An Inexpensive, Easy-to-Use, Safe Pipet Filler The disadvantages of the numerous devices available for filling pipets using bulbs with valves or finger control and with flanges into which the pipet must be inserted and subsequently removed, have been clearly outlined elsewhere [Cox, Dennis H., Chemist-Analyst, 56,68(1967)]. A simple pipet filler using finger control, which can be modified to fit d l pipet sizes from 2 to 100 ml, is easily constructed from readily available laboratory supplies. Because the device can be easily produced in quantity, undergraduate laborcttories can be provided with inexpensive, safe, easily used pipet fillers. Maleriala, Comtrnelion and Use. Into a rubber bulb (Will 23271) of greater capacity than the volume of the largest pipet which one desires to fill, insert the tubulated tip of a polyethylene drying tube (Fisher 9-242-10). A onehole rubber stopper, drilled in the manner described below, is then fitted snugly into the drying tube tip to complete the device. The rubber stopper should be drilled from the large end with a. conicd ddrl bit, the top of the cone being slightly smaller than the top diameter of the smallest pipet one wishes to fill and the bottom of the cone being slightly larger than the diameter of the largest pipet one wishes to fill. (A countemink serves quite well to drill an opening of the proper shape). Freezing the stopper by placing it on dry ice prior to drilling fscilitates the drilling. The cost of materials for construction is approximately 60 cents. To fill a. pipet, exhaust the bulb and insert the pipet into the conical hole until the pipet fits the hole snugly. Release the pressure on the bulb and allow liquid to enter the pipet. Remove the bulb, adjust the liquid level in t,he pipet to the calibration mark using theindex finger, and allow the pipet to drain in the customary manner. If the rubber stopper pops out of the drying tube tip, as i t sometimes will if the inside of the tip is allowed to become wet, the stopper can be removed, dried, and reinserted. A small amount of Elmer's glue can be used to permanently affixthestopper into the tip. A thin coating of glycerol inside the conical hole will insure a proper seal between thestopper and the pipet top. jess^ G. SPI,:NCI:R
MORRISHARVEY COLLEGE CHARLESTON, WESTVIRGINIA 25304
166 / Journal of Chemical Education
