Solenoid Stirring Device for Use in Confined Spaces H. H. ROWLEY AND ROBERTB.ANDERSON State University of Iowa, Iowa City, Iowa
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stirrers have been devised f o r a g i t a t i n g liquids in closed systems. Most of these are of the -R magnetic type which require a rotating field outside the reaction flask. This is very cumbersome and impractical when the reaction flask must be kept in a constant-temperature bath, particularly when the temperatures desired require the use of a vacuum flask. The apDaratus described belowa solenoid stirrer-is very simple to construct and has proved practical and convenient for solubility determinations in nonaqueous solvents from which moisture must be excluded. This type of stirrer can be used in small cells, such as test tubes, in which a mercury-seal stirrer would be impractical. The solenoid, controlled by a make-and-break device, is placed about the upper part of the cell. It alternately raises and lowers the glass stirrer, the upper part of which encloses an iron core.
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Referring to the diagram, a variable-speed motor turns a crank, A , which raises and lowers a cop er rod, B. Contact is made and broken in the 6-volt circuit by Jpping B into a mercury cup, C. Relay D, rovided with graphite contacts, makes and breaks contact in tBe 110-volt circuit. A solenoid, S, lifts and drops a stirrer, R. For optimum results with this type of stirrer, which is partially buoyed up by the solution, it is necessary to synchronize the frequency of stirring with the eriod of vibration of the stirrer in the solution. To accomplisi this, it is essential to control not only the frequency with which contact is made, but also the duration of contact. The frequency can be controlled by varying the speed with which crank A revolves, and the duration of contact is controlled by raising or lowering mercury cup C with an adjustment screw, E . The amount of current flowing (approximately 1.5 amperes) through the 110-volt circuit can be controlled by the variable resistance, F (60 t o 80 ohms). The stirrer was made from a thin-walled test tube, 15 X 1.2 cm. (6 X 0.5 inch), drawn out as indicated. In the upper end of the stirrer was sealed a small bundle of soft iron wire, 3 X 0.4 cm. (1.25 X 0.125 inch). The total weight of the stirrer was about 6 grams. The solenoid consisted of 720 turns of No. 24 enamel-covered cop er wire, wound on a flanged metal spool 3.5 cm. (1.5 inch) in fength, through which the solubility cell passed. The solubility cell itself was a large test tube, 20 X 2.5 cm. (8 X 1 inch).
An Improved Three-way Stopcock MARVIN A. SMITH AND FRANK L. HAYES Universal Oil Products Company, Riverside, 111.
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HREE-WAY stopcocks with two stems on one side and one on the other as shown on the attached drawing are
often not only useful but indispensable in a piece of apparatus. This type of stopcock in the conventional design has the disadvantage of having the two holes I through the plug so close together that troublesome l e a k s often develop. This has been overcome by placing holes E and D through plug 2 a t right angles to each other, which means thatthe openings are spaced 90" -apart. Afurther advantage is that a one-quarter turn of the plug will change the direction of flow from C to B when A is the inlet. 397
