An Electrolytic Clock

Wednesday, May 6, 1891
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May6,1891.] THE EL'sc_'rR1c.A1. ENGINEER-. 51" AN ELECTROLYTIC CLOCK. BY #tag/»//_ éafa, If a delicately pivoted and well-balanced metal disc or cylinder be placed in a proper plating solution midway be- tween the anode and cathode, one half of the disc becomes electro positive and the other half electro negative. Owing to this fact metal is deposited on one, and taken off from the other half, and the disc is caused to rotate under the action of gravity. As the amount of metal deposited and taken off is proportionate to the current strength, the speed of rotation, if it be small, is proportionate to the current. The first device of this kind was operated by me early in 18z»S, in the endeavor to construct an electric meter. Upon learning, however, that I had been anticipated by others, as far as the principle is conccrned,‘ I devised the apparatus illustrated in the accompanying engraving. Here lf is a rectangular frame of hard rubber which is fastened upon a wooden base. This frame is about inch thick, 6 inches long and 5 inches high, (lu both of its upright sides are fastened thick metal plates which serve as the electrodes. These plates are held firmly against the rub- ber frame by the binding posts T 'r and 'r‘ 'r.‘ On the lateral sides of the frame are fastened the brass plates B and n,‘ respectivly, of the same shape as the rubber frame i-. These brass plates serve to keep in place two plates of F l‘ 1' |h ..,h l'illli,'il“ ° T, *Y , \_," I il l L, ‘ii,,,,\;,`ii ‘iff_igT ,b T T ,i tiiiriiillllil" W., tc tii < hi iuiiinhpii ° TE§LA'S Ei.isc'rrtor.v'rxc Ctocn. polished glass, and the vessel is hermetically sealed by placing a soft rubber washer under and above each of the glass plates. In this manner the plates may be screwed on tight without fear of breaking them. The plating solution, which in this ease is a concentrated solution of sulphate of copper, is poured in through an open- ing on the top of the rubber frame, which is closed by a lu It. P IE the center of the vessel is placed a light and delicately balanced copper disc im, the axis of which is supported by a capillary glass tube which is fixed to one of the glass plates by means of sealing wax, or other material not attacked by the liquid. To diminish the friction as much as pos- sible, the capillary tube which serves as a bearing contains a drop of oil. The center of the disc should be equbdis- tant from both the electrodes. To one side of the axis of the disc is fastened rt very light indicator or pointer con- sisting preferahly of a thin glass thread. The glass plate next to this pointer has a circle with the usual hour divis- sions engraved upon it, as on aclock dial. This circle_ma_y be movable so that it can be put in any position relatively to the pointer. If the dial is not movable then a tlun wire of annealed iron may be used as on a pointer. The wire d I The same invmitlou is at!-ribuletl tcxffdprague and '1‘. A Edlson. should then be so placed that it is exactly in the centre of the solution. By means of a horse-shoe magnet the disc may then be rotated and set in proper position. The copper solution being carefully poured in, and the plug it replaced, the terminals of a constant current bat- tery are connected to the binding-posts 'r 'r‘, and from time to time the rotation of the disc is observed. A shunt is connected to the other two binding-posts T 'r‘, and by vary. ing the resistance of this slnmt, or other disc, the speed of rotation is regulated until it is made to correspond to the division of the dial; that is, until, for instance, one turn is made in 12 hours. Obviously this instrument was not devised for a practi» cal purpose. Neither will it be quite exact in its indica- tions. '1‘here are certain errors, unavoidable from the principle; for instance, the friction, which cannot be com- pletely overcome. But the device is interesting as a means of indicating time in a novel manner. It_will, however, be found that by a careful construction, constant cur- rent, and a temperature compensator, it may be made to rotate with almost perfect uniformity. The current den- sity should, of course, be very small to secure the best re- sults, and the disc of about 3 inches diameter should turn once in 6 hours. It is probable that with a silver solution and a silver plate better results would be obtained. It is very interesting to note the appearance of the solu- tion and disc in such a narrow transparent vessel. The solution appears a clear blue, one side of the disc seems to be silver white in a certain position, and the other half is dark like tarnished silver. There is no line of demarca- tion, but the shades melt beautifully together.