A Magnetic Stirrer for Static Vacuum Systems Using High Temperature Baths A significant variation in the conventional magnetic stirrer has provided adequate stirring in the otherwise difficult situation depicted in Figure 1. Item A is a high temperature, constant temperature bath such as that required for kinetic experiments (ex., molten salts. T = 200-1000DC), B is the resction vessel which may be outgassed or subjected to other reaction condi&s, C i s the stirrer, and D is a magnetic stirrer attachment for B Stirrer mitor which may be purchmedfrom A. H. T h o m a Co. [Cat. No. 9236-51.
Figure 1. Iabove) Figure 2. (right)
Stirrer &up.
Construction of the Pyrex version of the stirrer.
A workable model for tempemtures up to 500°C may he constructed from Pyrex rod and tubing, and a cylindrical bar magnetic as shown in Figure 2. The materials can he varied [e.g., quartz, Vycor, Teflon, etc.] depending on the temperatures and reactants involved. The construction of the stirrer from Pyrex provides a surprisingly strong and dependable piece of equipment. A piece of tubing A, whioh is close fitting for the cylindrical magnet D, should be attached to the shaft B prior to sealing the magnet D into the tube with a. torch E. The angle C can then be made, adjusting the height of the stirrer in the reaction vessel a t the same time. The angle C in the shaft B should be approximately half-way between the surface of the solution and the bottom of the reaction vessel for best results. Where stainless steel, Teflon, or other machineable materials are used to construct the stirrer, threaded connections between the shaft B and the magnet housing A would he useful, especi&llyif shaft material of suitable nature for specific experiments or simply for repair could be provided. I t must be emphasized that this stirrer adaptation is most useful in experiments where a vacuum system and constant temperature bath are necessary. Several types of magnetic and mechanical stirrers are commercially available which o m he used with temperature baths, but they are rather expensive where they claim to handle vacuum stirrine. and reauire a dvnamic vacuum to maintain low messure. The stirrer used in our exoeriments works under
Volume 49, Number 4, April 1972
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