THE CLEMENTS LIBRARY
oo
Books of Industrial Technology
from the
FREDERICK S. UPTON FUND



с нE MI CAL
A N D
ECONOMICAL ESSAYS,
DESIGNED
TO ILLUSTRATE
THE CONNECTION BETWEEN THE THEORY AND PRACTICE
OF CHEMISTRY, AND THE APPLICATION OF
THAT SCIENCE TO SOME OF THE ARTS
AND MANUFACTURES OF
THE
UNITED STATES OF AMERICA.
IT IS A PITY SO FEW CHEMISTS ARE DYERS, AND SO FEW DYERS
CHEMISTS."
BY JOHN PENINGTON.
PHILADELPHIA:
PRINTED BY JOSEPH JAMES.
M, DCC, XC.


TO
Caspar Wistar, junior, M. D.
AND
PROFESSOR OF CHEMISTRY
IN THE COLLEGE OF
PHILADELPHIA,
THE FRIEND AND PATRON OP
CHEMICAL ENQUIRIES IN AMERICA,
THESE ESSAYS ARE INSCRIBED, BY
HIS
SINCERE
FRIEND,
AND
PUPIL,
JOHN PENINGTON.
PHILADELPHIA,
MAY 259 1790.


PRE FACE.
FOUR
OUR of the eſſays, contained in this volume,
bave already appeared in the Columbian Maga-
zine, and, for very obvious reaſons, it is proper, in
this place, to lay before the reader ſome little ac-
count of the occaſion of their publication.
In February, 1789, the editor of that work pub-
liſhed ſeveral recipes for making Pruffian blue,
which, in the preſent improved ſtate of chemiſtry,
are far from being ſo economical as they might be.
I offered ſome remarks on them to him, which he re-
queſted me to draw up for inſertion in the next num-
ber, and accordingly I gave in thoſe obſervations onz
Prufan blue which were printed in the number for
March following, part of which I have retained in
this volume. In conſequence of this, one of the
pro-
prietors, and the editor, expreſſed a wiſh that I would
furniſh them with chemical recipes for a part of the
Magazine dedicated to “ uſeful hints and recipes."
I did not feel ambitious to be a mere copier or com-
piler of proceſſes, but gave it as my opinion, that an
attempt to illuſtrate the connection between rational
chemiſtry and many of the uſeful arts, would be much
more likely to anſwer their purpoſe: they concur-
red in this idea, and I ſupplied them with the firfi
four of theſe eſſays. But a Magazine was found to
be an improper place for them, becauſe the ſubjects
they treat of are intereſiing only to a particular claſs
of readers, and on that account we mutually agreed
to diſcontinue that mode of publication; the printer,
however, thought it would be proper to publiſh then
colle&tively, and frequently offered me a liberal com-
penſation for the copy: from his profeſſional know-

( vi )
ledge, as well as his literary abilities, I had reaſon
80 confide in his opinion; and although the readers
of the eſſays that have been publiſhed, for a reaſon
already given, may have been but few, yet I bave no
cauſe to be diſatisfied with the reception they have
met with ; many good judges in chemiſtry have alſo
been pleaſed to expreſs their approbation of ſome ideas
I have advanced; beſides, I refle&ted that if it were
proper to begin ſuch an undertaking, it would cer-
tainly be improper to leave it unfiniſhed: all theſe
circumſtances concurring together have induced me to
commit them to the world in their preſent form.
With much heſtation, I announce myſelf as the
author: at this early period of life, I may appear
vain and ofteniatious, for in moſt caſes the authors
name need not appear with this work; and as I am
totally unknown in the literary world, I cannot hope
that my name will recommend this production: but
on anonymous publication, reſpecting faets, carries
with it the appearance of extreme and unneceſſary
timidity, or want of candour.
The ſubjeets of theſe eſays are acknowledged, by all
chemiſts, to be of much importance; bow I have
handled them, is not to be enquired of me: but the
reader may depend upon it, that what I have de-
clared to be facts, are either abſolutely ſuch as I re-
late them to be, or at leaſt they appeared to me to be
fo.
PHILADELPHIA:
MAY 25th, 1790:

CON TEN T S.
1
Introductory Efſay,
Ejay I. Chemical Apparatus---Furnaces--- Earths, II
II. Earths continued.--their uſes in pottery, 25
III. Salts in general, chryftallization--Sea falt, Ep-
ſom falt ---Preparation of magneſia,
36
IV. Chemical attractions, with a table of ſingle, ſingle
elective, and double elective attractions,
45
V. Analyfis of the twenty-four falts moſt commonly
known and uſed, with the acids and bafes which form
them,
68
VI. Purification of aqua-fortis without a ſolution of
filver,
85
VII. On the uſe of the pig-nut as a vegetable aſtring-
ent---ideas on the uſes of allum in dying,
90
VIII. Calcination of metals --a defence of the doc-
trine of phlogiſton, with certain modifications,
IX. An analyſis of the ores of metals by ſolution, 112
X. An economical method of obtaining regulus of
antimony,
XI. The proceſs of making Pruffian blue, with facts
and obſervations on the theory,
15
XII. The proceſs of making patent yellow, with ne-
ceffary cautions and directions,
134
XIII. Sulphur---American pyrites---copperas--- hints
of improvements in making vitriolic acid from ſul-
phur,
140
XIV. Unctuous oils---foap--- fome curious facts re-
fpecting it---it's decompoſition by hard water,
151
XV. Colouring matter of vegetables---fome ideas n
the cauſes of the changes of colour in growth,
XVI. An explanatory eſſay.
100
I21
158
168
Α Ρ Ρ Ε Ν Ο Υ Χ.
Eſſay on the phenomena, cauſes, and effects of fermen.
tation.
173


C H E M ICAL
A N D
E CON OM I CAL
ES SAY S.
INTRODUCTOR Y ESSA Y.
B
Y chemiſtry we ought to underſtand in the
fulleſt extent, that ſcience which doctor
Black, profeſſor of chemiſtry in the univerſity of
Edinburgh, defines to be “the ſcience which
teaches the effects of HEAT and MIXTURE upon
all matter;" and to give a clearer idea of a che-
mical operation, we may add, that an alteration
of the ſenſible properties of the body operated
upon, is always produced. Under this view, the
ſubject muſt appear to be infinite, and not that
confined ſcience that thouſands look upon it to
be, even in the preſent times; and as both heat
and mixture are made uſe of in many of the arts
and manufactures, we may venture to call them
chemical arts. Few people have a right idea of
chemiſtry. By the generality of mankind, a che-
miſt is ſuppoſed to be a perſon that compounds
drugs and medicines for the uſe of phyſicians.
The art of preparing medicines is called phar-
B

2
AND
CHEMICAL
macy, which itſelf is but a branch of chemiſtry:
Since all ſciences have aſſumed a more liberal
appearance, and gentlemen who were neither
phyſicians or druggiſts had purſued the ſtudy of
chemiſtry, it was thought to conſiſt in a number
of pleaſing and entertaining experiments; it
appeared deep and abſtruſe to the uninformed,
and the writings of philoſophical chemiſts be-
ing utterly unintelligible to every beginner, it
became, of conſequence, diſguſting: and a-
midſt a multiplicity of technical terms, without
previous explariation, the enquirers after uſeful
knowledge, found it difficult to perceive the end
to be anſwered by a knowledge of the ſcience.
We have mentioned already, that chemiſtry, as
a ſcience, firſt took its origin among phyſicians;
and was from thence thought to be an appendage
to the healing art--this happened, moſt probably,
becauſe the medical character requires an exten-
five education, and an habit of reaſoning upon,
or at leaſt an attempt to account for all the
phænomena they obſerve.
The object of chemiſts is to reduce all matter
to their moſt ſimple forms; and ſuch ſubſtances
as they can neither ſimplify nor compofe by unit-
ing any more ſimple ſubſtances together, they
call chemical elements, which means nothing
more than that they are yet unable to ſimplify
them; for, perhaps, what may with juſtice be
called a chemical element at the preſent time,
may be found by more ſucceſsful chemiſts in the
courſe of twenty years to be a compound body:
this is called the method of inveſtigating chemi-
ſtry by analyſis, ſtrictly ſo called; a means that is
frequently doubtful: with more ſucceſs we make
uſe of ſyntheſis to direct us, by which term we

ECONOMICAL
3
ESSAYS.
mean the power of adding certain ſubſtances,
whoſe nature is already known; to a body whoſe
properties are unknown, when, by obſerving cer-
tain appearances which take place in the mixture,
we become enabled to know the nature of the
ſubſtance we are examining: in this caſe we an-
alyſe a body by ſyntheſis.
When we conclude from our experiments that
any ſubſtance is a compound body, we muſt al-
ways unite together all thoſe parts which we
fuppoſe compoſed it; and if we find that the ar-
tificial compound reſembles the natural com-
pound in all its ſenſible qualities, we may juſtly
infer that our analyſis is juſt, otherwiſe it muſt
be doubtful. To illuſtrate this idea with a fa-
miliar example: we procure fome fea-water; its
fiuidity convinces us that there is pure water in
it, whilſt our taſte proves there muſt be ſome-
thing beſides pure water, conſequently ſea-water
cannot be a ſimple ſubſtance. Every one has
ſeen that pure water boiled in an open veſſel,
will in time entirely boil away. Let us then try
a chemical experiment with ſea-water; we boil
it in an open veſſel until all the water is gone,
when we find remaining in the veſſel a white
maſs, that has a faltiſh taſte, almoſt exactly re-
ſembling our table falt: from this rough analyſis,
therefore, we conclude that ſea-water conſiſts
of a certain quantity of common falt diffolved in
pure water. But a chemiſt aſks us, how are
you certain that ſea-water contains this falt? May
not the ſalt that you have obtained from ſea-
water have been formed or created by the heat
of the boiling fluid ? We anſwer theſe queſtions
by an experiment or two:
a certain
quantity of pure water to the ſalt we obtained
we add

4
AND
CHEMICAL
from the ſea-water, and then find that it makes a
mixture exactly reſembling the original ſea-
water in all its properties; therefore our analyſis
was juſt. But to prove it ſtill more, we add as
much common falt to a ſimilar proportion of
common water, as the ſea-water contained, and
then we ſhall find that we have got a genuine
artificial ſea-water.
This method of inveſtigating chemiſtry, would
to a manufacturer or artiſt, appear endleſs, and
in a great meaſure unproductive : the deſign is
not immediately ſeen, and we follow with a
good deal of difficulty any author, when he can
neither afford us pleaſure, or a certain proſpect of
advantage. Chemiſts themſelves belong to two
great and diſtinct claſſes, which, it is a pity are
not connected; in the one claſs we may rank
thoſe who perform a great number of operations
by heat and mixture, without ever knowing the
ſecondary cauſes of the effects produced ; theſe
are called practical chemiſts, ſuch are dyers,
who cannot account for, or conceive why, allum,
for inſtance, ſhould be of uſe in their art; or
why galls and copperas ſhould produce a black
dye; fuch alſo are tanners, who cannot explain
the action of the oak bark upon the hides ; fuch
likewiſe are many apothecaries, who can make
aqua fortis, &c. &c. but know nothing of the
rationale of the proceſs; the other clafs is the
mere theoriſt, who is well acquainted with the
" effects of heat and mixture” upon all bodies,
and can account for them all, but never foils his
fingers with a piece of charcoal, or has had oc-
cafion to break a crucible; ſuch a chemiſt can
inform us admirably how the changes of colour
in dying are produced, but would be unable to

ECONOMICAL
5
ESSA Y S.
produce them himſelf; he can account for the
action of oak bark upon animal ſubſtances, with-
out ever having ſmelt the odour of a tan-yard;
he could explain the theory and proceſs of mak-
ing aqua
fortis; and perhaps were he to attempt
to make it, he would be two hours kindling a fire
in his furnace, break his diſtillery apparatus,
loſe all his aqua fortis, and fuffocate himſelf
with the fumes. From the compariſon every
one will allow that the practical chemiſt is the
moſt reſpectable character; but many worthy
gentlemen of this claſs have contended, that
theoretical chemiſtry could be of no uſe to them.
This idea, however, will admit of much diſpute :
if we appeal to fact, we find that many of the
moſt uſeful diſcoveries in the arts have been
made by men who have combined fome kind of
theory with their practice. Aqua fortis and fpi-
rits of ſalt, ſo uſeful in many chemical arts as
our future eſſays will evince, were both diſcover-
ed by ſuch chemiſts. It is true that many have
itumbled in the courſe of their proceſſes, upon
facts of importance, undirected by theory or de-
fign, ſtill, however, mere theory has ſuggeſted
conſiderable improvements. For inſtance, a the-
ory of the nature of fulphur, has ſuggeſted a plan
which has been realized to the great advantage of
mankind, of making oil of vitriol from this min-
eral. Many ſay that philoſophical chemiſts ſpend
all their time in experiments that either are mere-
ly amuſing, or elſe only tend to the improvement
of the medical art. This, I confefs, is an ob-
jection to the men, not to the ſcience; others ſay
that their diſcoveries refpe&ting the nature of
bodies are of no uſe. It is difficult to ſay how far
a new fact, at preſent apparently uſeleſs, may be

6
AND
CHEMICAL
The mag-
converted to the intereſt of the arts.
netic needle was for ſeveral hundred years an
uſeleſs diſcovery, at preſent there is ſcarce one of
more advantage. The power of ſteam was for
a long time conſidered as a pretty philoſophical
experiment; it is now the means of immenſe
wealth to a number of individuals in Europe.
The inveſtigation of the * chemical attractions,
has diſcovered thoſe moſt beautiful pigments, the
Pruffian blue, and the patent yellow. By having
ſome kind of theory to direct us, we ſtand a
much better chance of making improvements in
our reſpective arts; thus a potter, who wiſhes
to procure an earth fit for making elegant or uſe-
ful veſſels, is always directed in his choice by
ſome theory, although generally imperfect: he
firſt knows that white clays are moſt likely to re-
main white after baking: he knows that a ductile
clay will be eaſieſt to mould: he finds ſuch a clay;
truſting ſomewhat to his theory, he goes to work,
but his wares become red: he cannot account
for it: he gives up the idea of truſting to thoſe
appearances, and is diſcouraged from making a
freſh attempt: he reſts in the rational concluſion,
founded on experiment, that all white clays will
not make white ware: a chemiſt enquires into
the cauſe of the red colour, and finds he has rea-
ſon to conclude that it is owing to iron: before
be recommends an earth as a ſubject of pottery,
he examines it to find if it contains iron, if it
does, he concludes from ſimilar experiments,
that it will become red in baking, and he rejects
it as improper.
When theory is founded in experiment, as all
* See Eſſay IV.

ÉCONOMICAL
7
ESSA Y S.
rational theory ought to be, its importance muſt be
obvious; for no artiſt, however uninformed he
may
be of true fcience, performs any operation
without ſome kind of explanation or theory. Aſk
a dyer the uſe of allum in his art, he thinks he
explains it fufficiently by telling you it ſets the
colour; or aſk a black-ſmith the uſe of heating
and hammering caſt-iron, in order to make bar-
iron, you will find if he is a ſenſible man in his
profeſſion, he afferts that fulphur, the cauſe of
its firſt brittleneſs, is beat and burnt out in that
operation; whilft a rational chemiſt can fairly
prove that a great deal of brittle caſt-iron does
not contain a particle of fulphur.
After all, it would, perhaps, be loſt time for
any manufacturer or chemical artiſt to ſtudy the
theory completely; it may, perhaps, be well
enough, if each one would perfectly underſtand
as much theory as is neceſſary for information
in his own buſineſs. In the following eſſays we
mean to adhere to this idea, we ſhall diveft them
as much as poſſible of all technical terms, and
whenever they unavoidably occur, we ſhall at-
tempt ſuch explanation of them, as the moſt igno-
rant may be able to comprehend. We will not
pretend to any merit for originality or novelty, our
intention is only to fuggeſt ſome improvements,
in the arts and manufactures dependent upon
chemiſtry, adapted to the United States of Ame-
rica: theſe ideas we ſhall attempt to lay down in
a clear intelligible manner, ſeveral eſſays how-
evers, will be merely ſpeculative, and intended
to afford fome amuſement to the theoretical che-
miſts who ſhall have patience and perſeverance
enough to peruſe the other eſſays. The firſt
ſcheme has never been attemped in America, and

8
AND
CHEMICAL
ever now we are certain that our mode of execu-
tion will fall far ſhort of perfection. If however, it
ſhould ſuggeſt an hint to an abler hand to purſue
the ſame ſcheme upon a more extenſive ſcale ; if
it ſhould turn the attention of one manufacturer
to the cultivation and improvement of his own
buſineſs, or even if our familiar manner of hand-
ling the ſubjects, ſhould make but one young man
fond of the ſcience of chemiſtry, we certainly
ſhall not have written in vain, and our moſt fan-
guine hopes will be anſwered by the event. The
reader will find us occafionally recommending
fome manufactures unattempted in America.
Many are the difficulties attending ſuch attempts ;
in a general way ſcheming is an unſafe and un-
profitable purſuit; thoſe, however, that we mean
to recommend, we hope will be found to be ſuch
as will turn out profitable, when cultivated with
prudence.
We cannot preſume to ſuppoſe that any man
already in a good buſineſs, would leave it to
purſue any of theſe ſchemes, but whilft ſuch
numbers complain of the want of fufficient buſi-
nefs to occupy their time, and to gain them ſuch
a mode of fubfiftence as they would wiſh, ſeveral
may venture upon new ſchemes, with conſidera-
ble advantage to themſelves. The manners of
the people in America are not yet fufficiently a-
dapted to manufacturing; the people in general
are violently induſtrious, but not perfevering ; a
manufacturer ought not to make violent exer-
tions, but to contine a moderate exertion for a
great length of time. The ſmall quantity of cer-
tain manufactures, that are uſed in America,
which would yield a conſiderable proportion of
neat profit, would not maintain an American ma-

ECONOMICAL
9
ESSAYS.
nufacturer. In England the caſe is very different,
a manufacturer there can obtain a genteel living
by making a ſingle article, which, in itſelf,
would appear to be of inconſiderable conſequence.
Thus a perſon that could manufacture the fa-
mous patent yellow, would be able to ſell it at
an hundred per cent. profit, it would coſt but
about one ſhilling per lb. and it would ſell by the
quantity at two ſhillings per lb. yet even if by
patent he could command the ſale of all that is
uſed in the United States, ſtill he would not find
it worth his whole attention to make it. By the
beſt information, it appears, that not more than
1000 lb. are uſed annually, the profits then on
one hundred pounds Pennſylvania currency,
would never be an inducement to any man to
follow that for a buſineſs, when he could make
a much greater ſum by the ſame ſtock to begin
with. The manufacturer of this article in Lon-
don, was able to monopolize the ſale and manu-
facture of it, and fold, perhaps, fifteen times the
quantity uſed in America, as he not only ſuppli-
ed all Great-Britain, but exported it to foreign
nations. Thus it happened that he made a for-
tune there, whilſt a manufacturer here would be
almoſt ruined by it. Nay, ſo great is the demand
for every article of manufacture in London, that
we know of one practical chemiſt there, who
lives very comfortably, merely by making large
quantities of aqua fortis, when we could not
diſpoſe of thirty pounds worth of it in North
America in a year.
From a variety of arguments, it appears moſt
rational to eſtabliſh chemical laboratories for
miſcellaneous manufactures. Thus I ſhould ſup-
poſe a careful man would make out very well in
С

19
AN DE
CHEMICAL
manufacturing ſeveral kinds of painters colours,
and to follow it as a buſineſs, he might, in one
laboratory, manufacture with the ſame time,
labour, and attention, the Pruflian blue, the
patent yellow, the white lead, and the verdi-
greaſe; a ſecond laboratory might be erected
for preparing dye ſtuffs, and things uſeful for
dyers; a third would certainly be very uſeful to
manufacture drugs and medicinal preparations
for the apothecaries ſhops; and ſeveral others
might be mentioned of a ſimilar nature: thefe,
however, are hints which every perſon would
weigh with the moſt ſerious deliberation, before
he attempted to purſue a new method of buſineſs.
They are juſt thrown out at random in this place,
becauſe from the arrangement of theſe eſſays,
they cannot be introduced into any other.
other. As
theſe effays are intended to inform the enquirer,
the readers of them may depend upon their be-
ing founded on fact. The writer never means
to introduce a proceſs unleſs he can either an-
ſwer for the ſucceſs of it from his own experi-
ments, or is very certain from the principles of
chemiſtry, and the reputation of the author from
whom he takes it, that it is true; and even in
this latter caſe, he means to announce the autho-
rity upon which the aſſertion refts.

ECONOMICAL
II
ESSA Y S.
ESSA Y I.
Chemical Apparatus. Furnace. Earths.
tion, beſides the ſeeming difficulty of the
ſubject, is the expence attending it; this to ma-
ny appears to be conſiderable. The apparatus
uſed by the earlier chemiſts were indeed expen-
five, but the ſame found and rational philoſophy
which has fimplified all the ſciences, has reduced,
not only the apparatus, but the materials to be
operated upon, by chemiſts, to a very ſmall
compaſs. Few chemiſts of the preſent day know
more than the names of the Athanor Furnace,
the Reverberatory, the Alludel, the Alembic,
the Bolt Head, the Matrafs, the Philofophic Egg,
the Hippocratic Sleeve, with a dozen other uſe-
leſs and intricate pieces of furniture, employed
in the old Chemical Laboratory:
The very elegant furnace lately invented by
Dr. Black, will anſwer every purpoſe, where
heat is required, by the philofophic manufactur-
er, and the expence of this furnace will fcarce
amount to four pounds, which, in fact is the
moſt conſiderable expence attending chemical
enquiries. It is true, there are ſome few other
inſtruments that will be found neceſſary for par-
ticular artiſts, ſuch as the crucible, or earthen
melting pot, for thoſe who work in certain me-
tals, but theſe are ſo inconſiderable, and ſo eaſily
obtained as ſcarce to deſerve attention.
The furnace here recommended, we have al-
seady ſaid, was invented by Dr. Black, and has
been found by him, adequate to all the purpoſes
of chemiſtry. To fuch an expert operator as the

12
AND
CHEMICAL
doctor, one ſtill leſs perfect might have been ſuffi-
cient; but the author of theſe eſſays candidly
confeſſes, that although his firſt furnace was
made exactly upon the model of Dr. Blaek's, he
has always found much difficulty in ſeveral pro-
ceſſes. In the annexed plate we have given an
engraving of Dr. Black's portable furnace, ta-
ken from the Edinburgh New Diſpenſatory, with
a deſcription of its parts and uſes.
References to Figure 1 and 2.
" To render our deſcription of this furnace as
ſimple as poſſible, let us ſuppoſe that the body of
the ſtove, figure I. is of an oval form, and cloſed
at each end by a thick iron plate. The upper
plate, or end of the furnace, is perforated with
two holes: one of theſe, A, is pretty large, and
is often the mouth of the furnace; the other hole
B, is of an oval form, and is intended for ſcrew-
ing down the vent. The undermoſt plate, or
end of the furnace, has only one circular hole,
fomewhat nearer to one end of the ellipfis than
the other; hence a line paſſing through the cen-
tre of both circular holes, has a little obliquity
forwards : this is ſhewn in fig. II. which is a ſec-
tion of the body of the furnace, and exhibits
one half of the upper, and one half of the un-
der, nearly correſponding, holes. The afh-pit,
fig. 1. and 2. C, is made of an elliptical form,
like the furnace; but is ſomewhat wider, ſo that
the bottom of the furnace goes within the brim;
and a little below this is a border, D, fig. 2.
that receives the bottom of the furnace. Except
the holes of the damping plate, E. fig. 1. and 2.
the parts are all cloſe, by means of a quantity of
foft luting, upon which the body of the furnace is

ECONOMICAL
13
ESSA Y S.
preſſed down, whereby the joining is made quite
tight: for it is to be obſerved, that in this fur-
nace, the body, alh-pit, vent and grate, are all
ſeperate pieces, as the furnace comes from the
hands of the workman. The grate H, fig. 5.
is made to apply to the outſide of the lower part,
or circular hole, it conſiſts of a ring ſet upon its
edge, and bars likewiſe fet upon their edges.
From the outer part of the ring proceeds four
pieces of iron, by means of which it can be
ſcrewed on: it is thus kept out of the cavity of
the furnace, and preſerved from the extremity
of the heat, which makes it laſt much longer.
The ſides of the furnace are luted to confine the
heat, and defend the iron from the action of it.
The luting is ſo managed, that the inſide of the
furnace forms in ſome meaſure the inſide of an
inverted truncated cone. We have thus combi-
ned the two fig. 1. and 2. in order to deſcribe,
as exactly as poſſible, this furnace in its entire
ftate ; but to prevent confuſion, it muſt be un-
derſtood, that fig. 1. repreſents the body of the
furnace, with its bottom received within the aſh-
pit. As in this figure then, we could not exhibit
the bottom of the furnace, we have in fig. 2.
ſuppoſed the body of the furnace to be cut down
through its middle; whereby one half of the un-
dermoſt hole, with a proportional part of the
grate G, applied to it, is exhibited along with,
and nearly oppoſed to, one half of the under-
moſt hole, F. the ſame hole, which in fig. 1.
is repreſented in its entire ſtate by A. By fig. 2.
then the relation of the upper and under holes
to one another is explained. It is alſo to be un-
derſtood, that the aſh-pit of fig. 2. is not, like
the body of the furnace, divided in its middle,
but is the aſh-pit of fig. 1. only detached from

14
AND
CHEMICA L.
the bottom of the furnace, in order to repreſent
the border D, on which the bottom of the furnace
is received.
0-
Now to adapt this furnace to the different
perations in chemiſtry, we may firſt obſerve,
that for a melting furnace, we need only pro-
vide a covering for the upper hole A, which is
in this caſe made the door of the furnace. As
this hole is immediately over the grate, it is ve-
ry convenient for introducing and examining,
from time to time, the ſubſtances that are to be
acted upon. The cover for the door may be a
flat ſquare tile or brick. Doctor Black uſually em-
ployed a fort of lid made of plate-iron, with a rim
that contains a quantity of luting. The degree
of heat will be greater in proportion as we length-
en the vent B, and to the number of holes we
open in the damping-plate E: by this means the
furnace may be employed in moſt operations in
the way of eſſaying; and though it does not ad-
mit of the introduction of a muifle, yet if a ſmall
piece of brick is placed on its end, in the middle
of the grate, and if large pieces of fuel are em-
ployed, ſo that the air may have free paſſage
through them, metals may be aſſayed in this
furnace without coming in contact with the fuel.
It may therefore be employed in thoſe opera-
tions for which a muffle is uſed, and in this
way, lead and fundry other metals, may be
brought to their calces.”
But as ſome inconvenience attends the uſe of
this furnace to a beginner, that repreſented in fig.
3. has been ſince contrived.

ÉCONOMICAL ESSA Y S. 15
Reference to Figure 3.
This furnace is made to be movable, and to
ſtand in a chimney-two-circumſtances which
make it very convenient for perſons who have
not a regular laboratory. The obſerver at firſt
fight will ſee a confiderable difference between
it and doctor Black's. The doctor's is of a cy-
lindrical form like our cannon ftoves, and yet it
is directed that the inner ſurface maſt be lined
with a mixture of clay and fand, fo as to make
it of the form of an inverted cone, that is, the
bottom part, where the grate is fixed, muſt be
but half as wide as the top. To make it of this
form, ſuch a large quantity of plaiſtering muſt be
uſed, that it becomes very bulky and difficult to
be moved, on account of its weight, which
is a great diſadvantage in that reſpect, without
any other good effect, that I know of, therefore
I have ſo conſtructed mine, as to need no more
plaiſtering below than above, which will be the
caſe if the body of the furnace is made of the
ſhape repreſented in the figure.
The whole furnace is made of ſheet-iron : the
whole of the inner ſurface is to be plaiſtered
with a mixture of four parts, by weight, of
fand, and one of our common brick-clay, laid
on to the thickneſs of two inches, the plaiſtering
ſhould be perfectly dry before any fire is made
in the furnace: this plaiſtering will be ſufficiently
thick to prevent the iron from burning away.
I preſerve the hole A, and the vent B, as in
Black's furnace. At C, I have a door in the
fide, becauſe I find it can be of no inconvenience
to thoſe who find it uſeleſs, and can uſe Black's
furnace; and particularly, becauſe many cannot

16
AND
CHEMICAL
make a fire by introducing the fuel into the hole
which I indeed, have found to be very inconve-
nient.
At the dotted line, D, I have a moveable
grate, which can be taken out at pleaſure. When
it is neceſſary to heat the top of the furnace, I
find it moſt convenient to make the fire upon
this grate, for by bringing the burning fuel fo
near to the top, the fand, or any thing elſe that
may be on it, can be heated much more readily,
than if the fire was made on the ſecond grate.
This grate is only uſed when a moderate fire is
required, that will continue for ſeveral hours if
neceſſary. The fire in this grate is renewed
either by putting in the fuel by the hole A, or
the door C.
At E, we have a ſecond door, and at F, a grate
that is fixed in by the plaiſtering: on this grate
a moſt intenſe heat may be made fufficient to
fuſe copper, and the other metals.
and the other metals. The door E,
will be found very convenient to introduce the
fubftances to be operated upon on this grate.
The other part is obviouſly the aſh-hole,
which is too ſimple to need any deſcription. We
ſee that the holes repreſented at E, fig. 1. are
omitted here, becauſe if the aſh-hole door is left
open, it anſwers all the purpoſes.
To increaſe the intenſity of the heat, we have
ſmall pieces of ſtove pipe, that fit the vent B,
and by lengthening the pipe from one foot to
twelve, we in the ſame proportion increaſe the
degree of heat.
We have the holes G, and H in the ſide of the

ECONOMICAL
17
E S SAYS.
furnace, through which the necks of earthen
Retorts may be protruded, when we wiſh to dif-
till with a naked fire.
This furnace alſo anſwers extremely well for
diſtilling with a ſmall copper ſtill, of about ten
gallons, for by having a moveable cover, and
the hole A, cut in the middle and of ſuch a fize
as to admit exactly the bottom of the ſtill, we
have nothing more to do than to put into it ſuch
matter as we wiſh to diſtill, and to make our fire
with ſmall pieces of wood like the ſtove-wood,
on the upper grate.
We can have a ſheet-iron pan about fix or
eight inches high, to hold ſand when we wiſh
to make uſe of what the chemiſts call a fand-bath;
this is very uſeful where a gradual heat is requi-
red, when it is to be uſed, the hole A, in the fur-
nace is to be ſhut with a piece of ſheet-iron, and
the pan ſet on the top of the furnace-in this way
we can uſe the furnace for diſtilling in glaſs Re-
torts: the fire is ſtill to be made on the firſt grate.
And laſtly this furnace will do for a family
ſtove: it can be ſet on an iron plate in the middle
of the floor, and it even draws extremely well
with an elbow to the pipe which conveys the
ſmoke to the chimney; and the wood being ſplit
ſmall, the fire is made on the upper grate as
before.
THE DIMENSIONS.
The length from the top A, to the ſecond
grate at F, is two feet. From A to D, is about
twelve inches, and a fimilar length from D to F.
The breadth at top, is twenty one inches : at
D

18
AND
CHEMICAL
bottom, one foot. The diameter of the grate
at D, ought to be about fixteen inches, which
will leave fufficient room for the lining, or
plaiſtering. The diameter of the ſecond grate
may be about ten inches. The dimenſions,
however, may be greater or leſs, to anſwer
any
particular purpoſe or convenience.
The other apparatus of the moderr chemical
laboratory, are remarkably ſimple: ai oil-flaſk,
an earthen cup, a chaffing diſh, with half a peck
of charcoal, will be nearly all that can be requi-
red to conduct the operations of moſt manufac-
tures. To theſe may be added a good blow-
pipe, which, with a facility in uſing it to the
greateſt advantage, will be found remarkably
uſeful as will be perceived in the courſe of theſe
eſſays: in the plate fig. 4. we have given a
drawing of one, as improved by the celebrated
Swediſh chemiſt mr. Bergman. If any other
inſtruments ſhould be found neceſſary, they ſhall
be noticed in their proper places.
As the foundation of all other matter is earth,
theſe EARTHS naturally preſent themſelves as
the firſt objects of our examination. To a ſu-
perficial obſerver they appear to be infinite : ſuch
a variety of foils, with their different colours
and properties, would ſeem to place this part of
our ſubject beyond reſearch, but the rational
enquirer will be delighted, when he is informed,
or diſcovers by his own experiments, that all
the earths and ſtones are formed of five ſimple
elementary earths, and that from different pro-
portions of theſe, together with the addition of
fone ſubſtances that is not earth, or ſome pecu-
liarity in the mechanical arrangement of parts,
all the immenſe variety in the appearance and pro-

ECONOMICAL
19
ESSAYS.
perties of earth and ſtones are produced. In this
place, as I wiſh to be underſtood by every reader,
I will explain what is meant by the term mecha-
nical arrangement, as not conſtituting a real dif-
ference in properties, and this will be moſt eaſily
and effectually done, by a very familiar exam-
ple. Every one has ſeen a piece of roll-brim-
ſtone, this we may call a piece of folid matter;:
if we pound this brimſtone, we obtain a very
fine powder, but the virtues, or diſtinguiſhing
qualities of the brimſtone have not been altered
by the operation, though the mechanical ar-
rangement has been changed: and here we will
obſerve, once for all, that a proceſs which alters
the diſtinguiſhing qualities of any ſubſtance, we
call a chemical proceſs, but if the change pro-
duced relates only to the figure, ſpecific gravity,
bulk, &c. the operation has only been mechani-
cal. But to return :
The diſcoveries of thoſe philoſophers, which
teach us the ſimplicity of the earths, and the
method of knowing their conſtituent principals,
have paved the way for bringing thoſe arts and
manufactures, in which earths are uſed, to the
higheſt degree of perfection.
The ſimple earths here fpoken of, as compof-
ing all the others, are heavy earth, lime, mag-
neſia, pure clay, and the flinty earth.
HEAVY-EARTH was never diſcovered in
America, either ſimple, or in combination with
other earths. It is remarkable for reſembling
burnt lime, in many of its properties, but its
great weight far exceeding any other earth or
ſtone, not only points out an eſſential difference

