Copy 1

The laboratory, or school of arts ... / Compiled from German, and other foreign authors. Illustrated with copper plates. By G. Smith.

  • Smith, Godfrey, active 18th century
Date:
1750
Catalogue details

Licence: Public Domain Mark

Credit: The laboratory, or school of arts ... / Compiled from German, and other foreign authors. Illustrated with copper plates. By G. Smith. Source: Wellcome Collection.

    29/418 page 9
    place to dry ; when dry repeat rubbing it over again as before and let it dry : this you do for 3 or 4 times. This done, warm your crucible again, and fmear it both out and infide plentifuliy with loap, then put it to dry, and before you ufe it, put it on a charcoal fire, and the foap will burn in a flame, when it is burnt out, then you may ufe it for melting gold or filver, and it will attradl nothing of thefe metals as your common crucible will. A Method of purifying Gold^ hy way of Cementation, CEMENTATION is a fingular and ufeful art, by which gold may be purify^ from the allay of any other metal; and this is done by means of a moiftened pow¬ der, which eats and confumes the impurer metals in it ^ But it is to be ohfervM, that this cementation is only to be ufed where the gold has the predominancy ; otherwife if there fhould be more filver or other metal than gold, it is better to perform the reparation with Aqua Fortis^ as has been directed. The cementing powders are prepared of fuch falts and in¬ gredients as by their acrimony or flaarpnefs confume the filver c?r copper. To thefe are alfo added, * jFls ußum^ which gives the gold a fine colour ; alfo Blood-ßone^ Tutia^ Crocus Martis^ cal¬ cin’d Vitriol^ and feveral other things, heighten the beauty of that metal. Bnck-duft is ufed in this cement, in order to receive the allay, whether it be filver or copper, or any other metal, from the ingredients that attradl and feparate them from the gold, which otherwife would adhere to the gold. I (hall here fet down a few receipts of fuch cements as have been tried with fuccefs, TAKE f JEs üßuTn is prepared thus ; Stratify plates of copper with powdered fulphur in a large crucible, cover and lute it with a cover that has a hole in the middle ; to give vent for the fumitation, give it a ftrong fire in a wind-furnace, fo long till you fee no exhalation of vapours; then take off your plates whilll hot, feparate themi and when cold, beat them to a powdef, which is the Ms ußum^
    digitised image 1
    digitised image 2
    digitised image 3