The efforts which have been made to produce diamonds artificially, although they have not been fruitless, have not as yet led to the production of large-sized crystals, because those means by which crystals are generally formed are inapplicable to carbon. Indeed, carbon in all its forms being insoluble and infusible does not pass into a liquid condition by means of which crystallisation could take place. Diamonds have several times been successfully produced in the shape of minute crystals having the appearance of a black powder, but when viewed under the microscope appearing transparent, and possessing that hardness which is the peculiar characteristic of the diamond. This diamond powder is deposited on the negative electrode, when a weak galvanic current is passed through liquid chloride of carbon.19
Moissan (Paris, 1893) produced diamonds artificially by means of the high temperature attained in the electrical furnace20 by dissolving carbon in molten cast iron, and allowing the solution with an excess of carbon, to cool under the powerful pressure exerted by rapidly cooling the metal.21
K. Chroustchoff attained the same end by means of silver, which dissolves carbon to the extent of 6 p.c. at a high temperature. Rousseau, for the same purpose, heated carbide of calcium in the electric furnace.
There is no doubt that all these investigators obtained the diamond as a transparent body, which burnt into CO2, and possessed an exceptional hardness, but only in the form of a fine powder.
Judging from the fact that carbon forms a number of gaseous bodies (carbonic oxide, carbonic anhydride, methane, ethylene, acetylene, &c.) and volatile substances (for example, many hydrocarbons and their most simple derivatives), and considering that the atomic weight of carbon, C = 12, approaches that of nitrogen, N = 14, and that of oxygen, O = 16, and that the compounds CO (carbonic oxide) and N2C2 (cyanogen) are gases, it may be argued that if carbon formed the molecule C2, like N2 and O2, it would be a gas. And as through polymerism or the combination of like molecules (as O2 passes into O3 or NO2 into N2O4) the temperatures of ebullition and fusion rise (which is particularly clearly proved with the hydrocarbons of the CnH2n series), it ought to be considered that the molecules of charcoal, graphite, and the diamond are very complex, seeing that they are insoluble, non-volatile, and infusible.
The aptitude which the atoms of carbon show for combining together and forming complex molecules appears in all carbon compounds. Among the volatile compounds of carbon many are well known the molecules of which contain C5 ... C10 ... C20 ... C30, &c., in general Cn where n may be very large, and in none of the other elements is this faculty of complexity so developed as in carbon.22
Up to the present time there are no grounds for determining the degree of polymerism of the charcoal, graphite, or diamond molecules, and it can only be supposed that they contain Cn where n is a large quantity.
Charcoal and those complex non-volatile organic substances which represent the gradual transitions to charcoal23 and form the principal solid substances of organisms, contain a store or accumulation of internal power in the form of the energy binding the atoms into complex molecules. When charcoal or complex compounds of carbon burn, the energy of the carbon and oxygen is turned into heat, and this fact is taken advantage of at every turn for the generation of heat from fuel.24
No other two elements are capable of combining together in such variety as carbon and hydrogen. The hydrocarbons of the C n H 2 m series in many cases differ widely from each other, although they have some properties in common.