A RAPID SOLUTIONDISPENSING PIPET B. J. OTTE, P.J. THOMPSON, AND G. A. BARBER University of Florida, Gainesville, Florida
THE rapid dispensing of liquid unknowns has always been a problem in most chemistry laboratories. With this in mind the authors set out to make a cheap and fool-proof device. This pipet has been in use a t the University of Florida for two years and has cut the time for dispensing our liquid unknowns to about one-third of the former time. The pipet does not have any ground joints or glass stopcocks and has a rate of flow equal to that of a stopcock with an eight-mm.-bore. Many solutions will cause stopcocks to freeze, and breakage is always high
If stiff ~ b b e tubing r is used for the control loop C it is best to tape it loosely so as to make a seal a t the bottom, but not so tightly but that by pushing up on the bottom the air may be readily let into the line for dispensing. Pinch clamps may be used, but they are not necessary. It is well to keep all bottles that are connected to the compressed air a t approximately the same level. To care for the difference in pressure needed to force the float to the valve seat S a slit is placed in the Bunsen valve V , which is made out of rubber pressure tubing, about eight mm. long. A piece of glass stirring rod is inserted in the tube, and the length of the slit can be varied as needed.
