Holograph draft memorandum on methods of assaying gold and silver by refinement, such as should be used in assessing trial pieces

Author: Isaac Newton

Source: MINT 19/1/293, National Archives, Kew, Richmond, Surrey, UK

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- Revision History
  - 1 January 2001
    - Catalogue information compiled by Rob Iliffe, Peter Spargo & John Young
  - 29 September 2011
    - Catalogue exported to teiHeader by Michael Hawkins
  - 26 January 2017
    - Transcribed by Will Scott
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<293r>

Gold & Silver are assayed by refining them & observing how much they are lightned by refining.

Silver \about {illeg}b{illeg}/ is assayed & refined by me{illeg}|lti|ng it w^th thrice its weight of lead & keeping it in fusion till the lead fumes away & carries with the base metals. {sic} |&| The silver w^ch remains is fine silver. I{t}|f| it be refined again with thrice its weight of Lead it becomes finer then before, but|the| lead carri|y|ing away a little more of the base metals. But silver once refined is fine silver or silver 12 ounces fine by the laws of all Europe. And eleven ounces two penny weig weight of this silver melted in a mass\& well mixed/ w^th18^{dw^t} of copper makes standard silver by the law of England. And of such a mixture y^e standard trial pieces of silver ought to be made.

Gold is assayed & refined by melting it w^th thrice its weight adding it to it twice its weight of silver & melting the mixture with thrice its weight of led till the lead fumes away & carries away with it all the base metal & leaves the gold & silver alone, w^ch being hammered into a thin plate & put into a gla hot aqua fortis, the aqua fortis eats away the silver & leaves the gold alone. If this aqua fortis be poured off & fresh a{illeg}|q|ua forte|i|s be poured on, this second water \(especially/ if it be a little stronger then the former|)| & will eat away a little more of the silver & leave the Gold finer then before. And a third water will leave it still finer, & a fourth still finer. And But Assaymasters & Refiners proceed no further then to two waters. Gold assayed or refined with two waters is fine Gold i|o|r Gold 24 carats \fine/ by the laws of all Europe, & Eleven ounces of such fine Gold melted into a mass\& well mixed/ with one ounce of alla{illeg}|y| {in} f make standard Gold by the law of England: And of such a mixture the standard triall pieces of Gold ought to be made.

The standard pieces should be made by the Queens Order, as y^e Indenture of the Mint expresses, but were made the last time (A. C. 1707) by the Lord Treasurers warrant. The Iury did not then refine the Gold & Silver but bought \them/ of {sic} my Deputy M^r Carlich|.| & \They/ know not how he refined them, but\and/ wondred tha{illeg}|t| he could make them so fine.|:| The trial pieces Iury \But being generally of opinion that no gold or silver could be too fine, they made the trial pieces/ /thereof {illeg}|fo|r the money but absolutely\ refused to give receipts for of |of| their|m| trial pieces for making their plate \thereby/. And the{illeg}|se| \Trial pieces/ were never \yet/ established under the broad seal, {illeg} but being as they ought to be. And \if/ they be established the Merchants will thereby lose about 4 or 5^s in the pound w^t of all gold imported.