Rembrandt Portrait Residues
gaining access to the original could also secure copyright in his own reproduction.
Rembrandt Portrait. When the shaded side of a sitter is portrayed with the light more or less behind the head, the picture is given the above name, from a fancied resemblance to the works of that great master. (See Portraiture.)
Removal of Film. See Film ; also Negatives, Stripping of.
Residues. The saving of the unused silver and gold salts in use in photography may be said to be almost beyond the amateur, unless he is in the habit of doing a very large amount of work, but the following directions will prove useful: - To reduce the silver from the fixing baths, the old solutions should be placed in a tub with some crude sulphide of potassium (liver of sulphur), and the silver will be precipitated as a black deposit of sulphide, Ag2S. This shoula be allowed to collect at the bottom of the vessel till some considerable amount is ready, when it may be reduced to metallic silver, as described below, or sent to the refiner. All clippings and trimmings from untoned prints should be reserved, and when a fair quantity is obtained should be burnt, commencing at the top of the pile, or the paper may be beaten to pulp, with dilute sulphuric acid, and strips of metallic zinc or copper placed in the mixture; metallic silver will be precipitated, and the zinc or copper dissolved. The washings of untoned prints should be placed in a jar, and common salt added till no further precipitate is caused, and the precipitate may be collected and treated as above, or all the residues may be mixed with well-dried carbonate of sodium, and fused in a crucible. To reduce old toning baths, whether of platinum or gold, add solution of ferrous sulphate; a black precipitate, of carbonate and oxide of iron mixed with metallic gold, results. This may be digested in aqua regia, and the gold in the resulting solution reprecipitated by ferrous sulphate in a pure state, when it can be redissolved in aqua regia to form the auric chloride. Ordinary albumenised paper absorbs about 30 grs. of nitrate of silver, equal to 19 grs. of pure silver for every sheet. Each sheet weighs about 340 grs.; therefore a quire will weigh about 8,160 grs., and contain about 456 grs. of pure silver. Of the silver used in sensitising paper will be found -