Constant-Level Float Valve WILBURN A. BOGGS, 221 8-8. Cabrillo Ave., Torrance, Calif.
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HE constant-level valve illustrated in Figure 1 makes it possible to fill a glass bottle with distilled water from the still reservoir without running it over and without giving it constant attention during the last stages of filling. I t can be made from material available in any laboratory, and is efficient when gravity supplies the pressure. Its applications are numerous and varied. With the slit turned downward, the valve will release a vacuum drawing liquid into a bottle by by-passing the vacuum to the outside when the rising liquid opens the valve.
round Pyrex flask may be fused to a piece of Pyrex tubing. This will usually withstand the pressure developed inside the bulb.
If the pressure is very great, the valve will squirt a small stream of water high into the air during the last stages of closing. This may be prevented by a guard:
A section of flat rubber (tube patching is good) is cut in a rectangular piece about as long as the rubber tubing of the valve and as wide as the circumference. Two strips of the same material are wrapped, one on the other, around the upper section of the rubber tube, and the rectangular piece is placed on top of them, extending well over the slit and down over the sides. These pieces should be wired in place, or fastened with a rubber band.
H o t Distilled W a t e r Reservoir WILBURN A. BOGGS, 221 8-8. Cabrillo Ave., Torrance, Calif.
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H E arrangement shown in Figure 1, using the float valve described in the preceding article will provide a constant supply of about 6 liters (1.5 gallons) of hot distilled xater per hour, if only a small amount (500 ml. or less) is drained off a t a time. Fresh water is added continuously, but the volume is large enough to prevent variation of pH or temperature. The quality of the water is equal to that which has been boiled for 2 hours or longer, and is delivered from the buret a t a temperature of above 98' C. Tubes G , A I , and Ai are placed in the positions shown and held in place by clamps above the bottle's mouth. The top of the bottle is left open to allow the steam to escape. The steam coil is conveniently made by running 0.6-cm. (0.25inch) copper tubing through a piece of pipe and then winding it around the outside of the pipe. The buret shown may be made from a Pyrex test tube (3.75 X 50 cm., 1.5 X 8 inches), to which a 7-mm. tube is attached. It is filled by opening pinchcock RI and emptied N by Rz. The hole in the bottom of the Pyrex bottle is made by drilling with a piece of 1.9-cm. (0.75-inch) copper tubing rotated by hand or by a small motor. A small constant supply of wet Carborundum valve-grinding compound must be suppl to the drill. If steam is not available, the bottle is placed on a hot plate and supplemental heat furnished by a standard inside heating element. A more constant rate of heating can be attained by using a h o t plate i n conjunction with the steam coil.
Figure 1. Float Valve Upper.
Valve closed. Center. A . Glass bulb B . Rubber tubing C. Glass tubing E. Liquid level F. Capillary G . Slit
Valve open.
Lower. For use in hot water 1. Liquid flow 2. End open 3. End closed 4. Fire-polished
VALVE. A piece of 7-mm. soft-glass tubing is heated in a hot flame and turned to thicken it a t one end. When the glass is sufficiently thick, it is blown into a bulb 5 to 7.5 cm. (2 to 3 inches) in diameter. If it is to be used inside a bottle, the bulb should be as large as can easily pass through the mouth. The length of the stem may be varied; the longer the stem the greater the closing pressure, but 2.5 to 3.75 cm. (1 to 1.5 inches) is a convenient length. The end is sealed off in the flame. A piece of heavy-walled rubber tubing 3.75 cm. (1.5 inch) long is slit half through and the stem of the bulb is forced into the end nearly up to the slit. A piece of 7-mm. glass tubing, bent at an angle, is forced nearly up to the slit from the other end. This glass tubing is held in position by running it through a cork stopper and holding the cork in a clamp. If the angle of the glass tubing is about 120" instead of 90" as shown, the closing effect is better and the rubber is kept above the li uid level. The glass float must have a small hole in it, i? it is to be used in hot water. This can best be made by heating the float on one side, touching the heated portion with the molten end of a glms rod, and pulling out a fine capillary. When the end of the capillary is broken and fire-polished, a small hole is left, which will not fill with liquid. If sufficient heat is available, a small
Fiqure 1.
Reservoir
A . Pyrex bottle 5 gallons
Closed stoa; coil C. Float valve E . Pyrex buret F . Bare 5-gallon can G. Dlstiiled water Inlet M. Steam inlet N. Steam outlet 0. Rubber stoppen P. Glass tubing R. Pinchclamps S. Soh rubber tubing T. Stiff wire bracer U. Buret exhaust V. H o t water level B.
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