216 State of Chemical Science on the Continent. 
sulphur, and it resolves, on being isolated, into complete acid 
and oxide ; as the oxide of sulphur resolves itself into sulphur 
and sulphurons acid; and we may rigorously suppose that the 
one is a combination of carbonic acid with the oxide of carbon, 
and the other a combination of sulphurous acid with sulphur, 
formed both into salts. The weak oxides merely retain the 
carbonous acid long enough to strip it of its water, and after- 
wards they give up their oxygen to it, which is saturated into 
carbonic acid. The strongest oxides separate it instantly from 
its water; and as they do not give their oxygen to it, the car- 
bonous acid ‘on quitting them is resolved into oxide of carbon 
and cafbonic acid; and the oxides which retain it strongly, as 
well as its water, allow its oxygen to concentrate into a portion 
of its substance, and in such a manner that carbon is set free, 
and hydrogen is displaced from it, by the water: and this prin- 
ciple may form carbonated hydrogen and empyreumatic oil. 
M. Dulong was thinking of my metallofluores and metallochlores 
when he supposed it possible that reduced metals could be united 
to carbonic acid; but the case is very different; for the carbonie 
acid retains its own water, and deposits only the water of its or- 
ganization ; whereas the fluoric and muriatic acids deposit the 
first water, and unite dry with the reduced metals. The results 
of Dulong show that the oxides in the carbonates are propor- 
tioned to the quantity of oxygen belonging to the dry carbonic 
acid, which converts the carbonous acid into common carbonic 
acid. 
Count Real, who lately spent a few days with me, has in- 
vented an instrument for the extraction in the cold way of sub- 
stances of the organic kingdoms, which is very ingenious, 
simple, and convenient. The dissolving liquid, which sometimes 
becomes a displacing liquid, produces its own action. The in- 
strument is a cylinder of any given size; but it ought to have 
the power of considerable resistance. ft may be made of glass, 
wood, tin or copper, according to the use for which it is in- 
tended. Two diaphragms, or wire sieves, are fitted in at each ex- 
tremity, and are intended to contain the substance, which ought 
to be as minutely pounded as possible, and a little pressed down, 
that the liquid when entering it may be retained. Over this cy- 
linder a tube may be fixed, from two up to eight feet in height, 
destined to receive the menstruum, and to “produce a strong 
pressure, which may be rendered sudden or gradual at pleasure. 
If we fill the tube with mercury, the matter in-the cylinder being 
penetrated with spirits of wine, oil, or water, the pressure be- 
comes immense. This tube may be as narrow as you please, 
since a liquid, whatever be the base of its column, acts in pro- 
portion to the height of the latter, and not in proportion to the 
diameter 
