water to a perfectly smooth paste, then dilute the mass with a proper quantity of soft water. The product resembles Stephen’s ‘patent blue ink.’
7. (Rev. J. B. Reade—patented.)—a. A solution of his patent soluble Prussian blue in distilled water. Blue.
b. Prepared by adding to good gall ink a strong solution of his soluble Prussian blue. This addition “makes the ink, which was previously proof against alkalies, equally proof against acids, and forms a writing fluid which cannot be erased from paper by any common method of fraudulent obliteration without the destruction of the paper.” This ink writes greenish blue, but afterwards turns intensely black. Stephen’s ‘patent ink,’ which does the same, is a similar compound.
8. (Prof. Runge—CHROMIC INK.) Logwood, in fine chips, 1⁄4 lb.; boiling water, 3 pints; digest for 12 hours, then simmer the liquid down gently to 1 quart, carefully observing to avoid dust, grease, and smoke; when cold, decant the decoction, and add to it of yellow chromate of potash, 20 gr.; dissolve by agitation, after which it will be fit for use. Cheap and good. It resists the action of all ordinary destructive agents better than the tanno-gallic inks; it may be washed after use with a wet sponge, or steeped for twenty-four hours in water, or even tested with dilute acids, and yet preserve its original blackness. It is perfectly liquid, it scarcely thickens by age, and neither deposits a sediment nor corrodes steel pens.
9. (Ure.) From vanadate of ammonia decomposed with infusion of galls. It is of a perfectly black hue, flows freely from the pen, is rendered blue by acids, is unaffected by dilute alkaline solutions, and resists the action of chlorine.
Obs. The preceding formulæ, under proper management, produce excellent products, all of which are extremely mobile, and most of them of a more or less beautiful colour. The blue ones, when concentrated, dry of a blue black, whilst two or three of the others, though at first pale, rapidly pass into a deep black, when exposed to the air. Care must be taken in all cases that the ingredients be pure. The Prussian blue, except when directly prepared for the purpose, should be washed in dilute hydrochloric acid before attempting its solution by means of oxalic acid. Unless these precautions are attended to, success is unlikely. A little gum may be added, if required, to prevent the fluid spreading on the paper; but in most cases the addition is no improvement. Most of the blue fluids may be used as ‘indelible ink’ to mark linen, and will be found very permanent, provided the part be first moistened with alum water, and dried.
XYLOID′IN. When starch is immersed in concentrated nitric acid (sp. gr. 1·45 to 1·50), it is converted, without disengagement of gas,
into a colourless, tremulous jelly, which, when treated with an excess of water, yields a white, curdy, insoluble substance, which after being edulcorated with pure water, until every trace of acid is removed, is xyloidin. Paper, sugar, gum, mannite, and several other substances, treated in the same manner, become in great part changed to xyloidin or analogous compounds.
Obs. Pure xyloidin differs but slightly from pyroxylin, or pure gun-cotton.
XYL′OL. A hydrocarbon, homologous to benzol, found in wood-tar and coal-gas naphtha.