Question

why is it that the burette or pipet have to be returned to a detergent solution bath "tip side up" after using?

Answer 1

Two common methods of delivering an exact amount of solution are the pipet and the buret. In all lab they are kept in separate baths of mild detergent. After removal from the bath the detergent solution has to be rinsed away with tap water, then - the tapwater has to be rinsed away with distilled water. One large rinse is (of course) not nearly as effective as three small rinses. The stopcock on the buret has to be tightened until just snug (do not overtighten the nut). The stopcock on the buret also has to be closed. Then the equipment has to be rinsed with 3 small portions of the solution to be dispensed. (If they were directly filled, the distilled water on the inside walls would dilute the solution, resulting in an error). At the end of the lab the glassware has to be rinsed clean of the solution. Rinse this away with tap water only. (It would be a waste to use distilled water, as glassware will be stored in a detergent bath). The stopcock on the buret must be loosened and opened, then the glassware returned "tip-side-up" to the baths.