Inks are fluids of various kinds suitable for writing with pens. The chief inks in use are black, blue, and red writing inks, and indelible or marking ink, intended for marking linen which has to be washed. Indian ink is not used as an ink, properly so called. All the black inks in use are composed of green vitriol (sulphate of iron), in union with some astringent vegetable matter, the best is the gall-nut, although, for cheapness, logwood and oak bark have each been used. An excellent black ink may be made by putting into a gallon stone bottle twelve ounces of bruised galls, six ounces of green vitriol, and six of common gum, and filling up the bottle with rain water, this should be kept three or four weeks before using, shaking the bottle from time to time. Blue ink has lately been much used, it is made by dissolving newly-formed Prussian blue in a solution of oxalic acid. To make it, dissolve some yellow prussiate of potash in water in one vessel, and some sulphate of iron in another, adding a few drops of nitric acid to the sulphate of iron; now mix the two liquids, and a magnificent blue color will appear in the form of a light sediment; this is to be put upon a paper filter, and well washed by pouring over it warm water and allowing it to run through; a warm solution of oxalic acid should now be mixed with it, and the Prussian blue will dissolve into a bright blue ink. Red ink is made by boiling chips or raspings of Brazil wood in vinegar, and adding a little alum and gum; it keeps well, and is of a good color. A red ink of more beautiful appearance, but not so durable, may be made by dissolving a few grains of carmine in two or three tea-spoonfuls of spirit of hartshorn. Marking ink is made by dissolving nitrate of silver in water, and then adding some solution of ammonia, a little gum water, and some Indian ink to color it. Printers’ ink is made by grinding drying oil with lamp-black. CHARCOAL. Illustration: (‡ CHARCOAL OVENS.)