INK 283 A combination of nutgalls with sulphate of iron was long the only suitable black solution known. The galls contain four vegetable sub- stances, viz., gallic and tannic acids, mucilage, and extractive matter. The acids are regarded as more particularly necessary to a good ink, forming with the oxide of iron of the copperas a tanno-gallate of iron. Of the three causes of the deterioration of ink mouldiness, the sepa- ration of the black coloring matter, and the change of color Dr. Bostock, in an able paper in the " Transactions of the Society of Arts " for 1830, attributes the first to the mucilage, the second to the extractive matter, and the third to the tannin, which is disposed to de- compose and thus involve the destruction of the compound of which it is an ingredient. The more nearly the ink approaches the com- position of a gallate of iron, the more perma- nent he regards it. Several of the recipes re- quire long exposure of the decoction of galls to the air, after this is obtained by boiling in water, the effect of which is to convert much of the tannin into gallic acid. Dr. Bostock recommends that the galls should be macerated for some hours in hot water, and the fluid fil- tered ; the filtrate should then be exposed for two weeks to a warm atmosphere, when any fungoid growth that forms must be removed ; and the infusion being made stronger than usually directed, no addition of mucilaginous substance will be required to give it a proper consistency. The solution of sulphate of iron should also be boiled or exposed some time to the air, which causes a portion of sesquioxide of iron to be formed, the presence of which is advantageous. The recipes for this class of ink alone are very numerous. That of Booth for a fine black ink is : Aleppo galls 12 Ibs., sulphate of iron 4 Ibs., gum arabic 3 Ibs., water 18 gallons; the bruised galls to be ex- hausted by three successive boilings, each time with a reduced quantity of water ; the decoc- tion is strained, and while warm the solution of gum and copperas, also warm, is to be add- ed, and the mixture is left for several weeks to deposit its sediment. A few drops of creosote added will prevent mouldiness. Among the other kinds of ink, the following appear par- ticularly worthy of notice. The blue ink first introduced by Mr. Henry Stephens of London, remarkable for a blue color which soon after drying changes to deep black, for perfect fluidi- ty, and tenacious adherence to the paper, is a tanno-gallate of iron dissolved in sulphate of indigo, the coloring matter thus not being sus- pended as in the ordinary inks, but in complete solution. Another variety, also invented by Mr. Stephens, and remarkable for its tendency to fade by continued exposure to light, and to recover its hue when excluded from it, is made by submitting Prussian blue for two days or longer to the action of strong nitric or hydro- chloric acid, then washing it well with water till all acid is removed, and finally dissolving it in oxalic acid. Ilornung's recipe is to mix 4 parts of solution of perchloride of iron with 750 parts of water, and precipitate with 4 parts of cyanide of potassium in solution ; the precipitate collected is washed with several ad- ditions of water, and allowed to drain until it weighs about 200 parts ; it is then dissolved in one part of oxalic acid. Bunge's ink, remark- able for its clearness and fitness for steel pens, which it does not corrode, is a cheap compo- sition prepared by gradually adding one part of solution of chromate of potash to 1,000 parts of a strong cold decoction of logwood, 22 Ibs. of logwood being boiled down with water to 14 gallons. The ink thus made is very black, and is not affected by weak acids, nor can it be washed out with water. It is, however, liable to become viscid and gelatinous. Dr. Nor- mandy's indelible writing ink, which is re- markably permanent, is made by grinding 24 Ibs. of Frankfort black with mucilage obtained by adding 20 Ibs. of gum to 60 gallons of water, straining through a coarse flannel, then adding 4 Ibs. of oxalic acid, and as much decoction of cochineal and sulphate of indigo as will give the required shade. Berzelius invented an ink which he regarded as the best writing ink known, and also nearly indelible ; it is vana- dic acid combined with ammonia and mixed with infusion of galls. Copying inks, which are intended to give an impression of the wri- ting made with them to a second or a third sheet moistened and pressed upon the original, are the f erro-gallic inks with a larger proportion of gum than they usually contain, and a portion besides of sugar or of sugar candy. Red ink may be made by the recipe of Heusler, which is to boil 2 oz. of Brazil wood, oz. alum, and the same of crystals of tartar, in 16 oz. of pure water, till the water is reduced one half ; in the strained liquor J oz. of gum arabic is to be dissolved, and a tincture added made by digesting 1^ dram of cochineal in 1J oz. of alcohol of specific gravity 0'839. Booth employs Brazil wood 2 oz., chloride of tin 4 dram, gum arabic 1 dram, water 32 oz., and boils the whole down to 16 oz. Various recipes may be found for different colored inks, but there is little use for them. They are generally composed of coloring matter held in suspension by thickening the liquid with gum arabic. The nature of the Chinese or India ink has been already noticed. Proust says that lampblack purified by potash lye and mixed with a solution of refined glue, moulded and dried, makes a quality of this ink preferred by artists even to that of China. Until some recent discoveries it was supposed that this ink used with acidulated water was inattaekable by chemical reagents that were not destructive to the paper. The so-called indelible or marking inks were formerly alto- gether made by dissolving nitrate of silver in water and add'ing gum arabic and sap green, and were used in connection with a pounce, which was first applied to the linen on the spot to be marked. The pounce was an aque-
