nitrous gas escape; the molydbena is then oxygenated as far as is
possible, and is found at the bottom of the retort in a pulverulent
form, resembling chalk. It must be washed in warm water, to separate any
adhering particles of sulphuric acid; and, as it is hardly soluble, we
lose very little of it in this operation. All its combinations with
salifiable bases were unknown to the ancient chemists.
TABLE _of the Combinations of Tungstic Acid with the Salifiable Bases._
_Bases._ _Neutral Salts._
Lime Tungstat of lime.
Barytes barytes.
Magnesia magnesia.
Potash potash.
Soda soda.
Ammoniac ammoniac.
Argill argill.
Oxyd of antimony(A), &c. antimony(B), &c.
[Note A: The combinations with metallic oxyds were set down by Mr
Lavoisier in alphabetical order; their order of affinity being unknown,
I have omitted them, as serving no purpose.--E.]
[Note B: All these salts were unknown to the ancient chemists.--A.]
SECT. XXV.--_Observations upon Tungstic Acid, and its Combinations._
Tungstein is a particular metal, the ore of which has frequently been
confounded with that of tin. The specific gravity of this ore is to
water as 6 to 1; in its form of cristallization it resembles the
garnet, and varies in colour from a pearl-white to yellow and reddish;
it is found in several parts of Saxony and Bohemia. The mineral called
_Wolfram_, which is frequent in the mines of Cornwal, is likewise an ore
of this metal. In all these ores the metal is oxydated; and, in some of
them, it appears even to be oxygenated to the state of acid, being
combined with lime into a true tungstat of lime.
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