Take a strong solution of quicksilver, made with spirit of nitre; dilute it with water, and pour it into a hot glass, rinsed in strong spirit of sea-salt, and it will instantly become coloured. Or, if a solution of silver, made with spirit of nitre, considerably diluted, be poured into a glass, prepared in the manner above-mentioned, it will produce the same effect. And if you pour hot water upon new-made crocus metallorum, and put it into a clean glass, rinsed with any acid, it will produce an orange colour.
To produce a Colour which appears and disappears by the Influence of the Air.
Put into a decanter some volatile spirit, in which you have dissolved copper filings, and you will have a fine blue tincture; and if the bottle be stopped, the colour will soon return again; and this experiment may be repeated a considerable number of times.
To turn a colourless Liquor Black, by adding a White Powder to it.
Put a hot weak pellucid infusion of galls into a glass, and throw into it a grain of the vitriol of iron, calcined to whiteness, and considerably heated; then, as it falls to the bottom, it will make a black cloud, which will uniformly diffuse itself through the transparent liquor, and gradually turn it black.
The same effect may also be produced by the addition of a little vitriol of iron calcined to a yellow colour, or by the colcothar of vitriol calcined to redness.
The black liquor, produced as above, may be rendered pellucid again, by pouring the liquor hot into a glass rinsed with the pure acid of vitriol. And to make this transparent liquor black again, pour to it as much hot oil of tartar per deliquium as will saturate the acid, which has attracted the metallic matter.
Freezing Mixture.
In the time of snow, a freezing mixture may easily be made, by mixing a little snow and common salt in a basin near the fire. If water in an iron cup or phial be put into this mixture, it will immediately be frozen; and if pounded ice and common salt be added, it will have a still more powerful effect.