Shirley Walter Gaddis Bethany College Bethany, west Virginia
An Inexpensive Centrifuge for Micro Qualitative Analysis
The illustration shows the construction of an inexpensive centrifuge. I n the years past we have built and used a number of these for micro and semimicro qualitative analysis laboratory. The phonograph motor (cost: about $1, available from radio supply houses) is nailed through two No. 2 one-hole stoppers to the bottom of a 11- X 11- X Sin. wooden box. The aluminum rotor arm is attached to the motor by being sandwiched between two rubber bushings cut from small-bore latex tubing. The microswitch (for example, Allied Radio No. 33B968; cost: $1.65) is positioned so that it is closed by the shutting of the lid. This arrangement encourages the students to keep the lid down as a safety measure while the centrifuge is running. The rotor arm is shaped from a 5- X 1-iu. piece of aluminum. -43/& hole is bored a t each end. Then EDITOR'S NOTE: Probably readers who have had the experience of similar demands on ingenuity to replace funds will be able to contribute t o a. series of articles of this theme. We solicit only descriptions of instruments proved to he satisfactory 40, 641 (1963); 41, by 18,bborrttory use. See also THIS JOURNAL, 12, 130 (1964).
the aluminum is ground down on an emery wheel to the proper shape for balance. The rotor arm should be as light as possible. The location of the central hole for the arm is found by its pivot point.
DUNL OF4UMINUM
QUTOR ARM lraalrarri
Each student makes his own centrifuge tubes by using a Bunsen flame and a carbon rod to shape the lips. A 13-cm length of 8-mm Pyrex tubing is heated in the middle and pulled apart to make two tubes. These tubes hold only 15 drops, so starting samples must not be over one or two drops.
Volume 41, Number 1 1, November 1964
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