A CONSTANT-LEVEL DEVICE for CONSTANT-TEMPERATURE WATER BATHS J. H. ROBERTSON The University of Tennessee, Knoxville, Tennessee
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HE maintenance of a constant water-level in a bath requires the continuous addition of enough water to replace that lost by evaporation or otherwise. The expedient of running in a stream of water and maintaining the level by means of an overflow pipe may he unsatisfactory because of the cooling or heating effectof the tap water when its temperature differs considerably from that desired. This di5culty is usually avoided by connecting the bath to an overflow pipe at the desired level outside of the bath. If the connection is made by means of a siphon tube its operation may be stopped occasionally as the result of the accumulation of air in the tube. Furthermore, with the usual arrangement, the quantity of water nau used is likely to be wasteful. It may be convenient to have constant-temperature baths per- -- . manentlv installed and orovided with an easy means of filling and draining. Then, should the need arise, they may he utilized temporarily as ordinary laboratory sinks. An arrangement of this character in which the constantlevel device serves as a convenient stopper for the bath outlet and which appears topossess, also, certain improvements over the ordinary type of constant-level devices is shown in the accompanying figure. The bath is constructed of Alberene stone. The coefficient of heat conductance of this material is approximately the same as that of dass.
through one side. Through this opening is inserted a short piece of '/z" copper tube which has been cut away along its axis to a distance of about s/iK from the end, forming a trough. I t is then soldered in position, the end of the trough being closed by soldering to the inner wall of the larger tube. The open end of the small tube is projected.downward some distance into the bath by means of an elbow so as to avoid fluctuations in the water level in the trough caused by waves when the water is vigorously stirred. When it is desired to drain the bath the device is merely lifted, the end projectingabove the water serving as a handle. The device is held in position by means of a permanently installed rust-resistingsteel clamp having flexible jaws so cranp that the tube may be slipped in
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WATER INLET
A water spigot having a small taperingnozzleisinstalledperpendicularly above the trough. By means of an additional valve locatedsome distance from thebath, the supply of water reaching the spigot is cut down to a maximum --of a few liters per hour. The spigot valve is then nearly closed allowing the water to drip a t the rate of about one drop in five secouds, or faster under conditions of rapid evaporation. Excess of water over that required to maintain the level does not enter the bath, but overflows from the trough into the larger pipe leading to the drain. The use of two valves makes the final adjustment of water CONSTRUCTION OF LEVELING DEVICE flow easier. It also practically eliminates the use of the A 1"copper (or brass) tube about equal in length to spigot as a source of water for other purposes, thereby the depth of the bath is enlarged a t one end with a reducing the chances of having its adjustment disturbed. layer of lead thick enough to make it nearly as large The positions of the spigot and the outlet pipe should as the mouth of the drain iixture in the bottom of the be such as will interfere least with the use of the bath. bath. The lead is tapered to a slightly smaller diameter If the drain is not suitably located an offset may be at the end and is surrounded by a wide, tight-fitting made in the copper tube near its lower end. Three baths of 125-liter capacity provided with the rubber band so that it will fit snugly into the mouth of the drain fixture serving as a stopper. At the desired constant-level device described have proved quite satiswater level on the tube a hole 9/16" in diameter is drilled factory in our laboratories. 377
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