A Technique for Simultaneously Stirring and Monitoring the Temperatures of Semimicro Reaction Mixtures

The need to mechanically stir and a t the same timemonitor the temperatures of small scale reaction mixtures can often oresent oroblems. Amone the difficulties en- ~ ~~~

countered arc thermomrwr intprferenc; with stirrer mtation, th&mometer brrakagc due t u impact with the stirrer, and insuffment liquid to ruwr both the stirrer and rhermc,meter. The system to be drscrihrd orrumvents thew prohlems by wmbinmg the stirrmg l h d e and thermometrr into a smde n>tnrmg unlr. S I D E T O P

A Teflon t h d e havinr the l'om shown in the figure can he d i ~ ~ e d over the hulh of an ordinary thermometer whirh is then attached to a stir& motor bv means of a rubber sleeve. In &er to read the temoerature of a&tina thermometer it is advantageous to examine the sc& ahead of time and indicate boundary temperatureskth a marking pen. ?his procedure permits fairly easy reading of the scale. I t is particularly easy to note whether or not a reaction temperature is being maintained within desired limits.

A blade of the suggested design was machined from 22-mm Teflon rod.' An 8-mm slice was cut from the rod then cut in half to make two blades. The vertical hole should be bored to a diameter slightly smaller than the diameter of the ther- mometer bulb that i t is intended to fit. The two vertical slots which lead from this hole provide "give" to permit easy and safe attachment of the hlade to the thermometer. These slots were made with a coping saw assembled in the vertical hole. The large hole through the side of the hlade permits good heat exchange between the thermometer bulb and the reaction mixture. The edges of the hlade were bevelled with a sharp file to complete the unit.

'A suggested supplier is Laboratory Supplies Co., 29 Jefry Lane, Hicksville, New York 11801 which lists Teflon rod in diameters up to 2 in.

Manchester College N. Manehester, Indiana 46962

Wilson B. Lutz

356 1 Journal of Chemical EducaHon