GB145018A - Improvements in primary galvanic batteries and electrodes for such batteries and methods of manufacturing such electrodes - Google Patents

Abstract

145,018. Jungner, E. W. June 17, 1919, [Convention date]. Carbon.-Carbon electrodes for gas batteries or batteries depolarized by atmospheric oxygen are so made or treated that thev will not become saturated when immersed in electrolyte. The electrodes may be treated with substances of a greasy or oleaginous nature such as animal or vegetable fats, mineral or vegetable oils, saturated hydrocarbons such as paraffins or their derivatives, resins, terpenes, shellac, tallow, wax, &c. The substance is dissolved in or mixed with a volatile solvent such as benzine, carbon bisulphide, turpentine, alcohol, chloroform or acetic acid, the electrode being dipped in the solution or mixture which is allowed to penetrate partly or completely into the electrode, the solvent being afterwards expelled by heat. Oils may be introduced into the pores of the electrodes without the use of a solvent. In one example a solution of 5 parts of solid paraffin in 100 parts of benzine or carbon bisulphide is used; the quantity of paraffin in the solution should not exceed 15 per cent. Another method of treatment consists in exposing the carbon electrodes to the vapours of substances such as coal tar or wood tar. A paste may be made of tar and powdered carbon which is heated to 550- 650‹ C., the heating being stopped before the tar has become coked. Heating may however be continued until the mixture is completely coked, whereupon it is treated with a mixture of tar and benzine and again heated to impregnate the carbon with the tar vapours. The mixture of tar and benzine, or tar and powdered carbon, may be applied only to the surface of the carbon electrode, which is then heated to a low temperature. Instead of greasy organic compounds, certain inorganic substances may be used such as magnesium silicate, talc, lard-stone, serpentine, &c. These substances are added to the paste from which the electrodes are moulded. In one example 10 per cent of magnesium silicate is added. The electrodes are formed with very small pores by using the carbon and other materials from which they are moulded in a finely divided state, the binding-agents such as tar or molasses being diluted with water or alcohol, benzine, oils or other volatile liquids. When water is used it is added in such quantity that, including the water already present in the tar or molasses, the whole contains about 50 per cent of water. Crystalline substances may also be used to prevent saturation of carbon electrodes with electrolyte. Thus a paste of finely ground coke and tar may be mixed with 20 per cent of common salt, the whole being heated to 1000‹ C. In another method the electrode paste is mixed with a soluble salt which after the heating operation is dissolved out. The electrode is then dried and impregnated with a solution of sugar and again heated, being finally impregnated with an oleaginous organic substance. Electrodes may also be made of graphite by mixing together fine amorphous carbon and tar or molasses diluted with water or other volatile liquid and heating the mixture in an electric furnace to 3000‹ C. to convert the carbon into graphite. Electrodes so prepared do not readily become moistened by electrolyte but they may be further protected by impregnation with paraffin &c. When used in gas batteries the electrodes are hollow and formed with a supply pipe for the active gas, end when depolarized by air they are arranged horizontally and only partly immersed in the electrolyte.