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the colouring parts of vegetables. “ It is in its elaflic date 
(fays that great chymift) that the qualities of this air are 
belt difcovered. In a fand-bath is to be placed a glafs 
retort, in which muriatic acid has been poured upon 
manganefe ; to this (mall receivers are to be adapted, ca¬ 
pable of containing about twelve ounces each, into which 
are to be poured about two drachms of water, without any 
other lute than a flip of blotting paper about the neck of 
the retort. In about a quarter of an hour, a yellow air 
is perceived in the receiver, which is to be taken off. If 
the paper has been properly applied, the air rufhes out 
forcibly; the receiver muft be quickly flopped, and ano¬ 
ther applied. Thus many receivers may be filled with 
the dephlogifticated muriatic acid ; but it is neceffary to 
place the retort in fuch a manner that the drops which rife 
into its neck may be able to fall back. The water ferves 
to retain the vapours of the acid. I ufe many receivers 
that I may not be obliged to repeat a fimilar diftillation for 
every experiment. It is not proper to employ large ones, 
becaufe, every time they are opened, a great part of the 
acid is diflipated in the air. What I fubmitted to exami¬ 
nation with this dephlogifticated muriatic acid was placed 
in the neck of the receiver, which I had hopped. The 
cork was turned yellow, as by aqua fortis. Paper tinged 
withturnfol became almoft white ; all red, blue, and vel- 
low, flowers, as alfo green plants, turned yellow in a fliort 
time, and the water in the receiver was changed into a 
pure but weak muriatic acid. Neither alkalies nor acids 
were able to reflore the colours of the flowers, or of the 
plants.” 
I took up the experiments of Scheele, fays Mr. Ber- 
thollet, and I attempted to throw more light on the na¬ 
ture of the oxygenated muriatic acid, and upon its prin¬ 
cipal properties. 1 have fhewn that one portion of the 
muriatic acid diffolved the calx of manganefe, and fepa- 
rated a part of the bafe of vital air, or oxygene, (which 
was in excefs in the calx of manganefe,) that the diflolu- 
tion might be performed; that this oxygene, being in a 
non-elaftic date, or, according to the expreflion of Dr. 
Prieftley, in a nafcent one, and thereby very much dif- 
pofed to form new combinations, unites itfelf with ano¬ 
ther portion of the muriatic acid, and that this combina¬ 
tion conftitutes the oxygenated muriatic acid gas. 
According to Scheele, “ The muriatic acid deprived of 
phiogifton, which is one of its conftituent parts, does not 
unite with water but in very fmall quantity, and does not 
render it very acid.” He appears to have contented him- 
felf with examining the water which had not been in con¬ 
tact with the gas except during the time of the operation, 
and to have concluded therefrom that the gas was very 
flightly foluble therein ; fo that it appeared to him better 
to employ the gas itfelf in his experiments than the wa¬ 
ter, which would be but weakly impregnated ; and which 
at the fame time would contain fmall quantity of muria¬ 
tic acid, which comes over in the diftillation, when the ne¬ 
ceflary precautions are not taken to retain it by an inter¬ 
mediate bottle. 
The firft objeft which I propofed to myfelf was to exa¬ 
mine the folubility of the oxygenated muriatic acid gas in 
water, becaufe I imagined, that, if I was able obtain a 
flightly concentrated folution, it might be more eafy to 
fubmit this liquor to different experiments than the gas 
itfelf. I foon perceived that this gas diflolved in water 
more readily, and in greater quantity, than carbonic acid 
gas, or fixed air; and that the water which was faturated 
with it acquired a very ftrong odour, a yellowifh colour, 
and other properties very ftrongly marked. I had made 
my firft trials by agitating water in contaft with the gas, in 
the manner in which water is generally impregnated with 
fixed air ; but the fuffocating vapour which exhaled de¬ 
termined me to employ Mr. Woulfe's apparatus, inftead 
of that procefs. I placed, betweetr the retort and the 
bottles filled with water, (defignedto be impregnated with 
the gas,) a fmall bottle, which I furrounded with ice, to 
condenfe the muriatic vapour which was not oxygenated ; 
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I alfo furrottnded with ice the bottles filled with water. 
