translucent, they scratched a ruby, and they distinctly showed under the microscope the crystalline structure and cleavage of the diamond; their density was that of the precious gem, and they were completely consumed in oxygen at a temperature of 1,890°.
Mr. Marsden's experiment with silver was also repeated; but silver being a bad dissolvent for carbon, even at a high temperature, it was boiled for some time with sugar charcoal in the furnace, the cooling being operated in the same way as with iron. The result was extremely interesting. No diamonds were obtained, but a series of carbonados of different densities (from 2·5to 3·5 times heavier than water) were discovered, some of them in grains, some others in needles, or in conchoidal masses, the densest ones also scratching ruby and burning in oxygen at 1,800°. This is perhaps the most interesting part of Moissan's researches, as it confirms the long-since suspected fact that there is a whole series of carbon molecules each of which is composed of a different number of atoms, and some of which must be very complex.
As to the quantities of diamond dust obtained in this way they were extremely small. Several cylinders gave no diamonds at all, and from all his experiments Moissan could not collect even a few milligrammes (a few hundredth parts of a grain) of the precious dust, although the l)lack carbonados were quite common. But a sure method is now indicated, and its further development is only a matter of time and perseverance.
The scientific value of these researches is undoubtedly very great. Diamond, like graphite and simple charcoal, is pure carbon, but all attempts at fusing carbon or dissolving it have hitherto failed; it could not be brought into a liquid condition out of which it afterward might crystallize. However, the investigations recently made into the carburization of iron, especially by Roberts Austen, tended to prove that in steel and cast iron the carbon is not simply diffused through the iron, but enters with it into some of those combinations in definite proportions which like all solutions, occupy an intermediate position between real chemical compounds and purely physical mixtures. It was reasonable, therefore, to presume that carbon is brought into a liquid condition in molten iron, and that under certain conditions it may crystallize in the shape of diamonds within an iron mass. Moissan's discovery confirms this view. On the other side, the researches of Moissan and Fried el must also throw some light
- From a subsequent communication by Moissan we learn that the same varieties are found in the diamond-bearing earth at the Cape.
- See Recent Science, in Popular Science Monthly, October, 1892.