Volume 1

The chemical works of Caspar Neumann ... / abridged and methodized. With large additions, containing the later discoveries and improvements made in chemistry and the arts depending thereon by William Lewis.

  • Neumann, Caspar, 1683-1737.
Date:
1773
Catalogue details

Licence: Public Domain Mark

Credit: The chemical works of Caspar Neumann ... / abridged and methodized. With large additions, containing the later discoveries and improvements made in chemistry and the arts depending thereon by William Lewis. Source: Wellcome Collection.

    28/464 (page 8)
    Flint, niixed with Nitre, and expofed to a moderate fire? the Add of the Nitre will be remarkably extricated ; the known effed of the Vitriolic Acid alone. Ip a itrong fire indeed, the Flint as an Earth would expel the nitrous Spirit, by abforbing and vitrifying with its alcaline bafis : but here the extrication hap¬ pens long before the heat has been raifed high enough for vitrification (g). XL CRYSTAL. CRYSTAL Is one of the handed Stones next to the Gems (Jo): by fome it has been ranked STAL- in that clafs. It is fometimes colourlefs and pellu- cid as Glafs though often tinged of a yellowilh, brown- (g) Probably Vitriolic Acid in Flint.] In the making of common glafs with Flint, when the quantity of matter is large, a faline fubflance arifes to the fur face during the fufion, commonly called Sandiver or Glafs-gall : this, though no Vitriolic Salt was employed in the com- pofition, is found to participate largely of that Acid, and to be nearly fimilar to Sal Mirabile. Did the Vitriolic Acid pre-exill in the Flint, or was it generated during the procefs ? (/)) Gems.] The Gems or precious Stones are the hardefl; of all natural bodies. Art fas imitated mbit of them in other refpefts ; but no artificial compofition comes near them in point of hardnefs. They have been fuppofed to be entirely unfubduable by common fire 5 but ex¬ periment (hews, that they calcine and become pulv.erable like the cthey Stones of this clals, though more difficultly in proportion to their greater hardnefs. The Diamond itfelf, as Pott obferves, in a vehe¬ ment fire, lofes all its luftre and tranfparency, becomes milky, friable, and fplxts into fine leaves like Talc. The Hyacinth and Garnet come at length into aftual fufion , changing their red colour to a dark black, but preferying even in this form a great degree of hardnefs : both the colour and fufibiliiy of tliefe Stones appears to proceed from Iron, a portion of which is reparable from them by the Magnet. The blue tin6ture of the Sapphire, the purple of the Am e thy ft, and the green of the Emerald, are more perifhaldc 5 being totally deftroyed by a mo¬ derate degree of heat, io as to leave the Stones colourlefs as C'hryflal. The E -merald, in lofing its colour in the fire, tinges the flame bluifh. Mr. Pott, in the Berlin Memoirs, lias given a curious fet of expe¬ riments on the Saxon Topaz, which is reckoned the hardefl of all the' Stones, except the Diamond, Sapphire and Ruby. This Stone, reduced to powder after ignitions and extinftions, refilled to melt with even ten times its weight of fixt Alcaline Salt j great part of the Alcali tr^nfu- ding through the crucible, inftead of ailing upon the Topaz. A por¬ tion of Sea-Salt was added to the Alcali without any better fuccefs j but, on adding Borax, the cafe was altered ; two parts of Topaz, with no Natural Hiftory.