AN IMPROVED STIRRER JEROME H. LUDWIG and JOHN K. BLATCHPORD Applied Science Research Laboratory, University of Cincinnati, Cincinnati, Ohio
A SIMPLE, easily constructed, and rugged stirrer has been designed for use in our laboraTOD view tory. It combines the advantages of the Hershberg stirrer and the paddle Made stirrer in that it gives efficient stirring of viscous material while at the same time it scrapes the sides of the flask. The stirrer head can be disconnected and left in the flask while the shaft and stirrer seal can be removed and replaced with a stopper or other apparatus for subsequent operations. The stirrer blades are cut with a sharp knife or razor blade from '/gin. Teflon sheet in the shape of segments of a circle. A paper model which can be used as a template for the blades aids in getting a proper fit for a given size flask. The pivot holes are drilled at the positions shown in the diagram and the blades, joined together with bolts, rivets, or cotter pins, using washers to protect the Teflon blades. A '/,-in. stainless steel shaft
of a convenient length is jointed using fairly loose rightor left-hand threads depending on the stirring motor. The blades are then fastened to the shaft with a washer and a machine screw. For operation of the stirrer the blades are aligned along the shaft and are inserted through the neck of the flask. On touching the bottom of the flask the blades pivot to the proper stirring position. The shaft can be sealed at the neck of the flask with one of the conventional stirrer seals. At the end of the stirring period the shaft and seal are removed from the flask by first raising the shaft until the blades of the stirrer are forced against the top of the flask, then unscrewing the shaft from the blade assembly which falls back into the flask; the shaft and stirrer seal then can be removed and replaced with a stopper or other apparatus. At the end of the reaction the blade assembly is removed from the flask with forceps. We have used this stirrer with viscous, air- and moisture-sensitive mixtures of powdered metal and liquid with excellent results. When the shaft and stirrer seal were removed, very little decomposition due to access to moist air occurred.
JOURNAL OF CHEMICAL EDUCATION
