An Inexpensive Apparatus for Solubility Measurements
Vessel for Small-Scale Reactions Sidney Kasmon
Robert H. Schmin and E. 1. Grove Universitv of Alabama, University, Alabama
Polaroid Corporation Cdmbridge 39, Massachusetts
The solubility appamtus described is simple and inexpensive to makc. Most of the components are found in any chemistry laboratory. The main part of the apparatus (see figure), is a 100-ml (other sizes may be used) polyethylene bottle. To the cap of this hottle is welded a strip of polyethylene so that the system can be suspended with a wire from a variable speed motor. When small quantities of solution are used the bottle should be weighted. This can he done conveniently by using a piece of 17/, in. 1. Crorr section of solubility i.d. lead u i ~ eor a few Figure oppardu~. turns of lead wire slipped on or off the bottle as needed. Effective stirring is accomplished by the use of an ordinary plastic-covered magnetic stirring bar in the bottle and a more powerful magnet below the bottle. I t is to be noted that the bottle is rotated and the magnets are stationary. The outside magnet is held in place with #12 plastic coated copper wire, bent to cradle the magnet and to fit over the wall of the constant temperatnre bath.
I t is frequently desired to conduct reactions that require close temperature control and stirring on a scale of about 0.01 to 0.03 moles. If such reactions are not carried out in dilute solution, it becomes a problem adequately to immerse a thermometer in the reaction while the reagents are being effectively stirred. A simple apparatus that has been used conveniently by the author in many nitrations and diazotizations is shown. A side-arm of about 12-mm diameter is sealed onto the side of a 25 X 150-mm test tube a t the bottom. Sealed onto the end of the side-arm is a 30-mm length of 7-mm i. d. glass tubing which acts as a sleeve for thethermometer. The axis of the side-arm is adjusted so the thermometer bulb does not extend into the cylinder of the test tube. The thermometer can be prevented from rotating without obscuring the graduations by holding it in place with 25 mm of split medium wall rubber tubing. The capacity of the vessel can be increased by reducing the re-entrant as indicated. This does not diminish the depth of reagents bathing the thermometer when smaller volumes are employed. Additional side-arms and necks a t various levels may also be sealed on the vessel as required for the addition or removal of materials.
