"From their high price, however, and that of galls generally, sumach, logwood, and even oak bark are too frequently substituted in the manufacture of inks, but it need scarcely be said always injuriously. Ink made according to the receipt given above is much more rich and powerful than many of those commonly made. To reduce it to their standard one half more water may be safely added; or even twenty gallons of tolerable ink may be made from the same weight of materials. Sumach and logwood admit of only about one-half or less of the green copperas that galls will take, to bring out the maximum amount of black colour. The colour of black ink gradually darkens in consequence of the peroxidation of the iron in it on exposure to the air, but it affords a more durable writing when used pale; its particles being then finer, penetrate the paper more intimately, and on its oxidation is mordanted into it. It is advisable so soon as the ink has acquired a moderately deep tint, to draw it off clear into bottles and cork them well. "According to the most accurate experiments on the preparation of black writing inks, it appears that the proportion of the green copperas ought to be, and not to exceed, a third of the decoction of galls used; but the proportions used vary according to the practical experience of ink-makers, who have all receipts of their own, which they deem best, and, of course, keep secret. In the precipitate an excess of colouring matter, which is necessary for its durability, is preserved in it. The blue galls alone ought to be employed in making the best quality of black ink. Logwood is a useful. ingredient, because its colouring matter unites with the sulphate of iron and renders it not only of a very dark colour, but also less capable of change from the action of acids or of the atmosphere. Many attempts have been made by amateurs to make a good permanent black ink. A good story is told of Professor Traill. He had succeeded, after a long series of experiments, in producing an ink which he deemed to be in all respects A 1, and which resisted the action of all acids and alkalies alike. The pleased savant sent samples of it for trial to several banks and schools, where it gave general satisfaction; but, alas, an experimenting scribbler, thoughtlessly or otherwise, applied a simple test undreamt of by the Professor, and with a wet sponge completely washed off his 'indelible,' and thereby finished his career as an amateur ink-maker!" * * * * * * * "Nicholson, in his Dictionary of Chemistry, an old but valuable work, says that Ribaucourt found vitriol of copper, in a certain proportion, to give depth and firmness to the colour of black ink; but, from whatever cause, this has not taken a place among the commonly-used ink-making ingredients-- probably because it acts injuriously on steel pens." * * * * * * *