Weight Burets for the Quantitative Analysis Course The doll's nursing bottle, described in a previous note (THISJOURNAL, 36, 290 (1959)), can be used as a weight buret in the beginning quantitative analysis course. This polyethylene bottle costs only 10 cents, cannot be broken, and is easily cleaned. Since water does not wet the plast,ic tip, the drops delivered average 35 to the gram. These drops are half the sise of drops from a glass tip. Thus, a more precise titration is possible. Also, since the water does not wet the ~olypropylenenipple, the titrant does not spread out over the tip. This eliminates an "evaporaiioi:fro&-tbe-tip" error. Weight burets do not need t o be corrected for the density change of the titrant caused by a tem~eraturechange. Calculations are done by "weight titer." The titrant is standardised in terms of milligrams of constituent sought far eaih gra&of titrant used. Considering the merits of the weight burets, i t seems strange that this method for titratians is not more generally taught in the beginning course. Our experience has been that students report the same precision and accuracy using the weight burets as they get with a volumetric buret. When given a free choice of the two methods for doing a titration, our students without exception have elected t o use weight burets. The use of weight burets could cause a troublesome traffic baok-md-forth to the balance room. To eliminate this we have placed dial torsion balances in the working laboratory. With these automatic bbalances weixhinas can be done in less than 15 seconds. One balance serves 20 students without coneestions. ~ h e s balances e are sensitive to 5 mg, so weighing precision is better than 0.1yo.
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Journol o f Chemicol Education
