In case all the mercury should disappear at the end of the process, a little more may be added to the watery solution to ascertain whether it still contains silver.

(l) A method of reducing silver chloride to the metallic state, especially adapted to the practice of amateurs, formed the subject of a paper read before the Manchester Photographic Society recently by Mr. J. Leigh.

Many amateurs, said the author, trouble themselves very little about the reduction of photographic silver wastes, simply because they consider their small quantities not worth sending to a professional refiner, or that the process of reduction to the metallic state is troublesome, and not worth the expense. The process about to be described is simple, effectual, and economical, and particularly suited to the amateur who has comparatively small quantities to operate upon. As regards the precipitation of Ag Cl from solutions containing Ag NO2 we all make use of common salt. In my dark room is a large inverted bell-glass, into which are poured the washing waters of dry plates and paper prints, the rinsings of glasses, baths, and other vessels which have contained Ag NO, in solution; and, at the end of the season, all the nitrate baths are added to be precipitated as Ag Cl by the process just mentioned. The precipitated chloride should be well washed by de-cantation, dried, and weighed, or it may be poured into the evaporating basin without washing. Add to the Ag Cl about its own weight of KOH, or NaOH, and half its weight of cane sugar, with sufficient water to well cover the whole, and boil for about 15 minutes over a Bunsen's burner.

This solution turns muddy on applying the heat, but in a few minutes gets somewhat clearer, owing to the reduction of the silver, which ettles on the bottom of the basin in the form of a grey powder, lacking altogether'the metallic lustre of silver cast into ingots or buttons. The finely-divided silver is transferred to a precipitating beaker and well washed by decantation. The clear washing water is now tested with Ag NO, until no precipitate is obtained; the silver is then washed in two changes of distilled water. There is nothing new in the above process; it is based upon the fact that solutions of sucrose or dextrose in the presence of alkalies, reduce the salts of the noble metals to the metallic state; the chlorine, in the case of chlorides, remaining in solution.

At the commencement I stated that this was an effectual method of reducing Ag Cl, which I think I can prove. From one precipitation I had 5663 gr. of dried Ag Cl, which, according to calculation, would yield 4262 gr. of pure silver. I actually got 4250 gr., being a loss of 12 gr., possibly accounted for by the chloride having absorbed moisture between drying and weighing; or probably a small quantity of kaolin may have been mixed with the chloride. The process is also economical, NaOH costing about 4d. per lb., and sugar about l 1/2d. per 1/2 lb., which is sufficient to reduce considerably more than 1 lb. of Ag Cl to the metallic state, without the expense of building a furnace; also less the risk of a broken crucible, and possibly, the trouble of collecting the precious metal from the retrains of a coke fire, which is anything but amusement. Those who prefer a crucible can obtain sufficient heat on an ordinary blacksmith's hearth, with a small coal fire.

(m) Put well-washed silver chloride into an iron ladle, with a little pure water above the chloride. The greater affinity of iron for chlorine determines its departure from the silver; and, after standing 24-30 hours, throw the contents of the ladle upon a filter, and wash thoroughly with pure water, to remove the soluble iron chloride; the residue will be pure silver in a minute state of division. This method is rarely employed, on account of the length of time required.

(n) Well-washed silver chloride (water does not dissolve a trace of it) is put into a stoneware pan with two or three times its weight of zinc, and the whole is covered with water rendered acid by sulphuric acid. As soon as they are in contact, these substances react upon each other; the sulphuric acid and the zinc decompose the water, the oxygen of which oxidises the zinc, which then combines with the acid, and forms zinc sulphate, a very soluble salt; the hydrogen transforms the chlorine of the silver into hydrochloric acid, which is also very soluble in water. Before filtering, wait until all the zinc is dissolved. The remaining silver is in impalpable powder, and cannot pass through the filter. Wash the silver thoroughly with pure water, and it may then be dissolved in pure nitric acid to form a pure silver nitrate. This process is seldom employed, as it is difficult to find zinc without lead, which will unite with and follow the silver in subsequent manipulations.

(o) The silver chloride, freed from foreign metallic salts by washing, is mixed with four times its own weight of crystallised soda carbonate, and half its weight of pulverised charcoal. Make into a homogeneous paste, dry thoroughly in an iron pan, and then place in a red-hot crucible. After fusion, the heat is raised, in order to allow the smallest globules to reach the bottom of the crucible. Should the crucible be moved at the time of the solidification, the silver will be of a very irregular shape. To obtain granulated silver, pour it in a small stream, and from a height, into a large volume of water.

(p) To recover silver from trimmings of untoned prints, procure an old iron bucket or pot, and place the cuttings in a few handfuls at a time; and apply a light to them, when they will quickly burn to ashes. As they burn down, keep adding the cuttings, which must be stirred up frequently with an iron rod, so as to completely reduce all the mass to fine ashes. Of course the burning must be done out of doors, owing to the dense smoke and disagreeable fumes. If in windy weather, place a piece of sheet iron partly over the bucket to prevent the ashes from blowing away. The fire will be a long time dying out. After the trimmings are reduced to ashes, the ashes can then be reduced to metallic silver in a crucible with equal quantities of soda carbonate and borax.