(see that article Encycl. and Chemistry, n° 114. Suppl.) is composed of iron and carbon. In addition to the old proofs which we had of this fact, it occurred to Morveau, alias Guyton, to attempt to convert soft iron into steel, by using the diamond instead of charcoal in the process of cementation. This expensive experiment, which was suggested by M. Cloquet, was made, by inclosing within a small crucible of very soft iron a diamond, and shutting up the crucible by a stopper well adjusted. This crucible of iron, with its contents, was placed, without the addition of any surrounding matter, in a very small Hessian crucible, and the latter in a second crucible of the same kind; but the space between the two latter crucibles was filled with fibrous sand, free from all ferruginous particles. In the last place, the large crucible was fitted with earth arising from pounded crucibles and unbaked clay, and the whole was exposed about an hour to a three blast forge fire. When the whole was cooled, the iron was found in the interior Hessian crucible converted into a solid ingot of cast steel. Thus the diamond disappeared by the affinity which iron exercised on it by the help of the high temperature to which they were both exposed, in the same manner as a metal disappears in the alloy of another metal. The diamond therefore furnished here the same principle as carbon, since the product of the union has the same properties.

The conversion into steel could not be doubted. The ingot having been polished on a lapidary's wheel, a drop of weak nitric acid immediately produced a dark-grey spot, absolutely like that exhibited on English cast steel, and on cast steel produced by the process of C. Cloquet. Those who have often tried steel by this kind of proof, long ago pointed out by Rumann, had occasion to remark, that the spot of cast steel, though very sensible, is, however, less black than that of steel made by cementation, which depends perhaps on the different degree of oxidation of the carbon which they have taken in.

The process of M. Cloquet here mentioned, for producing cast steel, consists in nothing more than throwing a quantity of glass into the mass of iron and charcoal during the formation of the former into steel. The same chemist has ascertained that iron, during its conversion into steel, absorbs 0.203 of its weight of carbon; and that the affinity of iron for carbon is so strong that, at a white heat, it is capable of decomposing carbonic acid gas. This he proved by the following experiment.

If six parts of iron be mixed with four parts of a mixture composed of equal quantities of carbonate of lime and clay, and kept in a crucible at a white heat for an hour or longer, according to the quantity, the iron will be converted into steel. The decomposition of carbonic acid is evidently the consequence of a compound affinity; part of the iron combining with the carbon, and another part with the oxygen of the carbonic acid gas. Accordingly the commissioners, who were appointed to examine the process, remark, that a quantity of oxid of iron was always mixed with the melted earthy substance, which was separated from the steel.