Transactions of the Historic Society of Lancashire and Cheshire for the Year Volume 14

Transactions of the Historic Society of Lancashire and Cheshire for the Year Volume 14

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This historic book may have numerous typos and missing text. Purchasers can usually download a free scanned copy of the original book (without typos) from the publisher. Not indexed. Not illustrated. 1862 edition. Excerpt: ...necessary to maintain their ships efficiently sheathed, and Sir Humphrey Davy was requested to undertake an investigation into the cause of the rapid decay of copper sheathing, and the best means of preventing it. He made many experiments and, by applying his electro-chemical theory to the solution of the question, he successfully explained the reasons why copper was acted upon by sea water, and suggested a remedy for the evil complained of. When he considered that copper is but weakly positive in the electro-chemical scale, and that it can only be acted on when in a positive state, it occurred to him that by rendering it slightly negative, the corroding action of sea water would be prevented. The plan he devised was extremely simple, being nothing more than to attach to different parts of the sheathing strips of iron or zinc, which, acting as the positive pole of a galvanic arrangement, effectually prevented the corrosion of the copper. Practice, however, does not always bear out theory, and the results obtained from experiments on a small scale are often found to be fallacious, from causes which are only noticed when the operations are extended. So it was with Davy's experiments; they were tried in a tank of salt water and were eminently successful; but, when the vessels were protected according to his plan, it was evident to all on board, from their dull sailing, that the bottoms had become very foul, and on being examined, it was found that the copper was completely covered with sea weed, shell fish of various kinds, and myriads of small marine insects. Upon their removal, however, it was found, on weighing the sheets, that the copper had suffered little or no loss, thus proving that the principle of protection was true, although its...
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Product details

  • Paperback | 70 pages
  • 189 x 246 x 4mm | 141g
  • United States
  • English
  • black & white illustrations
  • 1236861361
  • 9781236861368