BLOWPIPE REACTIONS. 89 
Silver.—If the silver is in very small quantities, as in argen- 
tiferous galena, the assay is put into a little cup made of bone 
ashes (bone burnt white and finely pulverized), and subjected 
to the oxidizing flame ; the lead is oxidized and sinks into the 
bone ashes, leaving the silver a brilliant globule on the cupel. 
Before cupellation it is often necessary to melt the assay to- 
gether with some borax and pure lead in a hole on charcoal. 
By this process the sand and impurities are removed, and a 
globule of lead is obtained which contains all the silver, and 
which may be separated from the slag and be oxidized as 
above. 
Arsenic.—In the closed tube arsenic sublimes and coats the 
tube with brilliant grains, or a crust, of metallic arsenic. If 
the mineral contains “sulphur as well as arsenic, sublimates of 
the yellow and red arsenic sulphides (orpiment and realgar) are 
often formed. Jn the open tube a sublimate of white arsenous 
acid is formed, which condenses in bright crystals on the walls 
of the tube, and a strong garlic odor is given off. On charcoal 
the alliaceous odor is at ouce perceptible. 
Antimony.—In the closed tube, when sulphur is present, the 
assay yields a sublimate which is black when hot, brown-red 
when cold. In the open tube dense white vapors are given off 
and a white amorphous sublimate covers the inside of the tube, 
which, for the most pirt, does not volatilize when reheated. 
On bhancoal the assay yields dense, white, inodorous fumes. 
Tellurium.—In the open tube a white or grayish sublimate 
is obtained, which may be fused to clear, colorless dr ops: On 
charcoal a white coating is produced, and the reducing flame is 
colored green. 
Sulphur.—All sulphates, and other sulphur-bearing miner- 
als, when heated on charcoal with soda, produce a dark, yellow- 
ish brown sulphide of sodium; and if a fragment of this is 
moistened and placed on a polished plate of silver, it turns it 
immediately brownish black, or black. Pure soda, and a flame 
wholly free from sulphur, is fieeded for the trial, since the least 
trace of sulphur in either vitiates the result. Many sulphides 
give fumes of sulphur on charcoal. The higher sulphides afford 
these fumes in a closed tube. The others afford fumes of sul- 
phurous acid in an open tube, which redden a moistened bluv 
litmus paper placed in the upper end of the tube. 
Selenium.—Selenium and many selenides afford a steel-gray 
sublimate in an open tube, which at the upper edge appears 
red. On charcoal brown fumes ave given off with an odor like 
that of decaying horse-radish., 
