METALS AND THEIR TREATMENT

METAL CEMENTS: See Adhesives and Lutes.

METAL CLEANING: See Cleaning Preparations and Methods.

METAL INLAYING: See Damaskeening.

METAL POLISHES: See Polishes.

METAL PROTECTIVES: See Rust Preventives.

METAL VARNISHES: See Varnishes.

METALS, HOW TO ATTACH TO RUBBER: See Adhesives, under Rubber Cements.

METALS, SECURING WOOD TO: See Adhesives.

Metals, Brightening And Deadening, By Dipping:

Brightening Pickle.

For a burnish-dip any aqua fortis over 33° Bé., i. e., possessing a specific gravity of 1.30, may be employed. It is advisable not to use highly concentrated aqua fortis, to reduce the danger of obtaining matt work. It is important that the quantity of oil of vitriol, which is added, {470} is correct. It is added because the action of the aqua fortis is very uncertain. Within a short time it becomes so heated in acting on the metals that it turns out only dull work, and pores or even holes are apt to be the result of the violent chemical action. If the aqua fortis is diluted with water the articles do not become bright, but tarnish. For this reason sulphuric acid should be used. This does not attack the metals; it only dilutes the aqua fortis and distributes the heat generated in pickling over a larger space. It is also much cheaper, and it absorbs water from the aqua fortis and, therefore, keeps it in a concentrated state and yet distributed over the space.

In the case of too much oil of vitriol the dilution becomes too great and the goods are tarnished; if too little is added, the mixture soon ceases to turn out bright articles, because of overheating. On this experience are based the formulas given below.

Dip the articles, which must be free from grease, into the pickle, after they have been either annealed and quenched in diluted sulphuric acid or washed out with benzine. Leave them in the dipping mixture until they become covered with a greenish froth. Then quickly immerse them in a vessel containing plenty of water, and wash them out well with running water. Before entering the dipped articles in the baths it is well to remove all traces of acid, by passing them through a weak soda or potassium cyanide solution and washing them out again. If the brightly dipped goods are to remain bright they must be coated with a thin spirit or zapon lacquer.

Following are two formulas for the pickle:

I.—Aqua fortis, 36° Bé., by weight100 parts
Oil of vitriol (sulphuric acid), 66° Bé., by weight 70 parts
Cooking salt, by volume  1 1/2 parts
Shining soot (lampblack), by volume  1 1/2 parts
II.—Aqua fortis, 40° Bé., by weight100 parts
Oil of vitriol, 66° Bé., by weight100 parts
Cooking salt, by volume  2 parts
Shining soot, by volume  2 parts
Matting Or Deadening Pickle.

Nitric acid of 36° Bé., 200 parts, by volume; sulphuric acid of 56° Bé., 200 parts, by volume; sea salt, 1 part, by volume; zinc sulphate, 1 to 5 parts, by volume.

With this proportion of acids the articles can remain from 5 to 20 minutes in the mixture cold; the prominence of the matt depends on the length of time of the immersion. The pieces on being taken from the bath have an earthy appearance which is lightened by dipping them quickly in a brightening acid. If left too long the matted appearance is destroyed.

Cotton Matt.
Silver Matt.
Dangers Of Dipping.

Coloring Metals:

See also Plating.

Processes By Oxidation.

Bronzing of Steel.—I.—The piece to be bronzed is wet by the use of a sponge with a solution formed of iron perchloride, cupric sulphate, and a nitric acid. It is dried in a stove at 86° F., then kept for 20 minutes over boiling water. It is dried again at 86° F., and rubbed with a scratch brush.

This operation is repeated several times.

Bronzing of Steel.—II.—Rust and grease are removed from the objects with a paste of whiting and soda. They are immersed in a bath of dilute sulphuric acid, and rubbed with very fine pumice-stone powder. They are then exposed from 2 to 3 minutes to the vapor of a mixture of equal parts of concentrated chlorhydric and nitric acids.

