DECEMBER, 1947
A STIRRER FOR VISCOUS LIQUIDS JOSEPW J. WOBASEK Marqustte University
DURING THE course of an investigation of synthetic drying oils it was found necessary to agitate thoroughly a mixture of two viscous immiscible liquids and a t the same time to keep in suspension a solid heterogeneous catalyst. Because of the nature of the work, metal stirrers were thought to be undesirable, hence a glass device was required. The reaction vessel was of 500 ml. capacity, and wide vane stirrers could not pass through the narrow neck. Swivel-type stirrers in which the vanes are attached by means of glass rings were found to be too fragile for the liquids and speeds used. Cdntrifugal stirrers could not be used, for the combination of viscous liquid and solid catalyst formed a thin slurry which soon clogged the exit holes. The successful stirrer was made from a damaged volumetric pipet whose bulb was just small enough to pass through the neck of the reaction flask. The long end served as the shaft of the stirrer, and the other end was cut off and sealed so that when immersed in the reaction vessel the surface of the liquid would contact the stirrer at a point about halfway between the narrowest and widest portion of the bulb, as shown in the figure. The sealed stem penetrated the liquid almost to the bottom of the vessel and assured good mixing at a point in round-bottomed flasks not usually reached by vane-type stirrers. In operation the level of the liquid is depressed somewhat by the whirling pipet; a film of the mixture, however, is drawn up along the stem of the stirrer and receives acceleration as it encounters the widening of distance from the stirrer so that new material is conthe bulb. At the point where the sides of the bulb stantly being agitated. The apparatus has been used with non-viscous become vertical the film is moving rapidly and is suddenly detached from the bulb. The result is a liquids with equal success, and when completely subspray thrown to the sides of the vessel in a direction merged has been found to keep the water of a large almost perpendicular to the stirrer. There is no splash- constant temperature bath in 'good circulation. In ing or loss of contents by contact with the stopper. this latter case a tendency toward sidewise wobbling Further, the material is delivered to a point a t greatest was overcome by filling the pipet bulb with sand.
