. The Civil engineer and architect's journal, scientific and railway gazette. Architecture; Civil engineering; Science. other substances, forming compounds, capable of being dissolved, and held in solution by acids and certain alkalies; thus, tor example:—When pure silver is put into pure nitric acid and heated, the metal is rapidly dissolved, forming the nitrate of the oxide of silver, or, as commonly designated, the nitrate of silver, and this may be held in s ilution in water. In forming a metallic salt for the purpose of electro-deposition, one general rule holds good in all cases, and may
. The Civil engineer and architect's journal, scientific and railway gazette. Architecture; Civil engineering; Science. other substances, forming compounds, capable of being dissolved, and held in solution by acids and certain alkalies; thus, tor example:—When pure silver is put into pure nitric acid and heated, the metal is rapidly dissolved, forming the nitrate of the oxide of silver, or, as commonly designated, the nitrate of silver, and this may be held in s ilution in water. In forming a metallic salt for the purpose of electro-deposition, one general rule holds good in all cases, and may be considered a law (and if this law is attended to, no difficulty whatever can in electro-depositing); and this is, that the metal dissolved in acid or other solvent must have a greater affinity for such solvent, ihan the metallic article to be coated with the metal thus held in solution—for this simple reason, that if the article to be coated hA% a greater affinity for the solvent than the metal held in solution, a chemical substitutionjpreceding the galvanic action) takes place ; the acid in preference combining with the metal, for which it has the greatest affinity, forming an oxide upon its sur- face, which oxide intervenes between the article and the metal depoiited upon it. Such failures therefore as have taken place in electro-depositing have not been the result of any defect in the principle, but from want of knowledge in the operator, and principally from ignorance of the law just stated. For this reason the nitrate of silver cannot be used ; the nitric acid having a stronger affinity for most other metals than (or silver ; another and better solvent therefore must be obtained, and this will be spoken of under the metal, silver. Operation.—In proceeding to plate metals, it is necessary that the battery should be so arranged, that the quantity of electricity generated, should cor- respond with the surface of the articles to he coated, and the intensity sh
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