1, Reade's Patent. Prepare a solution of iodide of iron, from iodine, iron, and water; add to the solution half as much iodine as first used. Pour this solution into a semi-saturated solution of ferro-prussiate of potash, containing nearly as much of the salt as the whole weight of iodine. Collect the precipitate, wash it, and finally dissolve it in water, to form the blue ink. The solution from which the precipitate is separated, evaporated to dryness, and the residue fused, redissolved, and crystallized, yields pure iodide of potassium. [This process being patented, ink must not be prepared by it for sale.]

2. Add a pint of a cold solution of persulphate of iron (prepared as directed, further on) to a solution of 6 oz. of ferro-cyanide of potassium in 2 pints of water. Collect the precipitate, wash it with distilled water until it begins to dissolve, then triturate it in a mortar with sufficient distilled water to form a blue ink.

3. Chemic, or Saxon blue (sulphate of indigo), diluted with water to the desired shade, with a little gum.

4. Pure Prussian blue, triturated with a sixth part of its weight of oxalic acid, with a little water, to a smooth paste, and more water added to bring it to the proper colour. A larger proportion of the acid is ordered in some recipes.

5. Dr. Normandy's Blue Ink. Chinese blue (ferro-cyanide of iron) is ground in water with binoxalate of potash and gum arabic, in the following proportions: - 7 oz. of water to 3 drs. of Chinese blue, 1 dr. of binoxalate of potash, and 1 dr. of gum arabic.

6. Stephen's Patent Blue Ink. Common Prussian blue is first macerated in strong sulphuric acid, then repeatedly washed in water, and afterwards dried. This process is to render it more soluble in oxalic acid, which is now to be gradually added in the proportion of about 1 part to 6 of the Prussian blue (as before maceration), together with sufficient water to yield a dense blue solution.

7. Digest 2 oz. of the cuttings of tin plate with 4 oz. of nitrous acid, and add the solution to a gallon of water in which 2 oz. of prussiate of potash have been dissolved. [This requires frequent shaking to keep the precipitate (which is Prussian blue) suspended.]