4. Cochineal (in powder), 1 oz.; hot water, 1⁄2 pint; digest, and when quite cold, add of spirit of hartshorn, 1⁄4 pint (or liquor of ammonia, 1 oz., diluted with 3 or 4 oz. of water); macerate for a few days longer, and then decant the clear. Very fine.
5. (Buchner.) Pure carmine, 20 gr.; liquor of ammonia, 3 fl. oz.; dissolve, then add of powdered gum, 18 gr. Half a drachm of powdered drop lake may be substituted for the carmine where expense is an object. Colour superb.
6. (Henzeler.) Brazil wood, 2 oz.; alum and cream of tartar, of each 1⁄2 oz.; rain water, 16 fl. oz.; boil to one half, strain, add of gum (dissolved), 1⁄2 oz.; and when cold, further add a tincture made by digesting powdered cochineal, 11⁄2 dr., in rectified spirit, 11⁄2 fl. oz.
7. (Redwood.) Garancine and liquor of ammonia, of each 1 oz.; distilled water (cold), 1 pint; triturate together in a mortar, filter, and dissolve in the solution, gum Arabic 1⁄2 oz.
Ink, Se′pia. See Sepia.
Ink, Sil′ver. From silver leaf or powdered silver, as GOLD INK.
Ink, Sympathet′ic. Syn. Diplomatic ink, Invisible i. Fluids which, when used for writing, remain invisible until the paper is heated, or acted on by some other chemical agent. Sympathetic inks have been frequently employed as the instruments of secret correspondence, and have often escaped detection; but by heating the paper before the fire until it begins to grow discoloured by the heat, the whole of them may be rendered visible.
The following are the most common and amusing sympathetic inks:—1. Sulphate of copper and sal ammoniac, equal parts, dissolved in water; writes colourless, but turns YELLOW when heated.—2. Onion juice; like the last.—3. A weak infusion of galls; turns BLACK when moistened with weak copperas water:—4. A weak solution of sulphate of iron; turns BLUE when moistened with a weak solution of prussiate of potassa, and BLACK when moistened with infusion of galls.—5. The diluted solutions of nitrate of silver and of terchloride of gold; become respectively DARK BROWN and PURPLE when exposed to the sunlight.—6. Aqua fortis, spirits of salts, oil of vitriol, common salt, or saltpetre, dissolved in a large quantity of water; turns YELLOW or BROWN when heated.—7. Solution of chloride or nitromuriate of cobalt; turns GREEN when heated, and disappears again on cooling. If the salt is pure, the marks turn BLUE.—8. Solution of acetate of cobalt, to which a little nitre has been added; becomes ROSE COLOURED when heated, and disappears on cooling.—9. A weak solution of the mixed chlorides of cobalt and nickel; turns GREEN. The last three are about the best of our sympathetic inks.—10. Solution of acetate of lead; turns BROWNISH-BLACK when exposed to the fumes of sulphuretted hydrogen.—11. A weak solution of nitrate of mercury; turned BLACK by heat and sulphuretted fumes.—12. Rice water or decoction of starch; turned BLUE by a solution of iodine in weak spirit, and by the fumes of iodine, if the paper is first slightly moistened by exposure to steam or damp air.
Ink, Vi′olet. The same as PURPLE INK, but weaker.
Ink, Yel′low. 1. From gamboge (in coarse powder), 1 oz.; hot water, 5 oz.; dissolve, and when cold, add of spirit, 3⁄4 oz.