Wash the 12-well strip at the sink. Use a cotton swab to scrub each well. Go to Top Safety Wear safety goggles and an apron in the lab at all times. Do not ingest the chemicals. Wash your hands after working with the chemicals.
Sodium oxalate is toxic.
Drop sizes must be uniform in this experiment. See the special technique in which a thin stem pipet and a plastic pipet tip are combined to make a device that delivers uniform drops.