211 
CHEMISTRY. 
orifice at D, flopped with a ground-ftopper, at which an 
additional fupply of either acid, or water, or chalk, may 
be occafionally introduced. The middle vefiel B, is per¬ 
forated both above and below. Its inferior neck is fitted 
by grinding into the neck H of the lower vefiel. In the 
former is a glafs valve, formed by two pieces of tube, 
with a lens, which is moveable, between them. This 
valve opens upwards, and fufFers the air to pafs; butthe 
water cannot return through the tubes, partly becaufe 
the orifice is capillary, and partly becaufe the flat lens 
covers the hole. The middle vefiel is furnifhed with a 
cock E, to draw off its contents. The upper veffel A is 
fitted, by grinding, into the upper neck, of the middle 
vefiel. Its inferior part confifts of a tube.that pafles al- 
moft as low as the centre of the middle veffel. Its upper 
orifice is clofed by a ground ftopper F. When this ap¬ 
paratus is to be ufed, the effervefcent materials >are put 
into the lower vefiel, the middle veffel is filled with pure 
water, and put in its place ; and the upper veffel is nearly 
flopped, and likewife put in its place. Theconfequence 
is, that the carbonic acid gas pafling through the valve 
at H, afcends into the upper part of the middle veffel B, 
where by its elafticity it re-afiis on the water, and forces 
part up the tube into the veffel A; part of the atmof- 
pherical air, in this laflr, being comprefled, and the reft 
efcaping by the ftopper, which is made of a conical fi¬ 
gure, that it may be eafily railed. As more carbonic 
acid gas is extricated, more water rifes, till at length the 
water in the middle vefiel falls below the lower orifice 
of the tube. Carbonic acid gas then pafles through the 
tube into the upper vefiel, and expels more of the atmof- 
pherical air by railing the ftopper. In this fituation the 
water in both vefiels being in contact with carbonic acid 
gas, becomes ftro'ngly impregnated with that fluid, after 
a certain time. This effect-may be haftened by taking off 
the middle and upper veflels together, and agitating 
them. The valve is the moft defective part of this appa- 
tus ; for the capillary tube does not admit the air through, 
unlefs there be a confiderable quantity condenfed in the 
lower veffel; and the condenfation has in fome inftances 
burft the veffel. 
Progreflive improvement has fuggefted more Ample me¬ 
thods of effecting the fame purpofe. A little calk filled 
with half carbonic acid gas, and half water, agitated by 
fufpenfion in the air, may ferve the purpofe of a flight 
experiment. But the moft complete apparatus for pro¬ 
moting the diffolution of acid gas in water, is the follow¬ 
ing; which may ferve not only to make carbonats of fo- 
da and potafh, but in general to mix all gafes which re- 
fufe to unite with liquids, becaufe the furfaces are re¬ 
newed. This machine is reprefented in the fame plate, 
at fig. 3, of which the following is the explanation : 
A, B, are bottles to a£l alternately; chalk is firil putin, 
and over that pour fulphuric acid weakened with water, 
by means of a convoluted columnar tube, with a funnel 
at the top, to pour in the liquor; it is thus conftrudted 
to counterbalance the expanfion of the gas, and thus 
force the acid to combine with the water. The tube 
which goes from G to the jar I, is to laturate with the 
acid in gas when required. E and F are bottles of equal 
fize. Put the water to be acidulated in E ; it might in¬ 
deed be put into C; however the firil bottle may be left 
to receive the impure acid which pafles off; but then the 
branch which comes from the bottle F mull not be 
plunged therein. When preffure is ufed in E, it com¬ 
municates to G and F, and even to D, by means of the 
fyphons ; fo that the liquor is moved in fucceflion : when 
all the fluid is arrived, the acid is made to a£l on the 
chalk in B, which a£ls by preffure in its turn, and drives 
it back to the other fide, and fo in conflant alternate fuc¬ 
ceflion, till any quantity of water is aerated that may be 
required. 
