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362 THE PHOTOGRAPHIC NEWS. LJUNE 8, 1883. Patent Jntelligente. Application for Letters Patent. 2677. Alexander Melvill Clark, of the firm of A. M. and W. Clark, of 63, Chancery Lane, in the county of Middlesex, Fellow of the Institute of Patent Agents, for an invention of “ Improt enients in and in apparatus for changing and storing photographers’ backgrounds and other movable scenery.”—A communication to him from abroad by William Evans Lindop, of St. Thomas, in the province of Ontario and dominion of Canada.—Dated 30th May, 1883. Patents Granted in Austria-Hungary. M. Jaffe, of Vienna, for “Obtaining semi-tinted plates of old manuscripts for printing-presses.”—Dated 23rd December, 1882. Patents Granted in Germany. 22,668. R. T. Wall, of Longfleet (England), for “ Improvements in photography.”—Dated 2nd September, 1882. Class 57. 22,679. F. NEUBER, of Hamburg, for “An adjustable light frame for transparent photographs.”—Dated 14th November, 1882. Class 34. 22,675. J. Chaine, A. Durand, and S. De CHALIGNY, of Lyons, for “Coloured photographs.”—Dated 2nd November, 1882. Class 57. Specifications Published during the Week. 4954. J. TEMPLER, for “Utilizing balloons for photography, &c.” —A communication from H. Elsdale. This specification was published on page 250 of our present volume. 4749. J. H. Johnson, for “Zinc plates or blocks for printing, &c.”—A communication from J. A. Silvestre. This invention relates to improvements in the preparation of zinc plates or blocks, for printing, gilding, decorating, and other purposes, and it consists in plating or covering the surface of such plates or blocks with a coating of nickel after the design or drawing has been engraved on the said plates as herinafter described. The employment of zinc plates for etching by photographic, paneiconographic processes by transfer presents serious disadvantages. In many cases it is impossible to employ this metal in gilding; it is too soft or yielding, and in typography it is objectionable on account of its coarseness, which renders the lines harsh, whilst the number of copies that can be printed from one plate is relatively small. In line engraving it is absolutely impossible to use zinc, its softness and porosity rendering it incapable of taking the degree of polish that is essential in the mode of printing necessary for this class of engraving. Attempts have been made to obviate these disadvantages by nickel plating the zinc plates before engraving thereon, but no practical success has been attained by these means ; the strong acid required to dissolve the nickel being liable to very rapidly destroy the other parts of the work directly it worked through the thin layer of nickel and come into contact with the zinc underneath the latter. According to this invention, however, the desired result is attained by first engraving the zinc plates or blocks by any suitable means, and then nickel plating the engraved plates or blocks, thus im parting to the engraving the strength and hardness of the nickel, which is deposited in a thin layer upon its surface.—Provisional Protection only. TWELVE ELEMENTARY LESSONS ON SILVER PRINTING. Lesson XII. Residues.—To the amateur, who, more frequently than not, uses only limited quantities of material, it is not so much a matter of importance whether he recovers seventy- five per cent, of the silver used, or not; but the pro fessional, who deals with hundredweights, takes care that the precious metal does not return to mother earth again if he can prevent it, and therefore adopts various methods, more or less complicated, to secure that end. With these complications we do not propose to deal, beyond stating a means by which silver and gold may be recovered ; but rather advise all those who have not time and the con venience at their disposal, to collect the residues from the first washing waters, gold toning, and fixing baths respectively, and forward on to the refiners. At the commencement of this series we printed a sketch of a suitable printing bench (see fig. 1, Lesson I.) The section F is designed for the reception of cuttings from sensitized paper, waste prints, and blotting-paper which has been used for soaking up any nitrate of silver solution that may have been spilt, also old filtering papers that have done service for silver solutions ; these should be burnt in an ordinary shut-up stove which has been pre viously freed from cinders, fine dust, and ashes, &c. Very little should be burnt each time if the draught of the stove is great, because, by creating a fierce fire, a loss of silver will be sustained, on account of paper containing silver passing up the chimney. When small quantities are to be burnt, an ordinary flower-pot may be filled with paper cuttings, and ignited from the top; the fire will slowly consume the whole of the paper if the pot is placed in a good current of air. When the paper is all consumed, and the stove or other contrivance has become cold, the ashes may be collected, either for further treatment at home, or to be disposed of to the dealers in photo graphic residues, who have every facility at their command for the economic recovery of the metals contained therein. The further treatment of the paper ashes consists in mixing them with one-fourth their weight of sodium carbonate, and heating up in a crucible; after the moisture has been driven off, the crucible should be removed from the fire, and one-fourth part of potassic nitrate (nitre) added, together with a small lump of sodic biborate (borax) ; heat again, and the silver will run down to the bottom of the crucible. Supposing only papers which have been used for silver solutions have been treated, the metal button at the bottom of the crucible will consist of pure metallic silver, which only requires dissolving in strong nitric acid, and evaporating, to obtain crystals of silver nitrate pure enough for further use. The details of this latter process will be found very fully described on page 586 and 587 of our last volume, “ Lessons in Photographic Chemistry.” Referring to Lesson VII. of the present series, it will be remembered that we advised the collection in a suitable jar of the washing waters used for soaking the prints previously to toning them, also the rinsing waters from cleansing the sensitizing dish and silver bottles. This water being the most valuable of any of the residues, care should be taken to save it, and, having saved it, to extract all the silver from it. Among photographers it is customary to add sodium chloride to the vessel containing these washing waters, and after allowing twenty-four hours for the precipitate to subside, the supernatant liquid is poured or drawn off to make room for the next lot of washings (see fig. 1). The Fig. 1. action which takes place is simply this: the water may be considered to contain silver carbonate, silver nitrate, and silver chloride ; the two former, when acted upon by sodium chloride, form sodium carbonate and nitrate (soluble in water), and silver chloride (insoluble in water), which, being a heavy flocculent precipitate, falls to the bottom of the vessel and remains there. If too much sodium chloride is added, a portion of the silver chloride formed will be re-dissolved; and if an insufficient quantity