Colour development is normally complete within 1 minute. If colour development continues after that time, it is likely that iron complexes are present. Wait further time for colour to stabilize, allowing up to 15 minutes
Fill to the 10 mL line with sample.
Use this to "blank" the instrument. Place in cell holder and press Blank.
Then, prepare sample by adding an Iron LR tablet and crush and stir.
Place in the cell holder and press Measure.
Allow timer to count down 1 minute. The concentration of Iron will then be displayed.