GRAPHITE 309 



so-called artificial graphite is produced by subjecting anthra- 

 cite coal, coke, or charcoal, together with a small proportion of 

 some oxide or sulphate, to the intense heat of an electric-arc 

 furnace; the impurities are eliminated, the ash being reduced 

 in some cases to as low as five tenths of 1 per cent. 



The so-called artificial graphite, w^hich is in the form of 

 grains or powders, is used chiefly in the manufacture of paint, 

 dry batteries, and commutator brushes, although a considerable 

 quantity is used in the manufacture of lubricants for high 

 grade work, in electroplating, and in certain chemical processes 

 which require a carbon of exceptional purity. Experiments 

 have been made with this material as a coating for the grains 

 of high explosives, to prevent the generation of the static 

 charge of electricity, the spark from which is supposed to 

 cause the spontaneous ignition of the powder. 



Graphitized electrodes possess special qualities which 

 render them valuable in electrolytic processess for the produc- 

 tion of caustic soda and of chlorine and metals in chloride solu- 

 tion, and in electro-metallurgical processes, such as the pro- 

 duction of calcium chloride, the electric smelting of copper and 

 iron ores, and the manufacture of various iron alloys. 



In spite of the development of artificial graphite, however, 

 in recent years there has been a large increase in the demand 

 for natural graphite, due to the growth of the iron and steel 

 industries, the largely increased use of copper and its alloys; 

 the development of electrical machinery, which calls for graph- 

 itized products; and the increased need for special lubricants 

 to be used at comparatively high temperatures. 



Graphite is used for making refractory crucibles, stove 

 polish, foundry facings, paint, and lead pencils ; as a lubri- 

 cant; and in powder glazing, electrotyping, steam packing, etc. 



For the making of crucibles crystalline graphite is re- 

 quired; the fibrous or laminated variety is used, because its 

 superior binding qualities add to the strength of the cruci- 

 ble. The ordinary mixture consists of 50 per cent of graphite, 

 from 35 to 45 per cent of air dried clay, and from 5 to 15 per 

 cent of sand. The graphite is ground to a fineness of from 

 40 mesh to 100 mesh size, according to the special use to which 

 the crucible is to be put; if coarse it will give a porous cruci- 



