39.37 inches) long, and, for smaller furnaces, 50 to 60 centimeters (19.68 to 23.62 inches). Scorification tongs

Fig. 46.

Fig. 46a.

Fig. 466.

Fig. 47.

with one arm forked, as shown in Fig. 46a, the horse

Fig. 48.

shoe part just large enough to fit the scorifier, 60 millimeters (2.36 inches) long and 45 millimeters (1.76 inches) wide; crucible tongs (Fig. 47) for wind and blast furnaces. Small assay plates of sheet iron, with handles. They are about 14 centimeters (5.5 inches) square, and are provided with 9 depressions each 28 millimeters (1.1 inches) wide, in which cornets, simple weights of lead (Bleischweren), etc., are kept. The following implements are required for manipulations in the furnace during roasting, fusing, etc.: curved stirring rods and spatulas of iron; iron ladles; tongs with curved tips (Fig. 466) for taking hold of cornets, buttons, etc.; cooling iron (Fig. 48). The blade of this for large muffle-furnaces is 9 centimeters (3.54 inches) long, 7 centimeters (2.75 inches)

wide, and 1 centimeter (0.39 inch) thick. It is provided with a handle 85 centimeters (33.4 inches) long. For small furnaces the respective dimensions are: 5 centimeters (1.96 inches), 4 centimeters (1.57 inches), 0.7 centimeter (0.27 inch), and 70 centimeters (27.55 inches).

C. Implements required for the reception and further treatment of the assay samples after they have been taken from the furnace.

1. For the reception of the assay samples are required; sheet-iron plates with handle. They are divided into squares by strips of sheet iron crossing each other, or have depressions, each about 4 centimeters (1.57 inches) wide, in which the assay vessels are placed; open and closed ingot moulds for casting lead and silver bars, ingots, etc.; small iron or leaden plates (Kornbleche), about 10 centimeters (3.93 inches) long and 60 millimeters (2.36 inches) wide, with depressions 3 centimeters (1.18 inches) wide for the reception of gold and silver buttons from the cupel; and boards of wood with larger depressions for the reception of buttons of base metals.

2. For the further treatment of the samples after they have become cold.—Hammers for breaking the clay crucibles, etc., and removing the slag from the buttons. The body of these is about 9 centimeters (3.54 inches) long, the head square, the other end running into a point (also smaller hammers); an anvil with a plate beneath it about 6 centimeters square (2.36 inches); cupel tongs (pliers), 160 centimeters (63 inches) long, for taking the buttons of silver and gold from the cupels; a button brush consisting of a brass holder with bristles at both ends; a bar magnet for extracting particles of iron from the slag, etc.

VII. Assay Reagents.

22. REAGENTS' FOR DRY ASSAYS.

According to their action they may be divided into1. Reducing agents.-Charcoal in the form of powder, or of small pieces placed on top of the charge (assays of lead, copper, etc.), or of crucible lining (assays of iron); when it is generally mixed with other reducing agents (potassium carbonate, sodium carbonate, etc.), because the presence of a large percentage of charcoal without additions in smelting processes renders the charge more difficultly fusible.

Powdered coke, anthracite, and graphite2 may also be used instead of powdered charcoal, but they are less combustible. Rosin, fat oils, tallow, sugar, etc., were formerly also employed. Bitartrate3 of potassium (argol) (KC,H,O), either crude or refined, yields considerable carbon in becoming carbonized, and in consequence exerts a vigorous reducing effect, but causes refractoriness. For this reason its percentage of carbon is reduced, if necessary, by mixing it in different proportions with saltpetre. The mixture is poured into a red-hot crucible, placed under a well-drawing chimney. The mixture deflagrates and emits empyreumatic vapors, when, by reason of a partial oxidation of the carbon, a mixture of potassium carbonate and carbon is formed. This is known as black flux. For vigorous reduction it is made from 1 part of saltpetre and 3 parts of argol; for less vigorous, either of 1 and 2, or 1 and 2 parts respectively. Another flux

Muspratt's techn. Chemie, 3d Aufl. Bolley, Handb. der techn. chem. Untersuchungen, 1879.

