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162 THE PHOTOGRAPHIC NEWS. [February 27, 1891. ounces For toning I have used one of the baths recommended for the aristotype paper with good effects, as follows :— Perchloride of mercury Bromide of potassium Distilled water ... 5 drops 5 ounces Nitrate of silver (crystals) Cyanide of potassium ... Distilled water ... ounces drachm grains to 4 . 1 . 96 . 40 to 4 have been using, and which I have found to give fairly satisfactory results with long exposures and after- After bleaching, the plate must be again thoroughly washed ; for a lantern plate, one hour in running water is suflicient ; then immersed in this solution :— 4 ounce 4 >> 24 grains 160 „ 2 ounces 40 grains 40 „ 20 „ 12 ,, 2 ounces 1 drachm 1 » 8 ounces 1 drachm 1 » 8 ounces A.—Pyrogallol Sulphite of sodium Sulphurous acid ... Distilled water ... B.—Ammonia (’880) ... Bromide of ammonium ... Ferrocyanide of potassium Distilled water ... toning: — A.—Eikonogen Sulphite of sodium Warm distilled water B.—Carbonate of sodium Carbonate of potassium ... Ferrocyanide of potassium Bromide of potassium ... Distilled water ... Equal parts of A and B for development. This developer I find to work quickly, gives rich, warm tones with correct exposure, and the same solution may be used for at least two plates. I am rather doubtful as to the utility of the ferrocyanide, but am inclined to think it has some effect in preventing fogging or veiling. If the slide should, after development, show any fogginess—which will not occur if correct exposure has been given—it may be quickly removed by using Farmer’s ferridcyanide reducer, consist ing of a weak solution of hyposulphite of sodium, about one ounce to a pint, to which are added a few drops of a ten per cent, solution of ferridcyanide of potassium. The action is very rapid, and any filminess or veil soon dis appears, when the plate should be quickly removed from the dish and rinsed well under a tap. If the fog has been caused by over-development, the reducing action may be allowed to continue until the image is of the right density ; but if a case of over-exposure, it should be stopped immediately the veil is removed, and the slide intensified after thorough washing. With eikonogen as a developer for lantern plates I have had little experience ; like pyro, it has a tendency to fog if not well restrained with bromide. With com paratively short exposures it gives good black tones similar to those obtained with hydrokinone, and with long exposures and powerful restrainer an olive green image is obtained, which is capable of taking a fine purple tone in a sulphocyanide toning bath. I append the formula I Sulphocyanide of ammonium ... ... Alum ... ... ... Saturated solution of carbonate of ammonium Distilled water ... The plate should be removed from the cyanide as soon as it is thoroughly blackened; if allowed to remain, a reducing action soon commences. The cyanide of potassium, Dr. Reynolds tells me, should be the pure crystalline, not the commercial. This intensifier not only greatly improves the colour of the image, but also appears to give it greater brilliancy. The use of a clearing solution after development does not appear to me to be always necessary. I have found that recommended by Mr. Edwards useful, consisting of ferrous sulphate, citric acid, and alum. If the slide has been, or is to be, reduced by the ferridcyanide method, the ferrous sulphate must be omitted, or a blue stain in the film will result from a deposit of Turnbull’s blue. After the final washing of the plate, it has been my practice to immerse the slide for five or ten minutes in strong methylated alcohol. I do not know if this has any bad effect, but it seems to me to have two great advan tages : firstly, the spirit hardens the film ; and secondly, the slide dries so quickly after this treatment that there is little chance of particles of dust collecting upon the wet gelatine film, which often occurs when slides are left for one or two hours to dry in an ordinary room. For binding the slides when finished, I prefer a good Dissolve, and add one grain of chloride of gold. This bath will remain good for a long time, but should be replenished with more gold as it becomes exhausted. The cyanide of silver intensifier is particularly useful in the making of lantern slides, especially when hydro kinone has been used as the developer. The disagreeable muddy tone caused by over-exposure may be entirely remedied by its means. In the case of such an over exposed slide, it is better, before intensifying, to immerse the plate for a few seconds in the above-mentioned ferrid cyanide reducer. This will remove any trace of fog which would otherwise be intensified with the image. Then wash perfectly free from hypo in running water, and soak in the following solution till well bleached :— 30 grains 80 2} drachms should contain about three times as much bromide as pyro by weight, a little more or less according to exposure and tone required. Ammonia with the pyro gives warmest tones. The alkaline carbonates of potassium and sodium give dirty green images, which, however, are capable of taking a purple tone in a sulphocyanide toning bath. Purple and blue tones may also be obtained with hydro kinone by giving a long exposure, and adding to the deve loper, as a restrainer, in addition to the ordinary proportion of bromide, about two grains of chlorate of potassium to each ounce, and afterwards toning as above. The addition of chlorate of potassium was suggested by Mr. Fitch, whose negative films on celluloid I have been using. Possibly bromate of potassium may be better than the chlorate, but I have not yet had an opportunity of trying it. Metabisulphite of potassium is recommended to be used with pyro developer by makers of some plates; it acts both as a restrainer of development, and as a preservative of the pyrogallol; but as, on dissolving the metabisulphite in water, it appears to be immediately decomposed, being reduced to sulphite with liberation of free sulphurous acid, I fail to see any advantage in its use above adding sulphurous acid to the solution of pyro with sulphite of sodium. The restraining power of the metabisulphite, I believe, is merely due to the neutralisation of a portion of the alkali used in the developer by the sulphurous acid liberated. The following is a formula which I have been using latterly, and find to give good results :—