laboratory Induction Stirrer for Closed Systems B. M. TOLBERT, WILLIAM G. DAUBEN, AND JAMES C. REID Uniaersity of California, Berkeley 4, G l i f .
UlMEltOUS internal stirrers have been devised for the agita,
N tion of liquids in closed systems. Most of the devices are of the magnetic type and are so designed that the mechanism required to estahlish a rotating or an alternating vertical field outside the reaction flask is cumbersome and impractical when the reaction flask must be immersed in a. cooling or B heating bath. Other drawbacks are low power developed, complex construction details, and lack oi versatility. An improved design of a simple induction stirrer which circumvents many of the above difficulties ( 1 ) is described in this paper,
Figure 1. Stirrers
The induction motor consists of a three-phase selsyn generator stittor, B glass-enolosed armature, and a hearing system (see
stirrer is over 3000 r.p.m. and suffioient power to stir r.,
RECEIVED September 3, 1948. Based on work perforiiied under euntra('t No. W-7405-Ene48 with t h e Atomic Energy Commission in connection with t h e Radiation Laboratory. University of California, Berkeley, Calif.
Modified Method of Charging the Poth Carbon Dioxide Generator P. L. PICKARD, T h e University of Oklahoma, .Vorman, Okla. S 1930, Poth ( 2 ) described a generator "which enables one to
store a quantity of carbon dioxide with complete assurance that it will represent a gas of consistent high purity" for use in microanalysis of nitrogen by the Dumas method. The generator has since been modified (3). This author's first experience with the modified form of the Poth generator was with a commercial model which had been discarded because the difficulty of charging according to the directions given had led to the conclusion that it was incorrectly built. After several attempts the generator was successfully charged and served for the duration of a problem which involved an extraordinarily large number of nitrogen analyses ( 1 ) . Because new generators from the same source (Scientific Glass Ipparatus Co.) have caused similar difficulty, a method of charging has been developed xhich is considered more convenient and rapid than that described by Poth. K i t h the generator (Figure 1)lying horizontally so that opening E is a t the top, a solution of 1 to 2 sulfuric acid in water is sucked into B by connecting D to an aspirator. The acid solution is not cooled after mixing, as the heat generated aids in exclusion of air from the apparatus. The generator is then raised to a vertical position, the aspirator is connected to C, and 1200 ml. of a hot a t u r a t e d solution of potassium bicarbonate are sucked into A . A few milliliters of water are pulled into A to rinse the bicarbonate from D. Sufficient water is added to D to cover the tip of the bubbler. Mercury is added to C until the level is about half-way to the
upper end of F . C' is connected to the leg of a T-type three-\\ ay stopcock. One arm of the stopcock is open to the atmosphere and the other connected through a T joint to a vacuum uumu which is adequately prbtecied hy a drying column. The other leg of thc T joint is connected to D . With Z) and I.' closed the varuum pump is started and I' openrd into C very cautiously to prevent too violent b u m p ing of the mercury. After the generator has txhtsn evacuated several minutes, D is opened slightlv. I3y adjusting I),the level of hu1furic acid in E may be maintained nearly constant. ;hould the lrvel of acid in E rise, D should bta shut off momentarily. After 15 minutes' evacuation, D and then Y are closed. D is opened slo\vlp, with the pump still operating, and acid is pulled up into E. As soon as a drop of acid falls, D is closed and the carbon dioxide evolved bubbles back through E and Figure 1 F to equalize the
