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THE PHOTOGRAPHIC NEWS Vol. VI. No. 220.—November 21, 1862. * Page 523, ving will hey and THE PHILOSOPHY OF POSITIVE PRINTING UPON ALBUMENIZED PAPER, IN CONTINUATION OF “ALBUMINATE OF SILVER AND THE ABBE PUJO." Albumen . . . . Paper Nitrate'of silver . . Pure metallic Gold . Making of— Terchloride more than 200 gallons 70 reams 2,400 ounces 35 „ farther results of Mr, Keene’s experiments. If the presence of a chloride in a dry plale really be antagonistic to sensi tiveness, it will be very easy to wash in successive baths of distilled water. es not anger iking how- th. •n for know give mind as its Yhen lower ated. 5 the i the ; the • that The ewed inger lens. y are itices pe i run rd yin slaid, very with vered odof tan- rhich isfor idge, nsert rne’S nina- id by were e to some 1ot of with cticle th we lish- i this inout inout gene- rit is ccess glad ,te of > cor* i eshly lume- grain then only ist on : less ition i you aiting lence reply it by irson- con- ;e the quent 2 pro- isibly using No. 2, ehind done, gram, only first: shall • THE COMMERCE OF PHOTOGRAPHY. In a recent article, we referred to the immense impetus given to the art, and its great commercial development, which re sulted from the spirited management of an enterprise like the International Exhibition photographic contract. We have just been favoured, in further illustration of this subject, with some very interesting facts, by Mr. England, to whose ability and fine taste, the public are indebted for the entire series of exquisite stereographs, and some other pictures, of the Exhibition interior and its contents. The number of these stereoscopic pictures alone, produced during the summer, by Mr. England, has been upwards of two thousand gross, or considerably more than a quarter of a million slides. The card portraits from the same negatives, have not been quite so numerous, but they amount to very many thousands. The materials used in the production of these, are stated as follows :— BY GEORGE PRICE. The Table No. 2, given in my last communication* shows a very great diversity in the proportions which the albumi nate, chloride, and free nitrate of silver bear to each other, in the various formulas I have analyzed ; as we may safely assume that each person has given that which he himself considers -will produce good, if not the best results, this extraordinary diversity goes far to prove how little is really known respecting “ the philosophy of positive printing upon albumenized paper.” Of the three compounds of silver, we find tXxefrec nitrale is, in every formula, considerably in excess of either the albuminate or the chloride; and in many cases, is more than double their united amounts. Comparing it with the chloride, we find it ranges between the two extremes, of less than twice the quantity, as in No. 7, Mr. Aleo’s, to more than thirteen times the amount, as in No. 12, Mr. T. R. Williams's. Warding action of a chloride on bromo iodized COLLODION. ‘z have recently received from Mr. Keene, of Leamington, note on the use of a collodion containing equivalent pro- Elions of a bromide and of an iodide, for dry plates, as pro- M by Mr. Sutton, and he calls our attention to the fact at he has, for some months past, prepared and advertised 1 collodion containing such proportions. Having referred Athis fact, Mr. Keene proceeds to another, which is at once . Mons and important, as it may possibly furnish the key to Jny varying experiences in reference to the sensibility of 7 collodion plates. We give this suggestion as Mr. Keene bites it — Have you ever noticed the retarding influence a chloride salt Bercises in combination with a bromide, when the latter is in 'large as equivalent proportions with the iodide ? During a sies of experiments with the above highly bromized collodion, Leonnection with the dry process, undertaken during the early Net of September, I added, to a portion of it, one grain per Bce of chloride of magnesium with the hope of combining the given by chlorides with the extreme sensitiveness of ’ bromides. The intensity I certainly obtained, but at the Tpense of sensitiveness, which was very materially reduced; ■ M upon reference to my journal, I find the result was the Be if the prepared albumen contained the chloride (in this T"lance ammonium) instead of the collodion. Evas not prepared for such a result as I had never noticed the shtest diminution in sensitiveness when the ordinary (bromo) i Ezed collodion was used in connection with a preservative Stion containing a chloride; and the very sensitive plates Bined by the Messrs. Walter, an account of the method of ^Paring which, appeared a short time since in the News, .flsprepared with a bromo collodion and preservative solution ‘Ptepared albumen containing chloride of ammonium. Ais is a circumstance of much moment at the present time, Bn bromides arc likely to bo used in largo quantities for all sk dry processes, and a thorough washing previous to the BPlication of the preservative solution—should any such be a J^ssity—for, if chlorides exercise the same retarding influence p e r all other circumstances, when a large quantity of bromide uM, as they do when albumen is used as a preservative—my BPerience does not go further—all waters containing chlorides J® have to be discarded for washing the sensitized plates, and Y rain or distilled water only employed. J hope shortly to be able to send you something of interest, iting to rapid dry process photography.—I remain, dear sir, T truly yours, Alfred Keene. IThat the use of chloride is inimical to sensitiveness in dry V has often been held, but the grounds upon which the p has been based have not always been very clearly stated. , 6 reason which has been alleged has been that free nitrate ,8 necessary to extreme sensitiveness, which could not, of . te, exist in the presence of a chloride. That the pre- CCe of free nitrate is not necessary to sensitiveness has been, u ever, repeatedly proved. The cause of the often-noticed jrding action of a chloride is not due, therefore, simply k ho f ac t that it removes free nitrate. M. Me. A. Gaudin EPresses a conviction that chloride of sodium will not fail (estroy H le sensibility of iodide of silver, in the same way W excess of iodide of potassium, and all solvents of iodide i,1 ver destroy if- The retarding influence of chloride of N er, formed in the film, and especially the especial action , he presence of large proportions of a bromide, are new Hr' and we think it worth while to call especial attention 0 Keene’s observations. We shall be glad to learn the Pelience of other operators in the same direction, and the of Gold . . ■ -I 20,000 grains Hyphosulphite of soda, 25 cwt., or ... . 1} tons The number of persons employed in Mr. England's estab lishment, in albumenizing, exciting, printing, toning, fixing, washing, mounting, &c., may easily be conceived ; and this is only one portion of the Exhibition work, and does not in clude any of the large pictures.