I obferved during this operation, that, when the water 
became faturated with the gas, this laft took a concrete 
form, and fell (lowly to the bottom of the water. 
If there is filled with water, impregnated with the gas 
that is difengaged, (that is to fay, with oxygenated muria¬ 
tic acid,) a bottle having a long tube bentand plunged un¬ 
der a recipient filled with water, and this bottle is expofed 
to the light of the fun, bubbles are foon obferved to be 
difengaged, which pafs into the recipient, and which are 
of pure air (vital air, or oxygene gas); when the bubbles- 
ceafe to be difengaged, the liquor has loft its odour, its co¬ 
lour, and all its diftinguifliing properties ; it is then no 
other than water impregnated with common muriatic acid. 
This fimple experiment is fufficient to convince us that 
the oxygenated muriatic acid is really nothing but a com¬ 
bination of the muriatic acid with the bafe of vital air, or 
oxygene, which is in fuch quantity in the black calx of 
manganefe, that we need only urge this calx by a violent 
heat to draw off a great quantity; and then it is no long¬ 
er proper for forming the oxygenated muriatic acid, inaf- 
much as it is deprived of that portion of oxygene which 
(hould combine with a part of the muriatic acid. 
It is obfervable, that light has the property of difcn- 
gaging the oxygene which has combined \\ ifh the muria¬ 
tic acid, by reftoring to it that elafticity of which it was 
partly deprived; which heat alone is not able to do. It 
appears that light combines with the oxygene, and that 
it is to this combination the elaftic ftate of vital air is ow¬ 
ing, which, in loflng afrefli its elafticity by combuftion, 
(that is to fay, by a rapid union with certain fubftances,) 
lets alfo the principle of light efcape, and at the fame time 
much heat is difengaged ; the true relation of which to 
light we are as yet ignorant of. 
If vegetable colours are plunged into the oxygenated 
muriatic acid, they difappear more or lefs fpeedily, and 
more or lefs completely ; when there is a mixture of dif¬ 
ferent colouring particles, fome of them difappear more 
eafily, and admit only thofe to be perceived which offer a 
great refiffance, but which have neverthelefs fuffered a 
greater or lefs alteration. It is moff commonly the yellow 
parts which refift the moff, but all at laft difappear; and, 
when the oxygenated muriatic acid has fpent its power, 
it is brought back to the ftate of common muriatic acid; 
the colouring particles have therefore taken away its oxy¬ 
gene, and have acquired by that combination new proper¬ 
ties, having loft; that of producing colours. We (hall not 
fay any more at prefent about the properties of thefe oxy¬ 
genated particles; the oxygenated muriatic acid evidently 
owes the property of deftroying colours to oxygene, with 
which it is combined in great quantity, but with which 
it is very loofely connefted, and therefore eafily enters in¬ 
to combination with thofe fubftances which have any affi¬ 
nity with it. The affinities of thefe colouring particles 
(fo various in nature) with oxygene, with light, with al¬ 
kalies, and other chemical agents, cannot but form a very 
interefting, and almoft entirely new, part of philofophy. 
ACIDITY, alfo AcoR,y. Difeafes from this caufe are 
frequent. 
The feat of acidity in our bodies, as a difeafe, is princi¬ 
pally the ftomach and the fmall inteftines. An acid acri¬ 
mony is never fenfibly prevalent in the blood; yet urine 
hath been fermented into wine. 
An acid acrimony may derive its origin either from too 
great laxity and debility of the organs of digeftion, or 
from an excefs of acefcent food. The ferment excited in 
our food by the ftomach is fui generis ; if any part of our 
aliment is not digefted by the proper ferment of the fto¬ 
mach, it will run into its own ferment, and if vegetable 
it will become four. The food of children is for the mod 
part of the vegetable kind, and readily turns four in the 
ftomach, if the body be any way disordered ; hence moft 
of their diforders are accompanied with the evident iigns 
of acidity, as green (tools, gripes, See. Many aflert a pre¬ 
vailing acid to be the caufe of all difeafes in children, but 
acidity 
