4.1 Stalagmometer, 2.5 ml, calibrated at 20 ± 1 drops of water at 25°C. (A 5 mL stalagmometer can also be used, but is not recommended).
4.1.1 Cleaning new stalagmometers: The cleanliness of a stalagmometer is essential for producing precise measurements of surface tension. Therefore, a new stalagmometer must be thoroughly cleaned before its first use. To clean a new stalagmometer, rinse the stalagmometer four times with distilled water using the following procedure:
(a) With a pipette bulb, pull up distilled water through the stalagmometer to above the top set of lines on the stalagmometer.
(b) Release the pipette bulb from the top and allow the water to drain.
(c) Blow-out any remaining water using the pipette bulb.
(d) Repeat steps (b) and (c) an additional three times.
(e) If beading occurs, clean the stalagmometer as per section 9.2.
4.1.2 Do not touch the flat part at the bottom of the stalagmometer once it has been cleaned.
4.2 Pipette bulb.
4.3 Sampling container.
4.4 Optional - A 100 mL or 200 mL wide bore pipette. (Note: The pipette must be long enough so that it can be placed at least 30 cm (12 in) below the surface of the solution, such that a sample of the solution from that depth can be drawn into the pipette).
4.5 Nitrile gloves.
4.6 Recommended additional equipment
4.6.1 Lab jack
4.6.2 Ring stand
4.6.3 Burette clamp
4.6.4 Hand tally counter
4.7 Waste receptacle: 500 mL or larger jar or beaker for collecting the solution after the surface tension measurement. (Note: After the surface tension measurement, the sample of solution can be returned to the tank). If not returned to the tank, then waste solutions are to be treated as hazardous waste.
