1819.] extracted from Pyrites at Fahlun. 41f 
sulphuric acid, selenic acid, and peroxide of manganese, are 
distilled together, the selenium does not unite with an addi- 
tional dose of oxygen, but oxygen gas is disengaged, and there 
are formed a sulphate and a seleniate of manganese. 
If the nitromuriatic acid solution of selenium be evaporated 
in a retort, the nitric and muriatic acids come over first, and the 
selenic acid remains in the retort in the state of a white saline 
mass, which sublimes at a higher temperature. The acid does 
not melt ; but it diminishes a little in bulk at the hottest place, 
and then assumies the gaseous form. Selenic acid gas has a 
déep yellow colour, but not so deep as that of selenium itself. 
Indeed it would be difficult to distinguish it from chlorine gas? 
I have not been able to determine the temperature at which 
selenic acid is converted into vapour; but if we heat a mixture 
of sulphuric acid and selenic acid, the latter acid sublimes first ; 
and when it is almost completely volatilized, the sulphuric acid 
begins to rise. 
Selenic acid condenses in the cold part of the apparatus in 
the form of very long four-sided needles. If the retort be large, 
they may have the length of two inches, or even more. If the 
part of the retort in which the acid is condensed be rather hot, 
the acid is deposited in a white, dense, semitransparent mass. 
At the mstant that selenic acid is taken out of the retort, it 
has a dry aspect and a peculiar lustre ; but when left in the air, 
the crystals adhere to each other, and the lustre becomes dull ; 
but they do not become liquid. The reason of this is, that the 
erystals combine with the water of the atmosphere, and produce, 
so to speak, a salt, having water for its base. A similar pheno- 
menon takes place with vitreous boracic acid. This affinity acts 
with a great deal of rapidity ; so that it is difficult to weigh a 
portion of the selenic acid without its absorbing during the ope- 
ration a sufficient quantity of moisture to alter its weight. When 
the acid is afterwards heated, it loses its water, which distils 
over for a long time before the acid begins to-be volatilized. 
Selenic acid has a pure acid taste, which leaves a slightly 
burning sensation on the tongue. When in the gaseous form it 
has the sharp odour which usually distinguishes acids, without 
having any peculiar to itself. It is very soluble in cold water, 
and dissolves in almost every proportion in boiling water. A 
saturated solution of selenic acid in water crystallizes when 
rapidly cooled in small grains, and when slowly cooled in striated 
risms. These crystals consist in a combination of selenic acid 
and water. The solution, when evaporated spontaneously, gives 
acicular crystals arranged in stars. Selenic acid dissolves with 
facility and in great abundance in alcohol. If we distil an alco- 
holic solution of it, the product has a distinct, etherial smell, 
between that of nitric and sulphuric ether; though the quantity 
of ether produced in my experiments was too small to be sepa- 
rated when the ethereal alcohol was saturated by muriate of lime. 
