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Book Description:
This historic book may have numerous typos and missing text. Purchasers can download a free scanned copy of the original book (without typos) from the publisher. Not indexed. Not illustrated. 1885 edition. Excerpt: ...and soaped water. Observations Relating To Organic Matters.--Although a silver bath is improved by the presence of a moderate proportion of organic matter, a too sudden introduction of the same, or its introduction in too large quantities at a time, must be guarded against. For instance, when candlesticks, which generally contain a mixture of rosin and pitch, are put into the bath without having been first emptied, a large proportion of the organic substances will be dissolved by the cyanide, and the conductivity of the bath will be reduced in a certain proportion; the deposit will be irregular and spotty. But when an old bath has gradually become charged with a small quantity of organic matter, the deposits obtained are brighter and more adhering than those obtained from a new bath. Oxidised Or Antique Silver.--The colour known as oxidised silver is obtained as follows: 1. The silver-plated object is brushed with a camel's-hair brush and a solution of platinum chloride in sulphuric ether, alcohol, or cold water. 2. The following solution is then applied on it in the same manner: Sulphate of copper 2 parts in weight. Potassic nitrate 1) dissolye fa acetic add Amnionic hydrochlorate.... 2) 3. The ammonic hydrosulphate, concentrated or dilute, gives a more or less deep shade. 4. Sulphurous vapours give a steel-blue shade. The parts which must not be touched should be protected by a coating. 5. Nitric acid alone produces the superficial oxidisation of silver. Weakened Solutions.--The gradual accumulation of potassic salts which results from the action of the air upon the free potassic cyanide comparatively rapidly alters the silver solutions; these do not then deposit the metal with the fine colour or the solidity with which they did it at first; it...