GB292798A - - Google Patents

Abstract

292,798. Gardner, D. Aug. 2, 1927. Carbon.-Carbon of high purity is obtained from charcoal and other pre-carbonized material by first pulverizing the material so that it can be passed through a sieve of about 300-350 mesh per inch, then treating with an alkaline solution, washing, treating with an acid, washing again and finally heating to a temperature of the order of 1000-1300‹ C. or over. Alternatively the alkaline treatment may be omitted, and the material, after the acid treatment, heated under fusing conditions with an acid salt, e.g. sodium or potassium bisulphate, and the product stirred into water. In the example given ,the charcoal after grinding is treated with a boiling six-normal. solution of sodium hydroxide, the product, after separation from the liquor, being given repeated washings with hot water. The material is next heated with nitric acid of 36‹ BeaumÚ until evolution of nitrous fumes ceases, and then washed repeatedly with water as before.. By using sufficiently strong acid heating may be omitted. To produce a very light and velvet black carbon, the material is next heated, e.g. in an electric furnace, to 1000-1300‹ C. under vacuum, or in a neutral, reducing or oxygen-free atmosphere, after first bringing it to a finely divided state. By heating above 1300‹ C. carbon in graphite form is obtained. Alcohol or other organic solvent may be used for some of the washing, or may be added to the wash water. The product is very hygroscopic and is preferably incorporated in turpentine, tetrachlorethane, tetrachlorethylene or other suitable protective material. The starting material may be that obtained on carbonizing lignites, brown coal, &c., but is preferably produced by carbonizing beach, oak, and other non-resinous hard woods at comparatively low temperatures, preferably not over 300‹ C. The Provisional Specification describes the treatment of the finely divided precarbonized material with alkalies, acids, mixtures of alkalies, and mixtures of acids in any order, preferably with intermediate and final washings. One or more of the acid or alkali treatments may be replaced by heating under fusing conditions with an acid salt.