A n electrical centrifuge very well suited for semimicro work has been constructed and is in constant use by the graduate students of this depart- ment. The cheap cost, small size, and light weight of the centrifuge has enabled the department to provide one centrifuge to each student.

The parts required to const,ruct the centrifuge are as follows:

P. B. Janardhan Madras Univers~ty

Madras 25, India

( 1 ) A Mini motor wit,h G v rating manufactured by the General Industrial Co. Thesise of the motor is ll/A-in. diamet,er, I1/rin. height, with a shaft of '/&. length.

( 2 ) An aluminum plate, 18 gauge, in. X 3 in., slotted a t the terminals as shown in the dingrams. Portions of the terminal pieces are bent upwsrds and holes pierced in them to hold the wire carrier of the centrifuge tube. A half inch of ' / I in. diameter aluminum tube is inserted tightly and vertically in the center of the plate so that t,he plate can be slipped over the shaft of the motor and fastened with the help of alat,eral screw.

(3) A metal s k a p (such ns the one used far packing boxes) is folded in the form of a d i p and attached to t,he tip of a galvanized iron rod '/-in. diameter and 2'/An. long.

(4) The opposite tip of t,he iron rod is driven by hammering into a heaug wooden base 4 in. X 6 in. The wooden base also car- ries two binding screws to make the connections wit,h a 6 v bat,tery substitute or a set of four dry cells.

(5) The m t v i j u g e tubes are made of 8-mm Pyrex glass tubing tapered as shown in the diagram and flanged so as to rest on the wire holder.

(6) The total length of the tube is i j 1 /3 cm and its capacity is very nearly 1 ml. The wire support for the tube is made of iron wire thick.

Mini Centrifuge

Figure 1. Mini centrifuge at rert.

744 / Journal o f Chemical Education

This centrifuge when tested with a stroboscope was found to give 1000 rpm without load and 900 rpm with full load (i.e., the tubes completely filled with water). Precipitates of BaSOn, CaF,, AgC1, etc., were found to settle within to a/q of a minute. The total weight of the centrifuge inclusive of woodeu base is 300 gm.

The total cost of such a centrifuge is to $2-$2.50.

Figure 2. Mini centrifuge in action.

Figure 3. Diagram of the mini centrifuge with ports disarrembled.