The manufacture of malleable iron castings is older than is generally thought, although the knowledge of the true principles on which it is based dates from the more recent period of the establishment of chemical science. In his work on the "Art of Converting Wrought Iron into Steel, and of Softening Cast-iron" (Tart deconvertir le fer forge en acier, et Tart d'adoucir fe fer fondu), published in 1722, Reaumur gives the numerous experiments by which he succeeded in producing malleable iron castings, which had already been made some twenty years before, but in a secret manner.

At the epoch in which Reaumur lived, the true era of chemistry had not yet begun, the relations of carbon to iron in pig metal were not known, and the various degrees of hardness and appearance in cast-iron were attributed to the presence of various impurities, sulphur especially.

After many experiments with all kinds of substances and salts - the results of which were noted with a remarkable acuteness of observation - Reaumur succeeded in his purpose with three different mixtures.

Having observed that a plate of cast-iron, exposed for a long time to the direct action of a fire, was covered with a coat of black and red oxide, and that the metal underneath had become softened (malleable), he collected such oxide for the purpose of packing with it small bars of white cast-iron, and after heating them in covered crucibles, he obtained a perfectly malleable iron. His other mixtures were powdered limestone and charcoal, and charcoal with calcined bone-dust.

The first mixture is evidently that used at the present time; the second may be explained by the oxidizing action, at a certain temperature of the carbonic acid disengaged, which parts with an atom of oxygen (CO2 + C = 2 CO) combining with the carbon of the cast iron, and which becomes carbonic oxide. In the third case, we may surmise that the carbon was burned out by the air of the fire-place, penetrating through the interstices of the cast iron plates forming the boxes in which the metal and the mixture were packed.

The air was prevented from acting violently by the mass of bone-dust and powdered charcoal with which the articles were surrounded. We do not believe that the temperature was sufficiently high to decompose the bone dust, even in presence of the charcoal.

The furnace employed was of brick, and square, and divided by vertical partitions of cast-iron plates, between two of which were packed the castings and the mixture, and around which were flues far the circulation of the gases of the fire-place.

However imperfect these dispositions may be when compared with the present ones, Reaumur ascertained that oxides of iron and cast-iron, heated together in closed vessels, produced malleable iron; that for malleable castings, white is preferable to gray metal; that the castings, previous to annealing, should be deprived of the adhering sand, which becoming fluxed, prevented the reaction; that too protracted and too intense a heat may harden the castings again; and that properly annealed articles may be bent, forged, welded, case-hardened, and present all the properties and even appearance of wrought iron.

After having explained the principles upon which the industry of malleable iron casting is founded, and given a historical notice of the first trials made, we cannot do better than to describe the actual processes, such as are applied at the Hardware and Malleable Iron Works of Messrs. Chas W. Carr, Jos. S. Crawley, and Thos. Devlin, successors to E. Hall Ogden, and whose store is at 307 Arch Street, Philadelphia.

In this large establishment, where everything is conducted with the best order and understanding, anything in the line of ordinary and malleable castings for building and cabinet, carriage and saddlery hardware, &c., is made complete, from the pattern to the casting, annealing, coppering, adjusting and japanning of the articles.