Newton's London Journal of Arts and Sciences Volume 39; Being Record of the Progress of Invention as Applied to the Arts

This historic book may have numerous typos and missing text. Purchasers can download a free scanned copy of the original book (without typos) from the publisher. Not indexed. Not illustrated.1852 Excerpt: ... stance being the most readily attainable in the market, and in no degree affecting the color of the paper. The mode of applying this substance is by mixing it with the pulp or size; or the paper maybe saturated with a solution of the metallic iodide. The ferrocyanide or ferricyanide of potassium is mixed with the size; or it may be applied subsequently to the sizing, as in the case of the metallic iodide. The starch is preferred to be mixed with the pulp in the engine; but it may, like the other chemical ingredients, be used in an after stage of the process. The proportions for these several materials, used for rendering paper sensitive to the action of re-agents, are by no means absolute; but, as a guide, it may be stated, that the following have been found to answer the purpose, viz., for a ream of post, weighing about 18 lbs., --1 oz. iodide (or bromide) of potassium, oz. ferrocyanide (or ferricyanide) of potassium, 1 lb. starch. On the application to paper, preparedas above set forth, of re-agents, to dissolve out or absorb any ink-markings therefrom, the tendency will be to break up one of the salts named: thus, on the application of chlorine or mineral acids, the iodine will be liberated, and, combining with the starch, will form an insoluble iodide of starch of a dark color; and, further, the iron, which ink generally contains, being attempted to be dissolved by either vegetable or mineral acids, the ferrocyanide of potassium will combine with it in solution, and form the well-known Prussian blue compound, which will become diffused over the adjacent portion of the paper. The patentee claims the application and use of iodine (or bromine), in its combined state, with a base of ferrocyanide (or ferricyanide) of potassium and of starch, for the purpose ...