Platinotype
by William De Wiveleslie Abney (9780217532136)

Purchase of this book includes free trial access to www.million-books.com where you can read more than a million books for free. This is an OCR edition with typos. Excerpt from book: CHAPTER II. THE SALTS OF IRON. It will now be abundantly clear from the above historical resume that the most practical results in platinotype are obtained by the use of iron as the chemical of which the provisional image is formed, and is replaced by the platinum according to a true chemical substitution process. We shall therefore proceed to examine the behaviour of the different salts of iron under the influence of light, borrowing largely for this purpose from the careful series of experiments that were made on this metal by Dr. Eder. It is known to chemists that all the ferric salts, in the presence of organic bodies, are more or less sensitive to light, being reduced to the corresponding ferrous stage; now the organic substance would of course be found in the paper itself, or in the different sizes, starch, dextrine, gelatine, etc., with which the cellulose fibre has been strengthened. But, in choosing the most suitable salt, many conditions should as far as possible be fulfilled; first, we naturally seek "Recent Investigations on the Sensitiveness of the Salts of Iron" (P/wtographiache Correipondenz, vol. xyii. p. 219). the mixture which is most quickly acted on by light; secondly, the reduction of the feme salt must not form any substance in the paper that would be deleterious to the platinum; thirdly, the salt must be more or less non-crystallizable? that is to say, it must be capable of being applied to paper in some form that will not crystallize and break up the surface in the way that nitrate of silver on a wet collodion plate, if allowed to dry, would do. Minor properties which are desirable are that some sort of a visible image should be formed on the paper to guide the printer as to the state of his print. Dr. Eder experimented with the followi...

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