The object is heated to 570° to 660° F. until the bronze color appears. When cooled, it is covered with paraffine or vaseline while rubbing, and heated a second time until the vaseline or paraffine commences to decompose. The operation is repeated. The shades obtained are beautiful, and the bronzing is not changeable. By subjecting the object to the vapors of the mixture of chlorhydric and nitric acids, shades of a light reddish brown are obtained. By adding to these two acids acetic acid, beautiful yellow bronze tints are procured. By varying the proportion of these three acids, all the colors from light reddish brown to deep brown, or from light yellow bronze to deep yellow bronze, are produced at will.

Bronzing.—III.—Under the name of Tuker bronze, a colored metal is found in trade which imitates ornamental bronze perfectly. It is obtained by deoxidizing or, if preferred, by burnishing cast iron. A thin layer of linseed oil or of linseed-oil varnish is spread on. It is heated at a temperature sufficient for producing in the open air the oxidation of the metal. The temperature is raised more or less, according as a simple yellow coloration or a deep brown is desired.

Lustrous Black.—In a quantity of oil of turpentine, sulphuric acid is poured drop by drop, stirring continually until a precipitate is no longer formed. Then the whole is poured into water, shaken, decanted, and the washing of the precipitate commenced again until blue litmus paper immersed in the water is no longer reddened. The precipitate will thus be completely freed from acid. After having drained it on a cloth, it is ready for use. It is spread on the iron and burned at the fire.

If the precipitate spreads with difficulty over the metal, a little turpentine can be added. It is afterwards rubbed with a linen rag, soaked with linseed oil, until the surface assumes a beautiful lustrous black. This covering is not liable to be detached.

Bluish Black.—Make a solution composed of nitric acid, 15 parts; cupric sulphate, 8 parts; alcohol, 20 parts; and water, 125 parts. Spread over the metal when well cleaned and grease removed. Dry and rub with linen rag.

Black.—Make a solution composed of cupric sulphate, 80 parts; alcohol, 40 parts; ferric chloride, 30 parts; nitric acid, 20 parts; ether, 20 parts; water, 400 to 500 parts, and pass over the object to be blackened.

Magnetic Oxide.—I.—A coating of magnetic oxide preserves from rust. To obtain it, heat the object in a furnace to a temperature sufficient to decompose steam. Then inject from 4 to 6 hours superheated steam at 1,100° F. The thickness of the layer of oxide formed varies with the duration of the operation. This process may replace zincking, enameling, or tinning.

II.—A deposit of magnetic oxide may be obtained by electrolysis. The iron object is placed at the anode in a bath of distilled water heated to 176° F. The cathode is a plate of copper, or the vessel itself if it is of iron or copper. By electrolysis a layer of magnetic oxide is formed.

In the same way other peroxides may be deposited. With an alkaline solution of litharge a brilliant black deposit of lead peroxide, very adherent, is obtained.

The employment of too strong a current must be avoided. It will produce a pulverulent deposit. To obtain a good coating, it is necessary after leaving the objects for a moment at the opposite {472} pole, to place them at the other pole until the outside is completely reduced, then bring them back to the first place.

Processes By Sulphuration.

Brilliant Black.—Boil 1 part of sulphur and 10 parts turpentine oil. A sulphurous oil is obtained of disagreeable odor. Spread this oil with the brush as lightly as possible, and heat the object in the flame of an alcohol lamp until the patina takes the tint desired. This process produces on iron and steel a brilliant black patina, which is extremely solid.

Blue.—Dissolve 500 drachms of hyposulphite of soda in 1 quart of water, and 35 grains of lead acetate in 1 quart of water. The two solutions mingled are heated to the boiling point. The iron is immersed, and assumes a blue coloration similar to that obtained by annealing.

Deposit Of A Metal Or Of A Non-oxidizable Compound.

Black.—I.—Make a paste composed of equal parts of chloride of antimony and linseed oil. Spread on the object, previously heated, with a brush or rag; then pass over it a coating of wax and brush it. Finally varnish with gum lac.

II.—Prepare a solution of bismuth chloride, 10 parts; mercury chloride, 20 parts; cupric chloride, 10 parts; hydrochloric acid, 60 parts; alcohol, 50 parts; water, 500 parts. Add fuchsine in sufficient quantity to mask the color.