20
AND
CHEMICA L.
between them, but even induced ſome miners,
who firſt diſcovered it, to think it was a metallic
ore.
LIME. By this we mean the pure white burnt
lime, for lime-ſtone is not a pure earth, but a
combination of the earth with another ſubſtance,
which it is not worth puzzling the reader with
in this place, and which we ſhall only ſay, is
diſcharged in the very common operation of
burning lime.
Lime, and lime-ſtone are, and
long have been, of eſſential ſervice to mankind
in many inſtances; the proceſs of making lime is
actually a chemical operation, but is ſo ſimple,
and fo well underſtood in practice, that as theory
cannot improve it in the leaſt, we ſhall content
ourſelves with this bare mention of it. The
making of mortar is an operation of mixture,
and conſequently conneeted with our ſubject, but
for a ſimilar reaſon, we omit the confideration of
it. We know of no manufacture in which lime
is concerned, that could be improved by chemiſ-
try. All the marble with which America, and
particularly Pennſylvania abounds, is a ſtone that
belongs to the claſs of lime-ſtone; they are, how-
ever, frequently combined, by nature, with the
fiinty earth.
As lime increaſes in bulk when heated, * and
* Every body is acquainted with the curious circumſtances that attend
the " lacking of lime." -To a lump of well burnt lime, juſt as much
water is added, as it is found to be able to drink up; in a few minutes time
the lump burſts into the fineſt powder, and a very great heat is produced, ſuffi-
cient to evaporate a conſiderable quantity of the water added to flack it; and
and in ſome caſes we are told, that a quantity of it ſlacked, in a waggon, by
a ſhower of rain, has produced ſuch an intenſe heat, as to ſet fire to the wag-
gon, and entirely confume it. -This note is inferred, to excite the attention
of the curious, to explain the cauſo of the heat, for no perſon has yet attempt.
ed it with even tolerable ſucceſs—when that is explained, the burſting of the
lime, & may be eaſily accounted for-for as the water, that is to flack it,

ECONOMICAL
2
ESSA Y S.
falls into powder upon the addition of water, it
is evident, that any clay that is united to a confi-
derable proportion of lime-ſtone (which is fre-
quently the caſe) muſt be totally unfit for the pot-
ters uſe, as ſhall be more fully explained here-
after.
MAGNESIA. It is but within a very few
years
that this has been found to be a diftinct earth.
When we ſpeak of this earth, we mean the white
magneſia of the apothecaries ; a variety of argu-
ments and experiments could be, and have been,
ſhewn to prove it a ſimple earth, but to enter in-
to theſe arguments in this place would be ſuper-
fluous. A perſon who could diſcover a large
quantity of it in America, would do an eſſential
ſervice to his country, and particularly to the ma-
nufacturers of earthen ware. When heated in
the moſt intenſe fire, magneſia is neither encrea-
fed nor diminiſhed in bulk, neither is it fused in-
to glaſs, and water does not alter it in the leaſt,
after it has been burnt, as it does lime. We
know of no uſes to which magneſia is applied but
as a medicine, and as an excellent ingredient in
pottery.
PURE CLAY.
Few chemiſts have ever ſeen
a perfectly pure clay. In all clays, there has
been diſcovered a peculiar earth which chemiſts
have been able to ſeparate from them by cer-
tain proceſſes: when this has been taken from
them, it deprives them of all their valuable pro-
perties as clays; they become utterly unfit for
muſt, by the laws of capillary attraction, inſinuate itſelf into every particle of
the lime, the heat, by rarifying every particle of the water, and converting it
into vapour, we could readily
conceive to be ſufficient to produce allthe other
effects. It is remarkable that the lime in ſlacking is luminous or phoſphoric
in the dark

22
AND
CHEMICAL
the potters uſe, they have no greaſy feel, they
cannot be formed into veſſels ; but all their pro-
perties are reſtored by again uniting them to this
earth. If then, there is only a part in all clays,
that gives them the character of clay, it is
very
proper to call that part pure clay, or as a certain
chemiſt propoſed, the principle of clay. Theſe
obſervations, we hope, will be ſufficient to con-
vey an idea of what we mean by the term pure
clay. We ſaid that pure clay has not yet been
found in a natural ſtate, but always combined
with ſome other ſubſtance ; nor would it be of
any uſe to mankind, was it ſo found : for al-
though pure clay is the baſis of pottery, it would
be quite unfit for that purpoſe, unleſs combined
with another earth. Pure clay, when obtained
by a certain chemical proceſs, which it would be
foreign to our defign to deſcribe in this place,
is found to be diminiſhed in bulk by burning,
which is a curious and fingular fact, as all other
earths increaſe in bulk when heated, and return
to their natural ſize when grown cold; but pure
clay contracts in bulk, and all common clays pof-
ſeſs the ſame property, according to their puri-
ty, and this in exact proportion to the degree of
heat, the ſmaller will be the piece of clay after
it is burnt: the common brick-clay, which is ve-
ry impure, and contains but a ſmall quantity of
pure clay, loſes about one nineteenth of its bulk
in the kiln, that is, a ſtrip of brick-clay meaſuring,
when perfectly dry, ten inches, will, after bur-
ning, meaſure but nine inches and an half; and
if it is put into an air-furnace, where the heat
can be raiſed equal to that of a glaſs-houſe fur-
nace, it becomes ſtill ſmaller, and will ſcarcely
meaſure nine inches, and what is ſtill more re-

ECONOMICAL
23
ESSAY S.
markable is, that although the heat is the cauſe
of the fhrinking, or contraction of the clay, it
never after returns to its original bulk, as all o-
ther earths do, which are made larger by heat.
This leads to a ſuſpicion, that the contraction of
clay is not owing merely to the addition of heat,
but to ſome change, either chemical or mechani-
cal, being produced on it. As clay then contracts
ſo much by heat, it is evident, it would be very
liable to crack and break in burning, for this rea-
fon, a mixture of earths has always been found to
produce the beſt ware : what ſome of theſe mix-
tures are, we ſhall endeavour to point out in our
next eſſay.
There are a pretty conſiderable variety of clays
in Pennſylvania and New-Jerſey, ſome of which
ſeem to have a tolerable good appearance for
fome branches of pottery; the virtues and imper-
fections of ſome of them we ſhall relate in our
examination into their properties.
FLINT Y EARTH. The character of this fpe-
cies of earths is, that it is much harder than any
of the other four, and that, when formed into
ſtones (which are nothing more than conſolida-
ted earths) they will ſtrike fire with ſteel, which
property does not belong to any of the others.
The earths and ſtones, of which this forms the
largeſt proportion, are the moſt abundant (as I
believe from tolerable good information) of all
others in the United States; I can ſpeak with
more certainty of thoſe found in the thick ſettled
parts of Pennſylvania, in ſome parts of New-jer-
ſey, and Delaware ſtates: in ſome counties, how-
ever, in Pennſylvania, where lime-ſtone abounds,
flinty earths and ſtones are very rare; all thoſe

24
AND
CHEMICAL
icy
rocks and ſtones which in breaking ſhew an
tranſparency, are almoſt entirely a pure flint.
We ſhall ſhew what are the chemical charac-
ters of the flinty earth in our next.

ECONOMICAL
2
ESSA Y S.
25
ESSAY II.
Analyſis of Earths.
O diſtinguiſh an earth from every other kind
of matter, we muſt be certain that it poffef-
ſes the following properties : to diſſolve, very ſpa-
ringly, or not at all in water, to poſleſs little or no
ſapidity, to be incombuſtible, that is, that it will
not burn, and to have little or no Smell; all the
earths poſſeſs theſe properties in an eminent de-
gree, there are however ſome fubſtances which
anſwer theſe deſcriptions, that are not earths,
and theſe we ſhall point out in proper order.
I know not at preſent of any uſe that an ana-
lyſis or chemical examination of the earths will
be of to the arts, except to the art of pottery :
and as it is equally to the potter's purpoſe to
know what earths are improper for his buſineſs as
to be acquainted with thoſe which are fit for
uſe, it will be neceſſary to direct the reader to
fome general rules, by which he may be able to
know any earth that falls under his notice.
The excellence of potter's ware, beſides other
circumſtances depends principally upon three
things.
1. The chemical nature of the materials he
uſes for the ware and its glazing.
2. The mechanical nature of the earth, ſuch
as its fineneſs, &c.
3. The colour of the materials after baking.
We have already hinted that a pure clay is not
the moſt fit for making earthen veſſels: as it
E

26
CHEMICAL AND
ſhortens in burning it is very apt to crack: and
it is probably owing to the too great purity of
ſome of our American clays, that our unglazed
earthen veſſels ſuffer water and other liquids to
paſs through them: a mixture of the flinty earth
which exiſts in common clays in conſiderable
proportion, prevents, if in proper quantity, this
contraction of the ware, and probably were the
quantity in ours greater than in is, that one in-
convenience would be remedied. The red colour
of our ware, is invariably owing to iron, which
exiſts very plentifully in America, and in ſome
degree in almoſt all our clays: the deepneſs of
the colour is in proportion to the quantity.
We will ſuppoſe a potter to have obtained fe-
veral ſpecimens of clays, and is anxious to know
whether they will do for he pottery; will find as
we ſuppoſe the following method the moſt eaſy,
deciſive and ſatisfactory.
He muſt procure, at an apothecaries, about half
gill [two ounces] of ſpirit of ſea-falt, which he
can get under that name, and then weigh off four
penny weights and four grains of ciay to be ex-
amined, firſt dried and reduced to powder: a
thin Florence oil flaſk, well cleaned, by waſhing it
in ſtrong lye, muſt be had, into which the pow-
dered clay is to be poured: we then mix the half
gill of ſpirits of ſea-falt with an equal quantity of
rain-water, which we prefer as being moſt pure,
then a half gill of this weakened ſpirits of Salt is to
be poured into the oil flaſk and mixed with the
earth. Great attention is to be paid to the ap-
pearance in the inſtant of mixture, whether there
is a hiling noiſe, and the appearance of boiling,
or whether a few large bubbles ariſe to the top,

ECONOMICAL
27
ESSAYS.
without any noiſe ; for if the firſt appearance takes
place, it will afford a ſtrong preſumption that the
clay contains a conſiderable proportion of lime,
and is likely to prove unfit for pottery, becauſe,
as we ſaid before, all earths containing burnt lime
(and the lime contained in the clay would be-
come ſuch, after the ware was burnt) would
{plit, or flack as ſoon as any liquid was applied
to them. We then ſet the oil flaſk on ſome bur-
ning coals in a ſhovel, nor need we be afraid of
its cracking from the ſudden application of heat,
for ſuch thin glaſs veſſels ſeldom break from the
changes of heat and cold: we ſuffer the mixture
to be heated ſlowly ſeveral hours, in which time
all the different earths that the clay contained,
together with the iron, if any, will be diſſolved,
except the flinty earth, which is of the nature
of fine powdered fand: now by attending to the
following operations upon the mixture, we may
be able to judge of the excellence of the clay :
they are rather difficult to be underſtood, but a
perſon whoſe intereſt it is to be acquainted with
this ſubject will take time to endeavour to com-
prehend them: I ſhall juſt lay down my method,
which is, I think, the eaſieſt, and ſufficiently
accurate.
I pour about half a gill of pure water into the oil
flaſk, after the clay &c. have boiled ſufficiently
and warm it over the coals again: I ſuffer it to
ſtand until the undiffolved part ſettles to the bot-
tom; then pour off the clear liquor from the ſed-
iment as exactly as I can into a glaſs veffel, for
inſtance a tumbler ; I waſh what is in the oil flaſk
with another half gill of water, and pour that
water when grown clear, into the other clear
liquor in the tumbler, I find that a certain quan-

28
CHEMICAL AND
tity of the earth is ſtill left in the flaſk, this I pour
out on a piece of clean blotting paper, dry it and
weigh it, the weight then gives me the quantity
of flinty earth contained in an hundred grains of
the clay : the proportion of this earth is fome-
times ſo great as to amount to fixty or ſeventy
grains per cent. even in a very good clay.
In the tumbler I ſhall find I have about a gill
of a clear fluid, of this I put the fourth part into
a wine glaſs, and drop into it a few drops of oil of
vitriol, which may be had of the apothecaries,
this experiment will ſoon ſatisfy me whether the
clay contains any lime ſtone in a powdered ſtate,
for it will immediately become of a milky white-
neſs, even if the quantity of lime is but ſmall;
and here we muſt not be deceived and conclude
too haſtily that the earth will not make good
ware, becauſe of the lime it contains; in a few
minutes the whiteneſs will ſettle to the bottom,
then by pouring away the clear fluid that is above
it in the wine glaſs, and putting the ſediment
upon blotting paper, drying it and weighing it
carefully, we ſhall have one fourth of the quan-
tity of lime contained in an hundred grains of
the earth.
The quantity of oil of vitriol to be added may
be thirty drops, which is always fufficient for that
quantity of diffolved earth, and never too much,
for a reaſon which a theoretical chymiſt would
well underſtand, but it cannot readily be explain-
ed to any one elſe: the fact however may be de-
pended upon.
If we find the quantity of lime by the laſt expe-
riment to be ſmall, amounting to no more than
four or five per cent. we can have no objection
to it upon that account, .

ECONOMICAL
29
ESSA Y S.
The quantity of lime and fiinty earth, being
thus aſcertained, it appears from the obſervati-
ons made in our laſt eſſay, that there can be no
other earth exiſting in the ſolution, than magneſia
and pure clay, for there are but five earths in na-
ture, and heavy earth has never been found in
America; it is not worth the potter's attention to
examine minutely into the exa&t proportion of
theſe, as a tolerable good eſtimate may be made
from the quantities of the other earths when
known. But it is of conſequence to aſcertain the
quantity of iron, which is very difficult to be done
by the common modes laid down by chemiſts;
but the following method when properly under-
ſtood and well attended to, will be found tolera-
bly eaſy.
We take one third of the remaining folution,
that is one fourth of the whole, and mix it with
a pint of clear rain water : in another pint of wa-
ter we diſſolve ten grains of green vitriol or cop-
peras which we may juſt mention in this place,
is a preparation of iron, and contains about one
fourth part of its weight of that metal; that is,
there are two and one half grains of iron in ten
grains of copperas. We then pour half a wine
glaſs full of each, obſerving to let the quantity
be exactly the ſame, into two ſeparate wine glaf-
fes, at the ſame time, and add to each a ſmall
quantity, for inſtance as much as can be taken up
between the finger and thumb, of the powder of
galls*, when both mixtures will become of a
black, dark purple, light purple, or red colour,
* The cold infiufion of the Pig-Nut we have found to be a very powerful
aftringent--as ſuch it will anſwer extremely well inſtead of powder of galls,
in the analyſis of earths. We hope we have ſhewn in Eſſay VII. that they
are equally valuable in every other inſtance,

30
CHEMICAL AND
according as the quantity of iron is larger or
ſmaller ; we then fill the remainder of the wine
glaſſes with water, and accurately attend to the
difference of colour, the one that approaches
neareſt to a black colour, always contains the
greateſt quantity of iron.
Let us now ſuppoſe that the fourth part of our
ſolution contained more than two and a half
grains of iron, or in other words, a greater quan-
tity than the folution of copperas: why then
with a given quantity of powdered galls, a given
quantity of folution will ſtrike a darker colour.
But we wiſh to aſcertain how much more. This
I think we may know, if we add to our ſolution
made from the clay, a gill of rain water; then
again we add an equal quantity of powdered galls
to equal quantities of the two ſolutions as before,
we compare the colours, and if they are exactly
alike, we fuppoſe the quantity of iron in a given
quantity of the ſolutions, is the fame; but of the
folution of the clay there is one fourth more than
there is of the ſolution of the copperas, conſe-
quently, there muſt be one fourth more iron.
Suppoſe it required that two gills of water ſhould
be added to the ſolution of the clay, before the
colour would be exactly like the folution of the
copperas, why then it is obvious it contains one
half more iron: but if the caſe was juſt the re-
verſe, then by adding ſo much water to the fo-
lution of copperas as would be neceſſary to re-
duce both folutions to the ſame colour, we ſhould
be able to know how much leſs iron the ſoluti-
on made from the clay contains; thus if it will
require one gill of water before equal quanti-
ties will exhibit equal ſhades of colour, it is

ECONOMICAL ESSAY S.
31
obvious that the folution we are to examine,
contains one fourth leſs iron, than the ſolution
of copperas, &c. &c. &c.
To prevent any fallacy, the wine glaſſes ſhould
be exactly of the ſame ſize, for every one knows
that a coloured fluid always appears deeper in
a glaſs of a larger diameter, than in one of a
fmaller: the colour ſhould be very attentive-
ly obſerved, and the opinion of a ſecond ob-
ſerver to be aſked, left the firſt by ſuch fre-
quent repetition ſhould be confuſed, as is ſome-
times the caſe : when theſe circumſtances are
attended to, the quantity of iron even to one
fourth of a grain, may be diſcovered in an hun-
dred grains of the clay we are examining: this
is not the method propoſed by Mr. Kirwan in
his examination of earths : but we are happy
in finding this method of analyſis altho' appa-
rently indeterminate, yet correſponds exactly as
to the reſult, with Mr. Kirwan: that is, an earth
was examined by his method, and was found to
contain ten per cent. of iron, and being after-
wards examined by our method, it gave ſuch
appearances as would have immediately inclined
us to conclude that it contained that quantity.
When the clay examined is found to contain no
more than three or four per cent. of iron, it may
be preſumed to retain its white colour in burn-
ing; if from twelve to twenty it will moſt cer-
tainly be red.
It is almoſt a maxim with the potters, that
all blue clays will burn red, and that all white
clays will retain their colour; this however is
too general; ſeveral blue clays owe their colour
to a mineral oil which is diffipated in burning,

CHEMICAL AND
and many white ones contain iron, which will
give them a red colour.
We now ſee that the chemical qualities of good
carths for wares, are a proper mixture of pure
clay and flinty earth; without the addition of a-
ny, or very little iron; that lime is an injurious
ingredient in proportion to its quantity, and that
magneſia, tho' feldom found in clays, is always
a valuable addition.
The Eaſt-India china ware is juſtly allowed to
be the moſt beautiful, the moſt valuable and pure
of any in the world : its compofition is now ge-
nerally known to conſiſt of two earths, which they
call PETUNSE and KAOLIN: thefe earths have
been obtained and examined by European che-
miſts ; yet obſerve the ſimplicity of their compo-
ſitions ! the petunſe contains ſixty-ſeven per cent.
of flinty earth, fourteen of pure clay, eleven of
heavy earth, and eight of magneſia, without any
iron. The kaolin (at leaſt one ſpecimen of it)
contains about fifty per cent. of flinty earth,
twenty-five of pure clay, fix of magneſia, five of
lime, and three or four of iron: the reſt was loft
in the experiment.
Now ſuppoſing theſe two earths to be united
together in equal proportion in china ware, as is
ſometimes the caſe, the chemical compoſition will
be
581
Heavy earth Lime Magneſia Clay Flinty earth Iron
55
21
7 192
4.
Why then ſhould not porcelain be made in
America, except the mechanical qualities of our
earths, and the workınanſhip are deficient in
goodneſs.

ECONOMICAL
33
ESSA Y S.
2.
We ſhould not ſuppoſe the mechanical quali-
ties of clays to alter the value of the wares made
from them: but it appears from very good au-
thority that, the celebrated Chineſe earth kaolin
differs from ſome pipe-clays, only in the fine-
neſs or ſubtilty of the flinty earth contained in
it; the want of fineneſs in any earth, otherwiſe
fit for pottery, we conceive might be obviated
by levigating; for the explanation of which tern,
and the manner of conducting the proceſs, we
refer to the article LEVIGATION, in any dicti-
onary of arts and ſciences.
« The colour of the materials after baking,
we ſaid was another circumſtance to be attended
to; the red colour of our American wares, we
aſſert to be entirely owing to iron, a metallic
ſubſtance, very abundantly diffuſed through moſt
of our earths : in many it is in fo large a propor-
tion as to give then a red colour before burning,
in which ſtate they might be uſed for ochres, or
paints; but as they are only valuable for the
iron they contain, we ſhall defer all obſervations
upon them, until we come to the metals.
Other metallic fubſtances are fometimes found
to colour clays, as copper and lead; but ſuch have
never been found in this country; the black co-
lour of ſome of the imported ware, we ſuſpect is
owing to MANGANES E, known better among us
by the name of MAGNES.
The metallic ſubſtances are uſed in painting
the ware, and give it different colours, after
burning, as copper makes a green, iron a red,
F.

34
AND
CHEMICAL
ſmalt prepared from cobalt, a blue colour, &c.
&c. but obfervations of this kind are not to our
purpoſe.
The glazing of ware is a matter of great im-
portance: the preparations of lead, ſuch as red..
lead, white-lead and litharge, are univerſally u-
ſed here: theſe ſubſtances by melting, very ſoon
give the ware a glazing, without a great degree
of heat; but vefſels glazed with lead ſuffer many
fluids to paſs through them, and many corroding
liquors, as vinegar, take off and diſſolve the gla-
zing, probably to the injury of the health of the
perſons who uſe them. Quere, would not a
mixture of calcined flints finely powdered and
mixed with pot-afh, make a glazing that would
be both eaſily fuſible and ſufficiently hard and
wholeſome!
The queens-ware is compoſed of the pipe-clay;
(one nearly like our common clays, but free from
iron) and calcined flints, the proceſs, &c. is very
beautifully deſcribed in Watſon's Chemical El
fays, in the Philadelphia library.
The clay of our potters is very coarſe; the
flinty earth in it is almoſt as coarſe as fand; a
fpecimen I examined, contained about fifty-four
per cent. flinty earth, twenty-fix pure clay, three
of lime, and ſeventeen of iron; which laſt ingre-
dient is the cauſe of the exceffive red colour.
There is an earth found at Gray's ferry, very
famous among our maſons as a mortar for work
in whieh fire is to be made, becauſe it neither
burſts by expanding, nor leaves crevices by con-
tracting. Although it poſſeſſes this valuable pro-
perty, it is unfit for pottery, from its mechanical

ECONOMICAL
35
ESSA Y S.
nature and coarſe texture; the whiteſt of it af-
fords, by analyſis, ſeventy-fix per cent. of flin-
ty earth, twenty-one of magneſia, without any
iron; the other three parts could not be account-
ed for in the experiment.
After all we have to lament that from the great
quantity of iron with which this country abounds,
we have but a poor proſpect of very pure earths.
There is a clay much like the pipe-clay, found
in great abundance in ſeveral parts of New-jer-
ſey, different parcels of this appears to be of ve-
ry different qualities. I have had two cups made
of it, which burn as white as the Engliſh queens-
ware: it appears by analyſis to contain about fix-
ty-ſeven per cent. of flinty earth, twenty-ſeven
of pure clay, a little lime, and as I believe, a little
magneſia; but this I have not fully proved.
The glazing of the foreign ware, is made ei-
ther by throwing falt into the kiln, by lead, or by
the vitrification of the ſurface of the ware with-
out addition, depending upon the fuſible nature
of the ingredients.

36
CHEMICAL AND
ESSA Y III.
Salts in general; Cryſtallization; Sea-falt; Epſom-falt; Pree
paration of Magneſia.
WE
E obſerved that we did not recollect any
uſe that an analyſis of the earths would be to
the arts, except the art of pottery ; as fuch we
have conſidered it pretty fully already, on the fub-
ject of clays ; we miglt indeed have lengthened
out theſe eſſays, with the reſults of the analyſis
of ſeveral others not mentioned in our laſt, but
we conceive them to be unintereſting, and there-
fore omit them. We may now diſmiſs the fub-
ject of earths ſimply conſidered.
The next
general claſs of matter that preſents itſelf to our
view are the SALTS: when we conſider thefe fub-
ſtances, either for their importance in the vari-
ous departments of life, or their curioſity in che-
mical operations, we find them worthy of a par-
ticular attention. The ſalts form a claſs more
extenſive than moſt people imagine, and eſpe-
cially when we take in all thoſe ſubſtances
comprehended in the following definition of a
falt; a falt is ſoluble in water, Sapid, incombuſtible,
capable of aſſuming a regular form, or in other words
of cryſtallizing, and of combining in a PECULIAR
MANNER with other ſubſtances. It may be juſtly
remarked that there are but very few ſalts that
poſſeſs all the properties aſcribed to a falt in this
definition, and that there are many ſubſtances,
that are not falts, or of a faline nature, which
correſpond to ſeveral parts of it; thus oil of vi-
triol, or more properly ſpeaking the vitriolic acid,
is a falt, but it has not the property of cryſtalli-
zing; white ſugar is foluble in water, ſapid, and
capable even of aſſuming a regular form, yet it
is ſcarcely to be ranked among the ſalts; I ſay

ECONOMIC A L ESSAY S.
37
ſcarcely, for chemiſts are divided as to the place
it holds in a ſyſtem of chemiſtry; but fugar is not
incombuſtible, neither has it this peculiar tendency
to combine with other ſubſtances; the definition,
however exceptionable, is the beſt that has been
offered, and we may venture to pronounce any
ſubſtance a falt, that has ſeveral of the above-
mentioned properties.
We wiſh to make ſome obſervations on falts
in general, and as ſalt-petre, or nitre, is well
known to the people at large, we ſhall take that
as an inſtance of all the properties to be found in
it, in common with moſt other falts. If we take
an ounce of falt-petre, and mix it with an half
pint, and an half gill, i. e. ten ounces, or ten times
its weight of cold water, we ſhall have it com-
pletely diffolved: if we add any more of the falt-
petre, it will forever remain undiffolved, if the
water continues as cold as pump water, juſt
-drawn, uſually is; but if we beat the water, we
ſhall find that more will be diſſolved; we conti-
nue the heat until the water boils, but in ſuch a
veffel, that none of it ſhall eſcape in vapour; the
conſequence will be, that the water will diſſolve
its own weight of the nitre; that is, the applica-
tion of a boiling heat, will enable the water to
diſſolve nine ounces more of the falt than it did
when cold. This will not appear remarkable to
people in general, becauſe it is a common occur-
rence: but let us extend our inveſtigation a lit-
tle further; the heat muſt certainly have been
the cauſe that nine ounces of the nitre diffolved
in the water, if therefore we ſuffer the water to
cool, and the heat to paſs off, the nine ounces of
nitre ought to be found undiſſolved as ſoon as
the water acquires its former temperature; and

38
CHEMICAL AND
this is the fact, but attended with one wonderful
circumſtance that few who had not ſeen it would
have ever fufpected; the falt-petre is found cry-
Stallized, in a regular form, reſembling ſeveral
kinds of natural cryſtal, from which reſemblance
the proceſs has its name: this is the ſimpleſt idea
of cryſtallization, a proceſs the moſt beautiful and
moſt inexplicable that chemiſtry affords us; with-
out attenipting to explain the cauſe of this phe-
nomenon, let us juſt eſtabliſh the following laws,
which are both elegant, and uſeful to be known.
1. All falts attend to aſſume a regular form,
and this tendency takes place, as well in ſmall
maſſes, as in larger. A cryſtal of a falt, a thou-
fand of which would not weigh one grain, is of
the ſame preciſe mathematical figure, as a cryſtal
of the ſame falt weighing fifteen or fixteen oun-
ces;* the figure of the cryſtals of falts is diffe-
rent in different falts, but they always tend to af-
fume the ſame figure in the fame falt; this tenden-
cy however is often deſtroyed by certain acci-
dents, ſuch as extremes of heat and cold, an ill
ſhaped veſſel, agitation of the veſſel during the
proceſs, and the cryſtals running againſt each
other.
2. Salts more ſoluble in hot than in cold water,
and diffolved in hot water, will cryftallize, when
the water grows cold; that is, all the ſuperabun-
dant falt that the heat had enabled the water to
diſſolve, muſt be rendered up again when the
heat, which was the cauſe of its ſolution, is loſt;
and then in a cryſtalline form.
* It is really wonderful, that the figure ſhould be exa&ly the ſame, altho'
the ſize be as 7680000 to 1.

ECONOMICAL ESSAY S. 39
3. Salts equally foluble in cold and in hot wa-
ter, if diſſolved in hot water will not cryſtallize
when the water cools, for the cold water will be
fufficient to hold all the falt diſſolved; by expo-
fing the ſolution of ſuch a falt to the air, fuffer-
ing the water to waſte away, or by applying a
very gentle heat, ſo as to evaporate part of the
water, it will then cryſtallize very regularly;
both of theſe methods are occaſionally uſed to
obtain common falt in a cryſtalline form.
4. All falts diſſolved in water and cryſtallized,
abſorb a certain quantity of the water, neceſſary
to the formation of the cryſtal; the proportion is
very
different in different ſalts. It is very re-
markable, that the water thus abſorbed is abſolute-
pure, even though the water in which the falt
was diſſolved before cryſtallizing, ſhould be ve-
ry impure.
5: Two ſalts diſſolved in the ſame veſſel ſeldom
cryftallize at once, and NEVER unite their par-
ticles into one cryſtal; to illuſtrate this law more
clearly, ſuppoſe ſalt-petre and common falt were
diffolved in a cup of hot water, in cooling, one of
the ſalts only cryſtallizes, and thoſe cryſtals are
as abſolutely pure as if none of the other falt had
been diffolved with them; afterwards by a cer-
tain proceſs, the other falt may be obtained in
cryſtals, which will be alſo found to be abſolute-
ly pure, having even the ſhape peculiar to that
fpecies of falt; this is one of the moſt remarkable
laws we are acquainted with, and would ſeem to
imply a kind of intelligence among the particles
of falts; by this law we are inſtructed in the ve-
ry neceſſary method of ſeparating different falts
from each other in a pure ftate.

40
CHEMICAL AND
SEA-SALT, as moſt commonly known, is the
firſt to deſerve our attention, not becauſe it
ſhould occupy the firſt place in the fyſtem of che-
miſtry, for it is not a ſimple, but a compound falt;
the novice in chemiſtry will feel ſurpriſed at the
ſtrange "effects of mixture," and the amazing
“ alteration of ſenſible properties,” which we
aſſerted always took place in every operation
truly chemical, when he ſhall be informed of the
component parts of ſea-falt, and find what a
very
different compound they yield; he will ſcarcely
imagine that one of its ingredients is fo corroſive
as to be able to diſſolve iron, i. e, the ſpirits of
ſea-falt of the apothecaries, and that the other
is uſed as a cauſtic, to eat away proud fleſh from
ulcers, by furgeons, i. e. common cauſtic made
from kelp. An hundred experiments might be
ſhewn to prove that fea-falt contains one half of
its weight of the valuable parts of the aſhes of
ſea-weed, ſo uſeful in glaſs making ; this part
chemically ſpeaking, is called the “foſſil or mi-
neral alkali,” which is one of the principles of
fea-falt, the other is called ſpirit of fea-falt, but
by chemiſts the marine acid: eighty pounds [a
buſhel] of ſea-falt can be got for two ſhillings,
containg forty pounds of mineral alkali, or if you
pleaſe to call it by a common name, of kelp, baril-
la, foda, or glaſs wort, which is worth five pence
per pound, the great queſtion then is, how ſhall
we be able in a cheap manner ſo to deſtroy the
marine acid of ſea ſalt, * that nothing but this ve-
ry valuable part of it ſhall remain? Whoever
can anſwer this queſtion, will have diſcovered
one of the moſt impenetrable ſecrets of che-
* Several literary ſocieties have offered premiums for ſuch a diſcovery, but
I have heard of no ſucceſsful candidate.

