Volume 1

Elements of the theory and practice of chymistry / Translated [by Andrew Reid] from the French of M. Macquer.

  • Macquer, Pierre Joseph, 1718-1784.
Date:
1758
Catalogue details

Licence: Public Domain Mark

Credit: Elements of the theory and practice of chymistry / Translated [by Andrew Reid] from the French of M. Macquer. Source: Wellcome Collection.

    100/464 (page 74)
    of fmall crucibles, made of the affies of calcined bones, which are exceedingly porous and eafily per¬ vaded. They are called cupels, on account of their figure, which is that of a wide-mouthed cup : and from hence the operation takes its name ; for when we refine Gold and Silver in this manner we are faid to cupel thofe metals. It is ealy to perceive that the more Lead is added the more accurately will the Gold and Silver be refined ; and that fo much the more Lead ought to be added as the perxedi metals are alloyed with a greater proportion of the imperfect This is the mod fevere trial to which a perfect metal can be put, and confequently any metal that ftands it may be fairly confidered as fuch. In order to denote the finenefs of Gold, it is fup- pofed to be divided into twenty-four parts called carats *, and Gold which is quite pure and free from all alloy is faid to be twenty-four carats fine ; that which contains part or alloy is caLed Goid of twenty-three carats ; that which contains ^ of al¬ loy is but twenty-two carats ; and fo on. Silver again is fuppofed to be divided into twelve parts on¬ ly, which are called penny-weights: fo that when absolutely pure it is faid to be twelve penny-weights fine ; when it contains -V of alloy, it is then called eleven penny-weights fine ; when it contains T* of alloy, it is called ten penny-weights fine, and fo on. In treating of Copper we promifed to fhew under the article of Lead how to feparate it from Iron. The procefs is founded on that property of Lead which renders it incapable of mixing and uniting with Iron, though it readily diflolves all other me¬ talline fubftances. Therefore if you have a mafs compounded of Copper and Iron, it muft be fufed with a certain quantity of Lead, and then the Cop¬ per, having a greater affinity with Lead than with Iron, will defert the latter and join the former, y/hich .being incapable of any union with Iron, as was.