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Assay Determination of Arsenic & Antimony

Determination of Arsenic and Antimony Together: Instead of separating arsenic from antimony in the hydrochloric-tartaric acid solution which was finally obtained, dilute the solution to four times its volume; pass sulphuretted hydrogen to saturation; filter the combined sulphides on a 4 cm. filter (weighed and dried in weigh-bottle at 110° C.); wash with water, absolute alcohol, carbon bisulphide, and finally absolute alcohol again, very carefully; then dry at 110° C., cool and weigh. More about Electrolytic Assay.

By allowing to dried filters in weigh-bottles the same time for cooling in the desiccator when getting weight of bottle and filter-paper only, as afterwards when filtered sulphides are dry and ready for weighing, very uniform results are obtained.

Arsenic being precipitated as As2S3 and antimony as Sb2S5, their respective factors being 0.609 and 0.600, the factor 0.6 is used in calculating, from the weight of the combined sulphides, the percentage of arsenic plus antimony.

Determination of Arsenic as Trisulphide

Re-dissolve the sulphides in a solution containing hydrochloric acid, water and chlorate of potash. Dilute to at least twice the volume. Pass through the warm solution sulphuretted hydrogen to saturation, to insure the thorough reduction of the solution. Arsenic will be precipitated as trisulphide. After 5 ….Read more

By | January 23rd, 2017|Categories: Assaying, Smelting - Melting - Refining|Comments Off on Assay Determination of Arsenic & Antimony

Tube Muffle Furnace

The Tube Muffle Furnace is practically the common laboratory analytical gas-fired combustion-furnace, with its glass tube replaced by the iron and copper tubes, G and M, and surrounded with brick-work to lessen radiation and to give better control over the temperature.

The burners, J, are those of the common combustion-furnace.tube_muffle_furnace

The bar, K, to be heated is laid on another, L, cut from the same rod, and inside the copper tube, G. L rests on little strips of iron, to raise it above the bottom of G, so that both bars may be heated alike by radiation rather than by conduction.

The copper tube, G, rests within the wrought-iron tube, M, and is held concentrically with M by packing a little ring of asbestos between them at either end of G.

The thermo-electric junction, N, formed by the junction of a wire of pure platinum with one of platinum alloyed with about 10 per cent, of rhodium, lies between the bars K and L, in a little notch filed in the latter. The leading-in wires pass to the galvanometer, which is at a convenient distance from the furnace, through the double-bored clay tube, O.

My ….Read more

By | January 18th, 2017|Categories: Equipment, Steel|Comments Off on Tube Muffle Furnace

Steel Quenching

Loss of Hardening-Power at and near V.—We know that steel is hardened by quenching from a certain red-heat or from any higher temperature; but that if the temperature be allowed to sink below this certain point in redness, quenching will not harden the metal. In short, as steel cools slowly through redness, it loses its hardening-power. Let us learn how and under what conditions this loss occurs, and especially how it is related to the V-change; and to this end let us quench many different pieces of steel, of each of many different grades of hardness, from different temperatures and under different conditions, and examine their ductility by bending tests and by tensile tests. The latter will incidentally inform us how tensile strength is affected by these various quenchings.

The object of this study is to learn whether the V-retardation, and hence the spontaneous evolution of heat which underlies it, corresponds to the loss of the hardening-power; and whether this loss begins at Va, ends at Vb, and progresses in the different parts of the V-range proportionally to the retardation.

Difficulty

As is pointed out at the end of (18), the progress of the V-retardation varies 60 much that, without very ….Read more

By | January 17th, 2017|Categories: Steel|Comments Off on Steel Quenching

Carbon-Steel Quenching & Thermal Curves Critical Points

Retardations

If high-carbon tool-steel be heated to very dull redness and then suddenly cooled, for instance by quenching in water, it is not thereby considerably hardened ; but such sudden cooling, if it be from bright redness, hardens the metal intensely. In the former case the steel can be scratched with a knife, in the latter it will scratch glass. The hardening power is thus acquired between low and high redness. As steel is gradually heated other striking changes occur in this range of temperature. The carbon changes from one state of combination with the iron known as that of “ hardening-carbon,” to another known as the “ non-hardening ” or “ cement ” state. “ The rise of temperature is retarded or perhaps even reversed; the expansion is checked and reversed, so that the metal contracts momentarily, and then re-expands; a dry crackling sound is heard ; the thermoelectric deportment becomes anomalous ; the coercive force and the power of being rendered a temporary magnet (whether by electric current or by another magnet) and hence of being attracted by the magnet, almost disappear, the latter at least through a series of distinct and separate diminutions; and the specific ….Read more

By | January 17th, 2017|Categories: Steel|Comments Off on Carbon-Steel Quenching & Thermal Curves Critical Points