410 Berzelius on a new Mineral Body, _[June, 
ing litmus paper feebly, and of becoming muddy when mixed 
with sulphuretted hydrogen gas. If we remove this first water, 
the air still retains a great part of its smell; and if we wash it 
with a new quantity of water, this additional liquid assumes the 
smell without being precipitable by sulphuretted hydrogen gas, 
or giving any traces of containing an acid. Selenic oxide gas 
is but very little soluble in water, and does not communicate 
any taste to it. This oxide is hkewise produced when sulphuret 
of selenium is dissolved in nitromuriatic acid. If the nitne acid 
is decomposed before all the sulphuret is decomposed, the sele- 
nic acid is in that case decomposed also, and selenium is 
reproduced, which precipitates in the form of a red powder, and 
the liquid exhales an almost insupportable odour of horseradish. 
If we distil together a mixture of selenium and selenic acid, 
there is disengaged likewise a little of this fetid gas; but the | 
greatest part of the mixture sublimes without alteration. [have 
not made the experiment of passing them together through a 
red hot tube ; in which situation the decomposition would pro- 
bably be complete. 
Selenic oxide gas does not combine with the caustic alkalies 
by the moist way; but the solutions of them assume the odour 
of it, as is the case with pure water. 
Selenic Acid.—If we heat selenium in a large flask filled with 
oxygen gas, it evaporates without combustion, and the gas 
assumes the odour of selenic oxide, just as would have happened 
if the sublimation had taken place in common air ; but if we 
heat the selenium in a glass ball of an inch in diameter, in which 
it has not room to volatilize and disperse ; and if we allow a 
current of oxygen gas to pass through this ball, the selenium 
takes fire just when it begins to boil, and burns with a feeble 
flame, white towards the base, but green or greenish blue at the 
summit, or towards the upper edge. The oxygen gas is 
absorbed, and selenic acid is sublimed into the cold parts of the 
apparatus. The selenium is completely consumed without any 
residue. The excess of oxygen gas usually assumes the odour 
of selenic oxide. 
If we pour nitric acid upon selenium and heat the mixture, the 
selenium dissolves with vivacity. At a low temperature this 
acid scarcely attacks it. If the selenium be in powder or in 
small fragments, these parts agglutinate together ; and towards 
the end, when the concentrated liqnid becomes boiling hot, the 
selenium melts, and forms black drops, which, buoyed up by the 
bubbles of nitrous gas attached to them, swim upon the surface 
of the liquid. If the liquid be now allowed to cool slowly, it 
deposits large prismatic crystals, longitudinally striated, which 
have a close resemblance to those of nitrate of potash. , 
Selenium dissolves still more rapidly in nitromuriatic acid : 
the same selenic acid is produced; and the body, by this way, 
cannot be united to a greater proportion of oxygen. Even when 