ECONOMIC A ESSA IS.
41
miſtry, immortalize his own name, render an im-
portant ſervice to mankind; and, if kept ſecret
for fome time, eſtabliſh himſelf in independence.
I ſhould be forry to damp the ardour of an ad-
venturer, by laying before him any of my very
numerous unſucceſsful experiments inſtituted for
this purpoſe: I hope this diſcovery may be re-
ſerved for an American chemift.
Can ſea-falt be an object of manufacture in the
United States ? I rather believe not, at leaſt for
a conſiderable number of years, till labour ſhall
become cheaper; we have had ſeveral ſpecimens
of ſea-water fent us from different parts, and we
are ſorry to find, the proportion of ſea-ſalt con-
tained in them, was in much ſmaller quantity,
than by the accounts of authors, we find the fea-
water in other parts of the world contains. We
hinted above, that fea-falt was obtained either
by ſpontaneous evaporation, ariſing from the fun
and air, or by the gentle heat of a ſmall fire; the
firſt means can probably never be practiſed, in
the more nothern ſtates at leaſt, for it is obſerved,
that in Pennſylvania, there are eight months in
twelve, in which fires are comfortable ; conſe-
quently the warm ſeaſon, in which only evapora-
tion takes place, to any conſiderable degree, muft
be very ſhort; when we alſo take into conſidera-
tion, the quantity of rain falling every ſummer
ſeaſon, which cannot be excluded from the falt-
ponds, the exceſs of evaporation muſt be ſtill
ſmaller; and we have great reaſon to believe,
that the quantity of rain falling in any given time,
on a given ſurface of ground, is nearly equal to
the quantity, that would evaporate from ſuch a
furface.
G

CHEMICAL AND
It is obſerved that ſea-water is not quite a
ſimple ſolution of fea-falt, but holds diffolved in
it ſeveral others : it is ſaid to contain Glaubers-
falt, EPSOM-SALT, and two other falts, contain-
ing marine acid united to magneſia, as one falt,
and the fame acid united to lime for the ſecond;
we have found that our fea-water contains a lar-
ger quantity of heterogeneous falts than others,
but the quantity we ſuppoſe is not ſufficient to
induce us to boil down the ſea-water to obtain
them.
There is not a part in chemiſtry, in which che-
miſts have committed greater errors, than in the
analyſis of ſea-water, and particularly in always
confounding the Glaubers-ſalt and the Epſom-fa
together ; which, however they may reſemble
each other in their ſenſible qualities, or medicinal
virtues, yet chemically conſidered are very diffe-
rent. Glaubers-falt, conſiſts of the foſil alkali and
the vitriolic acid; whilſt Epſom-falt is compound-
ed of magneſia and the vitriolic acid, and almoſt
all authors mention that Epſom-falt is found dif
folved in ſea-water. I will leave the poſſibility
of this obſervation to be conſidered by the che-
miſts, when they reflect on the principles of the
following economical proceſs, for preparing the
magnefia of the apothecaries, for whoſe uſe this
paragraph is intended.
Take fix and a quarter pounds of pure Epſom-
falt, and five pounds of the beſt coarſe falt, diſ-
ſolve them in four gallons of boiling water, fuf-
fer them to remain in a ſhallow tub for twenty-
four hours, when we obtain at leaſt NINE POUNDS
of a falt in fine long cryſtals, which will have all
the properties of Glaubers-falt; but it will be ut-

ECONOMICAL
43
ESSAY S.
terly impoſſible for any perſon to obtain from
this liquor one particle of a falt that ſhall have
the properties of Epſom-falt.
To the liquor
which ſhall remain after the cryſtallization, we
add fix pounds of pure pot-aſh, diſſolved in pure
water; mix them together, and follow the direc-
tions, as to the reſt of the proceſs, laid down in
the Edinburgh Diſpenſatory : this muſt be con-
feſſed to be a conſiderable improvement of the
proceſs, and the idea of it was ſuggeſted by the
knowledge of the chemical attraktions; which eve-
ry chemiſt will now know how to explain for
himſelf, but which would be extremely diffi-
cult to explain to a novice, without ſome previ-
ous obſervations on the attractions in general,
which however we ſhall do hereafter. I be-
lieve I may claim the merit, ſuch as it is, to the
diſcovery, both in theory and in fact; for I have
never met with either the one or the other in
any author: the Glaubers-falt obtained by means
of the Epſom-falt, will more than pay the price
of all the Epſom-falt uſed, and yet (which muſt
appear very ſtrange to the ignorant) the Epſom-
falt will ſtill yield as large a quantity of magneſia
as if no Glaubers-falt had been obtained from it:
no chemiſt can deny this, the coſt then of the
magneſia will only be the price of the fix pound
of pot-afh. I conceive this experiment to be cu-
rious as well as uſeful; if fea-falt and Epſom-fait
decompoſed each other in our laboratories, how
can they exiſt together in the ſea without altera-
tion? the ſuppoſition that Epſom-falt exiſted in
ſea-water, aroſe from the imperfect ſtate of the
chemical ſcience of the times, in which thoſe au-
thors, who aſſert it, lived; for they always con-
found the Epſom-falt and the Glaubers-Salt toge-

44
CHEMICAL AND
ther, as we mentioned already, but we can dili
tinguiſh them by chemiſtry, if not by our ſenſes
very eaſily; for this purpoſe, we diſſolve the ſalt
to be examined in water, and add to it a little of
the folution of pot-aſh in water; if it is Epſom-
falt, the two fluids will aſſume the appearance of
milk and water; if it is glaubers-falt, no apparent
change will take place in the mixture: we may
readily conceive therefore, that the ſalt obtained
by thoſe authors, might have been Glaubers-falt,
and not Epfom-falt, as they ſuppoſe ; the cauſe of
which miſtake we have already explained: but
Epſom-falt is made from ſea-water; luckily for
us, the celebrated Bergman has cleared up the
difficulty, by informing us that the makers of this
falt, add to the liquor which remains after the
fea-falt is obtained from ſea-water, the mother-
water of copperas; theſe thus united and fuffered
to cryſtallize, yield a true and perfeet Epſom-falt :
this curious faet can only be explained by a know-
ledge of the chemical attractions, but it is found.
ed in theory, and realized by experiments. Theſe
obfervations upon Epſom-falt, afford us a lament-
able inſtance, that authors frequently copy even
errors from each other, without ever referring to
their own obſervations and experiments for a
knowledge of the truth.

ECONOMICAL ESSA Y S.
45
ESSA Y IV.
Chemical attractions, with a table of ſingle, ſingle elective,
and double elective attractions.
A
S fundamental in the ſcience of chemiſtry,
the peculiar phenominon called attra£tion,
juſtly comes under our conſideration. It is al-
moft impoſſible to proceed any length in chemi-
cal inveſtigation, without being ſtruck with the
wonderful effects of this great agent; it is in
fact, as I conceive a thorough knowledge of
the effects of this attraction, between heterogene-
ous bodies, or bodies ienſibly different from
each other, that conſtitutes a knowledge of
chemiſtry. In the introductory eſſay we obſer-
ed, that a ſenſible change is alway produced in
any body that is chemically operated upon; this
we conſider can never be done but by the won-
derful power of attraction, and indeed there is
no chemical operation, whether complex or
fimple, in which we have not reaſon to believe
that attraction is concerned; and to a perſon
acquainted with the ſcience, it would be fuffi-
ciently defined, to call chemiſtry a ſcience which
teaches the laws of attraction between heteroge-
neous bodies in contact with each other.
It is very difficult to make this ſubject fuffi-
ciently plain to ſome readers, without deſcend-
ing to ſuch language, as to others would ſeem
inelegant, but fuppofing it neceſſary, for a par-
ticular claſs of readers, to expreſs myſelf in a dif-
ferent manner. I will endeavour to give as clear
an idea of it as I poſſibly can,
The moſt ſimple ſpecies of attraction is where
two bodies unite and form a compound, very

96
CHEMICAL
A N D
different in ſenſible properties from the compo-
nent parts; we have a very ſtriking and familiar
illuſtration of this, when we combine two culina-
ry articles together: let us add to about a pint of
good ſtrong* ley, ſuch as uſed in making
ſoap, &c. a quart of ſharp wine-vinegar, and
obſerve what a change of properties are pro-
duced by the mixture, The ley was remark-
ably acrid to the taſte, the vinegar very acid,
and both fo capable of acting on the tongue,
that no perſon could ſwallow a gill of either
of them, without the moſt diſagreeable ſenſation;
but mixed, they form a compound ſo mild, that
a quart of it might be drank in the ſpace of an
hour, with very little ſenſible effect upon the
body; the ley in this caſe has loſt all its acrid
taſte, and not only all its ſenſible properties,
but even its chemical charakter, for it is unable
when thus combined, to act upon fat to form
ſoap; the vinegar no longer taſtes four, and
it has alſo loſt its chemical properties, for where-
as, before its combination, it could be evapo-
rated by boiling, it cannot now be forced off
from its connection with the ley, but by a heat
very far fuperior to boiling; in this caſe we
have the idea of its being retained or held back
from evaporating by the ley.
It muſt have happened to almoſt every body
to ſee what is called aqua fortis by the apotheca-
ries, and be at leaſt in a ſmall degree acquainted
with its corroſive powers, ſuch as its defolving
the hardeſt and moſt compact metals, &c. we
would readily believe from ſuch knowledge,
without making the experiment, that if one fin-
* This a chemift would call an alkaline fluid.

ECONOMICAL ESSAYS.
47
gle drop of aqua fortis were put upon the tongue
and ſuffered to remain there, it would produce
a moſt violent inflamation : but let us obſerve
how the properties of this fluid ared eſtroyed by
combination : a tyro in chemiſtry cannot amuſe
himſelf more with any experiment, than by pro-
curing an ounce of aqua fortis, and combining it
with an equal quantity of potaſh diſſolved in boil-
ing water; four hours time will preſent him
with a miracle, which even an experienced
chemiſt cannot contemplate without admiration;
for in the veſſel in which he makes this experi-
ment, he will find a number of needle like cry-
Itals, which have all the qualities, and in fact are
nothing elſe than common ſalt-petre, ſo familiar
to every body. How different is this mild, cool
ſalt, from the corroſive, hot, and poiſonous a-
!
qua fortis !
Theſe are inſtances of the moſt ſimple attrac-
tion, as it falls under the obſervation of the
chemiſt. It had the name of attraction, from
that great philoſopher Sir Iſaac Newton, who
ſo happily explained many of the phenomena of
nature, by inveſtigating the laws of attraction,
which take place, between the larger maſſes
of matter in the univerſe. It is ſuppoſed for in-
ſtance, that the conſtituent particles of the pot-aſh,
in the laſt mentioned experiment, had a tendency
to unite with the conſtituent particles of the
aqua fortis, and that their union formed new par-
ticles, poſſeſſed of properties different from the
component particles, and capable of affecting the
organs of ſenſe in a very different manner. This
may be conſidered as an explanation of the effect,
not of the cauſe, for we ſtill remain as ignorant
as ever, when we come to enquire why this at-

48
CHEMICAL AND
traction takes place in ſome particular bodies and
not in others. It may poſſibly depend upon a
modification of the fame cauſe (whatever the
caufe may be) that tends to bring larger maſſes;
that are ſeparate, into contact, or that impels a
piece of cork fwimming in a glaſs tumbler of
water, to the ſides of the veſſel.
There ſeems to be however, ſome effential
difference in the attraction, we obſerve in chemi-
cal combinations, and thoſe taught in the ſchools
of natural philoſophy.
Natural philofophy teaches us that if two
globules of mercury, are laid on a ſmooth place,
at a very ſmall diſtance from each other, they
will unite by the power of attraktion, and form a
large globule; but this is by no means a chemi-
cal attraction: the large globule is ſtill mercu-
ry---it is ſtill fluid, reſembling a melted metal as
before--it has all its ſenſible properties as be-
fore--and it is ſtill capable of being acted upon
by chemical ſubſtances :
A itone thrown up in the air, in a certain time
returns to the earth; this tendency, which weigh-
ty bodies have to fall to the earth, has been call-
ed the attraction of gravitation; but it is not a
chemical attraction, for this always produces a
ſenſible change; but had a ſtone, or any other
folid body been thrown into the air a thouſand
times, Boerhaave himſelf with all his ſkill, would
have been unable, merely by his chemical know-
ledge, to have known that the attraction of gra-
vitation had acted upon it ſo often.
A glaſs tube, with a very ſmall bore, put into
water, the water riſes in the tube conſiderably

ECONOMICAL ESSAYS.
49
above the ſurface of the fluid in which it is im-
merſed; owing to an attraktion between the glaſs
and the water, which is called capillary attraction;
and two pieces of poliſhed marble, being ſlided
upon each other, unite fo firmly, by what is cal-
led the attraction of coheſion, as to be feparated
with much difficulty ; but neither of theſe are il-
luſtrative of chemical attraction: the glaſs tube
is ſtill tranſparent, brittle and folid, preſerving
at the ſame time its tubular form; the water al-
ſo that role in it, is ſtill unchanged water: the
pieces of marble are alſo unaltered, and conſe-
quently had not been aded upon by a chemical
attraction.
We obſerve in natural philoſophy, that attrac-
tion takes place among ſolid bodies---in chemiſtry
never : it is eſſential that at leaſt one of the ſub-
ſtances to be acted upon by chemical attraction,
be fluid, and before the operation is compleat,
it is neceſſary that the fluid render the folid bo-
dy, to be acted upon, fluid alſo, although af-
ter that operation, it may again reſume its ſolid
form. In natural philoſophy, we obſerve attrac-
tion to take pla e Letween bodies not in contact,
as between two globules of mercury; but che-
mical attraction never commences until the bo-
dies are brought into actual contact. Here let
us not be deceived; for we fee inſtances where
two bodies are firſt acted upon by the one kind
of attraction, and are brought into contact, and
then only, it is poſſible they may be acted upon
by chemical attraction. In natural philoſophy,
attraction operates frequently upon bodies pof-
ſeſſing the ſame ſenſible qualities, as in the in-
stance of the two globules of mercury abovemen-
H

so
CHEMICAL AND
а
tioned; but in chemiſtry this is never the caſe.
Some chemiſts indeed have ſuppoſed that the
contrary always happens, and that chemical at-
traction only appears in bodies diametrically op-
poſite in qualities to each other; this is probable,
but muſt be admitted with caution. The moſt
complete form of chemical attraction we have is
in the pot-afh and aqua fortis abovementioned, or
as a chemiſt would expreſs it, between the alka-
li and the acid. Theſe are ſuppoſed to be fo
op-
poſite to each other in their own natures, that the
writers of the Materia Medica, very generally
call all acids, antalkalines, and all alkalies, ant-
acids. It is true they deſtroy each others effects
in many caſes, but this might be explained in
different manner; for inſtance, if a piece of
dyed cloth is ſtained with an acid, ſuppoſe a lit-
tle vinegar, a ſmall quantity of an alkali [ſoap
ley] will inſtantly reſtore the colour, here we
evidently ſee that the effects which are cauſed by
the one, are changed by the addition of the o-
ther; but it is not neceſſary to ſuppoſe that this
ariſes from a contrariety of nature; we might
ſimply ſay that the acid had diſſolved or united
itſelf to the colouring matter of the cloth, but
that when the alkali was put on the cloth, the
acid was willing (if I may ſo expreſs it) to depo-
fit the colouring matter on the ſurface of the
cloth, that it might be ſo diſengaged as to unite
with the alkali: if we ſtain a piece of paper with
the blue violets, and rub a drop of a weak folu-
tion of an alkali upon it, we find the colour
changed from a blue to a green, if to the paper we
add a ſmall quantity of an acid, the blue colour
returns, not from any poſitive effect of the acid,
but upon the principles explained above, as I

ECONOMICAL
51
ESSAYS.
conceive; but add a little more acid than is juſt
neceſſary to reſtore the colour, and we find a
poſitive effect produced, the paper is changed from
a blue to a red colour; here then the poſitive ef-
fects of an alkali, is to change certain blues to a
green colour and of an acid to change them to a
red; this experiment, though it proves that acids
and alkalies are eſſentially different from each
other, as producing very different effects, yet it
by no means proves them to be exactly contrary,
for we have no facts in optics to prove that a green
colour is the very reverſe of a red. In chemiſtry,
the attraction is to be obſerved only among ſome
particular bodies, and not at all in others;
hence very different from the attračtion of gravi-
tation, which folicits all the matter of our globe,
however compounded or modified, as far as ex-
periments can teach us, to the centre of the
earth.
The alteration of the ſenſible properties of the
bodies operated upon by chemiſtry, is a more in-
fallible characteriſtic of a chemical attraction,
and the more complete the alteration is, the
more certainly chemical it is. We have to re-
mark, that the ſciences are very juſtly repreſented
under the figure of a circle, and that the part
where one ends and the other begins, is almoſt
imperceptible, for as countries are ſeparated on
the map by imaginary lines, fo in the ſciences
the diſtinction is in a great meaſure artificial.
Chemiſtry borders very much on natural philo-
ſophy, for whilft the chemiſt will view, as be-
longing to his ſcience, the ſenſible atlteration of
properties which take place, when a piece of ſolid
loaf ſugar is diſſolved in water, where a ſolid,
and a fluid both become fluid, the mechanical

52
CHEMICAL AND
philoſopher, will conſider it merely as a ſimple
deſtruction of the attraction of coheſion, fubfift-
ing between the particles of the ſugar; the che-
mift will ſee that there has been but one of the
ſenſible properties of the fugar altered in this
proceſs, i. e. its folidity, whilſt its ſweetneſs,
combuſtibility, &c. &c. all remain entire ; the
mechanical philoſopher will alſo find it hard to
conceive, by what means the particles of the fu-
gar are rendered fo inconceivably ſmall by the
water as to eſcape the fight, whilſt the ſenſible
properties abovementioned, remaining fo entire-
ly, muſt incline him to ſuppoſe that there would
be but very little difference, philoſophically con,
fidered, between two powders mixed together
by being pounded in a mortar, and the ſolution
of ſugar in water.
But perhaps there are no circumſtances in
which the peculiarity of chemical attraction ap-
pears more deciſively, than in thoſe which we
are now to mention. Let us take, for inſtance,
a given quantity of magneſia of the apothecaries,
and attempt to diffolve it in water, we find it
vain, it will not diſſolve, owing to thoſe ſubſtan-
ces not having any attraction to each other, here
then is a mechanical mixture or diffufon, for in a
little time the magneſia, thus diffuſed through
the water, will ſubſide to the bottom of the
veſſel, with all its ſenſible qualities unimpaired;
but let us add to ſuch a mixture, a certain quan-
tity of aqua fortis (nitrous acid) and the whole
of the magneſia diſappears, being perfectly dif-
folved; here then is a chemical union, or in o-
ther words, a chemical attraction takes place,
between theſe two ſubſtances, attended with fi-
milar phenomina as when we mixed aqua
fortis

ECONOMICAL ESSAYS.
53
with pot-aſh, viz. a conſiderable change in their
ſenſible properties, let us then add to this m x-
ture of aqua fortis and magneſia, a ſolution of
pot-aſh, and attend with accuracy to the pheno-
mina; another ſenſible change of properties a-
gain presents itſelf to us, viz. two tranſparent
colourleſs fluids, immediately become epaque
and of a milky appearance, and give us the idea
of a mechanical diffuſion of an inſoluble powder
in the liquor, which is actually the caſe ; let us
filter the liquor through paper, and then we ſhall
be able to detain this white powder for exami.
nation, when perfectly dried; thus examined it
turns out to be nothing elſe than the ſame pure
identical magneſia, with all its properties and qua-
lities reſtored to it. The coldeſt obſerver can-
not reflect on this fact without ſurprize. We
faw, that by the addition of one body, the mag-
neſia was deprived of all its ſenſible properties,
whilſt the addition of another, reſtored them all
to it again. Would not any perſon ſuppoſe that
this effect was to be aſcribed to the power with
which the pot-aſh was able to act upon the aqua
fortis, and thus deſtroy its effects? But if the
magneſia again reſumes its qualities, we cannot
conceive it to be done in conſquence of any other
power than that of the pot-afh aſſuming to itſelf
the aqua fortis, with which it was combined, and
that as it was the cauſe of its folution, ſo when
this is taken away, this effect muſt ceaſe; but let
us give a proof that this actually is the caſe. Tle
reader may remember the experiment mention-
ed in this eſſay, of making artificial falt-petre,
by combining aqua fortis and pot-aſh; now if
the potrafh, we added to this laſt mentioned mix-
ture, actually united to the aqua fortis, which

54
CHEMICAL AND
held the magneſia diſſolved, in ſuch a manner as
to deitroy the attraction between theſe two fub-
ſtances, they could not have united, we would
conceive, e priori, without forming falt-petre, as
happened in the experiment above alluded to;
but obſerve how admirably experiment in this
caſe realizes the theory; for we boil the liquor
which would run through the filtre, in order to
obtain the magneſia dry, until but very little
more is left than the quantity of aqua fortis,
which we uſed in the experiment, and we ſhall
actually behold with the higheſt ſatisfaction, af-
ter the fluid has grown cold, ſome fine needle-
like chryſtals poſſelling all the properties of ſalt-
petre. To recapitulate this laſt paragraph in a
few words, if we add ſome aqua fortis to mag-
neſia, they will unite in conſequence of a ſimple
chemical attraction; but if we add to ſuch a mix-
ture, a ſolution of pot-aſh, this and the aqua for-
tis will unite, and again ſuffer the magneſia to
aſſume its former qualities. Here we evidently
ſee ſomething like a choice or volition fubfifting
between the pot-aſh and aqua fortis, either the
pot-aſh tended to unite with the aqua fortis by
greater attraction, than the magneſia did, or the
aqua fortis had a greater tendency to combine
with the pot-aſh than it had to combine with the
magneſia. We obſerve nothing like this in na-
tural philoſophy, if we except the attraction of
electricity and magnetiſm, with which it will ne-
ver be confounded, and from which it ſtill dif-
fers very widely.
When chemical philoſophers firſt contempla-
ted ſuch phenomina as theſe in their experiments,
they knew not what to compare it to, except the
volitions of an animal, and a chemiſt, however
а

ÉCONOMICAL ESSAY S.
55
circumſpect in his language, is unable to deſcribe
his opinion upon this ſubject without having re-
courſe to a metaphor: even the moſt technical
tern now in uſe among chemiſts, is but a meta-
phorical illuſtration, for they will tell you that the
experiment related last is an inſtance of an elec-
tive attraction, implying that theſe inanimate bo-
dies, by a law of nature, had a power of making
a fit choice for themſelves.
Decompoſition is always the effect of an elec-
tive attraction, and I believe never happens but
in conſequence of it.
We are now prepared to underſtand the prin-
ciples on which the tables of elective attraction,
fo frequent in chemical authors, are founded :
a number of experiments are neceſſary in the firſt
place, to ſelect as many ſubſtances as poſſible,
which have any tendency to combine chemically
with any given body, and they aſcertain this ten-
dency by a phenominon, which cannot be too
often repeated, the attraction in the ſenſible qua-
lities of the ſubſtances acted upon : to illuſtrate
this by an inſtance of ſubſtances, which may by
this time have become familiar to the reader,
we will ſuppoſe that aqua fortis is placed at the
head of the column, and we wiſh to expreſs in
one view, the relative attractions, which diffe-
rent ſubſtances have to it: we have mentioned
that both pot-aſh and magnefia have an attracti-
on to it; but we ſtated a fact, which proved that
the attraction of pot-aih was greater than the
magneſia, therefore in making the table, we
would write the chemical name of pot-aſh, be-
fore that of magneſia, and in all the tables, prox-
imity always denotes ſuperiority of attraction:

55
CHEMICAL AND
if further experiments ſhould teach chemiſts that
there are ſome fubítances in nature having a
greater elective attraction to aqua fortis than
magnefia, but leſs than pot-ain, their names in
the table would and do occupy a ſpace, between
pot-afh and magneſia, according to their
powers.
The table, thus conſtructed, is wonderfully ex-
tenſive in its application; it teaches us in one
view, the reſult of an infinite number of experi-
ments; and all chemical profeffors, unite in de-
claring, that no friend to chemiſtry ſhould ever
be without one: we fee from it, that if the ſub-
ſtance which forms the head of the column, is
combined in conſequence of a ſimple attraction,
with any one of the ſubſtances under it, except
the one next to it, the combination can be decom-
poſed, in confequence of a ſingle elective attracti-
on, by any of the ſubſtances placed above it. Thus
if the ſubſtance at the head of the column is
united to a ſubſtance occupying the fourth place
from the beginning, it will be attracted by the
fubftance occupying the third place, or any
above it, but by none below it; whilſt this new
combination in its turn can be ftill decompoſed
by the two other fubftances above it; laſtly the
combination of the fubftance in the fecond ſpace,
and that at the head of the column, can only be
decompoſed by that immediately next it, whilft
this laſt compound cannot have this ſubſtance ta-
ken from it, by any of the bodies under it, or by
any known to chemiſts at the time the particular
table was made; although it is more than pofi-
ble that ſuch ſubſtances may exiſt in nature.
Thus much reſpecting the table we could not
Omit.
There are ſome facts reſpecting theſe two vas

ECONOMIC AL ESSA Y S.
57
rieties of chemical attraction, ſimple and elec-
tive, that may be conſidered as axioms, and are
invariable.
1. It is different from every ſpecies of attrac-
tion which philoſophers ever have to contem-
plate, as we have faid already.
2. It always produces a ſenſible change in the
ſubſtances which it influences.
3. It takes place among diſſimilar bodies only.
4.
The elective attraction is never difcerned
but when we add to a compound a body diffe-
rent from either of the ingredients; thus mag-
neſia will unite with aqua fortis, but we have no
evidence, that a freſh quantity of magnefia, will
cauſe the firſt portion to forſake its attraction
with the aqua fortis, and indeed it ſeems very
improbable.
5. We very feldom ſee inſtances of a chemi-
cal combination of more than two ingredients,
where three ſubſtances are united, it is moſt fre-
quent that two of them only are chemically com-
bined, the other mixed mechanically with them.
6. In chemiſtry, this elective property is al-
We know of no body in nature
which has an equal chemical attraction to any
two different ſubſtances : thus let A be a body
having an attraction to two others, B and C, if
A is united to B, and C is not able to decompoſe
it, reverſe the matter and combine A with C,
then B will undoubtedly decompofe it.
The only thing that we have to add on the
ways evident.
I

58
CHEMICAL AND
ſubject of ſingie elective attraction, which in fact
may apply to every ſpecies of chemical attraction,
is that we are entirely ignorant of every thing
like a cauſe: our limited ſenſes and intellects,
though aided by experiment, are inſufficient to
fhew us why any bodies tend to unite in this curio-
us manner, and much leſs, why a body ſhould pre-
fer an union with one certain ſubſtance, to an
union with all others, and will even caſt them
off to make way for it.
But this elective attraction is ſtill more exten-
five. Chemiſtry affords us innumerable inſtan-
ces, where two bodies, each conſiſting of two
other ſubſtances, will make a mutual exchange
of component parts, and theſe form two new bo-
dies that are alſo compounded: this is called a
caſe of DOUBLE ELECTIVE ATTRACTION,
and is chiefly ſuppoſed to take place among falts:
accordingly, in eſſay III. when we recommended
to the apothecaries, to add common ſalt to their
Epſom-falt, in order to make a Glauber's falt
from it, before they obtained the magneſia, we
at once have an inſtance of a double elective at-
traction, and of conſequence a double decompo-
ſition ; for ſea-ſalt conſiſts of two ingredients,
as we mentioned there, that is of a foſil alkali
and a marine acid, and having thus two ſuch op-
pofite principles, as chemiſts ſuppoſe them to be,
and the ſenſible qualities of each being deſtroy-
ed by combination, they call it and all other falts
compoſed of two ſuch ingredients, neutral ſalts,
for although compounded of an acid and an al-
kali, ſuch ſalts poſſeſs the properties of neither.
The Epſom-falt is alſo a neutral falt, compound-
ed of magneſia and vitriolic acid; now we ſee

ECONOMIC AL ESSAY S.
59
they will decompoſe each other, thus their in-
gredients ſtand in this manner before mixture,
Epſoin-S Vitriolic acid.
Sea-falt.
falt. Magneſia. Foflil alkali.
But after mixture the caſe is different, for the
vitriolic acid and foffil alkali will be found toge-
ther, and at the ſame time the magneſia and ma-
zine acid will unite; therefore, this will be the
ſcheme of their combination;
A falt not Marine acid. Vitriolic acid. Glau-
in ule. Magneſia. Foffil alkali. S ber's falt
Now, to know what theſe new compounds are
called, let us conſult any ſyſtem of chemiſtry,
and it will immediately inform us, that if by any
means it is poſſible for the foſſil alkali of ſea-falt
to unite with the vitriolic acid of the Epſom-falt,
it cannot be done without forming a Glaubers
ſalt, as thoſe two ſimple ſubſtances are the in-
gredients of that falt, which will always form it,
however united, and without which it can never
be formed; hence it appears how ſafe it was for
us to aſſert that that experiment was conceived in
theory, and realized in fact. To illuſtrate the
proceſs a little further, we can now eaſily con-
ceive how the addition of the fea-falt to the Ep-
ſom-falt, would allow us to extract Glauber's falt
from it, without rendering it it leſs fit to obtain
the magneſia from. We ſee by the above ſcheme,
that the magnefia had nothing to do with the
Glauber's ſalt, for after the Glauber's falt is thus
extracted, nothing remains but the magneſia u-
nited to the marine acid; we then mentioned
that a certain quantity of pot-aſh is to be added
to the reſiduum, this the chemiſts call vegetable
و

60
CHEMICAL AND
alkoli, and now our magneſia is nearly made :
the vegetable alkali attracts the marine acid from
the magneſia, and leaves it without any chemi-
cal combination whatever; for, by all the tables
of fingle elective attraction, we find that the ve-
getable alkali is always placed nearer to marine
acid, than magneſia is ; the magneſia is now on-
ly mechanically diffuſed through the veſſel, and
muſt in time by its own ſuperior gravity ſubſide;
the other part of the proceſs, though eſſential as
deſcribed in all diſpenſatories, is too mechanical
to deſerye our animadverſions as a theoretical
chemiſt.
The ſubject of double elective attraction is
fufficiently difficult to every perſon, not well ver-
ſed in the ſubject, and I am willing to advance
every obſervation in my power, to make it fami-
liar to ſuch, however trifling it may appear to
the adept; and I think the following entertain-
ing experiment muſt render it amazingly clear
and obvious, even to the moſt ſceptical obſerver:
Every one doubtleſs, who may peruſe this eſſay,
has ſeen that beautiful blue pigment called Pruf-
han blue. Chemiſtry teaches us, and twenty ex-
periments confirm it, that its proximate principles,
whatever may have been the proceſs uſed in ma-
nufacturing it, are a ſubſtance, called with juf-
tice, the colouring matter of Pruſſian blue, and an
earth ſomewhat analagous to the ruft of iron,
theſe two principles we ſay compoſe Pruſſian blue,
for the iron without the colouring matter is not
blue, and this colouring matter, although it can
impart a colour to iron, has none itſelf; for it is
as colourleſs and tranſparent as water;
us take two drams of Pruſſian blue, and boil it
with an half dram of pot-aſh, the colour is imme-
now let

ECONOMICAL
61
ESSAYS.
diately loſt; we muſt conclude that the pot-afh
has taken it, for the ruft of iron is found at the
bottom of the veſſel, in its natural brown ſtate,
the clear liquor ſwimming above it is pot-aſh,
united to the colouring matter of Pruſſian blue :
but are there no means of depriving the pot-afh
of this colouring matter and giving it to iron and
regenerate Pruſſian blue ? yes there are : the ſub-
ſtance ſo familiar to common people by the name
of copperas, conſiſts of oil of vitriol, and the
ruft of iron; and theory teaches us that this ſub-
ftance will decompoſe, by double elective attrac-
tion, the fluid we are ſpeaking of: this muſt be
the manner of it; the oil of vitriol of the cop-
peras muſt unite to the pot-aſh, whilſt the ruſt of
iron, contained in the copperas, muſt unite to the
colouring matter contained in the pot-aſh, rege-
nerating inſtantly a Pruffian blue: Let us then
to this liquor add an half ounce of copperas dif-
folved in water (to which a little more oil of
vitriol may be added) to make the ſolution
clearer, and a moſt beautiful blue powder wili
be found diffuſed through the liquor, which in
time will fubfide to the bottom of the veſſel:
this is an experiment that illuſtrates a double elec-
tive attraction, in the moſt elegant and entertain-
ing manner, and puts the reality of it beyond
doubt. We obſerved already that chemiſts un-
avoidably ſpoke in a metaphor reſpecting the
elective attractions, we frequently hear them ſay
that one ſubſtance chooſes, prefers or has a ſtronger
affinity with one particular ſubſtance than ano-
ther: and the reader perhaps will ſmile, when
he caſts his eye on the curious ufe I ſhall make
of this idea, but as I hope, to his advantage.
Some fanciful ancient chemiſt was deſirous of
making the ideas of a double elective attraction

62
CHEMICAL AND
as familiar as poſſible, and as he has been ſome-
what fortunate in that enquiry, I will relate the
reſult: he compared every combination of two
principles to a man and wife, which although
equally diſſimilar to each other, yet have (or
ought to have) an attraction to each other, but
when another combination of two ſubſtances
were added to it, or to carry on the metaphor,
when another man with his wife fell into the
company of the firſt couple, however well ſatiſ-
fied they were before with each other, a deſire
ariſes, in ſome of their minds, to ſeparate from
their former mates and take another, thus the
one man will take the other man's wite, whilſt his
own forſaken wife will ſeek an union with the
man whoſe wife is taken away.
There are four circumſtances particularly to
be attended to in caſes of double elective attrac-
tion:
1. We obſerve a very perfect decompoſition
between two neutral ſalts, or any two analagous
ſubſtances, where all the four different parts of
the two are very willing to exchange principles.
We have an inſtance of ſuch a double elective
attraction, when the ſalt compoſed of a vegetable
alkali and the acid of ſugar is added to the ni-
trous acid combined with lime.
2. The ſecond ſpecies of double elective at-
traction is leſs perfect: here only three of the
four principles in the two combinations of two
ſubſtances each, are ſolicitous for an exchange
of principles : Thus acid of tartar combined
with vegetable alkali, will decompofe lime united
to the nitrous acid, for the vegetable alkali pre-
fers the nitrous acid to the acid of tartar, and of

ECONOMICAL
63
ESSAYS.
conſequence is willing to give the one up for the
other; the nitrous acid alſo prefers the vegeta-
ble alkali to the lime, and is therefore willing to
leave it; the lime is as willing to ſurrender up
the nitrous acid to the alkali, as that acid is to
leave the lime, provided it can but get the acid
of tartar, which it prefers, but the acid of tar-
tar is the only one that is unwilling, for it does
not prefer lime to the vegetable alkali : here
three are for an exchange of principles, and but
one is againſt; and accordingly the majorityc ar-
ries it.
3. The third is ftill lefs perfect, but the moſt
common of all, in this only two of the princi-
ples of the four are agreed to ſeparate from their
firſt combination, and to unite together, but they
two being the moſt powerful, they overcome the
others.
We have an inſtance of this ſpecies in the decom-
poſition of Epſom ſalt by ſea falt. The vitriolic
acid of Epſom falt prefers the follil alkali of the
ſea ſalt to its own magneſia, whilſt the foſil alkali
in its turn prefers the vitriolic acid of the Epſom
falt to its own marine acid ; but the marine acid
does not prefer the magneſia to the foſſil alkali ;
neither does the magnefia prefer the marine acid
to the vitriolic acid, but being thus left together,
they will unite ; here the votes are equal, but
fuperior ſtrength is equal to a majority. The
inſtances of this kind are almoſt innumerable.
4. The fourth and laſt ſpecies is entirely inex-
plicable upon any principles, it is exactly the re-
verſe of the former; here a combination of two
ſtronger principles are decompoſed by a combi-
nation of two weaker ones. Thus Glauber's

64
CHEMICAL AND
falt is decompoſed by the ſalt formed of lime and
nitrous acid. Foſſil alkali prefers the vitriolic
acid, to which it is already united to form Glau-
ber's ſalt, to the nitrous acid, and is actually
ſtronger in chemical elective attraction than the
lime; the vitriolic acid alſo prefers the foffil al-
kali (which it has already) to the lime, and is
ſtronger than the nitrous, and yet the fact is that
thoſe combinations will mutually decompofe each
other. We meet with feveral theories to account
for it, but they all appear to me very inſufficient.
We have only to add to theſe obſervations on
double elective attraction, the three following
axioms. In order to produce a double elective
attraction, it is neceſſary,
1. That the two compounds conſiſt of two
proximate principles each.
2. That all the four different component parts
of the two compounds be different.
We may add as a third axiom,
3. That when all the four principles of the two
compounds are different, and no decompoſition
happens, they make a mutual exchange of prin-
ciples, and a double decompofition muſt happen.
Although a double decompoſition will not always
happen, even under the two firſt circumſtances,
yet it can never happen without them.
I ſhall conclude what I have to ſay on this fub-
ject with preſenting to the reader a NEW TABLE,
expreſſing, in one view, the names of the neutral
falts, compoſed by the union of two ſimple falts,
in conſequence of a ſimple attraction, and the
ſingle eležtive and double elective attractions of a

ECONOMICAL ESSAYS.
65
certain number of faline bodies, and the new
compounds formed in conſequence of it.
The table is compoſed of twenty-four ſquares,
containing the names of twenty-four neutral falts.
In an horizontal line above theſe ſquares are con-
tained the names of all the acids of which they are
compoſed, and in the perpendicular line at the left
hand of them, are what chemiſts call the baſes,
or moſt ſolid parts of falts; for all neutral falts
are compoſed of an acid and a baſe ; in the ſquare
paralel to either of the baſes, and under any par-
ticular acid we have the name formed by that
baſe and acid; thus if we wiſh to know what fea
falt is compoſed of, we ſeek its name in one of
the ſquares, we find the foffil alkali parallel to it
in the column of baſes; that therefore is its baſe,
and the marine acid directly above it in the co-
lumn of acids; therefore theſe two ſubſtances
compoſe it. Thoſe ſimple {ubſtances which have
the greateſt attraction to each other are here alſo
placed neareſt to each other; thus if we wiſh to
know, what acid the vegetable alkali prefers,
we ſee it is placed nearer to the vitriolic than
to the nitrous, but nearer to the nitrous than to
the marine, and this is the order in which all the
baſes prefer the acids ; on the contrary if we
wiſh to know the order of ſingle elective attrac-
tion of the acids to the baſes, we ſee that the
vitriolic acid takes vegetable alkali firſt, the
foffil next, and ſo on, and this is the order of all
the acids to the baſes.
Hence it will follow, that the vitriolic acid
will expel all other acids from all the baſes, and
conſequently we aſſert that the vitriolic acid will
decompoſe all the ſalts ſituated in the table below
K

66
CHEMICAL AND
it, and to the right hand ſide of it, and the ſame
holds good with the nitrous acid; but we wiſh
to know the new compounds formed by the de-
compoſition, and this may be done in a mechani-
cal manner; let a diagonal line be drawn from
the acid to the ſalt to be decompoſed, then a cor-
reſponding diagonal line, diſſecting it in its mid-
dle, will point to the new falt, and the acid
which of conſequence muſt be left uncombined.
For inſtance ſea ſalt is below vitriolic acid, and
to the left hand, and muſt therefore be decom-
poſed by it, we then draw a line from vitriolic
acid to fea falt; the line which correſponds to it
and diffects it through the middle is Glauber's
ſalt and marine acid, hence when we add vitri-
olic acid in ſea ſalt, theſe two ſubſtances will re-
fult from them.
In like manner, all the baſes will decompoſe all
falts ſituated below them and to the right hand; the
new compounds are to be known in the fame
manner as above; thus Epſom ſalt is ſituated be-
low vegetable alkali (pot-aſh] and to the right
hand of it, and is decompoſed by it ; the lines
drawn as before will point at uncombined mag-
neſia, and tartar of vitriol : this illuſtrates the
proceſs of making magneſia as deſcribed in the
diſpenſatories.
The double elective attractions are known in
the ſame way, thus all thoſe falts marked i de-
compoſe all thoſe marked with the ſame figure,
below them; and to the left hand, all falts de-
compoſed in this manner, are inſtances of the
fourth fpecies of attraction mentioned above:
The manner of knowing the new compounds is
the ſame as before.

