Robert C. Brasled
An Exercise in Glass Manipulation
University of Minnesota Minneapolis
Preparation of a hypodermic syringe
The time honored exercise in glass manipulation, preparation of a wash bottle, may be varied or replaced-especially where a desk may be equipped with a polyethylene squeeze-type wash bottle. The syringe suggested here has applicability in any small-volumesolution transfer, for example in the removal of a supernatant liquid. The student has ample opportunity to carry out many ordinary glass operations of drawing, sealing, polishing, cutting, and bending. The last mentioned operation is applied directly to the syringe in forming the "finger loop" A (see figure) so that the syringe may be operated with one hand. A
476 / Journal of Chemkol Education
large diameter test tube selves well as an object about. which the heated rod may be molded. The only special precaution (see the figure) is to make sure that enough glass rod E is available, of such di-. ametcr that a snug fit is obtained when it is inserted into regular (about 7 mm) glass tubing. A rubber tubing of high pliability, B, is needed to provide a tight fit both to the tubing and to the rod when folded back on itself. A barrel length of approximately 12 em is suggested. An obvious variation or extension is to calibrate the. syringe. The total volume delivered between preestablished markings C and D (file scratches) is determined by water weight and known density. Fractional volume markings may be established assuming a uni-~ form bore along the length of the barrel. The accuracy may be checked, assuming time is available, with addi-tional weighing of water delivered.
