THE CONSTRUCTION OF AN INEXPENSIVE CONSTANT TEMPERATURE WATER BATH FOR SOLUBILITY MEASUREMENTS WILLIAM JACOB KNOX, JR. Tallsdega College, Talladega, Alabama
THE high cost of constant temperature water baths of a convenient size for certain types of solubility measurements is often prohibitive for small laboratories. The accompanying diagram shows the vertical cross-section of an inexpensive water bath, useful for such measurements, which can be very easily constructed. A crock ( A ) , sixteen inches in diameter and twentytwo inches deep, having a capacity of about 70 liters, is placed in a wooden box ( B ) , twenty-four and onehalf inches deep, the bottom of which is covered with a solidly packed three-inch layer of finely pulverized pipe lagging. The space between the box and the crock is also solidly packed with finely pulverized pipe lagging. This layer of insulation surrounding the crock is labeled C in the diagram. Inside the crock is placed two 2 X 4 uprights of white pine (D), each twenty-two inches long and each having been previously soaked in creosote. Each upright
is bored half-way through on one of the four-inch faces with two half-inch holes (E) a t a distance of about two inches from either end. These holes are fitted with the half-inch brass rods (F). Each rod carries a four-inch thread on either end and is provided with the washers and nuts (G) which when tightened press the uprights against the wall of the crock. This makes possible a very rigid frame for the support of the axle ( H ) . The axle ( H )consists of a half-inch brass rod provided with a six-inch grooved, aluminum pulley (0.The ends of the axle terminate in the black walnut bearings (J) fixed a t the middle of each upright. Another axle (K) provided with two one-inch grooved, alumhum pulleys (L and M ) is supported by the two black walnut bearings (0)screwed to the edges of the box ( B ) so that the axle (K) lies in the same vertical plane as the axle (13). Directly beneath the pulley is the pulley of the motor (P). Sample bottles are attached to the axle (H)by means
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of large casterloy clamps and clamp holders and are given a rapid end-over-end motion as the motor turns.
where stopcocks are used. This device lends itself readily to use in multiple units. At present we have eighteen of these connected to the same compressed air line. A bottle of any size may be used. To facilitate the construction and use of these pipets a few words of explanation are given. The glass from an enclosed porcelain scale thermometer is used to make the float. It is necessary that small vents be placed in stoppers K,r, and r' so that the float may rise as soon as the liquid is dispensed and the liquid is under atmospheric pressure when not in use. The volume of the h i d dispensed is controlled by the size of the bulb B.
Ii P(p-5J) The bath is equipped with a Precision Temperature Regulator, M ~ - A ~ and G a 600-watt knifi-heater. Constant temperatures within O.l°C. can be obtained.
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