AIR-DRIVEN CENTRIFUGE FOR SEMI-MICRO QUALITATIVE ANALYSIS WARREN C. VOSBURGH AND J. H. SAYLOR Duke University, Durham, North Carolina
FOR separations in qualitative microanalysis for undergraduate students Engelder and Schiller (I) and Gerstenzang (2) have suggested the use of a hand centrifuge built for macro work. The authors in their course in qualitative analysis, which is carried out on a semimicro scale, have used with success a number of airdriven centrifuges made in the laboratory shop by Mr. Fred Kuhn. The materials required are inexpensive, as most of them are stock materials. A diagram of the centrifuge is shown in Figure 1. A ball-bearing roller
an. (0.75 inch) aluminum rod and drilled with 1.3 an. (0.5 inch) holes, which accommodate the 3-ml. glass centrifuge tubes used.
Small holes were drilled through
FIGURE 3.-PHOTOGRAPH OF CENTRIFUGE WITHOUT WOODEN PROTECTING FRAME
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It was found that the use of a drawn-out glass tube for the air jet gave less noise in operation than the flattened copper tube shown in the photograph.
skate wheel A is mounted on a stationary vertical shaft B so that i t rotates freely about the shaft on its own bearing. On the top of the wheel a six- or eight-blade fan is bolted and on the bottom a two-tube head, C, also shown in Figure 2. The head bears two brass rings F
the bottoms of D and D' so that any liquid dropped in them is thrown out. The laboratory compressed air is used to operate the centrifuges. The opening in the laboratory air tap was adjusted until the speed was such that the more difficult precipitates were thrown down satisfactorily in thirty seconds. At this speed, about 1000 R.P.M., the noise is not excessive. For safety the centrifuges are surrounded by a square wooden frame. The strap-iron frame of the centrifuge (E in Figure 1) is fastened to the wooden frame by a rubber mountmg made from rubber stoppers. The centrifuges have been used with entire satisfaction during three semester. and two summer sessions. LITERATURE CITED
and F' (see Figure 2), which hold the aluminum tubes D and D'. The tuhes D and D' were turned from 1.8
(1) ENOELDER, C. J. AND SCAILLER, W., J. C ~ MEDUC., . 9, 1638 (1932). E. M., iw.,11, 369 (1934). (2) GERSTENZANG,
