Place 30 mL of sample, completely clear and free of any suspended or entrained water (see 9.3), into a chemically clean,
dry 25-mm by 150-mm test tube and, within 1 min after completing the final preparation (polishing), slide the copper
strip into the sample tube. If more than one sample is to be analyzed at essentially the same time, it is permissible to
prepare each sample in the batch by stoppering each tube with a vented stopper, such as a vented cork before placing each
tube in a bath maintained at 50 6 1°C (122 6 2°F), provided the elapsed time between the first and last sample prepared is
kept to a minimum.