Use of Plastic Syringes as Measuring Pipets A large number of accurate measurements of liquid volVolume of Water Delivered by Graduated ume is required for some general chemistry experiments. Cyllnder a n d Plastic Syrlnge For example, in a study of the kinetics of the iodine clack reaction,' a student has to dispense 48 portions of reagents Actual volumea at 20 'C (mL) ranging from 1to 8 mL. Since measuring pipets are difficult Nominal Volume (mL) to control and six different reagents are involved, the pipet ting takes up a lot of time. Graduated cylinders and burets 10-mLgraduated 10-mL plastic have heen suggested by the authors as alternative equipsyringeb cylinder ment, but they are not much of an improvement when bath 1.01 f .02 accuracy and efficiency have to be considered. Three years 0.94 f .03 1.0 ago, we switched to the use of disposable (reusable!) plastic 4.98 f .03 4.94 f .04 5.0 syringes for the experiment. The time spent on preparation 10.0 9.75 f .03 9.95 f .02 of the reactant mixtures was reduced significantly, and the 9.98 f .02 10.0 results obtained by our students were much more consistent. The table on the right indicastes that measurements 'Standard deviations were obtained fmm five trials, except for made with syringes are more accurate and precise than the last entty where five differentsyringes were used with one trial those made with graduated cylinders. The accuracy and pre- each. 'With Luer-Lok tip, manufactured by Becton-Dickinron and Co.. cisian rival those ohtained by inexperienced students using measuring pipets or burets. Besides being easy to operate, Ruthertord, NJ. these syringes are unbreakable and economical. They are applicable in other experiments a s long as the reagents do not react with the chemicals in the plastic. Instmctars of high school chemistry may find these syringes useful for their students as well. 'Mosws, Jr, P. C.; Petrucci, R. H.; Foster, J. C. Wnetia Sludy of achemica1 ~e&tion';in ModuIarLaboramryPmgraminChemistry:Neidig, H. A,. Ed.; Chemical Education Resources: Palmyra. PA, 1987: No. 340. Grace Chiu University of West Florida Pensacola, FL 32514
666
Journal of Chemical Education