ECONOMICAL ESSAY S.
67
All thoſe falts marked 2, decompoſe all thoſe
marked 2 below them, to the right hand ;
theſe furniſh inſtances of the third ſpecies of at-
traction.
Every perſon, at firſt fight, will find a confi-
derable difficulty not only in comprehending, but
even in retaining afterwards the ſcheme of this
table;
two or three days attention thereto
have in ſome inſtances been neceſſary, but upon
a ſubject fo intereſting, ſo beautiful and curious,
no perſon will grudge the labour neceſſary in ac-
quiring a knowledge of it.
I have dwelt thus long on the attractions be-
cauſe the knowledge of them is of the utmoſt
conſequence, without which chemiſtry degene -
rates into an empirical art, and the chemiſt into a
tradeſman, which however honorable the cha-
racter for its utility may be, yet it ought never to
be confounded with the title of a philoſopher.
It is impoſſible to ſay how far the doctrine will in
time apply, but I actually believe in an opinion
of the late chemical profeſſor * on this ſubject,
" that all the varieties of matter have as certain
a place in the ſcale of nature as an acid or an
alkali in a table of chemical attractions,”
* Dr. Benjamin Ruſh.

68
CHEMICAL AND
ESSA Y V.
Analyſis of the twenty-four Salts moſt commonly known and
uſed, with the Acids and Bases which form them.
is of conſequence to diſtinguiſh the falts from
each other, and this is often to be done ef-
fe&tually only by conſidering the influence of
other ſubſtances upon them, We will therefore
take a compendious view, or recapitulation, of
all that is neceſſary to diſtinguiſh theſe faline ſub-
ſtances not only from every other kind of matter,
but even from each other. We defined ſalts in
general to be ſuch ſubſtances as were incombuſtible,
Sapid, ſoluble in water, chryſtallizable, and tended
to combine in a peculiar manner with other ſub-
ſtances. We remarked, as we went along, that
although many faline ſubſtances did not poſſeſs
all of theſe characteriſtics, and many ſubſtances
that were not faline, did poffefs Some of the pro-
perties, yet we concluded that any ſubſtance,
whoſe chemical hiſtory was not yet known, might
with propriety be ranked with the ſaline ſubſtances,
if it poſſeſſed many of the properties aſcribed to
them in the definition. Suppoſe then a piece of
matter was preſented to us, that we did not re-
colle&t to have ſeen before, we add water to it,
if we find that leſs than twenty or thirty times its
weight will diſſolve it, we may think it tolerably
foluble ; part of the ſolution we expoſe to the
air, perhaps for three or four days, another part
we heat till it boils, and then put in more of the
ſubſtance to be examined, in order to give the
hot water as much as it will diffolve, we then try
if it will either by cooling or expoſing it to the
air yield any ſubſtance in a ſolid form, , or what
we have called chryſtals; but if the ſubſtance to

ECONOMICA L.
69
ESSAY S.
be examined remain inſoluble in four or five hun-
dred times its weight both of hot and cold water,
we heat it very hot in an open fire, and obſerve
whether it is combuſtible, or incombuſtible as falts
generally are, nay to be ſtill more certain, we
throw a little nitre upon it when perfectly red
bot, and ſee whether there is a phenomenon fimi-
lar to that which takes place on throwing nitre
upon burning charcoal, if it does not exhibit
any
ſuch appearance, we may in general pronounce
the ſubſtance, an incombuſtible body; we try the
effect of an acid upon it, and for many reaſons
we prefer the nitrous, if the acid loſes its acid
properties, whilſt the ſubſtance is foluble there-
in, but not in water, we may pronounce the ſub-
ſtance a ſaline or abſorbent earth, becauſe although
inſoluble in water, it poſſeſſes a tendency to com-
bination, which is at leaſt equivalent thereto. We
muſt rank falts under two very general beads, ſim-
ple and compound; the fimple are ſuch as in the
preſent ſtate of chemical knowledge cannot be
ſeparated into or formed by the union of any two
or more ſimple bodies; theſe we divide into
two kinds, acids and baſes in general; they are
called fo becauſe they as it were form the baſe or
folid parts of thoſe faline bodies called neutral
falts, and becauſe fire can convert but one vari-
ety of this claſs into vapour, whereas on the con-
trary almoſt all acids are volatile. Whenever
we meet with an homogeneous body (by which
term I mean a ſubſtance pofſeffing the ſame pro-
perties, in proportion to its bulk, in one particle,
as it does in a larger quantity) that is ſoluble in
leſs than nine or ten times its weight of water
that is able to deprive acids of their four taſte,
when put in contact with them, and has a pecu-

70
CHEMICAL AND
liar taſte, which ought to be well known, and
which, when united with an acid, and diſſolved
in no more hot water than is juſt ſufficient for
ſolution, depoſits a ſolid ſubſtance of a particu-
lar ſhape, by cooling, or even by long expoſure
to the air, and finally if that ſubſtance changes
blue vegetable colours green, and reſtores ſuch
colours as acids have changed, we may with fafe-
ty pronounce ſuch ſubſtance an alkali. There are
three kinds of olkalis, the vegetable, mineral and
volatile alkali. The properties juſt mentioned
belong alike to the vegetable and mineral alkali,
for we have found that theſe two ſubſtances un-
combined cannot be diftinguiſhed from each other
by our ſenſes: if the ſubſtance to be examined,
added to theſe properties that we have deſcribed,
has a ſtrong pungent ſmell, we may look upon it to
be the volatile alkali. The vegetable and mineral
alkali can only be diſtinguiſhed from each other
by the combinations they form with acids; thus
if we combine vegetable alkali and vitriolic acid
together, and uſe the means laid down in our
Eſſay on Chryſtallization to obtain the chryſtals
of neutral ſalt, we obtain very minute chryſtals,
difficultly ſoluble in cold water, and ſuch as are
unalterable in the air; but the ſame acid united
to the mineral alkali, yields a neutral falt, whoſe
chryſtals are very large, very ſoluble even in cold wa-
ter, and very ALTERABLE IN THE AIR,
ſequence of loſing the water it contained. Now
although to our unaffifted ſenſes the two fixed
alkalis appear exactly alike, yet as by combina-
tion they produce different effects, we muſt look
upon them to be different ſubſtances. Theſe are
all the alkalis that have yet been diſcovered ; we
have never ſeen a fixed alkali that did not form
in con-

ECONOMICAL
72
ES SAY S.
with the vitriolic acid a falt, that reſembled in
all its properties the vitriolated tartar, or Glau-
ber's falt, nor any kind of volatile that formed
with acids neutral falts, different from thoſe
which are formed by the fame acids and the
common volatile alkali. But ſometimes two alka-
lis may be mechanically combined with each other,
how therefore ſhall we diſtinguiſh them? If one
is a fixed alkali, and the other the volatile alkali,
the ſtrong pungent ſmell will be a fufficient teſt of
the laſt mentioned alkali, moreover heat applied
to the mixture, if ſtrong, will diffipate the vo-
latile alkali, whilſt the fixed alkali will remain.
If we ſuſpect that the two fixed alkalis are united
in one mixture, we add as much of the acid of
vitriol as will be juſt fufficient to prevent the
alkali from being able to change blue vegetable
colours green, yet not ſo much that the acid will
turn them red, which is called the ſaturated point
of acids and alkalis; we then diffolve the ſaline
maſs formed by this union in as much hot water
as it may require, and but very little more if any,
then, by cooling, chryſtals of one of the ſalts only
will be obtained, which will generally be vitri-
olated tartar, if the vegetable alkali exiſted in any
conſiderable proportion in the alkaline mixture,
we muſt then evaporate the fluid that remains
after the firſt chryſtallization to about half its
bulk, and ſet it to cool as before, we then obtain
other chryſtals of a different fort, moſt commonly
of Glauber's falt, and thus by being able to diſtin-
guiſh tartar of vitriol from Glauber's falt, we ſhall
be able to know whether our alkali to be exa-
mined is pure, or mixed with another, and by
colletting the different chryftals ſeparately, and
weighing them, we ſhall be able to form a to-

72
CHEMICAL AND
lerably good idea of the quantity and proportion
of each.
Although we mentioned four abſorbent earths,
yet not having opportunity fufficient to analize the
fourth particularly, we have noticed but three of
them. As yet we have not been able to find any
other beſides thoſe four that do not poſſeſs all the
ſenſible and chemical properties of ſome one or
other of them. LIME we find differs from MAG-
NESIA in being more foluble in water, * and form-
ing with the vitriolic acid an inſoluble falt. PURE
CLAY differs from both by poſſeſſing a kind of
duetility, and forming an aſtringent falt with acid
of vitriol, whilſt magneſia forms a bitter falt with
the ſame acid. HEAVY EARTH, whenever
found, may be known by its being able to take
away the vitriolic acid from all bodies, in which
it exiſts, even from tartar of vitriol and Glau-
ber's ſalt, which laſt property, in particular, is
not to be found in either of the other earths.
The acids that moſt deſerve attention are but
four, and we ſhall neither attempt to prove on
one hand with ſome celebrated profeffors, “ that
all acids are modifications of one acid,” or on the
other hand, with the French chemiſts, that all
the acids, that have been diſcovered, are eſſen-
tially different from each other; for we believe
with the ſupporters of the firſt propoſition, that
many
diſtinct acids have been reckoned, that are
evidently compound, and with the others we
would ſay, that as long as we are unable to pro-
* Magneſia is ſometimes adulterated with lime: to prove whether it is
pure or no, we diſſolve it in marine acid, which will take up both, and then
pour into it a few drops of the vitriolic acid, which will inſtantly make it
muddy if there is any line in it, but will not ſenſibly alter it if there is none.

ECONOMICAL
73
ESSAYS.
duce all theſe acids, by certain modifications of one,
they are to be accounted different fubftances.
All acids poſſeſs ſome properties common to
them, their taſte is four, whence their name,
they change certain blue colours to a red, and re-
ſtore ſuch colours as were altered by alkalies and
baſes, they unite with baſes, depriving them of
all their ſenſible properties, and forming with them
neutral falts.
The acid of vitriol, we can readily diftinguiſh
by its taſte, when mixed with a large quantity of
water; by its great fpecific gravity, when very
pure, and in that ſtate by being almoſt without
any imell; but better by the falt it forms with
the fixed foflil alkali.
The acid of nitre, when pure, we know by its
pungent ſmell, and the red vapours it emits when
a few filings of iron are dropt into ſome of it in
a veffel, but more certainly by combining it with
a fixed alkali, drying it and throwing it on burn--
ing charcoal, when it preſents us with all the
phenomena that are obſerved in burning char-
coal and nitre together; when adulterated, its ana-
lyſis would be ſomewhat difficult to underſtand.
The marine acid we can readily know by its
fuffocating ſmell, and by its white fumes, it can
only be miſtaken for nitrous acid, which it re-
fembles in its fenfible properties; but if we com-
bine marine acid with the vegetable alkali, and
throw the dried maſs on burning coals, we do
not obſerve any increaſed combuſtion in the
coals, as we did in the laſt experiment.
The aerial acid is eaſy to be diſtinguiſhed, as
L

74
CHEMICAL AND
There are no ſubſtances for which it can be mil
taken ; its agitating the air, deſtroying animal
life, extinguiſhing flame, and above all the mud-
dineſs that it cauſes in lime-water, are ſufficiently
characteriſtic.
Compound falts are fuch ſubſtances as confift
of two or more proximate principles, but we are
only to examine here ſuch compound falts as con-
fiſt of two principles, thoſe which contain three
(inſtances of which are very rare) are called
triple ſalts. Compound ſalts are divided in two
different ways. They are confidered,
1. As neutral falts, in which the mixture of the
baſe and acid is in ſuch proportion that the one
cannot change blue colours green, nor the acid
change them to a red.
II. As alkalino neutral falts, in which the ſalt
conſiſts of two principles, but from fome unae-
countable cauſe, always tends to ſuffer the baſe
to exiſt in a larger proportion; ſuch falts are
known by their changing fome blue colours to a
green.
III. As acido-neutral falts, in which an acid
predominates; theſe, like pure acids, turn vege-
table blue colours red.
On the other hand, compound ſalts are conſi-
dered as they conſiſt of an acid and a fixed alkali,
an acid and an abſorbent earth, and an acid and
the volatile alkali. The firſt claſs are called per-
feet neutral ſalts; the ſecond are called earthy ſalts;
and the third are the ammoniacal falts.
We muſt no doubt be juſtly furpriſed when we

ECONOMICAL
75
ESSA Y S.
obſerve that an acid, united to an alkali or any
other baſe, not only loſt all its ſenſible properties,
but deprived the baſe (to which it unites) of all
its power. We attempted to lay down the opi-
nions of ſome writers upon the ſubject more as
a matter of curioſity than uſe, but we ſtill left it in
obfcurity, and it remains to be to this day a che-
mical miracle, and only explicable by referring
to one of the laws of matter; this law we called
the law of attraction, and in the explanation of it,
we juſt hinted at the ſeveral phenomena which
take place in mechanical philoſophy, which are
referred to the laws of attraction, and we alſo
attempted to ſhew that they all differed very ef-
ſentially from chemical attraction, and I think all
arguments and experiments tended to
confirm what might be called a ſhort defini-
tion of chemical attraction, viz. " That an al-
teration of ſenſible properties always takes place in
thoſe bodies which are ſubjected to chemical at-
traction.
our
In the courſe of our eſſay on the attractions,
we found that although one body would have an
attraction for a ſecond body, yet a third would
have an attraction ſo far greater for the firſt
body, as abſolutely to unite with it, deprive the
ſecond body of it, and thus leave it uncombined;
we inſtanced this in a very familiar experiment :
we found that magneſia had an attraction for the
acid of nitre, that in conſequence of that attrac-
tion, they united with an alteration in their fen-
ſible properties, the acid was no longer four, nor
the magneſia inſoluble in water, but then we
found that vegetable alkali alſo had an attraction
for acid of nitre, which proved to be greater
than that which the magnefia had, for upon pour-

28
AND
CHEMICAL
ing a ſolution of vegetable alkali into a ſolution
of the compound, conſiſting of the acid of nitre
and magnelia, the acid unites with the alkali, and
the magneſia is left uncombined, being inſoluble,
it only remained mechanically diffuſed through
it, and after a certain length of time it ſettled to
the bottom, and then poſſeſſed all the ſenſible pro-
perties that it had at firſt. This experiment we
repeat, as an inſtance of ſingle elective attra&ion.
We divided neutral falts into four general
claffes, merely from the acids they contained :
thus we called fix falts, vitriolic falts, becauſe
they were formed of the fix baſes united to the
vitriolic acid: The nitrous falts are ſuch as con-
tain nitrous acid; the marine falts have the acid
of fea falt united to them; and the aerated con-
tain, for their acid, that peculiar acid called for-
merly “ fixed air.”
Before we go to analyze a neutral ſalt we muſt
be certain that it is pure and combined with
none other. This muſt be done by uſing for that
purpoſe the moſt regular chryſtals of that falt,
and when this precaution has been attended to,
the analyſis of ſalts will not be difficult.
When we have reaſon to fufpect that any fa-
line body, that we would wiſh to examine, is
made up of more than one neutral falt, we muſt
have recourſe to repeated chryftallization, which
inuſt be conducted differently according to the
properties of the ſalts; for inſtance, nitre is often
mixed with ſea ſalt, we conſider firſt one property
of nitre, which is that it is ten times more fo-
luble in hot water than in cold, whilft fea falt is
equally foluble in both: having made therefore
22

ECONOMIC AL ESSAYS.
an hot ſaturated ſolution of theſe two falts, we fuf-
fer the liquor to cool, we then obtain only chryl-
tals of nitre, without any fea-falt; becauſe it re-
quires no more cold water than it does of hot to
diſſolve it, and as it had enough of hot water for
this folution, that quantity when grown cold will
fuffice to keep it diſſolved: but fuppoſe we heat
the liquor which remains, and which we know
muſt contain an exact cold faturated folution of
nitre in water, and which we would ſuppoſe con-
tained an exact cold ſaturated folution of ſea ſalt,
we apply beat to the fluid and evaporate ſome water
gently, now we know that we may evaporate nine
tenths of the water, before we obtain an hot ſa-
turated ſolution of the nitre that is left, but
we can ſcarcely evaporate any before we get an
hot faturated folution of the ſea falt; and every
particle of water, which after that period is eva-
porated, muſt deprive the ſea ſalt of ſome water
abſolutely neceſſary to hold it diſſolved, and as the
evaporation proceeds, the ſalt, the water couid
not keep, chryftallizes in ſmall cubic chryſtals
which fall to the bottom; after continuing the
evaporation until no more cubic chryſtals appear,
we fuppoſe that we have again a hot ſaturated
ſolution of nitre, and then, by ſuffering the liquor
to cool, we obtain more chryſtals of nitre, theſe
different means of chryſtallization are to be uſed,
until almoſt all the water is evaporated. If two
falts are mixed togther, which are both more
foluble in hot water than in cold, yet by making
an hot faturated faline ſolution of them, the one
which is leaft foluble will chryſtallize firſt; nay,
even if they both chryſtallize in one cooling, yet
they form into very different ſhaped chryſtals,
which may be diſtinguiſhed by the eye, and con-

78
CHEMICAL AND
fequently ſeparated from each other, as no iwa
different neutral falts can ever be made to unite
in one chryftal.
Having therefore obtained the ſalt to be exa-
mined in a chryftalline form, we proceed to the
analyſis, and ſuppoſe it to be one of the twenty-
four we are now ſpeaking of.
The pare vitriolic falts may be eaſily known,
by yielding no ſmell, when the vitriolic acid is
poured upon them, and more particularly by the
following teſt. If we heat ſome of the ſalt in
powder, with ſome powdered charcoal, or almoſt
any other combuſtible body, in a crucible, then
pour the mixture into cold water, a ſmell reſem-
bling ſulphur, or the waſhing of a gun, will be per-
ceived, if the falt examined was a vitriolic falt;
but then after knowing the acid, we would wiſh to
know the baſe to which it is united, and in or-
der to know that, we muſt pay a very particular
attention to the following circumſtances, its ſolu-
bility in water, its taſte, the form and ſize of its chry-
stals, and bow a ſolution of vegetable alkali affects
it. If we know it is a vitriolic falt, very infoluble
in water, and reſembles an earth, its baſe is cer-
tainly lime, and the falt is ſelenite as we know of
no other baſe in this country, that forms an info-
luble falt with vitriolic acid. If a vitriolic falt is
ſoluble in water, we endeavour to know if it re-
quires, four or five times its weight, or fifty or
fixty times that quantity of cold water, if it is the
laft, we may with ſafety pronounce it vitriolated
tartar, and if we obtain it in chryftals, their ſhape
being like the buoys of a ſhip, together with their
tafte, will help to direct us. If to a ſolution of

ECONOMICAL ESSAYS.
79
a vitriolic falt, we add a folution of vegetable
alk li, and do not perceive either any ſtrong
ſmell, reſembling volatile alkali, nor a muddineſs
in the liquor, we preſume that its baſe is a fixed
alkali; having known this, we ſet a hot faturated
folation of the ſalt to chryſtallize, if we obtain
very ſmall chryſtals, of a ſhape that we have juſt
mentioned (like the buoy of a ſhip) and which
are not altered if left three or four days in the
open air, that are moreover very infoluble in
cold water, we can ſay that its baſe is vegetable
alkali, and its acid the vitriolic, and the ſalt for-
med thereby is called vitriolated tertar; but if
the chryſtals are thin and long, very ſoluble in wa-
ter, and which fall into a white powder when ex-
poſed a few days to the air, we can ſcarce have
any doubt that its baſe is the fofil alkali, and the
neutral falt is Glauber's falt. But although the
falt ſhould chryftallize in theſe kind of chryſtals,
and poſſeſs the ſame degree of folubility in wa-
ter, together with the ſame taſte, yet if it yields
a muddy mixture with a clear folution of vegeta-
ble alkali, the ſalt is not Glauber's falt, for its
baſe is magneſia, which forms with vitriolic acid,
an Epſom ſalt. But there are two vitriolic falts
that are very foluble in water, and which both
yield a muddy mixture with a ſolution of vegeta-
ble alkali, if the chryſtals are in lumps of an aſtrin-
gent, not a bitter taſte, they are allum, and not Ep-
Som falt; if a vitriolic falt yields a ſtrong pungent
ſmell when rubbed between the fingers with a
little pot-aih, its baſe is certainly volatile alkali,
and then it is called vitriolic ammoniac.
Nitrous falts in general are eaſily kown, for a-
ny of them thrown on burning coals, exhibit a

80
CHEMICAL AND
peculiar phenominon, i.e. that of increaſing their
combuſtion, and they yield the peculiar ſmell of
nitrous acid, when mixed with vitriolic acid.
Long priſmatic cbryſtals of a nitrous falt, that do
not grow muddy, or yield any pungent ſmell,
with a ſolution of vegetable alkali, may without
the leaſt heſitation be pronounced a common ni-
tre, conſiſting of vegetable alkali and nitrous
acid; were it not for its hape it might be con-
founded with the falt conſiſting of nitrous acid
and the mineral alkali, but this will be ſufficient
to diſtinguiſh them. If we have a nitrous ſalt, very
foluble in water, which does not eaſily chryſtal-
lize, which yields a muddy mixture with vege-
table alkali, it may be one of three falts, calcari-
ous nitre, magneſian nitre, and argillaceous nitre,
though moſt probably it will be one of the two
firit, as the argillaceous nitre never exiſts in na-
ture, and ſeldom falls under our obſervation as
made by art ; if it is calcareous nitre, a few drops
of vitriolic acid will diſcover it, for by uniting
with the lime, in conſequence of a ſingle ele&tive
attračtion, it forms a ſalt inſoluble in the quantity
of water that is generally made ufe of in ſuch ex-
periments, and of conſequence it renders the li-
quor muddy by being mechanically diffuſed thro'
it; if it is magneſian nitre, no fuch phenominon
will take place; but to diſtinguiſh magnefian nitre
from argillaceous nitre, the tartar alſo is ſuffici-
ent, for the firſt is nanſeouſly bitter, the ſecond is
aftringent without any bitterneſs.
Marine falts may be eaſily diſtinguiſhed from
all the other claſſes of falts, by two fimple experi-
ments; firſt, by pouring the vitriolic acid upon
them, in which caſe they yield a peculiar ſmell of

ECONOMICAL ESSAYS.
81
the marine acid; and ſecondly, by ſtrewing them
in powder, upon burning coals, when they do not
exhibit the appearance of increaſed combuſtion,
as the nitrous falts do, with which they might,
by the careleſs obferver, ſometimes be confound-
ed. The ſalts formed by the vegetable and mi-
neral alkali and marine acid, are difficult to be
diſtinguiſhed, as we find they reſemble each o-
ther in all their ſenſible properties, they taſte a-
like, they yield the ſame ſmell when the vitriolic
acid is poured upon them, their ſhape in chry-
ſtals is alike, being both in ſome meaſure cubes,
and vegetable alkali does not alter the tranſpa-
rency of their folutions, but we have an infallible
though ſomewhat tedious criterion to diſtinguiſh
them, we take a quantity of the ſalt, add its own
weight of vitriolic acid to it, and heat them to-
gether in a crucible, the marine acid is then diſſi-
pated, and the vitriolic acid unites to its baſe,
whatever it may be ; then by diſſolving what is
left in the crucible, in as much hot water as is
requiſite for the ſolution, and again ſuffer it to
cool, we obtain vitriolated tartar, if the baſe was
vegetable alkali, and the neutral falt examined
was febrifuge Salt of Sylvius, but a Glauber's falt
will be obtained if the ſalt examined was com-
mon falt, and of conſequence its baſe is the foffil
or mineral alkali.
Calcarious marine ſalt and magneſian marine
ſalt, both render the ſolution of vegetable alkali,
muddy, when mixed with it, as alſo does argil-
laceous marine ſalt, or marine allum as it is calle
ed; but as it will never be likely to fall under
our obfervation, we ſhall not lay down any plan
M

82
CHEMICAL AND
of analyſis. Calcarious marine falt may be dif-
tinguiſhed from magneſian marine falt, by adding
the vitriolic acid to it, in which caſe a copious
precipitate is formed, whereas the tranſparency
of the ſolution of the other falt is not altered
by it.
The nitrous acid united to volatile alkali, may
be diſtinguiſhed by one phenominon peculiar to
itſelf, for when heated it burns like nitre thrown
on charcoal.
Sal Ammoniac, conſiſting of marine acid and
volatile alkali, is very eaſy to analyſe, for the
powder of it, being rubbed in the hand, with a
little vegetable alkali, inſtantly betrays the fmell
of the volatile alkali, whilſt the vitriolic acid,
united to another portion of the powder, inſtant-
ly gives us the ſmell of the marine acid. I have
no doubt that almoſt any one can account for
both phenomena, we ſhall therefore not take up
our time to explain it.
Aerated falts have a few properties quite pe-
culiar to them. Heat diſſipates their acid, and
they all undergo a peculiar change called effer-
veſcence; and when this is effected by means of
the marine acid, we need have no doubt of the
claſs to which the falt belongs. We muſt be
cautious left we commit a very material error,
in calling theſe ſubſtances neutral ſalts, which
only contain ſome of this acid, and yet of call-
ing them baſes, becauſe they are not quite fatu-
rated with it. It is eaſy to conceive that a fub-
ſtance may contain enough aerial acid, to effer-
veſce with ſtronger acids, and yet that a part un-
ſaturated with it may have many of the ſenſible

ECONOMICAL
83
ESSA Y S.
properties of a pure baſe, [See Bergman's Eſſay
on fixed air.] Aerated vegetable alkali may be
known by its chryſtals (when we can obtain it
that form) becauſe they are unalterable in the
air, and ſtill better by its yielding chryſtals of
nitre, when decompoſed by the nitrous acid,
which we know by this time how to diſtinguiſh.
The aerated mineral alkali yields larger chryſtals
than the laſt mentioned falt, and they fall to pow-
der when expoſed to the air ; the ſuppoſition of
its being this falt may be confirmed by decompo-
ſing it with vitriolic acid, when it will yield a
Glauber's falt. Aerated volatile alkali, can never
be miſtaken for any other, its ſtrong pungent
ſmell, and its power of effervefcing, even with
marine acid, fufficiently characterize it.
Aerated lime, when decompoſed with vitrio-
lic acid, yields a new ſalt nearly inſoluble in war
ter, whilſt aerated magneſia decompoſed by the
ſame agent, yields us an Epſom ſalt, which is ve-
ry foluble in water.
With a careful attention to the diſtinguiſhing
properties of the faline bodies, both ſimple and
compound, I truſt any perſon will be able to a-
nalyſe either of them when they ſhall come un-
der his notice, and we may venture to declare,
that an accurate knowledge of the faline ſubſtan-
ces, together with their attractions being obtain-
ed, two thirds of the moſt effential, moſt diffi-
cult, and moſt beautiful parts of chemiſtry are
known. It is a part of our ſubject that admits
of almoſt mathematical demonſtration, and pof-
feſſes greater certainty, and more rational theo-
ry than any other diviſion of the ſcience; the

34
CHEMICAL AND
laws which are found to govern theſe, are alſo
daily diſcovering their influence over other clafr.
es of bodies. The metallic ſubſtances have alrea-
dy ſubmitted to their power, and the time pro-
bably will arrive, when all chemiſtry will be re-
duced tothe ſcience of ſimple and elective attrac-
tion.

ECONOMICAL ESSAY S.
85
ESSAY VI.
I
Purification of AQUA FORTIs, without a ſolution of ſilver.
N many of the arts, as well as curious chemi-
cal experiments, it is abſolutely neceſſary that
this fluid be had perfectly pure, and eſpecially
freed from another acid, which is very apt to be
combined with it. Salt petre or nitre is the ſub-
ſtance in which aqua fortis (hence called nitrous
acid) exiſts, and it is remarkable that although
nitre is generated merely by the putrefaction of
animal and vegetable ſubſtances, where we could
not fufpe&t any common ſalt to have been, yet
we never can obtain the one without having the
other mixed with it in the materials. On the
ſubject of chryſtallization, we have ſhewn that,
by that proceſs, two different ſalts may be ſepa-
rated from each other, but it ſo happens that for
want of proper care, in the purification of nitre,
the greater part of that which we find in com-
merce, is ſtill impure, by being mixed with ſome
common falt: now when we add to this impure
nitre fome oil of vitriol, and diſtill it, * we ſhall
find that the ſea ſalt will give up its ſpirit of ſalt
or marine acid alſo, hence in the receiver we
ſhall have a mixture of nitrous and marine acids,
and the greater the quantity of the latter, the
more impure the former will be, and this quan-
tity will vary according to circumſtances. The
theory of making the nitrous acid is very ſimple.
Nitre is a compound of vegetable alkali, a ſub-
ſtance perfectly analogous to pot-aſh, and of an
acid of a particular kind, hence properly enough
* See the proceſs for diſtilling the nitrous acid in the Edinburgh Diſpen-
fatory

86
CHEMICAL AND
called nitrous acid; and from its power of diffolv-
ing metallic and other hard ſubſtances, it is alſo
called aqua fortis. When oil of vitriol is added
to nitre, this being alſo an acid, it has a greater
attraction to the vegetable alkali than the acid of
nitre has, and then this acid is in an uncombined
ſtate, and capable of being diſtilled off from the
mixture, but when any fea falt is mixed with the
nitre, this alſo is decompoſed, that is, the oil of
vitriol unites, by its greater attraction, to the
alkali of the ſea ſalt, and thus leaves its peculiar
acid in a ſtate capable of being mixed with the
nitrous acid after diſtillation.
Another way in which the nitrous acid may be
impure is, that the maker of it is very liable to
put more oil of vitriol into his diſtilling appara-
tus than is requiſite, and alſo to apply too much
heat in the diſtillation, hence too fome oil of vi-
triol will be mixed with the acid.
In metallurgy and the aſſaying of metals pure ni.
trous acid is indiſpenſable, and the goldſmiths uſe
conſiderable quantities of it, for ſeparating gold
and filver from each other, which depends upon
a curious chemical fact, that gold will not diffolve
in pure aqua fortis, but if it is impure, by a com-
bination with the acid of ſea ſalt, it is then called
aqua regia, and acquires a new property, it can
diffolve gold, but it loſes the power of diſſolving
ſilver; if the quantity of falt, originally contain-
ed in the ſalt petre be ſmall, it pofſeffes the pro-
perties of aqua regia in a ſmall degree only;
hence it is that the aqua fortis of the apotheca-
ries, will act both upon gold and ſilver.
It has been long ſince known that we can puri.