2 Werthbestimmung in Fresenius' Ztschr. 1875, p. 394.

Werth bestimmung in Fresenius' Ztschr. vii. 149.

containing potassium carbonate (without carbon), mostly with undecomposed saltpetre, and known as white flux, consists of 1 to 2 parts of saltpetre, and 1 part of argol; gray flux has 3 of argol to 2 of saltpetre. A mixture of argol and saltpetre, before it is deflagrated, is called raw flux. As black flux, on account of its hygroscopic properties, must be frequently prepared fresh, and this work is unpleasant by reason of the evolution of bad odors, a mixture of potassium carbonate (or soda) and flour (starch = CH10O), which is also cheaper, is used in preference. Usually 20 to 25 per cent. of wheat flour is taken, but for more vigorous reductions 30 to 35 per cent. (for instance in assays of copper), and even as much as 50 per cent. (assay of tin). When this mixture is used, a separation of carbon, in a fine state of division, takes place, with the exhibition of a yellow flame of carburetted hydrogen, caused by the carbonization of the flour during the fusing of the assay sample. The flame of the carburetted hydrogen must not be confounded with the blue flame of carbonic oxide. Mixtures of potassium carbonate (or of sodium carbonate) and coal-dust are less intimate, and their action is consequently less energetic than that of mixtures in which the carbon has been separated from organic substances in a very finely divided condition (tartaric acid, flour). Potassium cyanide, with 64.1 K and 35.9 Cy, is an energetic reducing (also desulphurizing) agent, even at a low temperature (assays of tin). Potassium ferrocyanide, K,Fe(CN), yields, on heating, a mixture of iron carbide, ferrous and ferric oxides, free carbon, and a small quantity of potassium cyanide. It has also a vigorous desulphurizing action.

The reducing power is estimated from the quantity of lead which is yielded by fusing 1 to 2 grammes (15.43 to

30.87 grains) of the reagent with 60 grammes (926.30 grains) of litharge and 15 grammes (231.48 grains) of sodium carbonate or potassium carbonate.

According to Berthier the reducing power of the various agents is as follows: 1 part hydrogen, 104; pure carbon, 34.31; well-glowed wood charcoal, 31.81; ordinary wood charcoal, 28.00; tallow, 15; sugar, 14.5; kiln-dried starch, 13; ordinary starch, 11; tartaric acid, 6; oxalic acid, 0.90; black flux with 2 parts of argol, 1.40; black flux with 24 parts of argol, 1.90; black flux with 3 parts of argol, 3.80; 94 parts soda and 6 wood charcoal, 1.80; 88 parts soda with 12 charcoal, 3.60; 90 parts of soda with 10 of sugar, 1.40; 90 parts of soda with 10 of starch, 1.15; 80 parts of soda with 20 parts of starch, 2.30; crude argol, 5.60; purified argol, 4.50; pure argol (carbonized), 3.10; potassium binoxalate (salt of sorrel), 0.90; white soda-soap, 16 parts.

2. Oxidizing agents.-Saltpetre, KNO3, with 46.56 K2O, and 53.44 NO. It should be as free from sulphates as possible.-Litharge, PbO, with 92.83 Pb, and 7.17 0, exerts an oxidizing effect upon metals and metallic sulphides (scorification), as well as upon organic substances (assay of fuel). As generally used it is in the form of red litharge free from particles of metallic lead.' It should completely dissolve in acetic acid, and be as free from gold and silver as possible. When it contains silver, white lead not adulterated with heavy spar, 2(PbCO3)+ Pb(HO), with 86.27 PbO, may be substituted for it. It is best to prepare this by the wet method (for instance, by that of Dietel, of Eisenach, which yields a product free from gold, silver, antimony, and copper).

'Dingler, cxciv. 84.