36 SCIENCE PROGRESS 



(4) Specific heats 

 (All measured by H. F. Weber, Pogg. Ann. 154, 367, 553, 1875) 



Diamond (107" C.) 0*1128 



Ceylon graphite (io'8° C.) 0*1604 



Wood charcoal (o° — 24 C.) 0*1653 



(5) Electrical conductivity 



Diamond .... (i5°C.) o'2ii*io _u — o*309*io -1: 

 Graphite .... (i5°C.) 0*082* io 4 

 Charcoal .... (i2°C.) 0*25 



An inspection of this table shows that, with the single ex- 

 ception of the electrical conductivity, all the physical properties 

 are in the order we should expect. In the case of the electrical 

 conductivity, graphite occupies an anomalous position, in that 

 its conductivity is very much larger than that of either the 

 diamond or amorphous carbon. In this connection two facts 

 appear to be important. Firstly, the value of the electric con- 

 ductivity of graphite is so very much larger than those of the 

 other two forms that it would lead one to suspect that it is 

 occasioned by something quite different from the mode of linkage 

 of the carbon atoms in the different forms of carbon, since we 

 could scarcely expect that the differences in atomic linkage would 

 change a substance which is an insulator, like the diamond, into 

 a substance which is a metallic conductor, like graphite. And, 

 secondly, we can see that there is a real anomaly in the case 

 of graphite, because the thermal conductivities are in the order 

 expected, and thence, from the law of Wiedemann and Franz, 

 which states that the ratio of the thermal and electrical con- 

 ductivities is (at least in the case of metals 1 ) approximately 

 constant, we should also expect the electrical conductivities to 

 be in the same order. The abnormal electrical conductivity of 

 graphite is, in fact, a property which still awaits explanation. 

 Clearing up the ground so far as we can as regards the structure 

 of carbon molecules, we shall proceed with the consideration 

 of the process of oxidation and the complexes of the general 

 formula — CX)j, — formed during that operation. 



The whole process of combustion or oxidation can be repre- 

 sented in the following manner : 



1 11 in 



2C* + YO, -> 2QA -> aCO + (2X - a)C0 2 $ 2.rC0 2 



1 Cf. L. Cellier, IVied. Ann. 61, 511, 1897. 