The mercury chloride is poured into the hydrochloric acid, and the bismuth chloride and cupric chloride added; then the alcohol. Employ this mixture with a brush or a rag for smearing the object. The object may also be immersed in the liquid if it is well cleaned and free from grease. It is dried and afterwards submitted to boiling water for half an hour. The operation is repeated until the wished-for tint is obtained; then the object is passed into the oil bath and taken to the fire without wiping. The object may also be placed for 10 minutes in boiling linseed oil.

Brown Tint.—A solution is made of chloride of mercury, 20 parts; cupric chloride, 10 parts; hydrochloric acid, 60 parts; alcohol, 50 parts; water, 500 parts. The object is plunged into this solution after being well cleaned. The solution may also be applied with a brush, giving two coats. It is afterwards put into hot water. The surface of the object is covered with a uniform layer of vegetable oil. It is placed in a furnace at a high temperature, but not sufficient for carbonizing the oil. The iron is covered with a thin layer of brown oxide, which adheres strongly to the metal, and which can be beautifully burnished, producing the appearance of bronze.

Brilliant Black.—The process begins by depositing on the object, perfectly clean and free from grease, a layer of metallic copper. For this purpose the following solutions are prepared: (a) Cupric sulphate, 1 part; water, 16 parts. Add ammonia until complete dissolution. (b) Chloride of tin, 1 part; water, 2 parts; and chlorhydric acid, 2 parts. The object is immersed in solution b, and afterwards in solution a. In this way there is deposited on the iron a very adherent coating of copper. The object, washed with water, is afterwards rubbed with sulphur, or immersed in a solution of ammonium sulphhydrate. A dull black coating of cupric sulphide is produced, which becomes a brilliant black by burnishing.

Blue Black.—The iron object is first heated according to the previous recipe, but the copper is converted into cupric sulphide, not by a sulphhydrate, but by a hyposulphite. It is sufficient to dip the coppered object into a solution of sodium hyposulphite, acidulated with chlorhydric acid, and raised to the temperature of 175° to 195° F.

Thus a blue-black coating is obtained, unchangeable in air and in water. After polishing, it has the color of blue steel. It adheres strongly enough to resist the action of the scratch brush.

Deposition of Molybdenum.—Iron is preserved from rust by covering it with a coating of molybdenum, as follows: Water, 1,000 parts; ammonium molybdate, 1 part; ammonium nitrate, 15 to 20 parts. Suspend the object at the negative pole of a battery. The current ought to have a strength of 2 to 5 amperes per cubic decimeter.

Deposit of Manganese Peroxide.—The {473} iron or steel is first covered with a coating of manganese peroxide by immersing as an anode in a bath containing about 0.05 per cent of chloride or sulphate of manganese and from 5 to 25 per cent of ammonium nitrate. The bath is electrolyzed cold, making use of a cathode of charcoal. Feeble currents (1 or 2 amperes) produce an adherent and unchangeable deposit.

Bronzing of Cannon.—Prepare a solution of ferric chloride of density 1.281, 14 parts; mercury chloride, 3 parts; fuming nitric acid, 3 parts; cupric sulphate, 3 parts; water, 80 parts. Give to the piece of ordnance 2 or 3 coatings of the solution, taking care always to scratch the preceding layer with a steel brush before spreading the second. Afterwards, the object is plunged in a solution of potassium sulphide in 900 parts of water. It is left in this for 10 days. It is removed by washing with soap and hot water. The object is rinsed, dried, and finally brushed with linseed-oil varnish.

Green Bronzing.—Dissolve 1 part of acetate of silver in 20 parts of essence of lavender; coat the surface of iron with this liquid by means of a brush and raise the temperature to 292° F. A brilliant green color is developed on the surface.

