Patent GB-548174-A (GB)
Title: Improvements in or relating to the preparation or maintenance of an electrolyte having a desired characteristic or characteristics and to apparatus for determining the composition or changes in composition of an electrolyte
IPC: C02F1/72
Filed: 1940-04-24
Abstract: 548,174. Automatic control systems. WALLACE & TIERNAN PRODUCTS, Inc. April 24, 1940, No. 7419. Convention date, Aug. 18, 1939. [Class 38 (iv)] [Also in Group XXXVI] In the preparation or maintenance of an electrolyte having a desired characteristic, changes in the composition of the electrolyte are determined by contacting the electrolyte with a polarized electrode whilst cleaning the surface of the electrode, detecting the depolarization of the electrode thus produced and utilizing the determined depolarization to effect control of the amount of a reagent or reagents to be added to the electrolyte : Fig. 6 shows an arrangement for the determination of residual chlorine in water undergoing treatment. A cell 10 has two electrodes 14,15 and an inlet and outlet through which electrolyte to be treated is passed. The preferred cell is described in Specification 548,173, [Group XXXVI]. A cell 54, for supplying polarizing current to the cell 10, is connected through a variable resistance 53 across fixed resistances 50, 51. An indicating or recording potentiometer 55 is connected across the resistance 52 in the upward position of a switch 56 and across the resistance 51 in the downward position of the switch. With the switch 56 in the downward position and the cell 10 supplied with liquid which has not been chlorinated the resistance 53 is adjusted until a standard reading is obtained on the potentiometer. The liquid to be tested is then passed through the cell 10 and the key 56 released, so that the potentiometer indicates the voltage across the resistance 52. This resistance is adjusted in accordance with the reading of a thermometer in the cell 10. The effect of the residual chlorine in the water supplied to the cell 10 is to effect electrode depolarization, and consequent increase of current, to an extent depending on the amount of residual chlorine in the water, which is indicated by the reading of the potentiometer 55. Instead of the potentiometer a milliammeter may be arranged to be connected by means of a two-way key either in series with the cell 10 and resistance 52 or in series with the cell 54 and resistances 53, 50 and 51. In the system shown in Fig. 9 rectified A.C. is employed as the polarizing source. An A.C. supply line 65 is connected through a voltage regulator 66 and step-down transformer 67 to a full wave rectifier 68 of the copper oxide type, the rectified output of which is supplied to the resistances 50, 51, 53. With the key 69 in its normal position as shown the primary of a transformer 70 is connected in series with the temperature-compensating resistance and the cell 10 across the resistances 50, 51. When the key 69 is depressed the primary of the transformer 70 is connected across the resistance 51. The rectified current is pulsating and produces an alternating current in the secondary of the transformer 70, which is supplied to the input of an amplifier 71. The amplified current is supplied through a rectifier 72 to a recording galvanometer 73 having a smoothing condenser 74 connected across its coil. In another arrangement, Fig. 10, change in the depolarization produced by the treated liquid flowing through the cell 10, a fixed resistance 75, variable resistances 76, 79, and a calibrated slide wire resistance 77. Pulsating unidirectional current is supplied to the bridge circuit from a secondary winding of the transformer 79 through a half-wave rectifier 80. The potentiometer slider and the junction point of the resistances 76, 78 are connected to the input of an amplifier 82, the output of which is connected to the shading coils of an induction motor 83, which may be of the type described in Specification 493,457, [Group XXXVIII]. The field winding of the motor 83 is supplied with A.C. from a secondary winding of the transformer 79. A follow-up connection 84 is provided between the rotor of the motor 83 and the slider of the resistance 77. The rotor is also mechanically connected, as indicated at 85, to the control element of the chlorinator 86. The variable resistance 78 effects automatic temperature compensation and may be a liquid or other resistance of desired temperature coefficient, or a rheostat operated by a bimetallic thermostatic element, both housed in a sealed glass envelope containing hydrogen so as to give good thermal conductivity with the liquid in the cell. 10. Fig. 11 shows a recording galvanometer which may be employed in the system shown in Fig. 9. A winding 107 is wound on a spool 105 having a central slot for receiving a rotor or armature 106. This is mounted for partial rotation or oscillation about a geometric axis which passes through the rotor and is at right angles to the axis of the winding. The rotor 106 is imperforate and is fixed at a point on its periphery to a cranked axle 111 lying outside the winding. The rotor may be a disc of a magnetic alloy of high retentivity such as " alnico," and is magnetized along a diameter. The spool 105 may be of copper, to damp the oscillations of the rotor. The axle 111 is mounted in ball bearings 112, 113, adjustable axially, and carries a recording arm 122 having a marking pen or stylus 125 at its end. A balance weight 123 is adjustable on an arm 124. A permanent magnet may be mounted angularly with respect to the arm 122 to obtain an exponential law of deflection. Specifications 548,171, [Group XXXVIII], 548,186, [Group XXXVI], and U.S.A. Specification 1,530,833 also are referred to.