At a recent meeting of the Chemical Society, London, a paper was read entitled "Notes on the Condition in which Carbon exists in Steel," by Sir F.A. Abel, C.B., and W.H. Deering.
Two series of experiments were made. In the first series disks of steel 2.5 inches in diameter and 0.01 inch thick were employed. They were all cut from the same strip of metal, but some were "cold-rolled," some "annealed," and some "hardened." The total carbon was found to be: "cold-rolled," 1.108 per cent.; hardened, 1.128 per cent.; and annealed, 0.924 and 0.860 per cent. Some of the disks were submitted to the action of an oxidizing solution consisting of a cold saturated solution of potassium bichromate with 5 per cent. by volume of pure concentrated sulphuric acid. In all cases a blackish magnetic residue was left undissolved. These residues, calculated upon 100 parts of the disks employed, had the following compositions: "Cold-rolled" carbon, 1.039 per cent.; iron, 5.871. Annealed, C, 0.83 per cent.; Fe, 4.74 per cent. Hardened, C, 0.178 per cent.; Fe, 0.70 per cent. So that by treatment with chromic acid in the cold nearly the whole of the carbon remains undissolved with the cold-rolled and annealed disks, but only about one-sixth of the total carbon is left undissolved in the case of the hardened disk. The authors then give a resume of previous work on the subject. In the second part they have investigated the action of bichromate solutions of various strengths on thin sheet-steel, about 0.098 inch thick, which was cold-rolled and contained: Carbon, 1.144 per cent.; silica, 0.166 per cent.; manganese, 0.104 per cent. Four solutions were used. The first contained about 10 per cent. of bichromate and 9 per cent. of H2SO4 by weight; the second was eight-tenths as strong, the third about half as strong, the fourth about one and a half times as strong. In all cases the amount of solution employed was considerably in excess of the amount required to dissolve the steel used. A residue was obtained as before. With solution 1, the residue contained, C, 1.021; sol. 2, C, 0.969; sol. 3, C 1.049 the atomic ratio of iron to carbon was Fe 2.694: C, 1; Fe, 2.65: C, 1; Fe), 2.867 C, 1): sol. 4. C, 0.266 per 100 of steel. The authors conclude that the carbon in cold rolled steel exists not simply diffused mechanically through the mass of steel but in the form of an iron carbide, Fe3C, a definite product, capable of resisting the action of an oxidizing solution (if the latter is not too strong), which exerts a rapid solvent action upon the iron through which the carbide is distributed.
APPARATUS FOR EXTRACTING STARCH FROM POTATOES.
In the apparatus of Mr. Angele, of Berlin, shown in the annexed cuts (Figs. 1 and 2), the potatoes, after being cleaned in the washer, C, slide through the chute, v, into a rasp, D, which reduces them to a fine pulp under the action of a continuous current of water led in by the pipe, d. The liquid pulp flows into the iron reservoir, B, from whence a pump, P, forces it through the pipe, w, to a sieve, g, which is suspended by four bars and has a backward and forward motion. By means of a rose, c, water is sprinkled over the entire surface of the sieve and separates the fecula from the fibrous matter. The water, charged with fine particles of fecula, and forming a sort of milk, flows through the tube, z, into the lower part, N, of the washing apparatus, F, while the pulp runs over the sieve and falls into the grinding-mill, H. This latter divides all those cellular portions of the fecula that have not been opened by the rasp, and allows them to run, through the tube, h, into the washing apparatus, F, where the fecula is completely separated from woody fibers. The fluid pulp is carried by means of a helix, i, to a revolving perforated drum at e. From this, the milky starch flows into the jacket, N, while the pulp (ligneous fibers) makes its exit from the apparatus through the aperture, n, and falls into the reservoir, o.
ANGELE'S POTATO-STARCH APPARATUS.
The liquid from the jacket, N, passes to a refining sieve, K, which, like the one before mentioned, has a backward and forward motion, and which is covered with very fine silk gauze in order to separate the very finest impurities from the milky starch. The refined liquid then flows into the reservoir, m, and the impure mass of sediment runs into the pulp-reservoir, o. The pump, l, forces the milky liquid from the reservoir, m, to the settling back, while the pulp is forced by a pump, u, from the receptacle, o, into a large pulp-reservoir.
The water necessary for the manufacture is forced by the pump, a, into the reservoir, W, from whence it flows, through the pipes, r, into the different machines. All the apparatus are set in motion by two shaftings, q. The principal shaft makes two hundred revolutions per minute, but the velocity of that of the pumps is but fifty revolutions.--Polytech. Journ., and Bull. Musee de l'Indust.