Dissolve a small portion of green-copperas in water, and soak in it sheets of writing paper, so as to allow them to be taken out whole, and then dried; then, cover the paper with very finely powdered galls, and write on it with a pen dipped in water; when dry, brush off the galls, and the writing will appear.
TWO LIQUIDS MAKE A SOLID.
Dissolve muriate of lime in water until it will dissolve no more; make also a similar solution of carbonate of potash; both will be transparent fluids; but if equal quantities of each be mixed and stirred together, they will become a solid mass.
TWO SOLIDS MAKE A LIQUID.
Rub together in a mortar, equal quantities of the crystals of Glauber’s salts and nitrate of ammonia, and the two salts will slowly become a liquid.
A SOLID OPAQUE MASS MADE A TRANSPARENT LIQUID.
Take the solid mixture of the solutions of muriate of lime and carbonate of potash, pour upon it a very little nitric acid, and the solid opaque mass will be changed to a transparent liquid.
TWO COLD LIQUIDS MAKE A HOT ONE.
Mix four drams of sulphuric acid, (oil of vitrol,) with one dram of cold water, suddenly, in a cup, and the mixture will be nearly half as hot again as boiling water.