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June 26, 1891.] THE PHOTOGRAPHIC NEWS. 463 Tooth of a grain per ounce in "eikonogen" developer causes the negative image that first appears to change into a rich-coloured positive. Descriptive Part. A.—Compounds of Thiocarbamide with Ammonium Haloid Salts. It has been already mentioned that the well-defined crystalline solid (H,N,CS).NH,Br was obtained, in the first instance, by the action of ethylic alcohol on the com pound which results from the union of silicon tetrabromide with 8 mols. of thiocarbamide ; and that the same substance was subsequently prepared by the direct action of ammonium bromide on thiocarbamide. The latter or synthetic method is the only one with which I am now concerned; it afforded the best result when conducted in the following manner :—10 grams of ammonium bromide were dissolved in the smallest quantity of hot alcohol required for its solution, and this liquid was added to a boiling and nearly saturated alcoholic solution containing 30-4 grams (4 mols.) of thiocarbamide. The mixture was boiled for five minutes, and then allowed to cool in the containing flask. The contents soon began to deposit warty aggregations of radiating crystals which attached themselves to the bottom and sides of the vessel, and, when quite cold, the whole formed a nearly solid and beautiful white crystalline mass of characteristic appear ance. When drained, pressed, and recrystallised from alcohol, it is obtained in a perfectly pure state. In this condition it was analysed, with the results already stated (loc. cit.). Tetrathiocarbamidammonium bromide melts at 173— 174", but begins to decompose at 178—180°. It is easily soluble in boiling absolute alcohol, but is so much less soluble in the cold liquid that the hot saturated solution becomes nearly solid at ordinary temperatures. More dilute solutions, when slowly cooled, deposit the com pound in large and beautiful stellate groups of crystals, which often resemble sea anemones in appearance. It is almost insoluble in ether, chloroform, and benzene, but is rather easily soluble in water. When pure, its aqueous solution can be boiled violently for half an hour without undergoing sensible decomposition ; but if impure in the first instance, partial decomposition occurs. It is easily broken up by boiling with dilute acids and alkalis, and is readily desulphurised by alkaline lead tartrate. Having determined the composition and principal pro perties of the tetrathiocarbamide compound, it remained to be seen whether ammonium bromide could combine with 1, 2, or 3 mols. of thiocarbamide in presence of alcohol. To test this point three separate experiments were made, in each of which 1 molecular proportion of ammonium bromide was heated in alcoholic solution with 1, 2, and 3 mols. respectively of thiocarbamide under precisely the same conditions as those which suffice for the production of the tetrathiocarbamide compound. In each case a quantity of the tetrathiocarbamidammonium bromide was obtained proportional to the amide added, and the excess of ammonium bromide separated when the mother liquors were concentrated. No traces were observed of any but the tetra compound under the above- mentioned conditions, or under any other hitherto tried. It therefore appears that ammonium bromide and thio- carbamide do not combine in any other proportion than that of 1 mol. of the former to 4 mols. of the amide. (To be continued.) Notices: of 2ooks. Traite ELENIENTAIRE de L’OBJECTIF PHOTOGRAPIIIQUE. By E. Walton. (Paris: Gauthier-Villars etfIs.) The author of this book, M. E. Walton, who is professor of physics at the Lycee Janson de Sadly, has endeavoured to follow on and complete the work initiated by Monck- hoven in his “ Optical Photography,” and he has succeeded in producing a work which is a complete exposition of the subject with which it deals. Here we find explained the phenomena of refraction; the laws by which it is governed; a detailed account of the various lenses employed in photography, from simple forms to compound ones ; the effect produced by aberrations, and the means employed for correction, &c. The book contains 300 pages of most useful matter. It is well printed, and is fully illustrated with clearly drawn diagrams. It is issued in paper covers, the leaves arc uncut and have a very broad margin. Many of our English publishers would do well to take a hint from this commendable practice, for it is one which tempts the owner of such a work to have it well bound. HANDBUCII der PHOTOGRAPIIIE fur AMATEURE UND Touristen. By Major G. Pizzighelli. (With. Knapp, Halle aS.) Tins is a second edition of the first volume of a compre* hensive hand-book for the value of which the name of the author is a sufficient guarantee. The first edition was published in 1886, and consisted of 436 royal octavo pages; but since its issue the modifications and advances in photography have been so great and rapid as to necessitate not merely a complete revision, but a substantial enlarge ment of the book. The present edition is, therefore, ex tended to 486 pages, the text admirably elucidated by some 531 illustrations, and treats most fully of photographic apparatus. The succeeding volumes will deal with photo graphic processes, and the practical applications of photo graphy. Travellers’ Colloquial German. By H. Swan. (Lon don: David Nutt.) A useful little compilation, which forms No. 2 of the “Phonetic” series of hand-books for English-speaking travellers and students. No. 1, “Travellers’ Colloquial French,” in its third edition included an Appendix for Cyclists and Photographers. It may be hoped that, should the book before us attain, as it deserves, a third edition, it also will contain a section which could not fail to be useful to travelling photographers unacquainted with the German language; at present cyclists only are favoured. There is, however, a large amount of general information that will make the little book most serviceable. NEWCASTLE-OX-TYNE and Northern Counties Photooraphic Association.—The second out door meeting of the season was at Ripon and Studley Park, on Thursday the 18th. Upwards of 200 plates were exposed, mostly upon the ruins of Fountains Abbey. “Fallowfield’s Photographic Annual for 1891,” just received, is a book of over 500 pages, for the most part consisting of a comprehensive illustrated catalogue of photo graphic materials, chemicals, and apparatus, but containing also a large amount of useful information on various topics connected with the practice of photography.