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Permanence of Ink

The great difficulty with all iron inks is the precipitation which will take place, after a longer or shorter time, and which manufacturers have tried to obviate by substituting other materials. All ter, stirring it thoroughly, to remove the salts of iron; let it stand till all color has subsided, then draw off the clear liquid with a syphon; add fresh water, and repeat the washing until ferrocyanide of potassium ceases to produce a blue precipitate, and the water drawn off ceases to redden blue litmus paper, then filter the product. This treatment extracts much inks, however, the basis of which is not tan- of the iron from the Prussian blue, and takes nate and gallate of iron, are not black imme- away its liability to precipitate by long standlong standdiately, and consequently not SO agreeable to ing. Next add and carefully mix 1 part the eye when using them. The alizarine or oxalic acid to every 6 parts of Prussian blue; rather indigo inks have a greenish, the chromi- then dilute, by degrees, with water sufficient um inks a reddish hue, and are not better to make the blue ink any desired tint. The adapted to withstand chemical agents than influences of air and dampness have a tenhave a teniron inks are. dency to destroy the color of manuscript