C H E M I 
veau, renders them deliquefcent, and prevents their crys¬ 
tallization. 
The pyro-mucous acid, when eoncentrated by freez¬ 
ing, is very penetrating, and ftrongly reddens blue ve¬ 
getable colours. It fpots the fkin of a reddilh yellow 
colour; and this fpot does not difappear but with the epi¬ 
dermis. It rifes totally by the fire, and leaves only .a 
brown trace ; it.is changed, for the molt part, into gafe- 
ous carbonic acid and hydrogen gas, by cautious diftil- 
lation in well-cloled veflels ; it then affords a coaly refi- 
due, more abundant than when it is heated in open vef- 
fels: part rifes without alteration. Combined with ba¬ 
rytes, magnefia, lime, potafh, foda, and ammoniac, it 
forms neutral falts, which we call pyro-mucits, whofe pro¬ 
perties have hitherto been little examined, but which 
differ from all the known falts. It difengages the car¬ 
bonic acid from all thefe alkaline bafes with a ftrong ef¬ 
fervescence. 
Though the property of diffolving gold was formerly 
attributed to the fpirit of honey, it appears certain that 
the pyromucous acid does not touch this metal, nor pla- 
tina, nor filver, nor even mercury; but it may, perhaps, 
dilfolve their oxyds. This acid corrodes lead* and be¬ 
comes opake in confequence of the oxyd of this metal 
which is formed; the pyro-mucit of lead has the form 
of long cryfials : it likewife attacks copper, and becomes 
green; it diffolves tin, and attacks iron, with which it 
forms a cryftallizable fait. 
Its chemical attractions have been determined by Mor- 
veau in the following order : Potafh, l'oda, byrytes, lime, 
magnefia, ammoniac, alumine, metallic oxyds, water, 
alcohol. 
This empyreumatic ar id has not yet been much appli¬ 
ed to ule. The fpirit of honey, of manna, &c. was for¬ 
merly ufed in pharmacy, but this ul'age has long fince 
been abandoned The acid obtained by the diftillation of 
melafles is ufed in l'ome manufactories. 
Of the LIGNOUS MATTER. 
This name is given to a fubftance whofe properties 
agree not with any of the matters hitherto examined. 
From this definition, it will appear to be the fkeleton or 
laft remains of vegetable fublrances. By diltiiiing wood, 
we find diftinCt products, as, a particular acid, an oil, and 
fome carbonated hydrogen gas. The coal which remains 
in the retort is very confiderable; io that it may be faid 
that wood owes its hardnefs and other properties to the 
confiderable portion of carbon it contains. 
If lignous bodies treated with acids, which difunite 
their principles, they will be changed into vegetable 
acids which differ from each other only by the proportion 
of thofe principles. 
PYRO-LIGNOUS ACID. 
For obtaining this acid, Guyton direCts to diftil in an 
Iron retort, in the reverberatory furnace, little bits of 
very dry beech; to change the receiver when the oil has 
rifen; and to reCtify the prcduCt by afecond diftillation. 
The chemifts of Dijon found that fifty-five ounces of this 
wood in dry chips afforded feventeen ounces of rectified 
acid, of an amber colour, without mixture of oil, and 
whofe weight, compared with that of diftilled water, was 
in the proportion of forty-nine to forty-eight: 23A ounces 
of lime water were required to faturate one ounce of this 
acid. When gently heated, it rifes in vapour. A ltrong 
heat decompoles it, as well as all the other vegetable 
acids. It cannot be obtained in the concrete form, it is 
always liquid. 
It combines with earthy and alkaline bales, and forms 
peculiar falts, which we call the pyro-lignits of alumine, of 
barytes, of magnefia. of lime, of potafh, of foda, and of 
ammoniac. Thefe falts have not been yet examined with 
fufficient attention to enable us to give a fketch of their 
hiftory. Calcareous earths and barytes adhere more 
ftrongly to it than the alkalis 5 lime more ftrongly than 
S T R Y. 331 
barytes; and magnefia mere flrongly than ammoniac: 
fo that the order of thefe attractions alone might ferveto 
diftinguifh it from rhoft'of the other vegetable acids. It 
aCts on feveral metals, and dilfolves molt of their oxyds. 
