CHEMICAL SCIENCE. 275 



decomposed by metallic copper, chloride of copper being formed and silver 

 precipitated, it appeared to Mr. Frederick Field, an English chemist, resident 

 in Chili, highly probable that the copper and the yellow metal (Muntz's) 

 used in sheathing the hulls of vessels, must, after long exposure to sea-water, 

 contain more silver than they did before having been exposed to its action, 

 by decomposing chloride of silver in their passage through the sea, and de- 

 positing the metal on their surfaces. He soon had an opportunity of testing 

 the correctness of his surmise. The Ana Gutmaracns, a large vessel under 

 the Chilian flag, was hauled down to be repaired near Coquimbo, where Mr. 

 Field resides, and a few ounces of yellow-metal sheathing from her bottom 

 were obtained for analysis. The investigation was interesting, as the metal 

 had been on for more than seven years (an unusually long period), and the 

 ship had been trading up and down the Pacific Ocean all that time. The 

 metal, upon examination, was found to te exceedingly brittle, and could be 

 broken between the fingers with great ease. Five thousand grains were 

 dissolved in pure nitric acid and the solution diluted ; a few drops of dydro- 

 chloric acid were added and the precipitate allowed to subside for three days. 

 A large quantity of white insoluble matter had collected by that time at the 

 bottom of the beaker. This was filtered off, dried, and fused with one hun- 

 dred grains pure litharge, and suitable proportions of bitartrate of potash 

 and carbonate of soda, the ashes of the filter being also added. The result- 

 ing button of lead was subsequently cupelled, and yielded 2'01 grains silver, 

 or 1 Ib. 1 oz. 2 dwt. 15 gr., troy, per ton. This very large quantity could 

 hardly be nupposed to have existed in the original metal, as the value of the 

 silver would be well worth the extraction. It is to be regretted that none of 

 the original sheathing had been preserved, but a sample of ordinary yellow 

 metal, yielded only 18 dwt. to the ton. 



' - . 



A short time after, however, the captain of a brig, which had just arrived in 

 the Pacific from England, gave to Mr. Field a piece of Muntz's yellow metal 

 from his cabin, from the same lot with which the brig was sheathed, but 

 which had never been in contact with salt water, and also a small portion from 

 the hull of the ship, after it had been on nearly three years. The experi- 

 ments were performed as before, and the results were very striking : 



Grs. Gr- Oz. dwt. grs. 



1,700 from cabin gave '051 = '003 per cent = 19 14 per ton. 



1.700 from hull gave -400 = -023 -7 13 1 



That which had been exposed to the sea having nearly eight times as much 

 silver as the original sample. 



Many other specimens were examined of metals from the bottoms of ships, 

 and of pieces which are always kept on board in case of need, and it was in- 

 variably found that the former contained more silver than the latter. For 

 instance, a piece from the hull of the Bergmann, gave 5 oz. 16 dwt. 18 gr. 

 per ton, while that from the cabin yielded 4 oz. 6 dwt. 12 gr. Two hundred 

 grains from a piece from the hull of the Parga gave '072 gr., and a piece of 

 fresh metal '050 gr. ; while from the Grasincre, only coppered a few months, 



