 Filter each solution by Millepore filtration. 3B. Standard preparation 3.7 Prepare 100 mL of 200 mg/L K from the 1000 mg/L standard. 3.8 Pipette 0, 5, 10 and 20 mL of this solution into 100 mL volumetric flasks. 3.9 Add 5 mL of 0.01 M EDTA (measuring cylinder) and 5 mL of 1000 mg/L Li (pipette) to each flask. Make up to the mark with distilled water. 3C. Analysis 3.10 Set up the flame photometer and optimise using the top standard, setting its K value to about 1500. 3.11 Run each solution through the flame photometer, measuring K & Li for each solution before moving to the next. Reporting 

Enter the data into the spreadsheet found on the subject website. Transfer the final results – average %w/w and %recovery – to your Result Sheet and submit this.