A COMPACT, LOW-COST ELECTRODEPOSITION APPARATUS CLARENCE L. COOK Kent State University, Kent, Ohio
THEapparat~i~s shown in the photograph has been used surressfully by large numhers of students in the quantitat,ive analysis lahoratory. I t is constructed from cheap, readily available ~nat,erials. The instruments are mounted on a frame vhich slides vertically into a holder spaced to ar~.ommodatea conventional 150-ml. tall-form beaker. Connertion is made t o an external
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source of d.c. current a t the -Fahnstock clips shown. The rear wiring through the rheostat and ammeter t o the cathode is indicated in the photograph. The anode is made by sealing one end of a 15-in. piece of KO. 20 platinum wire into the end of a piece of 5-mm. glass tubing and wrapping the rest of the wire upward around the tubing. The 3-in. diameter pinwheel rotor, made from sheet aluminum, is mounted on the upp& end of this tuhing with the aid of two No. 0 rubber stoppers. (It is driven by an air jet properly located in the back panel.) A short length of larger diameter glass tubing pressed into the wooden mounting serves as a bearing. Fiber mashers reduce binding a t the moving surface. Mercury in the anode tubing makes electrical rontact with a copper mire leading to the Fahnstock clip. The cylindrical platinum gauze cathode is a standard one, approximately 11/* in. X 13/&in. in size. I t s stem is inserbed through the wooden base t o a screw connector. This is soldered t o a wire leading t o the ammeter. . The ammeter is a Triplett 321T, 0-5 amp. The rheostat is an Ohmite model H, 10 ohm, 25 matt. d portable voltmeter, serving one or several instruments, may be connected t o the exposed terminals. Good quality measuring instruments should be used to secure maximum accuracy. The moderate cost of these units means that it is feasible t o build enough t o accommodate an entire class a t one time. This has the advantage of eliminab ing repeated instruction sessions necessary when one costly piece of equipment must be used. An additional instructional feature is that the exposed wiring on the front and back of the panel is simple and easily followed by the student. Storage space for several of these compact units is a minor problem since the over-allsize is only 6 in. X 6 in. X 14 in.
JOURNAL OF CHEMICAL EDUCATION
