SEPTEMBER, 1951
A THERMOREGULATOR FOR GAS-HEATED BATHS JOHN A. BROWN Georgia Institute of Techmlogy, AUanta, Georgia
THISregulator is designed to control the flow of gas to a Bunsen burner heating a constant-temperature bath which must have a moderate degree of regulation. It is based upon a mercury-valve action, controlled by the vaporization of a "control liquid" boiling at the temperature desired for the bath. Operation is as follows: With the bath cooler than the desired temperature, the regulator is as in a, with gas flowing freely through it. When the temperature reaches the boiling point of the control liquid, this liauid vaworizes, forcine the mercurv uw into the unwer ch'amberAandcu'tting 0% the gas, as"inAb. A pilotacole in the inlet tube keeps the burner lighted. Construction and dimensions are given in the figure. These dimensions are not critical, but a few desien considerations should be borne in mind: (1) he-volume of the control liquid must be enough 'so that its vapor will nearly fill the bulb when hot. (2) The bulb must be large enough so that the mercury forced out of it will rise far enough into the upper chamber to cut off the gas. (3) The stem may be any length, but it should be entirely inside the bath, in order to avoid heat conduction and cooling of the control liquid. Note also that the longer the mercury column, t.he higher the boiling point of the control liquid. (4) The pilot hole should be large enough to give a flame which will allow the bath to cool very slowly. Advantages of this regulator are simplicity of con-
struction, self-adjustment, and lack of need for calibration. I t can be built by ordinary glassblowing techniques; any excess control liquid simply bubbles out the first time the regulator is used; and the control temperature is fixed by the boiling point of the liquid used. Regulation is only moderate. It has been found easy to control a bath to within one degree with no special precautions. Probably i t would do somewhat better than this with proper precautions.
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PILOT HOLE
MERCURY
CONTROL LIQUID
b
No great amount of originality is claimed for this regulator. The author has seen other gadgets using the boiling-point principle, but no regulator like this.
