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image of any colour, as though the process of this transformation had been born with the cinematograph.
As a matter of fact, it is only during the last fifteen years that chemico-photographic technique has been able to solve this problem in a really perfect manner. Formerly, the so-called iron intensifies — uranium and vanadium — were used in cinematographic technique, but these intensifies, if we except the iron ones, did not render brilliant hues and much less colours that lent themselves to bi-chromatic and tri-chromatic synthesis.
It was in 1909 that the writer of these notes presented to the Congress of Applied Chemistry in London the first specimens of fixing tar dyes on silver prints : and by later experiments he was able to perfect the process and to present fresh specimens tb the International Photographic Congress held in Dresden during the same year, and later on some final specimens to the Illrd National Photographic Congress in Rome in 191 1. The writer was thus able to ascertain that, just as in textile printing certain metallic salts act as mordants for a given category of tar dyes, it is possible in like manner in photography to attract and retain certain colours comprised in the category of basic tar dyes by substituting a metallic salt, or more precisely a copper salt, for reduced silver.
Certain distinguished experts in photo-chemistry devoted themselves to perfecting this process and rendering it more practical; among other Dr. Traube of Munich (who based on it the so-called Uvachrome process for the production of coloured slides for projections), M. Christensen, who advantageously replaced ferrocyanide of copper mordants by sulphocyanide of copper, as also Messrs. Lumiere and Seyewetz, who made a comprehensive study of the dyes best adapted for fixing by ferrocyanide and sulphocyanide of copper.
Methods for transforming cinematographic silverprint images INTO MONOCHROMES.
While it is not possible to describe in detail the physical and mechanical aspects of the methods pursued by the American
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