Coating on Steel Imitating Gilding.—The object is first covered by the galvanic method by means of a solution of cyanide of copper and potassium, then covered electrolytically with a thin deposit of zinc. It is dried and cleaned with a little washed chalk and finally immersed in boiling linseed oil. The surface of the piece after a few seconds, at a temperature of 310° F., appears as if there had been a real penetration of copper and zinc; that is to say, as though there were a formation of tombac.

Bronzing of Cast Iron.—The piece, when scraped, is coppered with the following bath: Cupric chloride, 10 parts; hydrochloric acid, 80 parts; nitric acid, 10 parts. It is rubbed with a rag and washed with pure water, and then rubbed with the following solution: Ammonium chlorhydrate, 4 parts; oxalic acid, 1 part; water, 30 parts.

Gilding of Iron and Steel.—Chloride of gold is dissolved either in oil of turpentine or in ether, and this solution is applied with the brush on the metallic surface, after being perfectly scraped. It is allowed to dry, and then heated more or less strongly for obtaining the necessary adherence. When it is dry the gilding is burnished.

Process By Deposit Of A Color Or Varnish.

The metallic objects are immersed in a colorless varnish with pyroxyline, and dried in a current of hot air at 176° F. When the varnish is sufficiently dry, the objects are bathed for a few minutes in a 2 per cent alcoholic solution of alizarine or of a color of the same group. By washing with water the yellowish color covering the object on coming from the coloring bath passes to the golden red.

Coloring Copper.
Coloring Brass.

To blue copper or brass any one of the following recipes may be used:

I.—Dip the article in a solution of 2 ounces of liver of sulphur and 2 ounces of chlorate soda in 1,000 ounces of water.

II.—Dip the article in a solution of ferrocyanide of potassium very strongly acidulated with hydrochloric acid.

III.—Stir the article about constantly in a solution of liver of sulphur in 50 times its weight of water.

Fusion Point Of Metals.

To Produce Fine Leaves Of Metal.

A thin sheet of polished copper is entered in the bath and connected with the {474} electric conduit. The current precipitates gold on it. In order to loosen it, the gilt copper plate is placed in a solution of ferric chloride, which dissolves the copper and leaves the gold behind. In this manner gold leaf can be hammered out to almost incredible thinness.

Metal Foil.

Tin foil is the most common foil used, being a combination of tin, lead, and copper, sometimes with properties of other metals.

I
Per cent		II
Per cent		III
Per cent
Tin97.6098.4796.21
Copper 2.11 0.38 0.95
Lead 0.04 0.84 2.41
Iron 0.11 0.12 0.09
Nickel—— 0.30

I is a mirror foil; III is a tin foil.

Tin Foils for Capsules.—

I
Per cent		II
Per cent
Tin2022
Lead8077
Copper— 1

Tin Foils for Wrapping Cheese, etc.—

I
Per cent		II
Per cent		III
Per cent
Tin979092
Lead 2.5 7.8 7
Copper 0.5 0.2 1

Tin Foils, for Fine Wrapping, I and II; for Tea Boxes, III.—

I
Per cent		II
Per cent		III
Per cent
Tin606540
Lead403558.5
Copper—— 1.5

Imitation Gold Foils.—

Deep
gold
Per cent		Pure
gold
Per cent		Pale
gold
Per cent
Copper84.57876
Zinc15.52214
Deep
gold
Per cent		Deep
gold
Per cent
Gold
Per cent
Copper918683
Zinc 91417
reddishdark
yellow		pale
yellow

Imitation Silver Foil.—Alloy of tin and zinc: harder than tin and softer than zinc: Zinc, 1 part; tin, 11 parts.

To Attach Gold Leaf Permanently.—Dissolve finely cut isinglass in a little water, with moderate heat, which must not be increased to a boil, and add as much nitric acid as has been used of the isinglass. The adhesive will not penetrate the cardboard or paper.

METH: See Mead.

METHEGLIN: See Mead.

METHYL SALICYLATE, TO DISTINGUISH FROM OIL OF WINTERGREEN: See Wintergreen.

METOL DEVELOPER: See Photography.

METRIC WEIGHTS: See Weights and Measures.

MICE POISON: See Rat Poison.

MICROPHOTOGRAPHS: See Photography.