Elements of the Art of Assaying Metals

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L. Davis, 1764 - Assaying - 471 pages
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Page xiv - Lipsiae, 1734, in three tomes, in folio : in the second and third tomes of which he has given the best accounts, not only of the methods and newest improvements in metallic works in all places beyond the seas, but also of those in England and our colonies in America, with draughts of the furnaces and instruments employed. It is to be wished we had extracts of this work in English.
Page xv - Rara Avis in Terris : or the Compleat Miner, in two Books ; the first containing, the Liberties, Laws and Customs of the Lead-Mines, within the Wapentake of Wirksworth in Derbyshire ; in fifty-nine Articles, being all that ever was made.
Page 100 - Plate (z), one Inch and a half long-, and of fuch Breadth and Thicknefs, as that it may freely move up and down, and yet not have too much play within the Hole. Moreover, let this Plate have a fmall Plook at each Extremity. 266. And as fuch a Balance is very ticklifh, and will hardly {hand flill in the open Air, and...
Page 77 - And that thisr being put on the Aperture (d) of the Furnace, may not be eafily thrown down, let an Iron Plate be rivetted to the right and left upper Edge of the Furnace (cc), and be turned down towards the Infide,' fo as to make a Furrow open before and behind, into which the lateral Edges of the Cover may enter and be fattened, and at Pleafure be moved backwards and forwards, whenever it muft be put on, or removed.
Page 248 - ... mercury is finally to be squeezed through thin leather and the solid amalgam distilled in a glass retort on a sand bath. He mentions the danger of precious metal passing into the receiver with the mercury when the fire is too strong. He adds the following caution (following Mortimer's translation): "If, for want of an apparatus for scorification and coppelling, you have a Mind to indicate by this method, the Quantity of Silver contained in the Body washed ; in this case the whole Amalgama must...
Page 51 - great many fluxes with the above-mentioned salts and with the reductive ones ; nay, 1 some use as many different fluxes as there are different ores and metals ; all which, however, ' we think needless to describe.
Page xv - Silver that fhall be extracted by the Art of Melting and Refining of Metals, and otherwife improving of them and their Ores, be from henceforth imployed for no other Ufe but the Increafe of Monies ; that it be carried to the Tower of London, where the Owner fhall receive the full Value.
Page xv - William and Mary, ch. 30. An Act to repeal the statute made in the fifth year of King Henry IV. against multiplying gold and silver. The Whole Act 5 William and Mary, ch. 6. An Act to prevent disputes and controversies concerning Royal Mines. The Whole Act 55 George III, ch.
Page 248 - Amalgama must be distilled through the Retort; because Part of the Silver and gold gets through the Leather: Nay, there remains nothing at all of the Silver or Gold within the Leather, if you use too great a Quantity of Mercury, to extract a small Quantity of these Metals : unless the Mercury be saturated with them, by a like previous Process; and even then, you may be easily deceived as to the Quantity and Quality of the Metal.
Page 244 - ... use of iron filings is mentioned by Mitchell and by Percy, both of whom refer to still earlier work. In fact, this seems to have been one of the earliest forms in which iron was used for assay purposes. In Cramer's work on assaying (Mortimer's translation, 2d ed., 1764) one section is devoted to " Precipitation by Iron and Lead of Silver out of a Mixture containing a great Deal of Sulphur...

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