The best methods of preparing these powders are probably kept secret. The following are some of the published recipes:

1. Gold leaf, or alloys of gold, reduced to powder by grinding them with sulphate of potash, or with honey, and washing away the extraneous matter with hot water, and drying the metallic powder.

2. Dutch metal, and other similar alloys, treated in the same way.

3. Verdigris 4 oz., tutty 2 oz., sublimate 1 dr., borax 1 dr., nitre 1 dr., mix them into a paste with oil, and fuse the mixture in a crucible. This has failed in some hands - perhaps from the tutty being factitious.

4. Mix together 100 parts of sulphate of copper, and 50 of crystallized carbonate of soda; apply heat till they unite. Powder the mass when cold, and add 15 parts of copper filings; mix well, and keep it at a white heat for 20 minutes. Wash and dry the product.

See also Aurum Musivum, and Argentum Musivum, further back.

Bronzing Liquids, for Bronzing Copper Medals, Figures, Instruments, etc. 1. Sal ammoniac 1 dr., oxalic acid 15 grs.,vinegar a pint: after well cleaning the article to be bronzed, warm it gently, and brush it over with the liquid, using only a small quantity at a time. When rubbed dry, repeat the application till the desired tint is obtained. [For copper medals, electro-type, casts, etc.]

2. Bronze for Plaster Figures. Dissolve palm soap in water, and add a mixed solution of sulphate of copper and sulphate of iron until no further precipitate occurs. Dry the precipitate, and mix it with oil of turpentine, or linseed oil. Sulphate of copper alone produces too bright a green. Palmitate of iron is yellow. These may be precipitated separately, and mixed to the desired shade after being triturated with the oil. Ten ounces of soap will require 3 ounces of sulphate of copper.

3. Sal ammoniac 1 oz., cream of tartar 3 oz., salt 6 oz.; dissolve in a pint of hot water, add 2 oz. of nitre, and 2 oz. of nitrate of copper dissolved in 1/2 pint of water.

4. Salt of sorrel 1 oz., sal ammoniac 2 oz., white vinegar 14 oz. [To give an antique appearance to bronze figures,

5. A diluted solution of perchloride of platinum. [For copper binding screws, and other small articles.]

6. A weak solution of hydro-sulphuret (hydro-sulphide) of ammonia, or of sulphuret (sulphide) of potassium. [For electrotype medals.]

7. Immediately on removing the electrotype cast from the solution, brush it over with good black lead; then heat it moderately, and brush it over with a painting brush, the slightest moisture being used.

8. Boil 2 oz. of carbonate of ammonia and l oz. of acetate of copper in 1/2 pint of vinegar, until nearly all the vinegar is evaporated. Pour into this a solution of 62 grains of sal ammoniac, and 15 1/2 grains of oxalic acid, dissolved in 1/2 pint of vinegar; boil the whole and filter. Apply it to the medal (which should be perfectly bright, and previously warmed) with a camel-hair pencil for half a minute; then pour boiling water on it; wipe it with soft cotton very slightly moistened with linseed oil, and rub it with clean cotton. For electrotype copper medals. [They may also be bronzed by applying oxide of iron (jeweller's rouge, or crocus) in the same manner as directed above, for plumbago; or a mixture of these may be used.]

9. Tin Castings. Wash them over, after being well cleaned and wiped, with a solution of 1 part of sulphate of iron, and 1 of sulphate of copper, in 20 parts of water: afterwards with a solution of 4 parts of verdigris in 11 of distilled vinegar; leave for an hour to dry, then polish with a soft brush and colcothar.