ECONOMICAL ESSAY S.
87
fy aqua fortis, by diffolving ſome fine ſilver in
very pure aqua fortis; we add gradually of this
ſolution to the impure aqua fortis, until no mud-
dineſs or precipitate is formed in it by the freſh
addition of the ſolution of filver. Before we go
on let us explain the theory of the operation.
When the ſolution of filver is added to the
aqua
fortis containing the ſpirit of ſalt, the ſilver
has a greater attraction to that fpirit than it had
to the acid which firſt diffolved it, but the new
compound of filver and and ſpirits of falt is not
ſoluble in a thouſand times its weight of any
flu-
id; hence both of them will be thrown down to
the bottom of the veſſel; collecting this ſediment
we may by a certain proceſs, obtain the ſilver a-
gain; the clear fluid that ſwims above it, is
nearly a pure aqua
fortis.
Three objections may be made to this manner
of purifying it.
1. The aqua fortis is not always abſolutely
pure, for we are very liable to err, either in ad-
ding more of the ſolution of ſilver than is necef
fary (which remaining in the aqua fortis renders
it impure) or in not adding enough, in which
caſe we do not effectually ſeparate from it the
impurities imparted to it by the ſea falt.
2. A part of the filver is always loft, which be-
ing a very dear and valuable metal, muſt render
the proceſs expenſive.
3. There is great trouble and difficulty, in
getting the ſilver again, after it has done its
work, hence it would be a very inconvenient pro-
ceſs to perfons unacquainted with metallurgy.

88
CHEMICAL AND
The following method will yield us an aqua
fortis perfe&tly pure, that may be depended up-
on in all chemical experiments, and other ope-
rations requiring accuracy.
Diffolve one ounce of lead in as much of your
aqua fortis as is neceſſary to deprive it of its me-
tallic appearance, by boiling it gently in an oil
flaſk, or other thin glafs veſſel; the quantity of
aqua fortis requiſite for this purpoſe, if good and
ſtrong, will be about two or three ounces; a
white fediment will appear in this ſolution, if the
aqua fortis is impure, and the quantity will in
fonie meaſure indicate the degree of impurity.
When the lead is perfe&ly diſſolved, pour the fo-
lution into a ſmall long necked retort, and then
add to it a pound or a pint of the aqua fortis you
would wiſh to purify; ſet the retort on a fand
heat, and diſtill off the fluid, till nothing but the
white maſs remains dry in the retort.
This proceſs occurred to me from theoretical
obſervation, and I have proved the idea to be
well founded, by experiment; for the aqua fortis
collected in the receiver, is fo pure, that with a
ſolution of filver, it cauſes no muddineſs. It dif
folves filver completely, without having the leaſt
operation upon gold. From theory we know
that (pirit of ſalt and oil of vitriol, have both a
greater attraction to lead than pure aqua fortis
has, therefore when a ſolution of that metal is
added to impure aqua fortis, theſe ſubſtances com-
bine with the lead, and being inſoluble, they fall
to the bottom of the veſſel. But to obviate our
firft objection on the one hand, we diſtill it, hence
none of the metallic folution is mixed with it, as

ECONOMICAL ESSA Y S.
89
it cannot riſe with it in diſtillation, on the other
hand we always find that one ounce of lead is
quite enough, and when it ſhould prove too much
we have directed how to remedy it.
N

go
CHEMICAL AND
ESSA Y
VII.
On the uſe of the Pig-Nut, as a vegetable aft, ingent,-
Ideas on the uſes of ALLUM in dying.
TI
HE pig-nut is a very powerful vegetable
aſtringent; this principle of aſtringency ap-
pears to be homogeneous in all vegetable aſtrin-
gents.
The peculiar diſtinguiſhing property of vegem
table aſtringents is, that beſides corrugating the
tongue, making it rough, or drawing up the
mouth, as the common phraſe is, they make a
black colour, when added to ſome ſolutions of
iron.
In the eſſay on Pruſſian blue, we treat of that
ſubſtance as being a compound of a peculiar
acid and iron, in like manner (after ſome other
author) we conſider the black matter formed by
a folution of iron and the vegetable aſtringents
to be compoſed of an acid ſui generis and iron:
We ſhall ſhortly have occaſion to enforce the
reſemblance more ſtrongly.
The pig-nut, as containing a great deal of oil
in the kernel, would appear to be rather uſeleſs
for moſt of the purpoſes of aſtringents, other-
wiſe it is a long time ſince I thought that they could
be very advantageouſly ſubſtituted for an expen-
five article in manufactures, I mean the galls:
I do not know whether the true galls have ever
been diſcovered in America ; but this I think
I can make appear very probable from facts and
experiments, that the pig-nut will anſwer all the
properties of them in
inſtance.
I conſider it, as a fact that many experiments
every

ECONOMICAL ESSAYS.
91
tend to confirm, and none to diſprove, that the
principle of vegetable aftringency is the ſame in
all vegetables, and like ſea ſalt, Pruſſian blue,
or any other bodies whoſe compoſition is per-
fectly known, which are always the ſame chemi-
cal ſubſtances, from whatever ſource derived;
and although I cannot find that the aſtringent
matter of the pig-nuts can be obtained from
them, in the preciſe mechanical manner that it
can from other aſtringents, yet I think they are
applicable to all the purpoſes of them. When
vegetable aftringents are uſed for dying, it is
the common practice to boil them to extract their
aſtringency; but this is an erroneous practice,
unleſs I am much miſtaken, for I have found
that a decoction of galis, made by boiling them
in water for ſome time, in a great meaſure lofes
the power of making a black colour with folu-
tions of iron.
To extract the aſtringent matter from the Pig-
nut, I think requires fome caution; if hot water
merely is added to them, without boiling them,
and the veſſel immediately ſtopped, the aſtring-
ency may be ſaved, but a quantity of the oil of
the nut is evolved, which is injurious, in many
caſes, where a pure aſtringent tincture is wanted.
I then thought that poſſibly the aſtringency re,
fided in the nut-ſhells, without reflecting that I
was firſt led to form an idea of their aſtringency
from taſting the kernel; theſe I found confider-
ably aſtringent, but much leſs ſo than the ker-
nels.
After many unſucceſsful trials to render theſe
puts uſeful, by extracting this principle from

92
CHEMICAL AND
them, I fell upon the following method, which
I could not improve further.
I put a pint, even meaſure, of the nuts, well
bruiſed, but not reduced to a very powdery
ftate, into a bottle holding exactly a quart, the
remainder of the bottle (which will ſtill hold
nearly a pint and a gill, as there are conſiderable
vacancies between the nuts) I fill up with wa-
ter; after ſtanding in a warm room for two or
three days, I pour off all the clear fluid, and if
muddy, ſtrain it through flannel; it is very re-
markable that the kernels of the nuts, which
were ſo diſagreeable before, are, if dried after
this proceſs, as mild and pure in their taſte, as the
fpecies of hiccory-nut, called among us the
Shell-bark, which affords us a tolerably good
proof that the whole of the aſtringent matter has
been extracted from them, and that cold water
is a proper menftruum for it. I can give no
clearer idea of the ſtrength, or quantity of aftring-
ent matter, of this cold infuſion, than by remark-
ing that it is now ſtrong enough, with a certain
quantity of copperas and gum-arabic, or any other
gum, to make a very good ink. I have paid a
particular attention to the word gum-arabic, be-
cauſe, without ſome gum, we cannot make ink;
and here the analogy of Pruſſian blue will ſerve
tis in excellent purpoſe, and to a chemift at leaſt
it will make the phenomena which appear in add-
ing vegetable aſtringent tin&tures to folutions of
iron rather more intelligible. When a tincture
of galls, or pig-nuts, is addded to folutions of
iron, the whole inſtantly becomes black, juſt as
when we add the phlogiſticated alkali to a folu-
tion of copperas, the whole becomes blue; in
both caſes the coloured ſubſtances formed by

ECONOMICAL
93
ESSAY S.
theſe mixtures fubfide to the bottom of the ver-
fel in which the experiment is made, leaving a
tranſparent fluid ſwimming above it, which will
be colourleſs as water, if the materials were
pure : How do we account for theſe appear-
ances ? We fuppofe that the aſtringent acid in
the one caſe, and the Pruffian acid in the other,
in conſequence of a double elective attraction,
becomie united to the iron contained in the cop-
peras; but theſe new compounds are inſoluble
in water, therefore, for a while, they become
mechanically diffuſed through the water, and at
laſt by gravity ſubſide, as the magneſia mentions
ed in a former eſſay.
The blackneſs of ink then depends upon an in-
ſoluble matter diffuſed mechanically through wa-
ter, or ſome other fimilar fluid; and the uſe of
the gum is not merely to give the writing a gloſs,
as many ſuppoſe, although it may anſwer that pur-
poſe alſo, but by its vifcidity and tenacity it may
prevent the colouring matter from fubfiding;
upon the fame principles I have thought of
making a blue ink, which I have done very ef-
fectually, by adding to a ſolution of the Pruffian
alkali fome gum-arabic, and then diffolving a
ſmall lump of copperas in it, which form a very
beautiful blue ink inſtantly. Which looks full
as well as the beſt black ink.
Having, as before obſerved, diſſolved ſome
gum-arabic in my cold infuſion of pig-nut, and
added ſome copperas, I had the ſatisfaction of
obtaining a very good ink.
Since I have had occaſion to ſpeak a little up-
on ink, it may not be amiſs to fay a few words

94
CHEMICAL AND
upon the cauſes of the changes which ſome ink is
apt to undergo, from time and air: In the firſt
place, I obſerve, that from theory it appears moſt
probable, that if the quantity of aſtringent mat-
ter (from whatever vegetable ſubſtance obtain-
ed) of gum-arabic and copperas were the ſame
in different parcels of ink, under ſimilar circum-
ſtances, they would be all alterable, or none;
and I have great reaſon to ſuppoſe that the yel-
lowneſs which writing is apt to acquire by age is
owing to an exceſs of copperas in the ink; this I
conſider probable, from the following circum-
ſtance; if a clear ſolution of copperas be expoſed
to the open air but for a day or two, it becomes
yellow, or it depoſits a ſediment, and has a thin
ſcum, reſembling very much, in every reſpect,
the ruſt of iron. Chemiſtry affords us an excel.
lent theory to explain this fact, and we ſhall af-
ſume it as an explanation of the cauſe of change
in ink.
To make the moſt durable ink, therefore, we
muſt ſtudy to find out the exact quantity of cop-
peras neceſſary to make it ſo that none ſhall re-
main which has not been acted upon by the
aftringent matter: This is, in many caſes, dif-
ficult, and, without ſome knowledge of che-
miſtry, impoſſible. I therefore think that I have
fallen upon a method of making an ink, that
ſhall be as unalterable as it is poſſible to make it
by any aftringent vegetable whatever; I diffolve
a quarter of an ounce of copperas in eight ounces
of hot water, and add it to about four ounces of
the cold infuſion of pig-nut (or the galls would
anſwer in the ſame manner) but without having
any gum diſſolved in it at firſt; the black infolu-
ble matter ſwims about like curds, for a while,

ECONOMICAL ESSA Y S. 98
and at length fubfides; after ſtanding two or
three hours, I find a quantity of colourleſs water
above the black matter; this I pour gently off,
and throw away, but without letting any of the
ſediment paſs off with it; I then pour into it
eight ounces more hot water, and having let it
ſtand, I draw it off as before ; and this waſhing
of the ſediment I repeat three or four times, and
in the laſt waſhing I contrive to pour off ſo much
of the clear liquor, that only four ounces remains
in my bottle, ſediment and all; and then adding
about an eighth of an ounce of gum-arabic to it,
my ink is made, which from theory I ſay might
be ſuppoſed to be unalterable ; I only ſuppoſe fo
from theory, for it will require a trial of forty
or fifty years, at leaſt, to prove its goodneſs:
but it appears probable to me, becauſe all the
copperas, which I am ſure all common ink con-
tains unaltered, is in this ink entirely waſhed out
by the repeated affufions of freſh water.
From what we have already ſaid of the uſe of
the pig-nut in making ink, and of vegetable
aſtringents in general, we might conclude that
this ſubſtance would be valuable in dying: I
confefs that as in dying there are ſo many things
ſeemingly eſſential, which I cannot comprehend,
I muſt therefore touch on this ſubject with un-
common diffidence.
The theory of the operation of allum, fo ge-
nerally uſed in every ſpecies of dying, as well as
in dying black colours, appears to me to be in-
volved in difficulties. I can adopt the common
expreſſion, that it ſets the colours; but that is to
ſay nothing, and can therefore never ſatisfy me,
neither ought it to ſatisfy any rational enquirer

96
CHEMICAL AND
after truth; and although I have induſtriouſly in-
yeſtigated the ſubject for three or four years, or
at leaſt had my attention awakened all that time
to any theory or fact that could fall under
my
notice, wbich might be likely to explain it, ftill
I am far from being certain that I have arrived
at the truth at laſt.
There are but two modes in which I can con-
ceive allum can operate: ift, it may act as an
aftringent by condenſing or hardening the fub-
ſtances to be dyed, as oak-bark conſtringes or
hardens the hide, and thus may envelope the co-
louring matter; 2d, it may operate as an acid in
– Some caſes, becauſe allum, though called a neu-
tral falt, ſtill retains a good deal of unſaturated
acid; by its firſt effect, I cannot conceive how it
can be neceſſary in black dyes, becauſe in all theſe
a vegetable aſtringent is uſed, which would ef-
fectually ſupply its place; and, as an acid, it
cannot be uſeful in theſe dyes; for when I men-
tioned, in the beginning of this eſſay, that vege-
table aftringents make a black colour, with ſome
ſolutions of iron, I reſerved it for this place to
mention, that if ſolutions of iron contain but a
little more acid than is fufficient to diffolve the
iron, and to hold it diffolved in the water, a
black colour will not be produced by theſe ſub-
ftances; hence, as far as the ſmall quantity of
acid in allum, as ſuch, can operate at all, its
operation muſt be bad in black dyes. Whether
allam is ever uſeful in dying by its aſtringency,
may be doubted, but if found fo, in its ſtead
may be fubftituted the cheap infufion of the pig-
nut; and when Mr. Fourcroy informs us, that
"it augments the intenſity and brilliancy of co-
lours," I ſuſpect that it only operates by its re-

ECONOMICAL ESSAY S.
97
dundant acidity, and only to advantage upon thoſe
dyes which are changeable by acids, upon the
fame irinciple as the juices of purple fruits, have
their brilliancy and intenſity augmented to a bright
red, by the addition of an acid, or even of allum.
To ſpeak candidly, it is my opinion, and this
opinion is corroborated, though not confirmed,
by a few experiments I have made, that allum is
uſed injudiciouſly, if indiſcriminately in all dyes;
that it is never uſeful but where it produces an
obvious change in the colour of the dye, and
that wherever that change is produced, an acid
might be very juftly ſubſtituted for it. I know
on one hand, what a tyrant cuſtom is, and on
the other, how eaſy it is to be deceived; I there-
fore propoſe it, with much diffidence, as a query,
whether vitriolic acid might not be ſubſtituted
for allum in dying? If ſuch a ſubſtitute would
do, I think I could prove that one pound of oil
of vitriol would anſwer all the purpoſes of fix
pounds of allum. The reader will pleaſe to ob-
ſerve, on this fubje&t, that I pretend to have
advanced nothing but hypotheſis.
I thought I ſhould have been able to have given
the reſult of ſome experiments, intended to be
inſtituted by a very ingenious friend of mine, to
aſcertain the uſes of this nut in tanning, but
fome unavoidable accidents prevented them: I
have no doubt, however, that they would anſwer
very well, and perhaps a much ſmaller quantity
of them would have the ſame effect as a larger
quantity of the oak-bark. I confeſs I am in-
clined to think that to propoſe any ſubſtitutes
for the oak-bark, in a country like this, where

98
CHEMICAL AND
it can be had ſo plentifully, is an unneceſſary
refinement. But it may not be ſo chimerical to
uſe the pig-nut as a ſubſtitute for the galls, as the
latter have once been ſo very difficult to obtain,
and the ſame difficulty may again occur. The
method of obtaining this aftringent matter, is to
make a cold infuſion of the nuts, firſt thoroughly
bruiſed.
I know of many objections that criticiſm may
oppoſe to this ſubſtitute; it is true that the pig-
nut does not contain as much aftringent matter
in as ſmall a bulk as the galls, but, this ought to
have no weight, when we conſider that theſe
nuts can be procured for very little more ex-
pence, than colleEling them. Prejudice may per-
haps declare, that the colour is not as good; to
ſuch perſons as are under its influence, I can
make no other reply, than that time and experi-
ence alone can aſcertain its real merit.
When we conſider, what a great quantity of
galls are annually imported into the United
States, and alſo what a variety of other mat-
ters for black dye are imported, we ſhall have
cauſe to lament that thouſands of buſhels of this
uſeful ſubſtitute have annually periſhed in our
woods, whilſt we have been purchaſing, in a fo-
reign country, what could be amply ſupplied in
our own; and if a pound of galls coſts a ſhilling
ſterli g, how much money might be ſaved to our
country, even if ten pounds of the pig-nut could
ſupply their place.
Before we conclude our obſervations on the
pig-nut, it may be acceptable to our readers to
give them a ſhort botanical account of the tree

ECONOMICAL
99
ESSA Y S.
which furniſhes it: for this information we are
indebted to the ARBUSTUM AMERICANUM,
compiled by our countryman, Humphrey Mar-
fhal, page 68 of the firſt American edition; he
places it in the 21ſt claſs, 8th order of the Lin-
nean Method, Genus, Juglans, and fifth ſpecies;
he thus defcribes it:
“ Species 5. Juglans alba minima. White
or pig-nut hickory.
This generally grows pretty large, ſometimes
to the height of eighty feet or more, and above
two feet in diameter. The bark of the tree,
when
young,
is ſmooth; but as the tree grows
older it becomes rough and furrowed. The
leaves are generally compoſed of five pair of
lobes and an odd one. The fruit is ſmall, * and
roundiſh, and covered with a very thin huſk, or
covering, opening in diviſions. The ſhell of the
nut is alſo very thin, and eaſily cracked with the
teeth; the kernel plump and full, but very bit-
ter.f The timber of this is not much eſteemed.
* I have ſeen it as large as any of the ſpecies of hiccory nuts.
# The ingenious author, like many others, miſtakes the taſte of theſe
auts; they are aſtringent, but not bitter; Aſtringents corrugate the tonguez
and ſtrike a black colour with copperas, but pure bitters do not.

100
CHEMICAL AND
ESSAY VIII.
Calcination of METALS A defence of the do&trine of Phlo-
GISTON, with certain modifications.
T has been long ſince known to chemiſts, that
I when metals (in general) are expoſed to a
certain degree of heat, in contact with air fit for
animal reſpiration, they loſe their metallic bril-
liancy, and are converted into an earth-like ſub-
ſtance: Thus if lead, a very fuſible metal, and
one that poſſeſſes this property in a very eminent
degree, is expoſed to a red heat in a ſhallow
veſſel, it firſt aſſumes the appearance of a yellow
earth, next it becomes brown and ſcaly, form-
ing the litharge of the ſhops; this being expoſed
to a ſtill greater degree of heat, it is changed
into a red powder of a brick colour, and which
is very well known by the name of red-lead.
As many metals during their calcination were
obſerved to emit flame, it was ſuppoſed (and is
now univerſally ailowed) that theſe ſubſtances
were combuſtible, and that the proceſs of cal-
cination was a true combuſtion; they are after
this proceſs, however, to be arranged with the
incombuſtible bodies, as no material change is
effected in them by further addition of heat.
Sulphur, in like manner, heated in reſpirable
air, takes fire, and continues inflamed (if the
quantity of air is ſufficient) until its nature and
properties are totally changed, and it becomes
converted into an incombuſtible body; for if
the vapours of burning brimſtone are collected
and condenſed in clofe veſſels, we find them to
be the vitriolic acid, which, when pure, ſhews
no combuſtibility.

ECONOMICAL ESSAY S.
101
A rational explanation of theſe phenomena
was never attempted, until Doctor Stahl of-
fered one to the world, which, for ſimplicity,
was very intelligible, and which would admit of
almoſt univerſal application.
He conſidered every combuſtible body as con-
ſiſting of a peculiar principle, which he calls the
imflammable principle or phlogiſton united to ſome
other body, either ſimple or compound. He
ſuppoſed that the lead, in the inſtance alluded to,
was compelled by the heat to ſurrender up its
phlogiiton to the air, and conſequently that its
other conſtituent principle, viz. the calx, re-
mained fixed in the veſſel : his theory of metals
was, that each conſiſted of an earth, or calx ſui
generis and phlogiſton, which he conſidered as
common to and homogeneous in all.
In like manner he maintained that ſulphur was
compoſed of an acid perfectly ſimilar to that
which the chemiſts in his time uſed to obtain by
diſtillation of green vitriol or copperas, hence
called vitriolic acid and phlogiſton: this laſt he
alſo ſuppoſed to be the ſame ſimple elementary
principle which gives brilliancy to the metals.
This very beautiful theory was not only ſup-
ported, but even amazingly illuſtrated, by a
variety of experiments and every phenomenon it
alluded to; but although the identity of this
principle was almoſt inconteſtibly proved, he
found that it was more diſpoſed to unite and to
remain united with certain bodies than with
others.
We take a quantity of the calx of lead, which
is deprived of phlogiſton (according to this the-

102
CHEMICAL AND
ory) and mix it with a ſufficiency of charcoal,
both being in powder; theſe being expoſed to a
certain degree of heat, in a cloſe crucible, we ob-
tain the lead in its metallic brilliant form, being
now a combuſtible body, whilſt the charcoal is re-
duced to aſhes, which we know to be incom-
buſtible: in this caſe we ſay, the phlogiſton, or
inflammable principle, has paſſed from the char-
coal into the calx of lead, which, when united
together, Stahl ſuppoſed to be the conſtituent
principles of lead. If this experiment is varied
by fubftituting any kind of vegetable oil, or ani-
mal fat, or moſt ſorts of inflammable fubftances,
the reſult will be the ſame.
If we burn fulphur in contact with air, we oba
tain an acid, if the fumes are collected, which,
united with iron, forms a falt exactly the ſame as
green vitriol or copperas; again, if we unite the
acid obtained by diſtillation from copperas, with
almoſt any fixed inflammable body (except fome
metals) and heat them together in any cloſe fu-
bliming veſſel, we obtain pure genuine ſulphur,
no way
different from that obtained by any other
means.
A number of ſimilar experiments ſeemed to
render this theory unqueſtionable, and to place
the exiſtence of phlogiſton beyond all doubt;
but alas ! the ſupporters of this doctrine neg-
lected the abſolute neceſſity of air in calcination,
and a very curious fact attending it, which is,
that the calx always exceeds the weight of the
metal ſubjected to the experiment.
Mr. Lavoiſier, a very accurate experimental
chemiſt, found that metals were calcined, when

ECONOMICALESSA Y S.
103
heated in cloſe veſſels, according to the propor-
tion of reſpirable air contained in the veſſel, that
the calcination of it rendered the air leſs fit for
animal reſpiration, and, after a certain time,
the proceſs was entirely ſtationary; the air in
this caſe was found conſiderably diminiſhed, and
totally noxious to animal life: upon weighing
the calx, he obſerved it weighed heavier than
the
pure metal; upon weighing the air, he found
it had loft part of its original weight, and the de-
creaſe was exactly the ſame as the increaſe of
weight in the calx; the air that remained was
impure, hence he concluded that the pure part
was abſorbed by the calx. From ſuch experi-
ments he deduced his theory, that metals, ful-
phur, phoſphorus, and other inflammable bodies,
are ſimple ſubſtances, and that calces of metals,
vitriolic acid, acid of phoſphorus, &c. are theſe
ſubſtances combined with the pureſt air. Every
chemiſt is acquainted with the air obtained from
nitre, and ſeveral other bodies, by certain pro-
ceſſes diſcovered by Doctor Prieſtly and Mr.
Scheele, which ſupports flame and animal life
fix times as well as the air of our atmoſphere.
Mr. Lavoiſier having introduced a quantity of
mercury, in a china cup, which was expoſed to a
certain meaſure of this very pure air, preſerved
from the common air in a receiver with mercury
underneath, he calcined it by means of a burn-
ing lens; as the calcination advanced, the air
was diminiſhed in bulk, and at the end of the
experiment, all but a few bubbles diſappeared,
as was evident from the riſing of the mercury in-
to the receiver; the calx in this experiment was
exactly as much heavier, than the metal made uſe
of, as the weight of the air that was loſt. This

104
CHEMICAL AND
of
experiment eſtabliſhed his theory fynthetically,
and he only required, as it appeared, that the ana-
lyſis of a calx, correſponding with that experi-
ment, ſhould be obtained. He expoſed the calx
mercury, obtained in the laſt experiment, to
a great degree of heat, in an apparatus contrived
for the purpoie, in ſuch a nianner that if any
air eſcaped from the calx, it might not only be
obtained, but its quantity aſcertained. The re-
fult was favourable to his utmoſt wiſhes. For
the whole quantiiy of air, which diſappeared in
his firſt experiment, was obtained in the ſecond,
and the mercury came over into a recipient
adapted to the apparatus; in its natural fluid
form, weighing as much as was firſt uſed. Si-
milar experiments were made upon other metals
and other combuſtible bodies, which ſeemed
greatly to confirm the theory he adopted. This
theory had its friends and ſupporters in different
parts of Europe ; its fimplicity recommended it
much, and as it was adequate to the explanation
of every phenomenon relative to calcination and
combuſtion, without involving us in the difficul-
ties attending Stahl's theory, in conſequence of
the increaſe of weight in the calx (as it is incon-
cieveable that a metal ſhould weigh heavier by
the loſs of its phlogiſton) three confiderations, I
ſay, ſeemed to place it beyond the reach of re-
futation.
Doctor Prieſtly, however, relates an experi-
ment, which, conſidering the ſtate of knowledge
at that time, tends not a little to ſhock Mr. La-
voiſier's theory.
This philoſopher expoſed a
quantity of red lead to the intenſe heat of a burn-
ing lens in inflammable air, confined over mer-
cury; the conſequence was, that the calx gra-

ECONOMICAL ESSAY S.
IOS
dually aſſumed its metallic form, whilſt the in-
flammable air was diminiſhed, and at length to-
tally abforbed, the calx being perfectly revived:
Here then we fee that the infiammable air was
perfectly analagous to the phlogiſton of Stahl,
which, entering the calx, metallized it; and
here the experiment of Mr. Lavoiſier, firſt re-
lated, and that of Dr. Prieſtly, form a chemical
paradox; the firſt gives us to underſtand that a
calx is a compound body, as a metal abforbs a
great quantity of pure air, the ſecond would
ſeem to prove that a metal was a compound body,
as lead was obtained by uniting inflammable air
with a calx of lead, and more eſpecially as each
gentleman mentions that there was no refiduum
in either inſtance: for my part I fully believe in
the authenticity of each experiment, and ſhall at-
tempt to explain the difficulty in the courſe of
this eſſay. It will be well enough to obſerve,
that the very celebrated Dr. Black, of Edin-
burgh, attempted to account for the increment of
weight, in the calcination of metals, by ſuppofing
that phlogiſton is the principle of levity, and thus
diminiſhes the weight of bodies with which
it is united. With all deference to ſuch reſpect-
able authority, however, I muſt obſerve, that
even were this ſuppoſition admitted, it could not
account for many phenomena of combuſtion and
calcination.
I ſhould have mentioned an experiment, that
ſeems to operate as a very forcible objection to
Mr. Lavoiſier's theory, and this is the production
of inflammable air from iron filings, by the ad-
dition of the acid of vitriol. The advocates of
Stahl's theory fay, that the acid tends only to
P

106
CHEMICAL AND
unite with the calx or earth of iron, with a pro-
penſity greater than that by which the phlogiſton
tends to remain united to it, and conſequently
that it is diſengaged from the iron, and fies off
under the form of inflammable air: but the fol-
lowers of Mr. Lavoiſier have invented a different
explanation of this fact, founded upon the diſco-
very of the compoſition of water, by Mr. Caven-
diſh of London. This philoſopher found by
firing inflammable air, in contact with pure or
dephlogiſticated air, in a cloſe veſſel, in order
to examine the reſiduum, that the whole bulk
diſappeared, except a few drops of a liquor,
which upon examination he found to be pure wa-
ter: in ſhort, by repeating this experiment upon
a very large ſcale, I think he obtained five drams
of pure water, which was exactly equal in weight
to the two airs made uſe of.
The component
parts of water being allowed to conſiſt of pure
air and inflammable air conſolidated together,
we can explain Mr. Lavoiſier's ideas of the cauſes
of the production of inflammable air in a mixture
of diluted vitriolic acid and iron filings : He ſays
that the pure air of the water, which is always
preſent in the vitriolic acid, tends to unite with
the iron, reducing it at the ſame time to the ſtate
of a calx, which is foluble in moſt acids, and is
then taken up by the vitriolic, whilſt the inflam-
mable air (which from this theory is ſuppoſed to
be the other conſtituent principle of water) is
left uncombined, and of conſequence affumes its
natural elaſtic ſtate.
It muſt be obvious, to every attentive obſerver,
that this theory, now fo generally adopted by the
French chemiſts, muſt ſuppoſe that the combuf-
tibility of different inflammable bodies does not

ECONOMICAL
107
ESSAYS.
depend upon one fixed principle, homogeneous
in all of them ; thus they ſay fulphur is a ſimple
inflammable body, forming vitriolic acid with
pure air. Charcoal, ſay they, is another ſimple
body, forming with pure air the aerial acid of
Eergmann, or, as Doctor Black calls it fixed air,
and Mr. Fourcroy, the cretaceous acid. The
inflammable air is alſo ſimple, and water is the
reſult of its combination with pure air ; and, in
fine, that combuſtion conſiſts in nothing elie than
the union of the inflammable body with pure air;
and as the reſults of theſe combuſtions are very
different, ſo the inflammable bodies themſelves
mult be eſſentially different from each other.
Without taking any notice of ſome collateral
paris of this theory, we ſhall attempt to fhew the
probability of the exiſtence of a certain principle
homogeneous in all combuſtible bodies
very
analagous to the phlogiſton of Stahl ; and ſhall
then attempt to account for the increaſe of
weight in the calcination of metals, by different
arguments than thoſe of Mr. Lavoiſier.
I. We take a certain quantity of pure nitre
(whoſe acid we know is totally convertible into
the dephlogiſticated air of Dr. Prieſtly) and com-
bine it with ſuch a quantity of charcoal, as by
previous experiments we find to be juſt fufficient
to olka ize that quantity; theſe we detonate in a
cloſe veſſel; the vapours, carefully colle&ed, are
found, by repeated experiments, to be pure we-
ter.
II. Spirits of wine, ſays Mr. Fourcroy, a very
ſtrong advocate for Mr. Lavoiſier, is a peculiar
inflammable ſubſtance, united to much water:
This fluid, when ſet on fire in a large glaſs vef-
fel containing pure air, cloſed in ſuch a manner

108
CHEMICAL AND
as to prevent the loſs of any vapours, is found
to contain nothing but pure water : Mr. Lavoi-
fier, in ſome of his experiments, relates, that
the weight of ſulphur and phoſphorus, when
burned in dephlogiſticated air, encreaſed three
times their original weight, in paſſing to the ſtate
of vitriolic and phoſphoric acids; the firſt, I
well remember, he ſaid was in a fluid form;
now it appears, from ſome obſervations of Dr.
Crawford, in the laſt edition of his treatiſe on
animal heat, that a very ſmall quantity of water
can be diſolved in air; and I can inconteſtibly
prove that vitriolic acid cannot remain in a fluid
form, unleſs united with at leaſt one fourth of its
weight of water; the water in this experiment
muſt have therefore been conſiderable, it could
not have been contained in the air, nor in the
ſulphur: hence I conclude that there is ſomething
contained in fulphur which with pure air will
produce WATER.
We have ſeen that charcoal, when burned
with the air contained in nitre, produced wa-
ter; when burnt in pure air, however, it will
yield fixed air, or cretaceous acid, owing to
Come inexplicable circumſtance attending the
combuſtion: Mr. Fourcroy ſays that this acid
is totally compoſed of charcoal and pure cir; but
Dr. Prieſtly relates an experiment, wherein he
obtained a very large quantity of fixed air, by
heating iron filings and red precipitate together ;
from hence inferring, with great probability,
that pure air and phlogiſton were the conſtituent
principles of it: in fact, it appears that the com-
ponent parts of water and fixed air are the ſame,
pind only differ in the proportions they contain.
It is proper to mention, in this place, that Mr,

ECONOMICAL
109
ESSAY S.
Lavoiſier accounts for the revivification of the
cals of lead, by inflammable air, fuppofing that
this laſt uniting with the dephlogiſticated air
contained in it, forms water, which Dr. Prieſtly
did not take notice of. Whilſt we are on this
ſubject, it may be well enough to mention a
pretty experiment, fomewhai connected with it;
it is the decompoſition of water, by means of
charcoal: A quantity of charcoal, kept red hot
in a copper tube, is expoſed to the vapour of
water, the pure cir of the water unites with the
charcoal whilſt its infiammable air eſcapes, and
may
be collected with a proper apparatus.
We come now to our theory, aſſuming it as
granted, that in every inflammable body there is
a ſubſtance analagous to the phlogiſton of Stahl;
and I have ſome reaſon to believe, from ſome
experiments I myſelf have made upon the ſubject,
that when united to a very ſmall quantity of de-
phlogiſticated air, it forms the phlogiſticated air
of Dr. Prieſtly; with a larger quantity, I think
water would be produced ; with a ſtill larger
quantity, it is probable the aerial acid would be
obtained; and if a very ſmall proportion of in-
flammable air (the elements of which I preſume
is contained in all bodies) was united with a
large quantity of dephlogiſticated air, I am almoſt
convinced that the nitrous acid would be the pro-
duct. Therefore,
Therefore, when a metal is heated in
contact with vital or reſpirable air, the inflam-
mable cir contained in the metal unites with this
air, and the compound in this inſtance is gene-
rally fixed air, though ſometimes I ſuppoſe it may
be water; this acid may have a very great ten-
dency to unite with the metallic calx, and thus
the weight may be encreaſed, and I now offer it

110
CHEMICAL AND
the pure
as anopinion, that no man ever ſaw a pure metal-
lic calx uncombined with any thing.
It will be in vain to object to this theory, that
the preſence of fixed air, in metallic calces, can-
not be demonſtrated. Analogies are numerous.
I get a piece of perfectly dry charcoal, and wet
it with water in the preſence of an hundred peo-
ple, yet I cannot prove to one of them that there
is the leaſt particle of water contained in it; if
I fubject it to diſtillation I obtain none, a large
quantity of infiammable air alone will be extri-
cated; this we have explained above. In like
manner we heat a metallic calx, but obtain no-
thing elſe than dephlogiſticated air.
This phe-
nomenon we explain in this marner:
metallic calx has an attraction for phlogiſton,
yet not ſo great as dephlogiſticated air has; this
air in calcination, therefore, unites with it, form-
ing fixed air; but the metallic calx has an attrac-
tion to the new compound, and actually unites
with it; but when a very great heat is applied to
this calx, the dephlogiſticated air having an at-
traction to elementary beat, its attraction for the
infiammable principle is diminiſhed, and when a
certain quantity is applied to it, the power by
which the pure metallic calx tends to unite with
the inflammable principle is greater than that
with which it tends to remain united to the pure
air; the pure air having now recovered its elaf-
ticity, which we suppoſe depends upon elemen-
tary heat, it is expelled by the rarifying power
of the ſenſible heat, which we know expands all
bodies : thus is the fixed air or water decompo-
fed ; the pure air flies off combined with heat,
and the intammable principle or phlogiſion, re-
maining with the pure metallic calx, reduces it

ECONOMICAL
111
ESSAY S.
to the ſtate of a metal again. I ſpeak of water
as being pollibly combined with the metallic calx,
and it may appear ſtrange that it cannot be dri-
ven off by the heat as water ; I can illuſtrate the
poſſibility, nay the probability of it, by an ana-
logy: I take a piece of well burnt lime, weigh-
ing exactly an ounce, I dip it into water of which
it abſorbs a conſiderable proportion, I expoſe it
to an heat of more than four hundred degrees of
Fahrenheit's thermometer, which is two hundred
degrees more than fufficient to make water boil
when uncombined, yet it ſhall even then weigh
conſiderably more than an ounce, a proof that
water remains ftill united to it: it is true a
greater heat might have reduced it to its original
weight; but, were lime capable of uniting with
the inflammable principle, I think it highly pro-
bable that the water would have ſuffered a de
compoſition, in this experiment.
This is the ſubſtance of the theory I at preſent
adopt for myſelf, and I know not how far it is
true, or whether it is ſo far original as to be al-
lowed of as a theory, it is however inſerted in
theſe eſſays for thoſe who are fond of theoreti-
cal and ſpeculative chemiſtry.

