In a work of this kind, dealing with the various elements, the boy should have at hand recipes or formulas for everything which comes within the province of his experiments. The following are most carefully selected, the objects being to present those which are the more easily compounded.

Adhesives For Various Uses

Waterproof glue. Use a good quality of glue, and dissolve it in warm water, then add one pound of linseed oil to eight pounds of the glue. Add three ounces of nitric acid.

Leather or Card-board Glue. After dissolving good glue in water, to which a little turpentine has been added, mix it with a thick paste of starch, the proportion of starch to glue being about two to every part of glue used. The mixture is used cold.

A fine Belt Glue. Dissolve 50 ounces of gelatine in water, and heat after pouring off the excess water. Then stir in five ounces of glycerine, ten ounces of turpentine, and five ounces of linseed oil varnish. If too thick add water to suit.

For cementing Iron to Marble. Use 30 parts of Plaster of Paris, 10 parts of iron filings, and one half part of sal ammoniac. These are mixed up with vinegar to make a fluid paste.

To cement Glass to Iron. Use 3 ounces of boiled linseed oil and 1 part of copal varnish, and into this put 2 ounces of litharge and 1 ounce of white lead and thoroughly mingle so as to make a smooth paste.

Water-proof Cement. Boiled linseed oil, 6 ounces; copal, 6 ounces; litharge, 2 ounces; and white lead, 16 ounces. To be thoroughly incorporated.

To unite rubber or leather to hard substances. One ounce of pulverized gum shellac dissolved in 9 1/2 ounces of strong ammonia, will make an elastic cement. Must be kept tightly corked.

For uniting iron to iron. Use equal parts of boiled oil, white lead, pipe clay and black oxide of manganese, and form it into a paste.

Transparent Cement. Unite 1 ounce of india rubber, 67 ounces of chloroform, and 40 ounces of mastic. This is to be kept together for a week, and stirred at times, when it will be ready for use.

To Attach Cloth to Metal. Water 100 parts, sugar 10 parts, starch 20 parts, and zinc chloride 1 part. This must be first stirred and made free of lumps, and then heated until it thickens.

United States Government Gum. Dissolve 1 part of gum arabic in water and add 4 parts of sugar and 1 part of starch. This is then boiled for a few minutes, and thinned down as required.

To Make Different Alloys

Silver-aluminum. Silver one-fourth part, and aluminum three-fourth parts.

Bell-metal. Copper, 80 parts; tin, 20 parts. Or, copper, 72 parts; tin, 26 parts; zinc, 2 parts. Or, copper 2; 1 of tin.

Brass. Copper, 66 parts; zinc, 32 parts; tin, 1 part; lead, 1 part.

Bronzes. Copper, 65 parts; zinc, 30 parts; tin, 5 parts. Or, copper, 85 parts; zinc, 10 parts; tin, 3 parts; lead, 2 parts.

German Silver. 52 parts of copper; 26 parts zinc; 22 parts nickel.

For Coating Mirrors. Tin, 70 parts; mercury, 30 parts.

Boiler Compounds

To prevent scaling. Use common washing soda, or Glauber salts.

To Dissolve Celluloid

Use 50 parts of alcohol and 5 parts of camphor for every 5 parts of celluloid. When the celluloid is put into the solution it will dissolve it.

To Soften Celluloid. This may be done by simply heating, so it will bend, and by putting it in steam, it can be worked like dough.

Clay Mixture For Forges

Mix dry 20 parts of fire clay, 20 parts cast-iron turnings, one part of common salt, and 1/2 part sal ammoniac, and then add water while stirring, so as to form a mortar of the proper consistency. The mixture will become very hard when heat is applied.

A Modeling Clay. This is made by mixing the clay with glycerine and afterwards adding vaseline. If too much vaseline is added it becomes too soft.

Fluids For Cleaning Clothes, Furniture, Etc

For Delicate Fabrics. Make strong decoction of soap bark, and put into alcohol.

Non-inflammable Cleaner. Equal parts of acetone, ammonia and diluted alcohol.

Taking dried paint from clothing. Shake up 2 parts of ammonia water with 1 part of spirits of turpentine.

Cleaning Furniture, etc. Unite 2.4 parts of wax; 9.4 parts of oil of turpentine; 42 parts acetic acid; 42 parts citric acid; 42 parts white soap. This must be well mingled before using.

Removing Rust from Iron or Steel. Rub the surface with oil of tartar. Or, apply turpentine or kerosene, and after allowing to stand over night, clean with emery cloth.

For Removing Ink Stains from Silver. Use a paste made of chloride of lime and water.

To clean Silver-Plated Ware. Make a mixture of cream of tartar, 2 parts; levigated chalk, 2 parts; and alum, 1 part. Grind up the alum and mix thoroughly.

Cleaning a Gas Stove. Make a solution of 9 parts of caustic soda and 150 parts of water, and put the separate parts of the stove in the solution for an hour or two. The parts will come out looking like new.

Cleaning Aluminum. A few drops of sulphuric acid in water will restore the luster to aluminum ware.

Oil Eradicator. Soap spirits, 100 parts; ammonia solution, 25; acetic ether, 15 parts.

Disinfectants

Camphor, 1 ounce; carbolic acid (75 per cent.), 12 ounces; aqua ammonia, 10 drachms; soft salt water, 8 drachms.

Water-Closet Deodorant. Ferric chloride, 4 parts; zinc chloride, 5 parts; aluminum chloride, 4 parts; calcium chloride, 5 parts; magnesium chloride, 3 parts; and water sufficient to make 90 parts. When all is dissolved add to each gallon 10 grains of thymol and a quarter-ounce of rosemary that had been previously dissolved in six quarts of alcohol.

Odorless Disinfectants. Mercuric chloride, 1 part; cupric sulphate, 10 parts; zinc sulphate, 50 parts; sodium chloride, 65 parts; water to make 1,000 parts.

Emery for Lapping Purposes. Fill a pint bottle with machine oil and emery flour, in the proportion of 7 parts oil and 1 part emery. Allow it to stand for twenty minutes, after shaking up well, then pour off half the contents, without disturbing the settlings, and the part so poured off contains only the finest of the emery particles, and is the only part which should be used on the lapping roller.