It feems as if all woods would afford the fame acid by 
diftillation, fince box, birch, and beach, have already 
afforded a fimilar one. We perceive, however, that a 
number of experiments remain to be made to complete 
cur knowledge of the properties and diftinCtive characters 
of this acid. 
The fourth genus of vegetable acids, contains fuch as 
are obtained by fermentation, as the acetous acid, &c. 
which we fhall examine in fpeaking of the products of 
fermentation. 
The fifth, comprehends vegetable acids formed by the 
nitric acid. There are four lpecies: 1. The oxalic acid, 
which is obtained from fugar by nitric acid, for the man¬ 
ner of operating, fee Oxalic Acid, p.32.9. a. Camphoric 
acid, of which we fhall ipeak under Camphor. 3. Suberic 
acid, which fee under the feCtion on Cork. 4. Saccho- 
laCtic acid, which we fhall make known when we come 
to treat of Milk. 
Of CORK, and the SUBERIC ACID, 
Before Brugnatelli, no accurate experiment had been 
made upon cork. Several modern chemifts fuppofed that 
the acid he obtained from it was oxalic acid. But La 
Grange has fet the matter in a new light, by his experi¬ 
ments and obf'ervations printed in the twenty-third vol. 
of the Annales de Chimie, from which this account is 
abridged. 
For obtaining the acid of cork, which he calls fuberic 
acid, from fiber, coik, fix parts of nitric acid at 30° are 
to be diftilled by a gentle fire, with one part of the rafp- 
ings of cork; nitrous vapours are dil'engaged, the cork 
fwells and affumes a yellow colour; and, in proportion 
as the diftillation advances, it finks. When the froth, 
which is formed, ceafes to appear n the lurface of the 
liquor, the acid which had paffed over into the receiver 
is to be returned into the retort, and the diftillation re¬ 
peated till no more red vapours are produced. The retort 
is then to be taken from the fand-bath, and, while it is 
Hill warm, its contents are to be poured into a glafs or 
porcelain cup, which is placed on a fand-bath, and ex- 
pofed to a very gentle heat. The mixture, which is to be 
conftantly ltirred with a glafs rod, gradually thickens ; 
and, as foon as white vapours are obferved to be difengag- 
ed, the mixture is to be removed from the fand-bath, and 
ftirred carefully till it cools. During the diftillation of 
one drachm of cork with fix of nitric acid, 113-63 inches 
of gas were difengaged; of this forty cubic inches were 
carbonic acid, and the reft: nitrous gas. The yellow fa- 
line mafs is now to be mixed with twice its weight of 
water, melted with a gentle heat and filtered. The liquor 
which pafles through the filtre, is of a clear amber colour, 
and has a peculiar fmell fomewliat fimilar to that of 
Prufiic acid. It becomes muddy by cooling, is covered 
with a faline pellicle, and depofits a pulverulent fediment. 
The precipitate is to be collefted and dried with a 
gentle heat, (not more than 30 0 of Reaumur,) and the 
liquor evaporated till the acid which it contains be all 
depolited. This acid is obtained by precipitation in a 
pulverulent form, and by evaporation in thin irregular 
pellicles. Difiolved in a fmall quantity of boiling water, 
it llimulates the throafand excites coughing. The acid 
obtained by this procefs is always coloured; hut it may 
be purified, 1. By faturating the fuberic acid with potafh, 
bringing the combination to the confidence of a fyrup, 
and then precipitating by an acid. 2. Boiling the acid 
with charcoal. The part not foiuble in water is a fub¬ 
ftance fimilar to wax. 
The fuberic acid is in a folid form, not cryftallizablej 
it is obtained in powder by precipitation, and by evapo¬ 
ration in thin irregular pellicles. Its tafte is fome what 
bitter, and acid. It reddens blue vegetable colours, and 
attracts 