12
CH E MICAL AND
ESSAY IX.
I
An analyſis of the ORES OF METALS by ſolution.
Y HAVE often regretted that many very re-
fpectable people have been much deceived,
for want of a proper knowledge of ores; when
a perſon unacquainted with firit principles, of me-
tals, &c. finds a ſubſtance, which a warm ima-
gination inclines him to believe is an ore of gold,
filver, copper, or ſome other valuable metal, it
is with the greateſt difficulty that he can be dif-
fuaded from the idea. A gentleman of this de-
fcription had the mortification to see the greater
part of a lump of imagined gold fly up the chim-
ney, in the itate of a fulphureous vapour; and
a mountain of it (being nothing but the Iron
Pyrites) which he had diſcovered in the weſtern
country, in the ſpace of ten minutes, loft its
immenſe value, and funk to a maſs of uſeleſs
matter : The Iron Pyrites, however, have al-
ways been a ſubject of deception, as appears
from the earlieſt account we have in chemiſtry,
and there are but very few people yet, not pre-
viouſly acquainted with them, that would not
fuppoſe them to contain a more valuable metal
than iron.
To a perſon tolerably well acquainted with the
ſenſible properties or appearance of ores, and who
has been long accuſtomed to ſee them in their na-
tive ſtate, it would perhaps be uſeleſs to make any
obſervations on this ſubject; but as ſome perfons,
of a very different deſcription from theſe, who are
intereſted in ſuch an enquiry, may chance to take
up this volume, I ſhall certainly be excuſeable
for entering upon a matter, on which but little
new can be ſaid.

ECONOMICAL ESSAY S.
113
As to the external appearances or natural pro-
perties of ores, they are fallacious; but where-
ever we find a mineral ſubſtance, either on the
ſurface, or below the ſurface of the earth, which .
bulk for bulk is conſiderably heavier than marble,
the pieces of which have little or no tranſparen-
cy, even when broken into ſmall plates or ſcales,
and more eſpecially if it has a certain brilliancy
of
appearance, and a regularity in the diſpoſition
of its parts, we have a tolerable, nay an almoſt
inconteſtible evidence that the ſubſtance is me-
tallic ; even Pyrites, as mentioned already, have
theſe appearances and are truly metallic, but,
from the braſly colour they exhibit, we are apt
to over-rate them. I ſay that when all theſe ap-
pearances combine, we may certainly pronounce
it an ore; but ſtill there are many ores which are
very valuable, and have ſcarce any of them; theſe
are of conſiderable variety, and I confefs I am far
from being able to lay down any general rules for
diſtinguiſhing them by their ſeſible properties.
The moſt ancient chemical method of ana-
lyzing ores is almoſt entirely by fire; as fulphur,
and other matters of a like kind, frequently torm
a part of the ore, heat is applied to it to diſſipate
it, after the ore has been previouſly broken into
very ſmall pieces, or perhaps ground, and then
waſhed from any dirt that might have adhered to
it; the waſhed ore is then mixed with powdered
charcoal, and pot-aſh, or ſome other ſubſtance
perfectly analagous to it, or a ſalt called borax :
theſe materials are then put into a crucible to be
fuſed, and the proceſs is much expedited by the
pot-aſh or borax: an air furnace, that will raiſe
a great heat, is neceſſary, and after ſome time,
the metal, if there was any in the ſuppoſed ore,
Q

114
CHEMICAL AND
will be found in a lump at the bottom of the
crucible. The quality, quantity, and the pro-
portion of it, may be aſcertained by means not
dependent on chemiſtry.
This proceſs is long, tedious, and in many
caſes impracticable, as we cannot always be fup-
plied with an air furnace, even of a portable
kind, at a time that our curioſity to know the
contents of the ore is the greateſt. A fimpler
method is followed by a very worthy friend of
mine, which cannot however be applied in all
caſes : he prepares the ore by roaſting, pound-
ing, and waſhing, as above; he then mixes it
with ſome powdered ſalt-petre and charcoal ;
having ſcooped out a pit in a large piece of char,
coal, and ſet the internal ſurface of it on fire, he
puts the ore thus prepared into it; the falt-petre
and charcoal burn fo ſuddenly and violently, as
to give heat enough to fuſe moſt ores, and to fe-
parate the metal they contain; the metal is then
found in the crevices of the charcoal, in the form
of ſhot. This little proceſs will only aſcertain
whether there is any metal in the ore or no, and
perhaps the operator may be able to tell, from
inſpection, what that metal is, but it gives us
but little idea of quantity.
A ſtill more elegant and ſimple method, is the
blow-pipe: We place a piece of the ore, not
larger than a pepper-corn, on a piece of char-
coal, and direct the flame of a candle or lamp
upon it, by that inſtrument, which quickly fuſes
it, and the little globule of metal is ſeen pene-
trating the charcoal. But I think the blow-pipe
may be uſed to greater advantage in another pro-
ceſs, to be mentioned preſently.

ECONOMICAL
IIS
ESSAY S.
But the moſt beautiful method of analyzing
ores is by diffolving the metallic parts of them in
certain fluids, and adding to the ſolution fome
fubſtances capable of producing peculiar changes
in its appearance if certain metals are diſſolved in
it; theſe are called teſts; and chemiſtry affords
us a particular teſt for almoſt every metal; there
are alſo ſome unequivocal teſts for the ſemi-
metals, as they are called, but, ores of theſe not
having yet occurred in America, we ſhall confine
this eſſay to the analyſis of the metals only.
Having prepared our ore by waſhing, pound-
ing and roaſting, we ſuppoſe it may contain ei-
ther gold, ſilver, copper, quickſilver, iron, tin,
lead, or a mixture of ſome two or more of theſe
forming a natural alloy : We muſt now prepare
ourſelves with the teſts, which by this proceſs
are but few; the Pruſſian alkali, the cold infufion
of galls, or of the pig-nut, (for the preparation
of which, ſee our eſſay on that ſubject) ſome
ſpirit of hartſhorn, and ſome poliſhed pieces of
iron and ſilver the operator muſt alſo be provided
with pure aqua-fortis, which may be procured
by the proceſs deſcribed in Eſſay VI. with ſome
ſpirit of ſea ſalt, called alſo marine acid; the blow
pipe, and two or three pieces of charcoal.
The method of making the Pruffian alkali is
very eaſy: We take about a pint of water, two
ounces of Pruſſian blue, and about an half ounce
of pot-aih; theſe are boiled together in a tin
cup, for an half hour, or perhaps much leſs; a
conſiderable variation in the time will do no
harm; we filtre or ſtrain the liquor through pa-
per, or fine flannel many times doubled; to this

116
CHEMICAL AND
liquor, when per/eally clear, as much aqua fortis
muſt be gradually and carefully added as will
juſt give it a very moderately four taſte, and no
more; the liquor will now be of a dark blue co-
lour, and when filtered again will be of a light
yellow, and then may be kept in a cloſe ſtopped
phial for uſe, being a folution of the Pruffian al-
kali.
We now put the ore into an oil flaſk, and for
every half ounce of the ore (an half ounce being
fufficient for the experiment) we pour two
ounces of the aqua fortis, and ſet the mixture on
hot coals, or rather hot aſhes, for iwo or three
hours at leaſt; after digeſting (as it is termed)
thus long, it may be made to boil for a minute
or two, by ſetting it on very lively coals; cer-
tain parts of the ore will be diffolved, and the
inſoluble parts, by a little repoſe, will ſettle to
the bottom of the flaſk, leaving the clear li-
quor in a condition to be decanted off ; this I
would preſerve in a phial, labelled, for fear of a
miſtake, THE NITROUS SOLUTION. This fo-
lution contains all that the nitrous acid or aqua-
fortis is capable of diffolving of what the ore
contains; that is, if the ore contained any of all
the metals that we have enumerated, they would
be held in this folution, except gold ; this metal
we know requires a particular fluid for folution,
called aqua regia, and if we have any curioſity to
know if there is any gold in the ore, we add to
the ſediment remaining in the oil flaſk, one ounce
of aqua regia, make by mixing three fourths of
an ounce, by meaſure or gueſs, of ſpirit of ſalt,
and one fourth of aqua fortis ; we treat the mix-
ture in the ſame manner as before; the clear li-
quor being obtained, we make an experiment

ECONOMICAL ESSAY S.
117
with this firſt, by rubbing a piece of bright ſilver
with a little of it on a rag wet with it, and if
there is any gold, in the finalleſt quantity imagi-
nable, the filver will be immediately gilded with
it; and as this folution can contain nothing but
gold, we may throw it away, as ufelefs, if it
does not gild the filver. The nitrous folution we
now conclude, contains all the metal that the
ore had in it.
This folution we muſt next proceed to exa-
mine, and for this purpoſe we muſt be provided
with a few wine glaſſes, and a mug of diſtilled or
rain water. We put a very few drops of the fo-
lution into a wine glaſs, and fill it nearly with
ſome of the water, and ſuſpecting that the ore
may contain iron, which is the moft common ore
that we meet with, we add a few drops of our
Pruffian alkali to it; if it is iron, we ſhall inftant-
ly have a dark blue colour produced, which is
an infallible teft of that metal, for no experi-
ments have been able to produce a blue colour
with this alkali, unleſs there had been a prepara-
tion of iron concerned in the operation; this ap-
pearance is confirmed by the cold infuſion of
galls, or the pig nut, which will make a little of
the nitrous folution turn red, purple, or black,
as the quantity of iron is leſſer or greater; this
teſt is alſo infallible, for we know of no metal-
lic or other ſolution, but that of iron, that will
produce either of theſe colours with either of
thoſe infuſions.
But the appearance of theſe colours ſhould not
deter us from hoping that there might alſo be
ſome other metal in the ore beſide the iron. If,
when we added the Pruffian alkali to the ſolution

118
CHEMICAL AND
in the laſt trial, we perceive no brown colour,
but a pure blue, we can have but little hopes
that any copper is contained in the ore; to be fa-
tisfied completely, however, in this point, we
may pour a few drops of the nitrous folution in-
to a wine glaſs, and fill it up with the pure wa-
ter, as before; if we dip into this mixture a
clean poliſhed piece of iron, and it is not foon
covered with a coppery coat, our chance is ſtill
leſs, and we may almoſt conclude that our ore
contains no copper; we may then pour a few
drops of the ſpirit of hartſhorn into the wine-
glaſs, and if it does not produce inſtantly a ſap-
phire blue colour, there certainly is no copper
in the ore worth attention.
We may, by chance, have tin united to our
ſolution; if ſo, it will form a white powder
with the Pruſſian alkali ; but the ſame appearance
is exhibited if it contains lead : How then ſhall
we diſtinguiſh them? To make the queſtion ſtill
more difficult, we will ſuppoſe that both metals
(which however is very rarely the caſe) were
contained in the ſolution; we would add to ſuch
a mixture ſeveral drops of the ſpirit of fea falt,
which will cauſe all the lead to fall to the bot-
tom of the wine-glaſs in a white powder; then,
by pouring off the clear liquor which ſwims a-
bove it, into another wine-glaſs, and adding a
few drops of Pruſſian alkali to it, we ſhall have
a white ſediment formed, which we may
be to-
lerably certain is tin; for a ſolution of tin in the
nitrous acid is unalterable by the addition of the
marine acid.
But when we added the ſpirit of ſalt to the
mixture in the wine-glaſs, upon the ſuppoſition

ECONOMICAL
I19
ESSAY S.
that the lead would be thrown to the bottom by
it, two other metals would have alſo been thrown
down along with it, if the ſolution had contained
them; that is, the filverand mercury : we have no
teſts to diſcover theſe, and in ſolution they may
be eaſily confounded together; for, iſt, ail three
are equally ſoluble in nitrous acid; 2dly, the
Pruffian alkali being added to all of theſe folu-
tions, precipitates them of a white colour; 3dly,
fpirit of ſalt, added to them in folution, alſo
changes them to a white colour.
Having there-
fore aſcertained, by the above experiments,
whether there was any iron, copper, or tin in
the folution, and whether there is any other me-
tal, we add to the remainder of the nitrous folu-
tion, either a conſiderable quantity of Pruffian al-
kali, or, what will anſwer equally well in this caſe,
of pure ſolution of pot-aſh, a ſediment will be
formed, this will contain all the metallic matters
which the ſolution contained, and muſt be either
lead, mercury, or ſilver, or a mixture of them;
the ſediment, being collected, muft be dried and
fuſed on a piece of charcoal, with a blow-pipe;
and now the effects of this treatment muſt be
well attended to; if it is mercury, it will fly away
in a white fume, which will filver a piece of
bright gold held over it; if it does not evapo-
rate, we apply the flame to it longer, for it may
probably be lead or ſilver: if lead, it will fuſe
very quickly into a little globule, which may be
eaſily known by the ſenſes, hy its readily extend-
ing under the ſtroke of a hammer, and by making
the lead-coloured mark, if rubbed on white pa-
per; it may be ſilver, though very few inſtances
of a pure ſilver ore do occur, if fo, its leſſer
malleability and more fplendid appearance will
belp to direct us.

120
CHEMICAL AND
This method of analyſis is indeed but very
crude, and the adventurer in mineralogy will
ſcarcely be ſatisfied, as to the fate of his ore,
from what he can know by making theſe experi-
ments upon it; but I preſume that every perſon
who has found that his ore is really valuable,
will ſeek more deeply for knowledge, than fuch
a work, however perfect and full, could poſſibly
afford. I hope, however, that they will be
found ſufficient to produce one very defireable
end, that is, to convince the unſucceſsful adven
turer that his ſuppoſed ore is of no value, and
thereby reſcue him from additional diſappoint-
ments and accumulated expence.

ECONOMICAL É $ SAYS.
121
ESSA Y X.
An economical method of obtaining REGULUS OF ANTIMONY,
T happens to the lot of but very few to bring
I , at
fame time be very uſeful to mankind. I cannot
pretend to much curioſity or novelty on this fub-
ject, and yet I am very certain, without either,
it may be of conſiderable uſe to individuals.
Whilſt the regulus of antimony continues to
be imported at an high price, we muſt either
fuppoſe that the method of making it is not ge-
nerally known to the perſons concerned, or they
muſt conſider it too difficult or too dear; under
either circumſtance, the ſubject is properly in-
troduced into theſe eſſays, and with this advan-
tage to the reader, that the leſs of a chemiſt the
writer is ſuppoſed to be, the eaſier the proceſs
muſt be in its own nature. It may not be amiſs
to enter alſo a little into the theory.
Crude antimony, from which the regulus is
made, is a compound conſiſting of a pure ſemi-
metal called the regulus of antimony and fulphur.
In order to procure the regulus, the firſt thought
that would occur to a chemiſt is, are there no
cheap ſubſtances, that would have a greater at-
traction to the fulphur than the regulus has,
which, when added to the antimony, would take
away the fulphur, and leave the regulus pure ?
By inſpecting the table of attractions, he would
foon be ſatisfied there is, and from theſe he
would ſelect the cheapeſt; but cannot we drive
off the fulphur with heat, and thus get the regu-
R

122
CHEMICAL AND
lus ? No, for experiment will alſo ſhew us that
the regulus will fly off as ſoon as the fulphur will.
Having then found the cheapeſt ſubſtances with
which we can decompoſe crude antimony, we
muſt reflect on the method ; it cannot be done by
ſolution, as the ſalts are decompoſed, for, nci-
ther the antimony, nor any of the ſubſtances to
be uſed, are ſoluble in water, the only cheap
fluid, in fuch experiments; and it is a chemical
axiom, “that bodies do not act chemically upon
each other, unleſs they are diffolved.” But heat
applied to crude antimony in a cloſe veſſel is able
to diſolve it, or, what is the ſame thing in che-
miſtry, to fuſe or melt it, without ſeparating any
of its parts; not if we add to the melted anti-
mony any ſubſtance having a greater attraction
to the fulphur, provided it alſo be capable of fu-
fion, we ſhall have the regulus left tolerably
pure, therefore this is the common proceſs.
Take
any quantity of coarſely powdered anti-
mony, and one fourth of its weight of powdered
ſea ſalt, put them, in a crucible furniſhed with a
cover, into a furnace that will raiſe a confider-
able degree of heat; as ſoon as the crucible ap-
pears of a bright red colour, add as much by
weight of ſmall nails (iron being a ſubſtance
having a greater aitraction to the fulphur) as
the antimony put in; cover up the crucible, and
let it ſtand on the fire a few minutes longer; it
may be then taken out, and ſtruck gently while
cooling, that the regulus may the better get to
the bottom; when cold, the regulus will be
found at the bottom, and the ſcoria, or drofs,
adhering above it, from which it may be ſepa -
rated by the ſtroke of an hammer. The regulus

ECONOMICAL
123
ESSAYS.
thus obtained is pretty pure. I have made regu-
lus equally good, by ſubſtituting an article other-
wiſe uſeleſs, for the nails, which will much di-
miniſh the price of the regulus, I mean the re-
fuſe clippings of tin, univerſally thrown away by
our tin-men in this city; theſe could be obtained
for a trifle given to their boys to ſave them, and
the nails will coſt ten pence or a fhilling per
pound, which makes the regulus come ſo high,
that it will be made by that proceſs to conſider-
able loſs; thus, by ſubſtituting even half the
weight of theſe clippings of tin for the iron, and
conducting the proceſs as laid down above, we
obtain a regulus equally pure, and nearly at one
half the expence. I have made it in this
way
fe-
yeral times, and can venture to affert that there
are few proceſſes in chemiſtry more eaſy, and in
which ſucceſs is more uniformly certain.
I am told that the type-founders in and near
this city frequently find it very difficult to pro-
cure the regulus of antimony at any rate; I
would recommend theſe to make ſome expe-
riment for themſelves; for I am confident, that
in a good large iron pot, well lined with the ma-
terials of which the crucibles are made (i.es
clay and fand) and firſt made red hot, fixty or
ſeventy pounds might be made in the ſpace of
four or five hours. As it requires a commercial
knowledge to ſay from whence the crude anti-
mony is to be imported at the cheapeſt rate, and
is not concerned with the ſubject of theſe eſſays,
I ſhall not enter into it.
The regulus, when broken, fhews a ſtar like
appearance on its ſurface, and this the type-
founders and other artiſts hold to be an infallible

124
CHEMICAL AND
fi n of its purity ; but, I think it is errroneous,
for I have ſeveral times had ipecimens of very
pure regulus, which did not ſhew this ſtar-like
appearance, though upon being melted, and fuf-
fered to cool again, it had the ſtarry chryftalliza-
tion; and I am far from being certain that the
regulus would not have this ſtarry appearance,
even when ſtill combined with a little fulphur.
The common falt, as it acts merely mechani-
cally, by being in a fluid ſtate, and lighter than
the other ingredients, ſwims on the top, and
thus may tend to prevent the antimony from fly-
ing off with the heat.

ECONOMIC AL ESSAY S.
123
ESSAY
XI.
FE
The proceſs of making PRUSSIAN BLUE, with facts and ob-
Jervations on the theory.
EW facts have engaged the attention of che-
miſts more than the theory and preparation
of this wonderful paint; it indeed preſents us
with what is called a chemical miracle, that is,
two colourleſs tranſparent fluids, immediately af
ter mixture, aſſume a dark blue colour.
But, before we enter into the theory of the
operation, let us attentively conſider the proceſs
itſelf, and lay down what we ſuppoſe the moſt
economical method of making it. It conſiſts in
heating a mixture of certain animal ſubſtances,
as dried ox blood, bones, horns, and ſome others,
with a fixed alkali, (pot-aſh] in the manner here-
after deſcribed.
It has been found, that almoſt any animal ſub-
ſtance may be uſed for this purpoſe; but, for å
variety of reaſons, I would prefer bones: they
can be procured more conveniently; they require
no previous boiling to render them folid, as blood
does; and they contain more uſeful matter in a
ſmaller bulk, which a manufacturer will find to
be of no ſmall importance,
One of the chief advantages of a chemical ma-
nufactory is, that nothing is loft. To procure
ſpirits of hartſhorn for medicinal purpoſes, bones
are diſtilled; the bones, after this proceſs, pro-
vided they are black, are as fit, or perhaps even
better, for the preparation of Pruſſian blue, than
ox-blood, or even bones, themſelves, in their freſh
ftate: they are more pulverable, and conſequent-

126
CHEMICAL AND
ly more eaſy to be combined with any other fub-
ftance. They are, in this ſtate, to be procured
at a very low price, perhaps for the trouble of
hauling them away, as ſeveral hundred cart-loads
have been thrown away, within a year, near the
city of Philadelphia.
I believe that any of our readers, who ſhall be
inclined to make this article, will find the fol-
lowing the cheapeſt and moſt caly proceſs, and
which I can recommend from many actual expe-
riments.
Take fix pounds of powdered black bones;
mix them well with one pound of pot aih; preſs
them cloſely into an iron pot, which ought to be
covered with an iron cover, well plaiftered with
clay or earth: let the whole be expoſed to a
bright red heat, during the ſpace of three or four
hours. After ſuffering it to cool, it ſhould be
taken out, all its ſoluble parts diffolved in hot
water, and made clear by ſtraining through flan-
nel. If we would wiſh the blue to be of the very
beſt quality (in which caſe the quantity will be
proportionably leſs) we pour into this liquor
Spirit of ſalt, or oil of vitriol, until we obſerve no
more boiling, or hiſling noiſe, on the freſh ad-
dition of it: we then pour the whole into a fo-
lution of only half a pound of green vitriol in
two gailons of water. If we wiſh to have a
lighter blue, we add a leſs quantity of the ſpirit
of ſalt, or oil of vitriol, to the liquor from the
bones, in which caſe we add a quarter of a pound
of allum to the ſolution of the green vitriol;
we then mix a little of the two liquors in a phi-
al, and if the colour is too light, we add more
of the ſpirit; if it is to our mind, we mix the

ECONOMICAL
127
ESSAYS.
whole together as before. In the inſtant of mix-
ture, the two liquors, which were before colour-
leſs and tranſparent, become of an opake blue,
darker or lighter, according as the firſt or ſecond,
direction has been followed; in a few hours, the
blue fecula fubfides, and leaves a tranſparent li-
quor on the top, which may be thrown away:
the ſediment muſt be ſtirred up with clean hot
water, and then ſuffered again to ſubſide: this
muſt be repeated ſeven or eight times, and then
be filtred through paper and dried on a large
cake of chalk. The other part of the proceſs is
fo mechanical, that I am certain it will occur to
any experimentaliſt who ſhall ever undertake it.
Ithall now only hint at fome advantages which
may be obtained from a manufactory of Pruffian
blue, in large quantities. Bones may
be ground
with no trouble, and very little expence to the
workman, by thoſe who grind the plaifier of Fa-
ris: large iron pots might be uſed, and a num-
ber of them filling and being filled whilſt one or
more was calcining in the furnace, a freſh one
might be put into it as foon as the other was
done, without ſuffering the fire to go out.
Mr. Macquer, who made many valuable expe-
riments upon this fubje&t, has found that a double
clective attraction takes place between the ley
drawn from the bones, the pot-aſh, and the green
vitriol; and that whilft the alkali tends to unite
with the * vitriolic acid of the green vitriol, a
Something united to the ley or alkali, at the fame
time leaves the alkali, and unites with the earth
* We will juſt repcat here, that copperas (called alſo green vi rial) is a
compound of vitriolic acid and iron.

128
CHEMICAL AND
of iron contained in the green vitriol, which
two laſt ingredients are the proximate or imme-
diate conſtituent parts of Pruſſian blue : this
ſomething, whatever it may be, certainly gives
the colour to the earth of iron, and this he mo-
deſtly calls the colouring matter of Pruſſian blue,
and, from theoretical principles, he ſuppoſed this
was # phlogiſton; hence he afterwards called
the alkali thus impregnated, the phlogiſticated
alkali; to this hypotheſis the ſame ingenious au-
thor who famed it, raiſed fome ſtriking objec-
tions, but not fufficient in his opinion to overturn
it, and having none better to offer, he was in-
clined to fupport it.
He extended his experiments ſtill further; he
proved that vegetable alkali, boiled with Pruſſian
blue, was able to attra&t the colouring matter
from it, and thus to decompoſe it, making an
artificial phlogiſticated alkali; whilſt the calx or
earth of iron, in the Pruſſian blue, remained like
ruft in the veſſel ; by adding to this new mixture
Come green vitriol, he was able to regenerate a
very pure Pruſſian blue, upon the ſame principles
as already explained.
We are told, by Mr. Fourcroy, that a Mr.
Sage preſented a memoir to a certain literary fo-
ciety, on the phlogiſticated alkali, in which he
ſuppoſes it conſiſts of a fixed alkali and phosphoric
ecid: before we proceed further, I will juſt men-
tion that many animal ſubſtances contain a cer-
tain acid, which, treated in a particular manner,
yields a ſubſtance capable of burning when only
expoſed to the air, and this is called phoſphorus,
See Efkay VIII. on the calcination of metals for ideas of this principle.

ECONOMICAL ESSAY S.
129
and the acid capable of yielding it is properly
enough called phoſphoric acid. But Mr. Sage is
not altogether accurate in his remarks on this
fubject; we have now in this city ſuch a falt,
conſiſting of a fixed alkali and this acid, called
ſoda phoſphorata ; but a ſolution of this falt, added
to a ſolution of green vitriol, will not yield a blue,
but a white colour; and we conclude, with the
above-mentioned author, that his theory cannot
be admitted.
Meff. Bergman and Scheele, in a variety of moſt
beautiful experiments, to which I refer the cu-
rious reader, have proved that this colouring
matter is an acid, and conſequently that the phlo-
giſticated alkali is a neutral falt, conſiſting of a
fixed alkali and the acid which he with great pro-
priety calls the acid of Pruſſian blue. Mr. Berg-
man conjectures that the acid is compoſed of
aerial acid, (fixed air] volatile alkali, and phlo-
gifton, but I ſhall venture to offer my doubts on
this head.
In the preparation of Pruffian blue, we find
that every ſubſtance, containing phosphoric acid
and volatile alkali, and is capable of burning, or
(as a theoriſt would expreſs it) that contains phlo-
giſton, are proper for the purpoſe. I have not
been able to find any animal matter that had not
the firſt and laſt ſubſtances in its compoſition,
that could be made to yield Pruſſian blue, and
experiments ſeem to fhew that the volatile alkali
is not eſſential to ſucceſs. Ox bile, according to
Fourcroy, diſtilled in Woulfe's apparatus, yields
concrete volatile alkali (the falt formed by aeriak
acid and pure volatile alkali) and inflammable
S

130
CHEMICAL AND
air (the phlogiſton of Bergman) with a conſi
derable quantity of uncombined aerial acid,
which Fourcroy always calls cretaceous acid.
Here then we find all the principles which Berg-
man ſuppoſes to be neceſſary to make his Pruſſian
acid, but I believe every chemiſt will fall ſhort
of ſucceſs, if he ſubſtitutes ox bile for dried blood,
&c. in his proceſs for making Pruffian blue. I
have twice attempted it, but in vain: and in
further confirmation of the uncertainty of this
method, we renark, that if ox bile is dried firſt,
and treated in the way that is neceſſary to obtain
phoſphoric acid from other animal matters which
yield it, yet it will not afford one particle of it.
To obtain fatisfaction reſpecting the theory, I
inſtituted the following experiments.
Experiment I. A quantity of bullocks bones
were ſubmitted to diſtillation in an iron retort,
to which a glaſs receiver was fixed, with a ſmall
quantity of an alkaline ſolution in it, to catch
and retain the acid of Pruſſian blue if it came
over, but nothing was obtained but ſome fætid
oil, and a ſpirit much reſembling the ſpirits of
hartfhorn, for after putting as much acid to the
fluid in the receiver as would be ſufficient to neu-
tralize it, and adding it to a folution of green vi-
triol, I got no Pruſſian blue, therefore the acid
muſt itill remain with the bones in the retort.
Experiment II. Part of the charred bones, when
cold, were taken from the retort, and treated, to
yield Pruffian blue, in the manner deſcribed in
the firſt part of this eſſay, and with the ſucceſs
there mentioned.
Experiment. III.
Some more of the charred

ECONOMICAL
131
ESSA YS.
bones were burnt in an open fire, till they were
perfectly white; part of theſe were powdered
and mixed with one ſixth part of their weight of
pot-aſh, and heated in a crucible as above, and
treated in a manner proper to yield Pruſſian blue,
but not even the ſmalleſt quantity was difcern-
able: hence it is evident that bones, when con-
verted from a black to a white ſtate, loſe ſome-
thing eſſential to the formation of Pruſſian blue.
I formed a conjecture that theſe black bones in
burning loft only their phlogiſton, as moſt other
inflammable bodies do ; if ſo, it appeared pro-
bable that merely by reſtoring phlogiſton to the
white bones, I ſhould be able to make it yield
the acid of Pruflian blue.
Experiment IV. The ſame materials as uſed
in the laſt experiment were treated in the ſame
manner as before, except the addition of a little
powdered charcoal; but when I came to add
ſome acid to part of the mixture, a ſmell like
burnt gunpowder iſſued from it, or, as authors
call it, an hepatic ſmell; but, when added
to the green vitriol, it made no blue colour; to
the reſt of the mixture I added ſome green vitri-
ol, without any acid, but this only made a brown
colour: chagrined at this experiment, which I
thought proved nothing, the phial containing the
laſt mixture ſtood in a cloſet for two or three
weeks, and one day, as I was juſt going to empty
the contents, I obſerved the ſediment at the bot-
tom of a greeniſh blue colour; I was much pleaſed
with the fight, and added a few drops of oil of
vitriol to it, for a very obvious reaſon to the
theoriſt, and found the colour changed inſtantly
to a fine dark blue, which I thought was the moſt

132
CHEMICAL AND
beautiful I had ever beheld. This experiment I
thought rendered it probable that the Pruffian
àcid conſiſted of phlogiſton and ſomething con-
tained in the white earth of bones. Now bones,
when burnt white, contain a pure lime, and the
peculiar acid which we have mentioned, viz.
the phosphoric ; therefore it would ſeem that the
proximate parts are phlogiſton and the acid of
phoſphorus, as the lime is entirely paflive in this
proceſs. I will not tire the reader with an ex-
planation of the fingular event related above,
though ſufficiently eaſy.
Experiment V. The laſt experiment, I ſhall
mention, is one in which I tried to confirm my
ideas on this ſubject by a pure ſyntheſis ; for this
purpoſe I procured ſome pure * phoſphoric acid,
combined it with pot aſh and charcoal, and
heating it in a crucible gave it a fair chance to
yield the Pruſſian blue; it did yield Some Pruffian
blue, but the quantity was much ſmaller than I
thought I had reaſon to expect. From theſe ob-
fervations, I ventured to give it as my opinion,
that the colouring matter of Pruſſian blue is an
acid compounded of the phoſphoric acid and
phlogiſton, bearing the ſame analogy to phof-
phorus, that the pblogiſticated vitriolic acid bears
to ſulphur.
However true or falſe this theory may be
found to be, upon more mature experiment, I
am pleaſed to have in niy poffeffion two facts,
that I conceive will tend greatly to illuſtrate it if
true. Some time ago, a gentleman in New-jer-
fey fhewed me a ſpecimen of a natural blue pig-
* See Fourcroy, 2d Edition, vol. IV. for the proceſs.