Water, thus faturated with carbonic acid gas, differs 
from natural mineral waters only by the other elements 
which they hold in diffolution. Hence by adding ten 
drops of tindlura martis cum fpiritu l'alis, to each pint 
of water, after it is impregnated with the carbonic acid 
gas,'it will referable the genuine pyrmont water. But 
to render it chalybeate, add only one grain of fait of fleel, 
to the fame quantity of water. It has the property of be¬ 
ing heavier than diflilled water; it turns blue paper red. 
If placed under the receiver of an air-pump, and a vacu¬ 
um be made, it imbibes falter than Ample water; and yet 
this gas, in its difengagement, takes away fome caloric, 
and occafions cold, which muft leifen the aftion of the 
fire; the water imbibes alfo, and the thermometer is far 
from 6o°. 
Water, charged with carbonic acid, lofes that acid by 
being expofed for a certain time to the air. Caloric dil- 
engages this acid with rapidity, and with a fort of effer- 
vefcence: but the latter portions adhere very ftrongly to 
the water, and muft he boiled a long time before they 
will leparate ; fo certain is it that the lalt elementary par¬ 
ticles of a compound body flick together with great ob- 
ftinacy. 
This liquid acid precipitates lime-water ; when the lime 
is faturated with theacid, the precipitate is infoluble ; but 
by adding more of the acid, the precipitate difappears. It 
is to be obferved, that it is no longer the lime which is dif- 
folved, butthe compoundcarbonatof lime which was form¬ 
ed ; this is proved by pouring cauflic potafh over it, which 
only abforbstheexcefsof acid, and the carbonatof lime ap¬ 
pears again. With airexpired from the lungs, afimilareffedl 
is produced. Lavoifier has proved, that refpiration is a 
continual combination of atmofpherical air with the hy¬ 
drogen and carbon of blood. This water appears in va¬ 
pours during refpiration in a cold air, and it is called pul¬ 
monary tranfpiration: carbonicacid gas is difengaged alfo. 
It is certain that carbonic acid gas is compofed of car¬ 
bon and oxygen. The following experiment will farther 
demonftrate the truth of the aflertipn. Take a glafs tube 
clofed at one end. Put in a bit of phofphorus, and then 
fome carbonat of foda dried and reduced to a fine pow¬ 
der; put one part of phofphorus to five of the carbonat 
of foda: then clofe the tube, making it end in a finall 
capillary tube. Place the tube in a furnace, but fo that 
the extremity where the phofphorus lies may not feel the 
adlion of the caloric; pafs it through the grate of the 
furnace, and furround the tube with lighted coals, and 
heat till the carbonat is melted: then raile the tube, and 
warm the phofphorus. The phofphorus burns, and de- 
compofes the carbonat of foda; pholphat of foda is form¬ 
ed, and the carbon of the carbonic acid is left to itfelf; a 
little phofphoric hydrogen gas is previoufly difengaged. 
Here then two affinities are employed: i. The affinity 
of the oxygen for the phofphorus ; 2. Of the phofphoric 
acid, which has been formed, for the foda. To get at 
the carbon refulting from the experiment, take the black 
mafs and wafh it in diflilled water; then ftrain. The 
phofphat of foda is held in folution in the liquor, and 
the carbon finks. Clouet has a very ingenious and Am¬ 
ple experiment, which fliews that carbonic acid may be 
difengaged to form Heel. For this we muft refer to the 
fefrion on iron. 
Several chemifts have obferved, that this acid, in its 
elaflic Hate, pofiefles the property of preferving animal 
fubftances, by retarding putrefadlion, and even diminifh- 
ing its effects after it has commenced. Hence it was, 
that M’Bride fuppofed that it unites with the putrid fub- 
ltance, and reftores the acid it had loft during the time 
of putrefaftion. This laft phenomenon, according to his 
doflrine, arifes from the natural decompofition of orga¬ 
nic bodies, andthediffipation of the carbonic acid, which 
he calls fixed air: for which reafon he fuppofed that the 
application of this acid was indifpenfably necefl'ary to 
compenfate the lofs fuftained in the animal economy, and 
to reltore the fluids to their former ftate when changed 
by heat and motion. He admits the exillence of this 
acid 
