Constant Temperature Air Bath A large servicahle constant-temperature air bath, has been constructed from two polystyrene packing cases in which ningle-pan Ainsworth t~nalyticslbalances were received. The eases are divided in two longitudinal halves and this division was utilized in the construction to make the interior of the compartment readily sceessahle. One side of each case was removed by cutting along a, plane approximately 4 in. from the edge. This eliminated the curved cornera of the case and facilitated attachment of the two parts. (An ordinary carpenter's saw cuts the material easily.) The "front halves" of the two cases were glued together with epoxy cement along the sawed planes and the rear halves were similrtrly joined. The front section was then cut laterally along a plane approximately 4 in. from the bottom. The 4-in. lower section was cemented to the rear section. The larger front section was used as a large removable cover to facilitate work inside the hath between thermostated periods. Two ring stands were joined a t tt distance of 12 in. by an aluminum rod and Flex-Frame clamps; the air hath was then placed on the hase of the ring stands. Extension clamps attached to the aluminum rod with clamp holders were extended through the rear wall of the ease. (Cork borers were u e d to cut through the ease so as to fit the clamp shaft snugly.) The clamp shaffts served to hold the bath securely on the ring stand hase and the clamps held equipment inside the bath. Additional holes were cut in the hath to place the thermoregulator, thermometer, and wiring far a heat source. A 10-W electric bulb made a convenient heat source, hut it was necessary to shield or wrap the bulb with foil to prevent direct radiant heating of the nearer parts of the apparatus. Air circulation was provided by a 6 i n . nylon, model-sirplane propeller cemented t,o an extended shaft of a continuous-duty electric motor (salvaged from an electric water cooler). The motor must be outside the hath because of the heatgenerated; hence, the extended shaft and lightweight propeller were necessary. Temperature control was maintained by a magneticslly set thermoregulator in conjunction with a. Precision relay control box. The hath was tested a t 1 5 T shove ambient temperature. I t reached and held this temperature easily. Temperature variation was negligible (fO.Ol°C) in the central part of the compartment but slightly cooler temperatures (-O.lDC) were observed in the "far corners" away from the heat source.
BILI,YJ. YAGER PATRICIA Y. SMITH SOUTHWE~T TEXASSTATEUNIVERSITY 78666 SANMARCOB.
Volume 48, Number 12, December 1 971
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