ECONOMICAL ESSA Y S.
133
ment which he found, as a cruſt on a ſtone which
he dug out of the earth; he obſerved, that when
firft dug up it had a white colour, but upon ex-
poſure to air, it aſſumed the blue colour; this I
make no doubt was a native Pruffian blue, and I
have further to remark, that it was found in a
part of the country where the iron pyrites are
very plenty; the iron we can account for, but
whence is derived the phoſphoric acid, that we
hold to be fo eſſentially neceſſary? I anſwer by
relating my ſecond fact obtained from Profeſſor
Bergman: he found, in all caſt iron, an hetero-
geneous ſubſtance, which gave the peculiar brittle-
neſs to that metal, by a number of very ingeni-
ous proceſſes, he was able to obtain this fub.
ſtance, as may be ſeen in his works ; at firſt it
appeared to him to be a new metal, and for cer-
tain reaſons he called it SIDERITE; a celebrated
Mr. Meyer, a German chemiſt, has analyzed the
fiderite of Bergman, and found it to conſiſt of a
pure iron and the acid of phoſphorus, and his
analyſis is, I believe, allowed to be juſt by all his
cotemporaries; but I have great reaſon to fup-
poſe that fiderite is a compound of iron and phof-
phorus itſelf, in the ſame manner as the iron py:
rites is a compound of iron and fulphur, hence
the ſiderite might be called phoſphoric pyrites:
however, the fact is, it is ſtill applicable to our
purpoſe, and our idea is, that the iron gives a
fufficiency of phlogiſton to the acid of phoſpho-
rus, to conſtitute it the Pruffian acid, or, if
you chooſe, the phlogiſticated phoſphoric acid,
which united to the iron is the Pruſſian blue itſelf.
It is in confirmation of this idea that all native
iron ever yet found is ſuppoſed by chemiſts to
contain fiderite.

134
OCH EMICAL AND
ESSAY
XII.
The proceſs of making PATENT YELLOW, with neceſſary
cautions and directions.
TH
HIS is a very beautiful, and perhaps a du-
rable pigment, it was firſt diſcovered, as it
is ſaid, by Mr. Turner of London, who got a
patent for the fole making and vending it, but I
have great reaſon to believe it was known before
to the illuſtrious Scheele of Sweden, from whom
Mr. Turner received the idea. Some time ſince the
recipe for preparing it has got abroad, and it has
actually been made by ſeveral people in this city,
by following the directions laid down in a news-
paper; ſeveral ſuppoſed that this recipe came
from me, becauſe it was known that by a chemi-
cal analyſis I had been able to aſcertain the com-
ponent parts of it, and of conſequence to make
it, but I have a very particular reaſon to declare,
publicly, that I never printed any proceſs for
making it, whatever.
The proceſs there deſcribed, which I believe
is the original one, conſiſts in grinding lithaige,
red lead, or any other calx of lead, with one
half its weight of ſea ſalt to which a ſmall quan-
tity of water only is added, it is then ſuffered to
ſtand for ſome time, perhaps twenty-four hours,
in which time the calx of lead will be changed to
a white colour, then a conſiderable quantity of
water is to be poured on, and the white maſs
well ſtirred up; after ſettling, the liquor ſwim-
ming above it is to be poured off, which may be
ſaved, as it contains ſomething valuable; the
waſhing thus repeated four or five times, or un-
til the clear liquor is quite taſteleſs; we have a
white maſs, much reſembling flacked lime, mix

ECONOMIC A L ESSAYS.
135
ed into a paſte with water, and we are only to
dry this before it is fit for the laſt part of the pro-
ceſs, which conſiſts in melting the white powder,
in a proper vefſel. Theſe are all the directions
that I have ever yet ſeen made public; to a che-
miſt the hints here might be fufficient, but I affert
them to be very inadequate to procure ſucceſs,
when attempted to be realized by others, part of
the proceſs expreſſes too much, and every part
but the fuſion is attended with obvious inconve.
niences, which I ſhall point out.
But firſt, if you pleaſe, we will theorize a
little upon the proceſs, and I hope the eſſay on the
attractions will prepare fuch of my readers for it
as have not been previouſly verſed in chemical
enquiries.
The calces of lead, all have a tendency to
combine chemically with acids, or,
or, in other
words, they have an attraction to them; when
we combine fea ſalt and calx of lead together, a
fingle elective attraction takes place; the marine
acid unites with the calx of lead forming the
white maſs above mentioned, whilſt the foſſil al-
kali (the other principle of fea falt) is left un-
combined; the firſt thought that would ſtrike us
here is that the grand defideratum fpoken of in our
third eſſay is here diſcovered, viz. a decompo-
ſition of ſea ſalt, to obtain its alkaline baſe; but
it does not come up to our ideas, for very obvi-
ous reaſons. Here we ſee that the proximate
principles of patent yellow are marine acid and a
calx of lead, hence, when I diſcovered it by a
chemical analyſis, I could only find that out, be-
ing ſtill quite ignorant of the particular proceſs,
which, however, afterwards occurred to me,

136
CHEMICAL AND
from a theory which I ſhall not trouble the read
er with
We have to remark, on the above recipe, that
it preſcribes any calx of lead; it may be right;
but I never could make it from any calx of lead
but litharge, and this is the calx that I would al-
ways recommend to be uſed for the purpoſe :
further, I do not admire the idea of uſing fea falt
to obtain the marine acid from, as I think it
much better to uſe the pure marine acid for the
purpoſe, although at firſt fight two advantages
would ſeem to ariſe from ufing ſea falt.
iſt. It is cheaper, and more economical.
2d. The foſlil alkali reſulting from it will be
of uſe afterwards.
But a great deal of experience, as far as mere
experiments can go, inſtructs me,
iſt. That if the manufacturer of patent yellow
would make his own marine acid, according to
the proceſs laid down in the Edinburgh Diſpen-
ſatory, the Glauber's falt reſulting from the pro-
ceſs will make it as cheap a method as uſing the
fea falt.
2d. The foffil alkali will be found to be of tri-
fing conſequence; a pound of litharge yielded
me but little more than an ounce and a half of
foffil alkali, and even were the proportion great-
er, I know of but very few uſes to which it can
be applied, as being combined with ſome fmall
quantity of lead, it muſt always be a fufpicious
and perhaps a dangerous article.
I have another objection to that proceſs: from

ECONOMICAL ESSAY S.
137
experience, I find that in waſhing the white maſs
the operator will unavoidably get a great deal of
it on his hands, which, long continued, would
expoſe him to the utmoſt danger of paralytic af-
fections : and this with perſons of ſente will no
no doubt be a very weighty one.
The laſt objection is that there is no mention
made, or cautions given refpeting the veſſel in
which it is to be fufed, which is alſo of great
conſequence; I hope therefore that the following
proceſs will at leaſt be free from all theſe objec-
tions, which I have often tried, and always with
fuccefs.
Take two ounces of ſpirits of ſea ſalt [marine
acid] made according to the proceſs laid down
in the Edinburgh Diſpenſatory, and one pound
of litharge, juſt mix them, and fuſe them, in a
proper veljel, in any good furnace capable of ex-
citing a great heat, for which purpoſe, our fur-
nace as delineated in theſe eſfays anſwers ex-
tremely well; the greateſt difficulty I found was
in getting a proper veſſel, for the land crucibles
it is true will anſwer, but they will ſtand one
heat only, and ſome of them not even that, with-
out breaking, conſequently to uſe them would
add conſiderably to the expenſe of making it;
black lead crucibles promiſed in theory much bet-
ter ſucceſs, but theſe turn the pigment into a
dark brown maſs; iron I thought would un-
doubtedly do, but for a pound of litharge put
into an iron pot, and fuſed, I got thirteen ounces
or more of a very pure lead; this I can account
for, but it will take room unneceſſarily; a fourth
attempt fucceeded----I procured a ſmall iron
T

138
CHEMICAL AND
mortar, holding about a pint, and lined it with
a mixture of four parts ſand and one of clay,
mixed up with water, and made it white hot in
the furnace, before I put the ingredients for the
paint into it, and this kind of veſſel anſwered
my purpoſe effe&tually. I adviſe an operator
never to ſtir his ingredients whilft in fuſion with
any iron inſtrument, but to beware of iren
throughout the whole proceſs as he values the
delicacy of his pigment.
As the ſpirit of ſalt, however carefully made,
may vary very much as to its ſtrength, ſo the
quantity above directed will not always be ex-
actly right; but when the pigment appears to
verge too much to the oras ge colour, more of the
fpirit of falt muſt be added to it; if the colour
is too light, and partakes in ſome meaſure of a
green, which however is thought to give a deli-
cacy to the pigment, for which it is much ad-
mired, the colour may be corrected by a little
more litharge. Here the operator will find great
advantage in the blow-pipe, for by fuſing a ſmall
quantity of his ingredients in a filver tea-fpoon
with the flame of a candle thrown upon it, he can
aſcertain the colour it will have after fufion, and
if neceſſary he can corre& it before he fuſes it.
The method of uſing the blow-pipe muſt be
learnt by experience.
It muſt ſurprize us to find the patent yellow
ſtill imported, when it could be made here by
any workman who uſes great fires, with but lit-
tle time and attention, without neglecting any
other buſineſs. Whoever wiſhes to make it here
would do well to imitate the Engliſh as much as
poflible; he ſhould not alter it in colour, even if

ECONOMIC AL ESSAY S.
139
he could improve it, for I found that fuch of my
ſpecimens, of the patent yellow only, were ad-
mired by our painters, which reſembled the
Engliſh, whilſt one in particular, which, by un-
prejudiced men of taſte, was thought far fupe-
rior to the imported, they eſteemed but little :
nay, if poſſible, I would even caft it in moulds
exactly like theirs, and, in fact, I would conccal
it from as many as I could that it was made in
America. I bluſh for my country, when I con-
feſs that the rage for imported articles has not
yet fubfided ; and a rational chemiſt, eſpecially,
will ſmile when he ſhall be informed, that many
inſiſt upon it that American Glauber's falt will
not operate as powerfully as that made in Eu-
rope. .
I forgot to add, in its proper place, that when
the paint is fuſed in the crucibles or iron pot, it
is to be poured out into proper moulds made of
clay, and when cold, the proceſs is entirely
finiſhed.
It is of ſome conſequence to mention that I
learnt the compoſition by following the princi-
ples mentioned in Eſſay IX. on the analyſis of
Qres.

140
CHEMICAL AND
ESSAY
XIII.
T
it may
Sulphur, American Pyrites, Copperas. Hints of improvements ..
in making VITRIOLIC Acid from ſulphur.
HE obtaining fulphur from the ore is un-
doubtedly a chemical operation, and is
therefore juſtly a ſubject of our inveſtigation;
theſe ores, I know, exiſt plentifully in the neigh-
bouring States, and I have no doubt, either will
be, or have been diſcovered in all the United
States; the ore moſt commonly uſed for this
purpoſe in ſeveral parts of Europe, and eſpeci-
ally in Italy, is the pyrites, which is a native com-
bination of fulphur and iron. As fulphur, is evapo-
rable like water, if heated in veſſels accurately de-
fended from the contact of the common air, ſo
be diſtilled from theſe pyrites like water
can from fubſtances which contain it, and it can
be collected like it, unchanged, in any veſſels
adapted to the purpoſe.
My readers will no doubt be pleaſed with
viewing for themſelves, a plate of a furnace and
other apparatus, very well adapted to anſwer the
purpoſe of manufacturing fulphur in the large
way, publiſhed in the Columbian Magazine.
It remains to be enquired whether in the pre-
ſent ſtate of arts and manufactures in America, a
manufactory of ſulphur ought to be recommend-
ed or encouraged. This is a queſtion that ought
to be decided by a perſon much my fuperior,
but when we conſider what a very low price ful-
phur is ſold for, perhaps eighteen or twenty
ſhillings per hundred weight, how little can be
obtained in the courſe of a day, without very
large works for the purpoſe, and the expence of

ECONOMICAL
141
ESSAY S.
fael, which is daily growing dearer in all thick
fettled parts of America, we ſhall have reaſon to
ſuppoſe that it can never be individually or ge-
nerally uſeful to erect manufactories of ſulphur,
and more especially, when we reflect how ſmall
a quantity of it is uſed in America, and that there
are but very few manufactories, likely to be
eſtabliſhed among us, in which fulphur will be a
neceſſary article.
In our eſſay on combuſtion we have hinted
that fulphur is a compound, of a certain ſubſtance
common to it and all other infiammable bodies,
called phlogiſton, and of an acid which is found
in the ſubſtance called green vitriol or copperas,
(known by the name of acid of vitriol) nor need
we be ſurpriſed at the ſtrange alteration of fen-
fible properties which takes place in the mixture
of theſe two ingredients, when we turn our at-
tention to fome equally ftrange, or perhaps more
ſo, in the illuſtrations of the attractions.
The iron pyrites (which alone are alluded to
here) are reckoned by authors to be of very
great variety; theſe varieties are only to be al.
certained by natural hiſtory, and by no means by
chemiſtry, for they chiefly relate to their appear-
ances as diſcoverable by the eye, ſuch as their
figure, whether cubic, globular, &c. or their
colour, whether braſſy, brown, yellow, or black.
I have ſeen the cubic pyrites which in this inſtance
is black, and called by ſome people the Lancaſter
Jack-ſtones, and another variety, found very plen-
tifully in New- Jerſey, of a ſhining appearance,
when broken, like bell-metal, called, by many
people there, braſs ſtones, copperas ſtones, mar-
cafite, &c.

142
CHEMICAL AND
When theſe pyrites are expoſed to the air
for ſome length of time, a double decompoſition
happens, which we can eaſily imitate by art, the
phlogiſton of the fulphur tends to unite naturally
with the pure air of the atmoſphere, as we have
more fully explained in the eſſay on combuſtion,
and this tendency is much favoured by the at-
traction which the vitriolic acid of the folphur
has to combine with the iron of the pyrites; this
is the cauſe of the ſplitting of the pyrites, and the
froſt-like covering that they often put on; we
can imitate the pyrites, by an artificial mixture
of iron filings and fulphur, which produces the
fame effect upon air as combuſtion, and it is de-
compoſed in the ſame manner as the pyriies:
when the phlogilton of the fulphur is united to
the air, and the other principle of it (its vitrio-
lic acid) is united to the iron of the pyrites,
theſe two laft ingredients form a ſubſtance very
well known and very uſeful in a great many arts,
called copperas, known alſo by the name of green
vitriol and martial vitriol.
Any perſon who has attentively read the eſſay
on combuſtion, however ignorant of the princi-
ples of chemiſtry, would anticipate me in pro-
poſing combuſtion as a readier way of decompo-
ſing the fulphur in the pyrites, and of diſenga-
ging the phlogiſton; for the decompoſition which
happens in the open air is ſo flow as to be totally
unproductive, and the pyrites, which muſt be
previouſly burnt) I believe are the fubftances
now generally uſed in all countries, for obtain-
ing fulphur.
It may perhaps be proper, in this place, to ſtep
aſide from chemiſtry to economy, to conſider

ECONOMICAL
143
ESSAY S.
whether (opperas is a proper object of manufac-
ture in America. And here I would beg leave to
remark, that but very few of the diffuaſive rea-
fons above mentioned, reſpecting fulphur, operate
here ; it is true, it is but a very cheap article,
but then a given quantity of pyrites I am certain
will yield three times as much, at the loweſt
computation, of green vitriol, as they will of
fulphur, in leſs time, with leſs expence, and by
perſons of leſs chemical knowledge, than would
be required to conduct a manufactory of fulphur:
the demand for green vitriol muſt riſe with the
growth of our cloth manufactories, as it is an
indiſpenſable eſſential in dying, and is very uſe-
ful in ſeveral other branches of trade.
To fhew the fimplicity of the proceſs of making
green vitriol, I ſhall give it to my readers in the
familiar relation of an experiment, which I my-
ſelf have made. I procured, by means of a
friend, twenty or perhaps twenty-five pounds of
the iron pyrites, from the State of New-Jerſey;
theſe I roaſted, or rather burnt, by putting al-
ternate layers of them and charcoal in a furnace
much like the one deſcribed in Effay I; I ſet the
charcoal on fire, and ſuffered the whole mafs to
burn as long as it would; this was about five or
fix hours; after they were cool, I poured a few
gallons of boiling water upon them, in a tub, in
order to diffolve all the copperas formed by the
combuſtion; the clear liquor was then evapo-
rated, until I had reaſon to believe that I had got,
what I have called in the eſſay on chryſtalliza-
tion, an hot faturated folution of the copperas ;
I then ſet it in the open air to cool, and obtained
a conſiderable proportion of fine green chryſtals

144
CHEMICAL AND
of copperas; the exact quantity I did not deter-
mine at the time.
That the ſcheme is very ſimple and practicable,
I can eaſily convince any perſon of, by the fol-
lowing relation.
In Lancaſter county, in this State, and about
twelve miles from the town of Lancaſter, a mine
was dug by a company of miners, who ſuppoſed
that there was a large body of copper ore there;
in the courſe of their ſearch, they threw up a pro-
digious quantity of the pyrites, which lay ſcat-
tered about the ground for ſeveral years, as uſe-
leſs: the copper mine being unproductive, the
whole ſcheme was abandoned, and the mine was
left unnoticed : during the war, however, when
copperas was very dear, and ſcarcely to be ob-
tained at all, an old miner, who lived near the
mine, conceived the idea of making copperas
from theſe pyrites, which he accompliſhed, and
made a conſiderable ſum of money by it: foon
after the peace, he was going to move off the
place, and for the benefit of ſelling his little ap-
paratus to advantage, he communicated his pro-
ceſs to two country lads, who continue to make
it occaſionally.
They take a quantity of the pyrites, and heap
them carelessly upon a row of ſticks of wood,
ſupported by ſtones, in the ſame manner as the
andirons ſupport the wood on an hearth; they
then lay another layer of wood acroſs theſe pyri-
tes, and ſo keep adding layer upon layer, imitating
in ſome meaſure a number of croſs bars laying
upon each other, until they put as much of the
pyrites on as they think proper ; the wood is then

ECONOMICAL
245
ESSAYS.
ſet on fire, and requires no further attendance:
the combuſtion ſometimes goes on by means of
the fulphur for two or three days, and by that
time the maſs is fit for the next part of the pro-
ceſs: they put the burnt pyrites into a wooden
caſk, holding about thirty or forty gallons, and
fill it about two thirds full, with them; the
reſt is filled up with water; after ſtanding a
while, the liquor, now ſtrongly impregnated
with copperas, is drawn from the bottom of the
caſk, by means of a plug-hole exactly in the ſame
manner as the ſoap-boilers make their ley this
copperas-ley they boil down in a little lec den boil-
er, holding perhaps fifteen gallons, and they fup-
ply the waſte by adding niore of the ley, and
when a ſmall thin cruſt forms on the top of the
hot liquor, they withdraw the fire, and ſuffer it
to cool, and from this quantity of materials, they
collect thirty pounds of as pure copperas as per-
haps was ever made in any country. The whole
of this proceſs (except the burning the pyrites)
is performed in a ſmall ſtone building, ſcarce
eight feet high and ten feet ſquare, and, except
the building, the utenlils were ſcarcely worth
three pounds; the trouble was ſo ſmall, and the
attention required, ſo trifling, that there two
lads only dedicated that time to the making of
copperas, which they ſnatched from the toils of
managing a large farm, and I have certain ac-
counts that the whole proceſs never required
more than three or four hours of their time.
If ſuch a quantity can be made, under all theſe
diſadvantages, how profitable might ſuch a ma-
nufacture be to a perſon who could dedicate all
U

146
CHEMICAL AND
his time to it, and with the ſmall expence of en-
creaſing the fize of the manufactory ten fold,
which would be very far from encreaſing the
difficulty in the like proportion: and if twelve
cords of wood can be fo applied, in a lime kiln,
as to keep ſeven hundred buſhels of lime red bot
for three days and three nights, how cheaply
might the pyrites be burnt in a well conſtructed
kiln, feeing it is not neceſſary to apply the heat
above a few hours, as the pyrites afford materi-
als for their own combuſtion ; if, to all theſe ad-
vantages, a ſituation favourable for a water car-
riage to a market, it appears to me very proba-
ble, that with but very little hazard and expence,
a very profitable manufactory might be erected:
ſuch a fituation, I think, may be found on the
river Delaware, and no doubt upon many other
navigable waters of the United States. A num-
ber of other facts might be mentioned to encou-
rage ſuch a deſign, but I truſt I need not enlarge
upon them in this place : one great objection is
already ſet aſide, and that is the difficulty, for,
furely no perſon will make that plea, when it
has been managed with ſucceſs by two fuch lads.
I will juſt add to theſe obſervations, on the
manufa&ure of copperas, that the pyrites, after
being waſhed, will yield a very beautiful purple
pigment, if calcined in the open air, and waſhed
afterwards; I have found it almoſt as fine as the
crocus martis of the ſhops.
That ſulphur at leaſt is fome how or other
an acid after combuſtion, is eaſily demonſtrable;
we take a piece of paper died with the tincture
of turnſole, or with any of thoſe purple fruits or

ECONOMICAL
147
ESSAYS.
Powers, which we have obſerved are change-
able to a red by acids, this being wet, we hold
it over the fumes of fulphur in the ſtate of a
vivid combuſtion, and the paper will inſtantly be
changed from a blue or purple colour to a bright
red; an infallible mark with us of the preſence
of an acid; if then the fumes of fulphur are in
themſelves acid, if they could be condenſed, we
ſhould certainly obtain its acid, and this would
be a cheap ſubſtance to obtain that peculiar acid
which ſome years ago was chiefly obtained from
green vitriol. This has been done to the great
advantage of a variety of arts: for a defcrip-
tion of the method of obtaining it by means of
burning fulphur in large glaſs veſſels, with a cer-
tain quantity of nitre, and the further improve-
ment of the proceſs, by fubftituting chambers
lined with lead to veſſels of glaſs, I muſt refer
my reader to the writings of Mr. Fourcroy, the
preſent chemical compendium uſed in America.
Nitre is an expenſive article in the proceſs, and
could we do without it, the price would be
much reduced. I have conſidered, that the chief
effect to be obtained in the proceſs of making
vitriolic acid from fulphur was, to produce a ra-
pid combuſtion of ſulphur in cloſe veſſels, capable of
confining and condenſing the vapours, without inter-
fering with the combuſtion. As no infiammable
body can burn long in confined air,
ſtant ſupply of pure air fit for combuſtion is ne-
ceſſary for this purpoſe ; nitre, as containing a
great quantity of pure air, capable of being fet
looſe or evolved in combuſtion, we remarked
would anſwer, but it is expenſive; a ſimple and
ſeemingly obvious contrivance immediately oc-
curred to me, I mean the idea of ſupplying the
a
con

148
CHEMICAL AND
air with a BELLOWS; this I am confident is to
this day unnoticed by any author whole works
have appeared in America.
Without troubling my reader with my dif-
ferent plans, I will juſt preſent him with two
drawings, the firſt containing an apparatus con-
trived for the purpoſe, with which I confeſs I did
not ſucceed; the ſecond repreſents the plan of
another, which I think I have reaſon to conſider
as an improvement, which perhaps when tried,
and ſome unforfeen diſadvantages of it remedied,
would anſwer extremely well; all trials, how-
ever, of this kind, muſt require time and ex-
pence; and as I have now in ſome meaſure left
chemiſtry as a profeſſion, I am willing to put
any perſon into the path as far as I have trodden
it, that he may not have the trouble of going the
fame round himſelf; and if my reader ſhould
happen to be a man unacquainted with chemiſtry,
he may take up thisſubject where I am forced to
leave it off.
The three veſſels B C D are oil jars, holding
about thirty gallons each, repreſented in the fi-
gure as tranſparent, that we may ſee their con-
tents; into a leaden pipe in the jar B the ſmiths
bellows, furniſhed with a double valve is inſert-
ed as in the figure, and cemented into it ſo as to
be air tight; the extremity of this leaden pipe in
the jar has a ſhoulder, as in the figure, which
muſt direct the courſe of the air downward. At
A there is an earthen veffel to be put of melted
fulphur, and from the lid of the jar B there is a
leaden pipe, of the form in the figure, entering
pretty low down into the jar C, filled with water
to the height repreſented in the figure, and ter-

ECONOMICAL
ESSA Y S. 149
minating after paſſing fome depth in the water,
in the end of a watering pot, being pierced with
a number of holes. From b there goes another
leaden pipe, which enters the ſide of the jar D,
terminating in the fame manner as the other
pipe, but the mouth of this jar muſt be left open. .
Having all things thus fixed, I put a quantity
of fuſed fulphur into the veſſel a and ſet fire to it,
afterwards cementing the cover of the jar B ſo as
to be air tight; I immediately ſet the bellows to
work, which blowing upon the fulphur kept it
burning; the fumes of the fulphur roſe with the
air, through the firſt leaden pipe, and deſcend-
ed into the water in the jar C, where the ſurface
of contact was much enlarged by the holes in the
termination of that pipe; if any vapour was left
without being abſorbed, it had to paſs into the
jar D, where it ſtood another chance : but if any
remained afterwards, in the ſtate of vapour, I
was forced to let it paſs off through the mouth of
the laſt jar.
My objections to this apparatus are certainly
weighty; the reſiſtance of the column of water
in the two jars C and D greatly impede the work-
ing of the bellows, and very violent exertions
muſt be made to overcome that reſiſtance, other-
wiſe the bellows cannot work at all; and I have
found that it was neceſſary to put upwards of an
hundred weight upon the bellows, before it
work, and with frequent trials I have found that
I could make the water ſenſibly acid, but I was
convinced that this plan would not do.
My improvement is, to have a ſmall iron ſtill,
ſo fixed, by means of a proper furnace, that wa-

150
CHEMICAL AND
ter in the ſtate of vapour might paſs into its pipe,
near where it is to terminate in the jar C, oppo-
ſite to the place where the bellows enter it; this
pipe I would keep red bot, conſequently an im-
menſe quantity of very forcible fteam would be
inſtantly generated capable of overcoming the
reſiſtance of the water in the other two jars.
If it is found uſeful to ſubſtitute air obtained
by means of a bellows, in manufacturing the oil
of vitriol, I have no doubt that a bellows might
be worked by means of ſteam, without any other
#gent.

ECONOMICAL
151
ESSAYS.
ESSAY
XIV.
A
UNCTUOUS OILS. SOAP, ſome curious fa&ts reſpecting it,
its decompoſition by hard water.
N unetuous oil comprehends all thoſe fub-
ſtances, whether fiuid or folid, animal or
vegetable, that have the peculiar feel called
greaſy, that are infiammable, not evaporable by
a boiling heat, and in their pure ſtate have little
or no ſmell; this definition comprehends more
than the common idea of an oil, for people, in
general, only apply that term to ſuch oils as are
Huid; but, as fluidity depends upon fo very trifling
a circumſtance as a ſmall increment of heat, it
can by no means be juftly confidered as effential
to or characteriſtic of oils.
All unctuous oils combine chemically with alka-
line ſubſtances, eſpecially the fixed alkali, and
form ſoaps. I ſay it is a chemical combination,
though perhaps leſs perfect than ſome others, be-
cauſe there is an alteration in the ſenſible proper-
ties of the two component parts of the ſoap, for
the alkali, or ley, has loſt its corroſive acrid
taſte, and although the oil ftill appears ſomewhat
greaſy to the feel, yet it is now rendered ſoluble
in water, and has loſt the property of greaſing
linen, or other things of that kind, for it will
even take out greaſe ſpots from cloths very ef-
fectually.
The proceſs of making ſoap is ſufficiently fim-
ple, and well known. A quantity of ley is made
from wood aſhes, pot-afh, foda, or any other
fixed alkaline ſalt, made ſtronger by quick-lime,
the unctuous oil is added to it, and they are boil-
ed together for ſome time, until the whole mix-

$52
CHEMICAL AND
ture appears of the conſiſtance of melted glue;
if it is then taken off and ſet to cool, we have a
ſoap very different in qualities, according to the
alkali made uſe of; if the ley was made from
wood-afhes, ſuch as the aſhes of oak and hickory
wood, or from pot-afh, which contain only a ve-
getable alkali, we invariably get ſoft foap, if foda
was made uſe of, that is, the alkali got from the
aſhes of plants growing near the ſea fhore, called
the foffil or mineral alkali, we ſhall always get
bard ſoap.
About two years ago, I laid before the Medi-
cal Society of this city a memoir on the forma-
tion of hard ſoap, when the vegetable alkali is
uſed, and there endeavoured to prove that when
ſea ſalt was put into the ſoft ſoap, a double decom-
poſition actually took place, contrary to the
ideas of many perſons, and even of ſome che-
miſts, who ſuppoſed, that as ſea ſalt required a
conſiderable quantity of water for its folution, it
took that water from the ſoft foap, and left it in the
itate of hard ſoap; this ideal ſuppoſed at that time
ito be entirely new, but I find that Mr. Nicholſon
ntroduced it into the ſecond edition of his Syſtem
of Philoſophy, which appeared in this city two
months before I read my eſſay to the Medical
Society, but I declare that I had not at that time
ſeen that book: Mr. Nicholſon fuppoſes, that
the ſea ſalt anſwers both the purpoſe of a double
decompoſition and of drawing the water off from
the ſoap, but I cannot agree with him in the laſt
fuppoſition. When ſea ſalt is added to foft ſoap,
a double elective attraction, and of courſe a
double decompoſition, enſues; the marine acid
of the ſea ſalt combines with the vegetable alkali

ECONOMICA I. ESSA. Y S. 153
of the ſoft ſoap, and at the ſame inſtant gives up
the foſil alkali, which it contains, to the unctum
ous oil, which two laſt ſubſtances form bard ſoap;
it is therefore the practice to add a certain quan-
tity of the ſea ſalt to the ſoft ſoap when boiling,
and when cold, the hard ſoap will form a cake,
on the top of the kettle, or whatever veſſel it may
have been boiled in.
That ſuch a decompoſition of ſoft ſoap hap-
pens, when ſea ſalt is added to it, and that the
ſalt anſwers no other purpoſe than merely to give
up its foſſil alkali to the oil, without which we
ſuppoſe no hard ſoap can be formed, we think is
certain from the following facts.
ift. Becauſe hard ſoap cannot be formed by
the direct combination of a vegetable alkali and an
unctuous oil.
2d. Becauſe no falts, however ſoluble in wa-
ter, which contain the vegetable alkali for their
baſe, can ſupply the place of fea falt in making
hard foap
For this experiment, we have tried nitre, vi-
triolated tartar, and digeſi'ive ſalt, which is the
falt formed by the vegetable alkali and the acid of
ſea ſalt.
3d. We conclude that all hard ſoap contains
foſſil alkali, becauſe if we burn any hard ſoap,
made by any means whatever, we ſhall deſtroy
the oil of the ſoap only, whilſt its alkali is left
pure ; if we combine the alkali thus obtained,
with a little oil of vitriol mixed with water, and
follow the directions laid down in our eſſay on
X

154
CHEMICAL AND
chryſtallization, to obtain the chryſtals of a falt,
we ſhall obtain a falt poſſeſſing all the properties
of Glauber's ſalt, which we know cannot be form-
ed without a foſil alkali, which in this caſe muſt
have come from the ſoap.
4th. If we are careful to add no more fea ſalt
than is juſt ſufficient to decompoſe all the foft
foap, (which is about a quarter of a pound to
every pound of oil made uſe of) and ſave the li-
quor which is under the hard ſoap, we ſhall find
it will yield chryſtals, if treated properly, which
chemically examined, will anſwer in every par.
ticular to the characters given of the ſalt formed
by the vegetable clkcli and marine acid.
5th. Hard ſoap is made in ſome countries in
Europe by the direct combination of foſil alkali
and an unctuous oil, without the leaſt addition of
ſea ſalt or any other ſalt whatever; here then is no
neceſſity for a falt to draw off the water. In this
way
it is that the Caſtile ſoap is ſaid to be made.
6th. We conclude alſo that a foffil alkali only
is neceſſary for making the hard ſoap, becauſe
we have actually found that even a ſolution of
Glauber's Salt, which contains the one clkoli
but cannot draw off any water, will anſwer all,
the purpoſes of fea falt.
And, laſtly, becauſe a ſolution of ſea ſalt inay
Le fubftituted for the ſalt in fubftance,
When ſoap is mixed with certain kinds of wa-
ter, called hard waters, a decompoſition of it
happens, and the oil or the fat being diſengaged,
it fioats on the water, and is in a condition to ex-
ert all the properties it had Lefore combination;

ECONOMICAL ESSAY S. 153
hence it greaſes any thing that is wallied with it.
The hardneſs of water is moſt commonly owing
to two cauſes, either fixed air, or an earthy falt;
and I have great reaſon to believe, that in this
city, the fixed air, diffolved in water, is the moſt
common cauſe. It is unneceſſary to offer any ar-
guments, in the preſent improved ſtate of chemi.
cal knowledge, to fhew that fixed air is an acid,
and it is alſo equally well known that all acids
have a greater attraction to all alkalies than oils
have, hence the fixed air is able to unite with the
alkali of the ſoap, and to leave its oil uncombined.
Pump water contains the greateſt quantity of
fixed air; and it is this kind of air, in the bottom
of wells, that has ſometimes proved fatal to well-
diggers, and extinguiſhes a candle lowered down
into it; and as this air can be diſſolved in water,
it is eaſy to conceive that it would make the wa-
ter hard.
That an acid in water can make it have the
properties of hard water, we can illuſtrate very
prettily; for a little vinegar which is acid will
curdle foap-fuds in the fame manner exactly;
that fixed air diffolved in water is acid we alſo
know by the taſte of the artificial Pyrmont
water, made frequently by many of our citizens.
We would conclude, from theory, that whatever
would deſtroy the acidity of the fixed air, would
purify the hard water, and experiment proves
our ſuppoſition right; for when rain, river, or
ſpring water, from certain circumſtances, can-
not be got, I have found that pot-aſh, added to
common pump water, in the ſmall proportion of
a quarter of a pound to twenty gallons, will make
it as ſoft as any water whatever, and equally.
uſeful for every purpoſe.

