Part 262

Mix thoroughly and gradually incorporate the shellac solution.

II.—Prussian blue 2 ounces Lampblack 1 ounce Gum arabic 3 ounces Glycerine, sufficient.

Triturate together the dry powders and then make into a suitable paste with glycerine.

«Indelible Stencil Inks.»—I.—Varnish such as is used for ordinary printing ink, 1 pound; black sulphuret of mercury, 1 pound; nitrate of silver, 1 ounce; sulphate of iron, 1 ounce; lampblack, 2 tablespoonfuls. Grind all well together; thin with spirits turpentine as desired.

II.—Sulphate of manganese, 2 parts; lampblack, 1 part; sugar, 4 parts; all in fine powder and triturated to a paste in a little water.

III.—Nitrate of silver, 1⁠/⁠4 ounce; water, 3⁠/⁠4 ounce. Dissolve, add as much of the strongest liquor of ammonia as will dissolve the precipitate formed on its first addition. Then add of mucilage, 1 1⁠/⁠2 drachms, and a little sap green, syrup of buckthorn, or finely powdered indigo, to color. This turns black on being held near the fire, or touched with a hot iron.

«SYMPATHETIC INKS:»

Table of Substances Used in Making Sympathetic Inks.—

For writing and for bringing out the writing:

Cobalt chloride, heat.

Cobalt acetate and a little saltpeter, heat.

Cobalt chloride and nickel chloride mixed, heat.

Nitric acid, heat.

Sulphuric acid, heat.

Sodium chloride, heat.

Saltpeter, heat.

Copper sulphate and ammonium chloride, heat.

Silver nitrate, sunlight.

Gold trichloride, sunlight.

Ferric sulphate, infusion of gallnuts or ferrocyanide of potassium.

Copper sulphate, ferrocyanide of potassium.

Lead vinegar, hydrogen sulphide.

Mercuric nitrate, hydrogen sulphide.

Starch water, tincture of iodine or iodine vapors.

Cobalt nitrate, oxalic acid.

Fowler’s solution, copper nitrate.

Soda lye or sodium carbonate, phenolphthaleine.

A sympathetic ink is one that is invisible when written, but which can be made visible by some treatment. Common milk can be used for writing, and exposure to strong heat will scorch and render the dried milk characters visible.