Removing Tin From Plates Without Acid

Boil the scrap-tin with soda lye in presence of litharge.

Welding Powders For Iron And Steel

(1) Iron filings 1000 parts, borax 500, balsam copaiva, or other resinous oil, 50, salammoniac 75. Mix together, heat, and pulverize. Weld at cherry-red. (2) Borax 15 parts, sal-ammoniac 2, cyanide of potassium 2. These constituents are dissolved in water, and the water itself afterward evaporated at a low temperature.

Black Color For Zinc

Clean the surface with sand and sulphuric acid, and immerse for an instant in a solution of sulphate of nickel and ammonia 4 parts, in water 40 parts, acidulated with sulphuric acid 1 part. Wash and dry. This takes a bronze color on burnishing.

Ink For Writing On Zinc Labels

(1) Verdigris 1 oz., sal-ammoniac 1 oz., lampblack 1/2 oz., water \ pint; mix well in a mortar, and shake before using. Write with a quill. (2) One drachm chloride of platinum dissolved in 1/2 pint water.

Painting Zinc

Use a mordant of chloride of copper 1 part, nitrate of copper 1, sal-ammoniac 1, dissolved in water 64. Add hydrochloric acid (commercial) 1. This brushed over the zinc sheets gives them a deep black color, turning grayish after drying, in from 12 to 24 hours. A coat of oil-color will adhere to this surface and withstand weather excellently.

How To Restore Zinc-White

This may be done by ignition in an earthen crucible.

How To Make A Cheap Leyden Jar

Line a thin glass candy-jar inside and outside with tin-foil, such as is used to wrap chewing-tobacco in. Stick the foil, on with mucilage, varnish, or flour paste. A still cheaper plan is simply to fill a glass jar nearly full of water, and place it within another vessel of water, so that the water, both outside and inside, shall be on the same level.

How To Find The Meridian

Mr. George W. Blunt says: "Take a piece of board, or any similar material, and describe on it a number of concentric circles. Place this in the sun; over the centre hang a plummet. Observe the shortest shadow from the plummet; the sun will then be on the meridian; draw a line to the centre of the circle, and that will be the true meridian-line. This will do to mark the apparent time, or to correct the compass for variation."

How To Make Globe Mirrors

Melt together 1 oz. clean lead and 1 oz. of fine tin in a clean iron ladle; then immediately add 1 oz. bismuth. Skim off the dross, remove the ladle from the-fire, and before it sets add 10 ozs. quicksilver; now stir the whole carefully together, taking care not to breathe over it, as the fumes of mercury are very pernicious. Pour this through an earthen pipe into the glass globe, which turn repeatedly around.

Thermometers

To change Fahrenheit degrees into Centi grade: C.=5(F.-32)/9 Centigrade into Fahrenheit: F. =9C/5+ 32.

Reaumur into Fahrenheit: F.=9 R/4+ 32. Fahrenheit into

Reaumur: R.=4(F.-32)/9• Reaumur into Centigrade: C=5 R/4

Centigrade into Reaumur: R.=4C/5.