288 DAY AND SOSMAN I EXPANSION COEFFICIENT OF GRAPHITE 



ite investigated by Dewar stands next in order, and very near 

 anthracite. This graphite has been formed in company with 

 intrusions of igneous rock into clay-slates containing organic 

 matter. The Batongol graphite, with a lower coefficient, occurs 

 in veins in granite and syenite. 2 Various samples of arc light and 

 retort carbon, all of which have probably been heated in the 

 process of manufacture to a higher temperature than any of the 

 natural graphites, stand next in the order of decreasing expan- 

 sion. Lowest of all (excepting one sample of arc carbon made of 

 coke) come diamond and Acheson artificial graphite. The for- 

 mation temperature of diamond is unknown. The artificial graph- 

 ite is made by heating anthracite, petroleum coke, etc., to a 

 temperature above 2200°. 3 



The view has been repeatedly expressed, by Moissan, 4 Luzi, 5 

 and others, that none of the three forms of carbon as at present 

 distinguished, not even diamond, can be looked upon as a sub- 

 stance of fixed and reproducible properties, comparable for in- 

 stance to the monoclinic and rhombic forms of sulfur. In the 

 case of graphite, there are wide variations in such physical prop- 

 erties as density and electrical conductivity, as well as in chemi- 

 cal properties such as combustibility and the formation of "graph- 

 itic acids" of widely varying composition when different kinds of 

 graphite are treated with nitric acid and potassium chlorate. 



If we look upon natural graphites as products of metamorphism 

 from organic matter, we may imagine the complicated carbon 

 chains and rings of the cellulose and resin compounds of bitumi- 

 nous and anthracite coal as persisting after the removal of the 

 hydrogen and oxygen, giving a whole series of "graphites" whose 

 properties change progressively as the molecules become simpler. 

 Berthelot 6 held this view as regards amorphous carbon. 



Arsem, 7 as a result of this studies on the graphitization of differ- 

 ent forms of "amorphous" carbon, and the densities of the result- 



2 Donath, "Der Graphit," 1904. 4 



3 Gillett, Journ. Phys. Chem. 15: 302, 1911. 



4 Chimie Minerale, 1905, II, 222. 



5 Donath, "Der Graphit," 1904, p. 11. 



6 Ann. Chim. Phys. (4) 9: 475. 1866. 



7 Jl. Ind. and Eng. Chem. 3: 799-804. 1911. 



