3o8 JOSEPH STRUTHERS 



(1) In the production of cast iron from ore containing 

 a large proportion of carbon, by allowing the molten mass to 

 cool slowly. As cast iron can retain in combination a much 

 larger proportion of carbon when molten than when soUd, 

 the cooling of the mass causes the carbon to separate out, 

 forming scales of graphite disseminated throughout the iron. 

 It is to the presence of the scales of graphite that gray pig iron 

 owes its peculiar properties and its gray color. When this 

 form of pig iron is dissolved in acid, the scales of graphite 

 remain as an insoluble residue. When cast iron is kept in a 

 molten condition for a long time, as in the manufacture of 

 converter steel, scales of graphite collect on the surface of the 

 molten metal, forming so-called kish. This source of artificial 

 graphite is of no commercial importance. 



(2) By the reaction or decomposition of various chem- 

 ical compounds containing carbon, notably the cyanide class 

 of salts. Graphite can not be produced commercially from 

 chemicals on account of the excessively high cost. 



(3) By the treatment of certain carbonaceous materials 

 in the electric-arc furnace, which is the process now used on a 

 very large scale. 



Pure graphite has many valuable properties, such as high 

 electrical conductivity, great resistance to chemical action, 

 and absence of the property of absorbing gases, which is pos- 

 sessed more or less by all forms of amorphous carbon. Nat- 

 ural graphites of the high degree of purity required for delicate 

 chemical and electrical processes are so expensive that in most 

 cases the cost is prohibitive. The inception of the artificial 

 graphite industry is due to the efforts and experiments of Mr. 

 Edward G. Acheson, who during 1897 manufactured more than 

 160,000 pounds of this product. In 1901 the output in the 

 United States reached 2,500,000 pounds. At first the oper- 

 ations were confined to the graphitization of carbon electrodes, 

 but since 1899 very large quantities of artificial graphite have 

 been made, to be utilized for purposes for which natural graph- 

 ite was formerly used. In graphitizing electrodes the ordinary 

 electrode, which is composed of a mixture of petroleum, coke, 

 pitch, and a carbide-forming material (silica or iron oxide), 

 is subjected to the intense heat of an electric-arc furnace. The 



