REPORT ON CHEMISTRY. 
471 
not been wrought for several years. The process for extract¬ 
ing the vanadic acid is very simple. The mineral is dissolved 
in muriatic acid,—the lead and arsenic separated by sulphu¬ 
retted hydrogen,—the filtered liquid reduced to smaller volume 
by evaporation, supersaturated at a boiling temperature with 
carbonate of ammonia, and filtered while hot. On cooling, the 
vanadiate of ammonia crystallizes, forming a white crust which 
adheres strongly to the sides of the glass. It may be purified 
by a second crystallization, and the vanadic acid is obtained 
from the purified salt by driving off the ammonia with the aid 
of heat. 
Tellurium .—Berzelius has for some time been engaged in an 
elaborate investigation of the properties and combinations of 
tellurium, and has already obtained many very interesting results. 
Several of these, which he has been kind enough to commu¬ 
nicate to me, I shall here insert. The following processes—the 
only ones yet given—by which it can be obtained perfectly pure 
from the tellurets of bismuth and silver, he has already pub¬ 
lished in his Arsberattelse for 1832, p. 104. The telluret of 
bismuth, from Schemnitz in Hungary, is reduced to powder, 
washed, mixed with twice its weight of carbonate of potash, 
made into a paste with oil, and placed in a well-covered crucible, 
to which heat is at first carefully applied, but which is gradually 
raised to full redness, and kept so as long as flame appears 
between the crucible and the lid. When cold, the mass is po¬ 
rous and of a dark brown colour. It is powdered and well 
washed (with cold water previously boiled to free it from air,) 
in a filter, by which an opaque purple red solution is carried 
through, and there remains a dark brown mass consisting of 
charcoal and bismuth, with very little tellurium. The solution 
is telluret of potassium. A current of air is passed through it, by 
which the potassium is oxidized and the tellurium precipitated. 
In the alkaline liquid remains a little sulphuret and seleniuret 
of tellurium, which may be thrown down by an acid. 
The precipitated metal is washed, dried, and melted. It is 
then placed in a small elongated capsule of porcelain, introduced 
into a porcelain tube, and exposed to the heat of a furnace while 
hydrogen gas is passed over it. The tellurium sublimes into 
the cool part of the tube, and there remains in the capsule a 
residuum, consisting chiefly of telluret of gold, but containing 
also tellurets of copper, iron and manganese, which had all been 
present in the alkaline solution. 
From the telluret of silver it is easiest prepared by heating 
it in a current of chlorine, by which the chloride of tellurium 
is driven off, and condenses in a solid form, leaving chloride of 
