GB431695A - Improvements in electrical purification of liquids - Google Patents

Abstract

431,695. Electrolytic purification of liquids. BILLITER, J., 2, Avenue St.- Phillibert, Paris. Jan. 13, 1934, No. 1299. [Class 41] In the electro-dialytic purification of liquids in a three-compartment cell, the anode space is not flushed, the anode liquor thereby increasing in acid strength and conductivity. Pure acid may be added from time to time to maintain an anolyte conductivity of 10-3 reciprocal ohms per cm. cube. The cathode liquor may similarly be allowed to increase in strength, and its conductivity further increased by the addition of pure bases. The process may be carried out in a cell comprising an anode 25, Fig. 1, of coiled platinum wire mounted within a porous pot 1 spaced from a perforated iron cathode 11 which is covered on the inside by a diaphragm 10 of asbestos paper closed at the bottom by a rubber disc 29. The liquid to be purified is supplied at 14 and withdrawn at 20. Loss of anodic liquor by endosmotic action is made up by addition of water from a pipe 23 having a valve 24 controlled by a float 12 ; alternatively the loss may be made up through a small hole at the bottom of the anode diaphragm. An overflow 22 for the cathode liquor is provided. The cell shown in Fig. 6 comprises concentric perforated cathodes 10, 11 covered on their facing surfaces with asbestos diaphragms 27. Between these are mounted spaced anode diaphragms 1 of ceramic material, between the diaphragms 1 an anode consisting of straight platinum wires 25. The water to be purified is supplied to a basin 14 overflowing into the space between the inner anode and cathode diaphragms from the bottom of which it passes to the space between the outer pair of diaphragms from which it overflows at 20. Liquid may be supplied to the anode compartment under control of a float 12. The space within the inner cathode may contain a sheetiron vessel 37 heated by steam or oil. In the cell shown in Fig. 4, a magnetite anode 25 is mounted within a ceramic diaphragm 28 having a constricted part 1 passing through the bottom of the cell and connected by a narrow pipe 4 to a supply cup 5 for make-up liquor. An overflow 7 within the cup leads to a similar device for a succeeding cell. The cylindrical cathode 11 of perforated metal is provided on its inner face with a diaphragm 10 of asbestos cloth. Liquid to be purified enters the space between the anode and cathode diaphragms at 20 and overflows to the next cell. A similar circulating arrangement is employed in a system of vertically superimposed cells. The issuing purified liquid may be employed to heat the incoming liquid. The cathode diaphragms may be of rubber fabric or of a composition of asbestos, rubber and kieselguhr. The purification may be furthered by the use of current densities of at least 4 amps. per sq. dcm., with platinum anodes whereby ozone is produced. Mercury cathodes may be employed ; in this case no cathode diaphragm is necessary. In one form, the cathode consists of a vertical gauze sheet down which mercury is allowed to trickle, the mercury leaving at the bottom by a syphon overflow ; the cathode space is separated by diaphragms from anodes mounted on either side. Liquids containing a high percentage of alkali metal salts are purified first in mercury cells and then in three-compartment cells.