Patent GB-191513452-A (GB)
Title: Improved Manufacture of Chlorates of Alkali Metals.
Inventor: GIBBS ARTHUR EDWARD
IPC: C25B1/26
Filed: 1915-09-21
Abstract: 13,452. Gibbs, A. E. May 5, [Convention dute]. Chlorates, p e r c h l orates, alkali, and chlorine, obtaining; electrol y t e s, circulating. - Alkali solution is treated with excess of chlorine outside an electrolytic cell, in order to produce chlorate, and is then returned to the cell, the process being repeated until the solution is sufficiently rich in chlorate, whereupon it is withdrawn, preferably at a point between the cell and the chlorine-treatment apparatus, so that the alkali is present. In the apparatus illustrated, brine is fed from a constant-level feedcup 6 into the anode compartment of a cell 2 of the kind described in Specifications 27,830/07 and 28,147/08, and filters through the diaphragm and perforated cathode. From the cathode compartment, the electrolyte is pumped to a tank 10 in which fresh salt may be dissolved with the help of an agitator 11. An overflow pipe 12 from the tank 10 leads to a settling tank 13, whence the clear solution is conveyed to the top of one or more towers 17, up which chlorine from the cell is drawn by a fan blower 19. A part or the whole of the solution then returns to the feed-cup 6 by way of two tanks 20, 20<b>. Overflow from the feed-cup 6 is pumped back to the second of these tanks 20<b>. Any lime or magnesia in the salt is precipitated by the alkali and may be removed from the mixing and settling tanks by cocks 14, 15. Some of the alkali is thus neutralized, so that the chlorine is in excess. If pure salt is used, a part of the alkali is drawn off by one of these cocks. The temperature of the electrolyte may be above 40‹ C., external heat being supplied if necessary. Sodium chlorate is obtained by repeatedly circulating the liquid and then withdrawing and concentrating it. The salt separated may be re-used. If potassium chlorate is required, a solution of potassium chloride, with or without sodium chloride, is used, or potassium chloride is added to a sodium chloride solution after treatment. The precipitated potassium chlorate may be removed as a sludge from the mixing and settling tanks 10, 13, separated centrifugally, and recrystallized. A by-pass may be provided for that tank from which the sludge is being removed. The electrolytic chlorine may be liquefied or used for other purposes, chemicallyprepared chlorine being supplied to the treating-tower. In any case, excess of chlorine is preferably employed. Carbon or graphite anodes are suitable. When a mercury or gravity type of cell is used, the chlorate liquors should be freed from carbon by filtration or settling. In a mercury cell, a part or the whole of the solution is allowed to enter the cathode compartment, preferably from the anode compartment. Addition of chromic acid to the electrolyte may be dispensed with. Specifications 6417/87 and 2987/02 also are referred to. The Specification as open to inspection under Section 91 (3) (a) states that instead of electrolytic alkali, a cheaper alkali, such as carbonate, may be used, and that perchlorate may be obtained by prolonging the circulation, or by using a chlorate electrolyte and lowering the temperature. This subject-matter does not appear in the Specification as accepted.