A STIRRER FOR USE IN DIALYSIS TREVOR ROBINSON Syracuse University, Syracuse. New Yo&
GENTLE stirring
of protein solutions during dialysis is useful in decreasing the time required for diffusion equilibrium to be reached. Where the volume of solution to be dialyzed is rather small U (e.g., 50 ml.), the larger, more I 8 B I comnlex tvnes of dialvsis a ~ paratus are not applicable; but the volume is still large enough so that stirring is of value. Commercial units are available for this purpose. However, one can easily be made for about two dollars. The basis of this stirrer is a slowspeed synchronous mot,or of which various types are available as surplus from electronics dealers.' The other essential element is a device for holding the dialysis bag concentrically around the stirrer shaft. A ring type radio tube socket neatly fills this role. Its la/,,in. diameter is just right to hold snugly ll/s-in. diameter dialysis tubing. The center hole of the tube socket must be bored out large enough to allow clearance for the rubber tubing which attaches the stirring rod to the shaft. The metal contacts are also removed and two of the smaller holes drilled out for wood screws. The base t o which the whole assembly is mounted can be a rircular piece of '/&. plywood or plastic which supports the apparatus on the rim of a beaker or large jar. Other construction details should be apparent from the diagram. 7
" A
' A suitable 4 RPM motor (order no. R4572A) may be obtained from the Radio Shack Corporation, 167 Washington St., Boston 8, Mass.
JOURNAL OF CHEMICAL EDUCATION