156
CHEMICAL AND
When ſoap is decompoſed by fixed air, we
faid that the fixed air and alkali united, and left
the oil uncombined; theſe two ſubſtances then
form a neutral falt, and hence we may conceive
the cauſe of an error propagated by a Mr. Beau-
ine, a French chemiſt, who ſuppoſed that BORAX
is formed in ſoap water, when it is left expoſed
to the air for a certain length of time. The af-
fertion is inexplicable upon any theory ever yet
accepted in chemiſtry. The air of our atmo-
fphere we know contains a certain quantity of
this fixed air, called alſo the aerialacid, and it is
very conceivable that when ſoap water is expoſed
long to the air, the aerial acid would by a fupe-
rior attraction attach itſelf to the alkali, which,
being a neutral falt, and chryſtallizing as the wa-
ter evaporated, might give him the idea of borax
being generated in it. The combination of the
foſſil alkali and the aerial acid, chemiſts have
agreed to call the aerated foſil alkali.
I thought, however, that the affertion of Mr.
Beaume, though improbable, was not impoſsible
to be true, and therefore I thought it moſt ad-
viſeable to make the experiment for myſelf. I
therefore fet about two or three gallons of a
ſtrong foap-water to undergo all the changes that
the ſun and air could make upon it; I found it
neceſſary to add frequently to it a little rain wa-
ter, becauſe the evaporation went on quicker than
the decompoſition; at the end of about three
months, decompoſition had gone on to a great
degree, as I found by the fat ſwimming on the
ſurface of the fluid, and ſuffering the liquor to
evaporate ſpontaneouſly, I found a conſiderable
number of ſmall chryſtals of a falt poſſeſſing
enough of the properties of borax, to lead one,

ECONOMICAL ESSA Y S. 157
that was not very attentive, to miſtake the one
for the other, for, like borax, this falt effloreſces
or falls into a white powder, if expoſed for a day
or two in a dry air; it is a very good menſtruum,
and affifts the fuſion of metallic ſubſtances, and,
laſtly, it reſembles borax very much in taſte and
the figure of its chryſtals; but the ſalt obtained
from ſoap-water in my experiment at leaſt differed
from borax, by making an hiſling noiſe like boil-
ing, called efferveſcence, if I added even a weak
acid to a ſolution of it, which borax will not do.

158
CHEMICAL AND
ESSAY XV.
COLOURING MATTER OF VEGETABLES, fome ideas 03
the cauſe of the change of colour in growth.
TH
HERE are many curious circumſtances re--
ſpecting the changes that vegetables take on
by the application of other matters to them; but
chemical experiments have been made upon very
few colours except thoſe which are red, purple,
blue and green. The blue colour of violets is im-
parted to the ſyrup, which the apothecaries keep
as a medicine, by the name of fyrup of violets,
and accident moſt probably was the means of
teaching chemiſts that its colour was vaſtly
changeable ; a number of experiments at laſt con-
firmed them in the opinion, that a certain claſs of
chemical agents were capable of producing one
certain effect only; as for inſtance, alkalies al-
ways change the blue colour of fyrup of violets
to a green, but they found that lime, and perhaps
ſome other earths, had the ſame effect upon it,
and hence may have been the reaſon why fuch
earths are called alkoline earths, and as they have
the power alſo of deſtroying the acidity of acids,
like alkalies, the term may be admiſſible; another
claſs of bodies have a very different action upon
the ſyrup of violets, theſe are acids which always
turn it red: hence we find the chemical writers
of a few years ago, aſſerting, as a proof of the
alkaline or acid nature of any matters they have
been examining, “ that it turns the ſyrup of vio-
lets green, or red.” It was for a long time fup-
poſcd, that the violet was the only vegetable
ſubſtance that aſſumed theſe colours, with ſuch
addition. It is very well worthy of remark, that
when the lyrup of violets is changed to a green

ECONOMICAL ESSAYS.
159
by an alkali, the colour may be reſtored by add-
ing a certain quantity of an acid to it, in which
caſe the alkali is ſaid to be ſaturated, that is, both
the acid and the alkali are in ſuch a proportion
in the mixture that no part of cither poſſeſſes its
ſenſible properties, and we ſhould carefully re-
member, that neither an acid or an alkali are ca-
pable of changing the colour of the ſyrup of vio-
lets, when in chemical combination with other
ſubſtances. An alkali, on the other hand, is ca-
pable of reſtoring the colour that an acid had al-
tered, if no more than enough to ſaturate the
acid is added to it; the red colour induced by it,
is brought back to a blue; but if in any caſe any
more of either of them is added than is juſt fuffi-
cient to obviate the effects of the other, then a
poſitive effect is produced, i.e. too much alkali
will change it from a red to a green, and too
much acid on the contrary will change it from a
green to a red colour.
When we have any faline ſubſtance in our pof-
ſeſſion, that will not alter the colour of the ſyrup
of violets, we call it a neutral falt, becauſe it is
formed of two fubſtances, one an alkali or of an
alkaline nature, and the other of an acid, united
in ſuch proportions as to completely deſtroy each
others ſenſible properties; hence ſyrup of violets
is not changeable by ſea ſalt, although it contains
nearly one half of its weight of a ſtrong acid.
Some falts conſiſt of two principles, of an al-
kaline ſubſtance and an acid, but in theſe one or
the other of the component parts exiſt in greater
quantity than is ſufficient for ſaturation ; hence
fome ſuppoſed neutral falts will change the co-
lour of fyrup of violeis like an acid or an alkali.

160
CHEMICAL AND
ſuch as allum, which, though compounded of
clay and the vitriolic acid, will change the ſyrup
of violets red, and for that reaſon we might call
it an acido-neutral ſalt, whilſt borax is ſaid to
change it green; ſuch falts we might call alkaline-
neutral falts.
Mr. Bergman ſubſtituted the tincture of turn-
fole, made by diffolving litmus (which may be
had of moſt apothecaries by that name) in pure
water, or made uſe of white paper tinged blue
by this tincture, for the ſame purpoſe. This is
an excellent and beautiful teſt of acids ; it is
changed red by them inſtantly, but alkalies pro-
duce no poſitive effect upon it, and to make it a
teft for them we muſt first tinge the paper or tinc-
ture ſlightly red by an acid.
Later experiments ſhew that many other blue
vegetables are changeable by acids and alkalies :
I have found that all the red and purple fruits or
berries, that have fallen under my obſervation,
are acted upon by both ſubſtances, except the
poke-berry; among theſe are, the juices of mul-
berries, blackberries, currants, cherries, and
ſtrawberries; the blue, red, and purple colour
of fome flowers are alſo teſts of this kind, we
have tried poppies, the ſeveral varieties of blue
flag, and a great number of blue wild flowers
whoſe names I do not know. I have alſo a note that
mentions fome vegetable greens that are changed
both blue and red by an acid. The flower called
delphinum, or lark-fpur, as well as the blue in-
digo, are unchangeable either by acid or alkali,
and litmus we find is only a teſt of acidity.
The production of a green colour, from certain

ECONOMICAL ESSAYS.
161
blue vegetables, by an alkali, made me once be-
lieve that the natural colour of all green vegeta-
bles is blue, eſpecially as we know that all of
them contain alkali, as is proved from their aſhes
in burning; but this cannot be true, for there are
but very few green vegetables that we can change
either blue or red by an acid, nay forrel itſelf is
green, though a native acid is generated in it.
When we reflect, for a moment, that a great
number of vegetables have their colours acted
upon in the ſame manner by the fame ſubſtance,
whilſt the ſame colour, in a different vegetable,
is only partially or not at all altered, we are in-
clined to conjecture, that many of them owe thoſe
colours to a ſimilar chemical ingredient, but that
this ingredient is not the ſame in all of them.
As ſeveral vegetables contain native falts, by
which term I mean falts exiſting formally in them,
and which may be obtained from them without
combuſtion, diſtillation, or fermentation, it is
natural to ſuppoſe that the difference of their co-
lour inay be in a great meaſure owing to theſe ;
what the colouring principle, unaltered by any
addition, is, we do not know, and perhaps never
will; but we have great reaſon to believe, that
the red colour of many unripe fruits is owing to
that acidity in them, with which they are always
connected; hence we always ſuppoſe fruits, that
ever aſſume a purple, to be four if they are red;
now as the acid in the courſe of their maturation
is changed into a ſweet faccharine matter, it no
longer poſſeſſes its ſenſible properties, and is then
incapable of continuing that colour in the fruit;
the ſame effect we have found may be produced
Y

162
CHEMICAL AND
upon the juices of unripe fruits, by deſtroying
the acid in them, for by adding different propor-
tions of an alkali to them, we change them from
a red to a purple, a blue or a green; this is more
eſpecially obſervable in the juices of cherries,
and the fruit called blackberry: we cannot pretend
to ſay by what means the acid is formed in theſe
fruits, as it requires a greater knowledge of ve.
getable phyſiology, than any philoſopher has yet
attained, but, ſuppoſing the acid formed, we
prefume that the red colour is owing to its action
upon the native colour of the vegetable, and
that, when deſtroyed, the other changes we have
mentioned muſt take place; how this is effected
by the living powers of the vegetable we are
next to enquire.
And here I preſume to ſuppoſe that the doc-
trine of phlogiſton will be admitted by thoſe who
peruſe this eſſay; it has long ſince been found
that if an animal breathes in any given quantity
of atmoſpheric air, it will die after a certain
time, becauſe the air is rendered impure; if
another animal is put into the ſame air, it will
inſtantly die alſo, or perhaps in a few moments,
and a candle immerſed in it is inſtantly extin-
guiſhed; we have great reaſon to believe that
animal reſpiration and combuſtion produce the
fame changes upon air, for if a burning candle
is confined in a given quantity of air, it will be
extinguiſhed, and will then prove fatal to animal
life inſtantly: if we are right, the impurity of
the air in theſe caſes is owing to the air being
combined with phlogiſton, which the burning
body and the animal both diſcharge from them-
felves. I cannot, and perhaps need not, enter
into all the proofs in this place that might be al-

ECONOMICAL ESSAYS.
163
leged to determine that, whenever air is ren-
dered impure, it is effected in one way only ;
this air has been called by the Engliſh philofo-
phers, the phlogiſticated air, for they ſuppoſed
it to be fo loaded with phlogiſton, that it is in-
capable of receiving any more either from ani-
mals by refpiration, or from combuſtible bodies
in the act of combuſtion. Dr. Prieſtly firſt held
forth the idea that phlogiſton is the food of vegeta-
bles; for having confined a large flouriſhing ſprig
of mint in a glaſs jar of phlogiſticated air, he was
very much furpriſed to find the plant grow more
rapidly than ſimilar ſprigs of mint in his garden,
for he expected to have found that air fatal to
vegetables as it is to animals; after it had grown
fome time in that air, he examined the air, and
found it equally pure as the air of the atmoſphere,
fupporting combuſtion and reſpiration full as long;
his explanation of it was, that the plant abforbed
the phlogiſton from the phlogiſticated air, and thus
rendered it pure, becauſe he ſuppoſed that this air
was a compound of atmoſpheric air, and phlogif-
ton, and by whatever theory it is explained, the
fact is now univerſally admitted, that plants
growing in impure air, have the power of purify-
'ing it; he alſo concluded, from this fact, that
vegetables could not grow at all without phlogif
ton, hence he fuppoſes that when vegetables
grow in open air, without being in contact with
earth, they abſtract fome phlogiſton from the air
which is contaminated with it from fires and the
reſpiration of animals, and we may ſuppoſe that
when ſome vegetables thrive very well in pure wa-
ter, they have the power of decompoſing that fluid
and of taking the phlogiſton (or the inflammable
air) which Mr. Cavendiſh, I think it was, proved
it contained. The French chemiſts, on the other

264
CHEMICAL AND
hand, would ſay that the vegetable had a power
of throwing out pure air, which being imparted
to the impure air, made it capable of ſupporting
Jife, &c.
Dr. Prieſtly alſo confined a ſprig of mint in a
fpecies of air which ſupports animal life and com-
buſtion ſix times as long as the atmoſpheric air,
which from theory he calls dephlogiſticated air;
but the plant fickened and died; this proves that
animals and vegetables both live upon air, but
the kind that is food to the one is poiſon to the
other; and for want of a knowledge of this fact,
the great Bergman truſting to a fancied analogy
between plants and animals, has fallen into the
greateſt error that perhaps he ever committed in
chemiſtry, for he thought that animals in refpira-
țion deprived air of its phlogiſton, becauſe he knew
that vegetables did; “ For whence, ſays he,
does a pine, which contains a great deal of phlo-
gilton in its turpentine, growing in the moſt
barren fandy foil, receive its phlogiſton? is
it not from the air?” but as Mr. Bergman's ana-
logy is not accepted by any one at preſent, we
need make no comments upon it.
It being admitted, on all hands, that vegetables
can purify air, and render it more capable of ſup-
porting animal life, we muſt either conclude with
the phlogiſtians, that ſomething is taken by the ve
getables from the impure air, or with the anti-
phlogiſtians that the vegetables give pure to the im-
pure air.
To reconcile our opinion to either doctrine,
we ſhall juſt obſerve, by way of illuſtration, that
when vitriolic acid is combined properly with

ECONOMIC AL ESSAYS. 165
certain ſubſtances that are inflammable, it is con-
verted into fulphur. One fect of philoſophers
would ſay, that the phlogiſton of the inflammable
fubftance combined with the vitriolic acid which
in their opinion is a ſimple body) and formed the
compound body called ſulphur. The others
would explain it by ſaying that the infiammable
body took away pure air from the vitriolic acid,
and left fulphur, which was only one of the con-
ſtituent principles of the vitriolic acid, and pure
air the other; and upon their theory they ſup-
poſe, that all the different acids are compounds
of pure air, which is common to them all, and
differ only in having different infiammable bodies
united to that pure air. Here we ſee upon the
confideration of either doctrine, that whenever
vitriolic acid is converted into fulphur, it loſes
all its acid properties, and we are now prepared
to explain how the acid of fruits are converted
moſt probably into Sugar, or at leaſt it is deſtroy-
ed as they grow ripe: we ſuppoſe the plant or
tree to be continually abſorbing phlogiſton, either
from the decaying vegetable and animal matters
in the earth, froin the air, or from the decom-
poſition of water;
or elſe that theſe ſubſtances
take away the pure air, which the acid of the
fruit is ſuppoſed to contain, upon the ſame prin-
ciple as vitriolic acid is converted into fulphur.
Wheneyer the acid is neutralized, or the fruit
becomes quite ripe, it is ſweet, or very ſlightly
acid, and of a purple colour; ſome cherries, as
the moreila, are never purple, but neither are they
ever ſweet.
A perſon acquainted with the two prevailing
theories can readily explain theſe facts upon ei-

166
CHEMICAL AND
ther of them; we ſhall finiſh what we have to ſay
upon this ſubject, upon the ſuppoſition that the
phlogiſtic doctrine is true : to ſum up all; we
fuppoſe that the red colour of certain fruits is
owing to an acid, that vegetables, by abſorbing
phlogiſton, abſorb a ſubſtance that tends to de-
ſtroy this acid, and in time accompliſhes it to a
very great degree, on the fame principles that
vitriolic acid loſes its acidity by phlogiſton, that
the acid of theſe fruits and phlogiſton form ſugar,
which is the cauſe of the ſweetneſs of ripe fruits,
and that the deſtruction of their acidity is the
cauſe of their purple colour, we conclude from a
fact related already, that an alkali added to the
red juices of certain unripe fruits, turns them
purple, and of the colour that the ripe fruits are.
That fugar conſiſts of an acid fui generis and
phlogiſton, we have great reaſon to conclude
from analyſis at leaſt, for if we boil ſugar and ni-
trous acid together, in ſuch a manner that any air
that may eſcape will be preſerved, we collect a
conſiderable quantity of nitrous air, that is, a
fluid compoſed of nitrous acid and phlogiſton ;
the phlogiſton we ſuppoſe muſt have been derived
from the ſugar, and we know whence the air ob-
tained its other principle, the nitrous acid; but
what is left of the ſugar ? If the liquor be left to
cool for a few hours, we obtain long priſmatic
chryſtals, poſſeſſing the general properties of an
acid, and ſome very peculiar ones, and therefore
very properly called the acid of ſugar; but we
have never been able to confirm this analyſis of
ſugar (which is Mr. Bergman's) by ſyntheſis,
that is, we cannot combine the two principles
of ſugar together, and form that ſubſtance ;
unleſs we admit the converſion of an acid into

ECONOMICAL ESSAYS. 167
ſugar by phlogiſton, in the proceſs of vegetation,
we cannot be certain of the conſtituent principles
of that ſubſtance; it is in favour of our opinion
that almoſt all the vegetable acids are converte
able into the acid of ſugar by chemical proceſſes,

368
CHEMICAL AND
ESSAY
XVI.
Explanatory Elay.
W!
THEN I reviſed the foregoing eſſays, for
the purpoſe of preſenting them to the pub-
lic, many things occurred to me that required
explanation; for although the ſcience of chemif-
try in itſelf is natural, yet it is neceſſarily illuſtra-
ted by its followers in technical terms, and, un-
fortunately, moſt of thoſe terms are far from be-
ing either expreſſive or explanatory; for render-
ing theſe terms fomewhat more familiar, and at
the ſame time to impreſs them more deeply upon
the memory of the mere beginner, I have com-
poſed the preſent ſhort eſſay.
ALKALI is a term uſed by chemiſts for three
ſubſtances which have the power of deſtroying
the ſenſible properties of acids: the etymology
does not give us any idea of their nature; and I
cannot at preſent tell whence I got the following
ideas of them, but I think them well worth com-
municating.
It is ſaid, by fome ancient hiſtorian, that a
number of failors were once caſt away upon a
fea coaſt where a peculiar plant, which bore the
name of kali, grew very plentifully; having oc-
cafion for a fire, they collected the dried plants
of a former year, and kindled a fire with them up-
on the ſand, by means of the flint and ſteel. We
are told that the failors were greatly ſurpriſed,
when their fire had burnt down, to find that the
fand next the fire aſſumed the appearance of ice,
or, in other words, that it was converted into
glaſs. When they divulged this fact, a great
many trials were made to effect the ſame change

ÉCONOMICAL ESSA Ý s. 169
upo'n fand by fire, but in vain ; but the experi-
mentaliſts having found the exact kind of plant
that was uſed by the ſailors, they ſubſtituted it
for a common fire, and with fuccefs; and it is
aſſerted, that this accident gave riſe to the im-
portant diſcovery of glaſs, which even derives its
name from the Latin word glacies, ice, becauſe
of its reſemblance to ice. After manufactories
of glaſs were eſtabliſhed, this weed was eſteemed
a specific, or a primary eſſential, in the proceſs;
but in a very ſhort time the aſhes were found to
contain all the virtues of the plant, and were
therefore always afterwards made, becauſe they
took
up
but little room.
Theſe aſhes foon be-
came an article of commerce, and it is ſaid were
firſt fold by the Arabians by the name of the plant
itſelf, kali, or with the particle the, which in
their language is al, making the compound word
al-kali; kali, if I miſtake not, is alſo derived
from the Arabic, and ſignifies glaſs weed, and it
is even now to be found in ſome of the old wri.
ters under the name of glaſs work. Theſe aſhes
are ſtill fold by the different names of barilla,
ſoda, and kelp, they are, however, not the pure
alkali, which we have referred to in theſe eſſays,
and the method of extracting this alkali from
them was reſerved for a much later period of
chemiſtry, which is done by making a ſtrong ley
of it, and boiling it down to perfect dryneſs.
The falt obtained in this way paſſed by the name
of ſal alkali, or falt of alkali, among the chemifts ;
but later chemiſts have either called it ſimply al-
kali, or they have named it from the fubſtance
from which it was obtained, as falt of barille,
ſalt of foda, or ſalt oj kelp.
Z

170
CHEMICAL AND
In the eaſtern countries a falt was found
chryſtallized on the ſurface of the earth, exactly
correſponding in properties with the falt obtained
from the aſhes of the kali, and if we call the last
falt an alkali, certainly the firſt determines itfulf
a mineral alkali. In time the aſhes of other ve-
getables were tried in order to extract the ſame
kind of falt from them, and in this trialthey were
fucceſsful, but the proportion was much leis than
that yielded by the marine plants. Chemiſtry
alſo teaches us that there is a chemical, though
not a ſenſible difference between the alkali ob-
tained from vegetables growing upon a ſea fhore,
and that obtained from all others, but that the
native mineral alkali was exactly like the alkali
from fea weeds, and moreover it was found that
the ſea ſalt contained a great quantity of it;
hence we may either call this ſpecies of alkali the
mineral alkali, becauſe it is ſometimes found na-
tive in the earth, whilſt the other is not, or the
marine alkali, as ſome have choſen to do, becauſe
it makes ſo great a part of the marine or ſea falt.
The alkali obtained from all other vegetables
is alſo exactly alike, and although the other is
obtained from vegetables, yet this has exclu-
ſively the name of vegetable alkali, and though
not ſtrictly proper, yet is allowable for the fake
of diſtinction.
VOLATILE OR ANIMAL ALKALI, has moſt of
the properties of the two others, eſpecially in its
effects upon acids, and its volatility very juftly
chara&terizes it.
ACIDS. The method of diftinguiſhing them
from other fubftances has been laid down in the

ECONOMICAL
171
ESSAY S.
effay on the colouring mat er of vegetables, and
we have ſhewn how four of them might be diſtin-
guiſhed from each other under the analyſis of
falts.
ACID OF VITRIOL. In many parts of the
world there are certain earths which have an
inky taſte, and the matter which affords this taſte
is capable of diffolving in water; if this water is
evaporated, until a thin cruſt appears on its ſur-
face, and then left to cool gradually, it yields
green chryſtals, very much reſembling glaſs.
This reſemblance to glaſs caught the attention of
fome of the ancient chemiſts who thought it a
Soluble gloſs, and we have reaſon to think that its
firſt name was vitrum, the Latin term for glaſs.
When chemiſtry made greater improvements,
every thing almoſt was ſubmitted to the action of
heat, to be diſtilled, and this ſubſtance among
others: it was found that a thick oily fluid came
over, and from this reſemblance to oil in its
thickneſs and feel only, though not in any thing
elſe, it was called vitrideum, or oil of glaſs; by
ſome ſtrange corruption of terms the chryſtals
Which yielded this fluid were called vitriolium,
and in Engliſh vitriol, a name which they bear to
the preſent day, and the fluid which they yielded
in diſtillation got the improper name of oil of vi-
triol, a name ftill very inuch retained; but the
more modern chemiſts percieving that it was an
acid, and not combuſtible as all oils are, they
rejected the term oil of vitriol, and call it the acid
of vitriol, or vitriolic acid, which implies nothing
more than that it is the acid which exiſts in the
falt called vitriol.
ACID OF NITRE.
This acid is actually one

172
CHEMICAL AND
of the conſtituent principles of ſalt-petre, as we
have fhewn in the eſſay on the attractions. Salt-
petre has got the name of nitre, becauſe when
thrown on burning coals nitet, it ſhines, by in-
creaſing the rapidity of the combuſtion of the
coals. The chemical term is acid of nitre; but,
becauſe it is obtained by diſtillation, it is alſo
called ſpirit of nitre, and becauſe it ſeems to have
great power in diffolving metals, it has been
called aqua fortis, or ſtrong water ; but it is the
{ame acid, under all theſe different names.
MARINE ACID is one of the conſtituent
principles of that falt, which exiſts ſo plentifully
in ſea water, and thence called excluſively fea
falt; it is known among apothecaries by the
name of ſpirit of ſea falt, and acid of ſea ſalt,
which laſt perhaps is a more proper name for it,
It is almoſt impoſſible to tell what other terms
will require explanation, for perhaps every dif-
ferent reader (I mean only thoſe who are quite
unacquainted previouſly with the ſcience) will
Itumble at a different term; when ſuch terms oc-
cur, it will be moſt adviſeable to conſult fome
dictionary of the ſciences.
bir

FERMENTATION.
T
HERE are perhaps few proceſſes, or phe-
nomena, that fall under the obſervation
of chemical enquirers, that are ſo little under-
ſtood as the ſubject of the preſent eſſay. This
want of certainty, we ſhould ſuſpect, aroſe more
from the difficulty, than from the want of oppor-
tunities, for inveſtigating the ſubject, becauſe the
materials for experiments are not only in every
one's power to obtain, but the proceſs is almoſt
daily obtruding itſelf upon us. The chief ob-
ſtacle to our advancement, in the knowledge of
the cauſes and effects of fermentation, is that we
reſt ſatisfied with explanations handed to us by
others. The fubject appears to be of much im-
portance, both as a curious chemical proceſs,
and as it reſpects the economical arts, and the
art of medicine.
6. There are many difficulties attending the in-
veſtigation, as every chemiſt muſt confeſs, and I
may perhaps aſſign the ſame reaſon for thoſe dif-
ficulties that Mr. Henry of Mancheſter did, when
treating of the ſame ſubject, that “ the obfcurity
and intricacy of the path, on which I an enter-

174
A P P E N D I X.
ing, the almoſt total want of guides and my in.
edequate abilities to clear away the obſtacles,
throw light on the dark parts, and point out thoſe
which may be traverſed with eaſe and certainty,
place me in a ſituation truly difficult.” Theſe rea-
fons being applicable to me, in all their force, I
hope for candour and liberality, whenever I may
be found to ſtep aſide, from the common and re-
ceived opinions of chemiſts, reſpecting fermen-
tation. Some new opinions will be found in this
diſſertation, but as the ſubject will admit of elu-
cidation from experiment, and as it would be
wrong to admit any thing as a fact, without hav-
ing afcertained it to be fo, I have introduced
fome experiments to prove acknowledged facts,
In handling this ſubject, I ſhall arrange it un-
der different ſections.
Section I. I ſhall conſider the definition of fer-
mentation, the Subſtances capable of it---
and its Phenomena.
II. I ſhall attempt an explanation of the Phe-
nomena attending the fermentation of vege-
table ſubſtances.
III. I ſhall mention the products of fermenta-
tion.
IV. I ſhall diftinguiſh between a mere eſcape
of air and a true fermentation.
V. I ſhall mention the principal Zymics and
Antizymics. And,
VI. I ſhall deliver fome analyſis of animal
matter; the difference between animal and
vegetable fermentation,

A PP E N D I X.
175
S E C Τ Ι Ο Ν
I.
F
Definition of fermentation---Subſtances capable of is.
ERMENTATION is a peculiar proceſs,
which certain parts of dead animal and ve.
getable ſubſtances are diſpoſed to undergo, when
combined with moisture, expoſed to a degree of
heat between 50° and 120° of Fahrenheit's ther-
mometer, and in contact with air fit for combul.
tion and animal reſpiration. The phenomena at-
tending the proceſs are,
1. The fermenting maſs becomes confiderably
warmer than the atmoſphere around it.
2. It emits a large quantity of a fluid, perma-
nently elaſtic, accompanied with an inteftine mo-
tion, and,
3. There is always a remarkable change in the
senſible and chemical qualities of all bodies that
have actually fermented.
I have here confined the definition to animal
and vegetable ſubſtances, but there is great rea-
ſon to believe, that ſeveral mineral mixtures will
undergo ſpontaneous changes, perfectly anala-
gous to fermentation; the gradual decompoſition
of the natural pyrites, and the changes which
take place in an artificial mixture of the four of
fulphur and iron filings, ſeem to depend upon the
ſame cauſes, and are really attended with the
ſame phenomena; I have alſo taken dead animal
and vegetable ſubſtances only into my definition;
this may not perhaps be quite accurate; it is pro-
bable that animals, while alive and in health,
have certain parts in them that are conſtantly pu.

375
Α Ρ Ρ Ε Ν DI X.
trifying or fermenting, and it is poſſible that the
fame thing happens in plants, but it is probable
that the living machunes have a power of ex-
pelling their putrid parts, as being incompatible
with their health ; beſides, we find in particular
diſeaſes, eſpecially in the order of Exanthemata,
that a ſmall quantity of a diſeaſed fluid has a pow-
er of aſſimilating a conſiderable part of the fluids
of another animal; as for inſtance, in the ſmall-
pox, in which Dockor Cullen allows that a fer-
mentation goes on in the body; for, ſpeaking of
the quantity of variolous matter, abforbed by
common infection, he fays, “ although it were
larger than that thrown in by innoculation, it is
not aſcertained that the circumſtance of quantity
would have any effect. A certain quantity of
ferment is neceſſary to excite fermentation in a
given maſs, but that quantity given, the fer-
mentation and aſſimilation are extended to the
whole maſs." But this kind of fermentation,
which occurs in the living animal body, cannot
be examined here, for it is fo connected with life,
(a principle which we do not well underſtand)
that we can by no means imitate it in the dead
body; it is probable that the contagious matter
acts upon the animal as an animated machine, as
well as matter, and that this action inodifies its
effects; it is alſo a ſubject of great curioſity both
to the Phyſiologiſt and to the Chemiſt, that the
blood of a patient, labouring under the ſmall-
pox, cannot communicate the diſeaſe to another
by inoculation, and it muſt certainly be very dif-
ficult to a Chemiſ to conceive, why after the flu-
ids of an animal have been once fermented by the
variolous matter, that the fluids of the fame ani-

A P P E N D I X.
177
mal ſhall never take on that fermentation again,
although they muſt have been changed twenty
times or more in the courſe of life.
MOISTURE ſeems to be an indiſpenſible requi-
ſite in the proceſs of fermentation; the moſt pu-
trefcent and fermentable ſubſtances we are ac-
quainted with remain unchanged as long as they
are kept dry; ſugar is perhaps the only part in
all vegetables capable of fermenting, and it is
notorious that it may be kept for many years,
and perhaps for ages unchanged: the practice of
the Indians in merely drying their veniſon, in or-
der to preſerve it, proves likewiſe that the ſame
thing is true reſpecting animal ſubſtances.
HEAT accumulated in a ſenſible ftate, to a
certain degree, ſeems alſo indiſpenſible to fer-
mentation, and a leſs degree than the loweſt we
have aſſigned abſolutely prevents it. A quantity
of ſugar and water which would have completely
fermented in 24 hours, in an heat of goº was
kept unfermented from November laſt, until the
middle of February, although the thermometer
for many days together, in that time ſtood be-
tween 50° and 60°.
The preſence of pure air, fit for ſupporting
animal life and reſpiration, is ſo eſſential to fer-
mentation, that without it, it cannot be excited ;
this opinion is generally admitted by chemiſts,
and perhaps may be founded upon the experi-
ments made by the air-pump. Natural philofo-
phy teaches us that certain fruits can be preſerve
ed in a vacuum for a long time, without becom-
ing acid; but here there is an entire abſtraction
Aa

178
APPENDIX.
of air: however, we find that the preſence of
air, unleſs that air be pure, is not fufficient to
excite fermentation. I believe ſeveral experi-
ments have been made by others upon the ſame
fubject, but it may not be improper to relate
two made by myſelf.
Experiment Firft.
Part of a mixture of ſugar and water, which
was very fermentable, was confined in a jar of
inflammable air, obtained from iron-filings and
diluted vitriolic acid, and ſet fo near a ſtove as
to vary between 80° and 90° of Fahrenheit, for
thirteen or fourteen hours of the twenty-four, the
other part was ſet along ſide of it; in this open
vefſel fermentation went on as ufual: in ore
week's time it had become highly acid ; in the
jar fermentation had not gone on, but the fluid
was perfe&tly ſweet and unchanged.
Experiment Second.
The ſecond experiment was with aniinal fub-
ſtances; I confined a dead wild pigeon in a glaſs
jar of inflammable air, in the ſame manner as in
the other experiment; another was left in a large
bowl, with ſome water in it, and expoſed to the
heat and air in the room: in about ten days the
animal thus expoſed was ſo offenſive to the ſmell,
that I diſcontinued the experiments; at the ſame
time the animal in the jar was ſcarce tainted in
the leaſt, it was liowever ſomewhat putrid, and
had a greeniſh appearance; but I think thoſe ef-
fects may be fairly attributed to the fmall quan-
tity of common air confined in the cavity of the
pigeon's body, which at that time I did know how
to extricate from it.

Α Ρ Ρ Ε Ν Ο Ι Χ. .
179
We are neceſſarily inclined to enquire what is
the nature of the fermentable materials which
characteriſe bodies ? and whether there is any
one ſimple principle in them that is the cauſe of
that change being effected in certain bodies ? we
fee but one character in common with them all.
they are all inflammable, but the cauſe of their in-
flammability cannot be the cauſe of their fermen-
tation, for all inflammable bodies are not fer-
mentable. In vegetables we believe that none of
them are fermentable, unleſs they contain the
ſaccharine principle, and I think it can be de-
monſtrated, that the products of all vegetable
fermentation aie the ſame. What is the fer-
mentable principle in animal ſubſtances, or what
parts are more fufceptible of this change than
the others, is yet involved in great obſcurity,
but I ſhall attempt to throw forne light upon it in
ſection fixth ; at preſent I ſhall only in general re-
mark, that the moſt inflammable and ſoluble ani-
mal ſubſtances are the eaſieſt to ferment, or to
putrify, as we ſay, when the term is to be applied
to animals.

180
Α Ρ Ρ Ε Ν Ο Υ Σ ..
SECTION II.
HA
Explanation of the Phenomena attending the fermen-
tation of Vegetable Subſtances.
TEAT, or a degree of it greater than that of
the atmoſphere, around the fermenting
maſs, is an uniform circumſtance attendin fer-
mentation; the increaſe of temperature, in my
experiments however, has ſeldom been more
than 10 or 12 degrees. When we reflect that
all putreſcent and fermentable ſubſtances are in-
flammable, and during fermentation generate
heat, we are immediately ſtruck with its analo-
gy to combuſtion ; here let us enquire, whether
the opinion of natural philoſophers refpe&ting
heat is well founded. They ſuppoſe that all
heat depends upon motion, and that the heat
produced in combuſtion and fermentation is ow-
ing to the ſudden deſtruction of the attraction of
coheſion of the particles of the body burnt or fer-
mented.
In the firſt place, I think we have no evidence
that heat and motion are the ſame thing.
2d. Although neither heat, nor even cold, nor
any thing elſe, can be produced without motion,
yet all motion will not produce heat: for in-
ſtance, mercury may be agitated in a phial for
ſeveral hours, without producing an increaſe of
one degree of heat, and the ſea itſelf, although
inoſt violently agitated, is ſtill cold.
3d. The quantity of heat generated by mo-
tion, is never in proportion to the rapidity of the
deſtruction of the attraction of coheſion, as we
ſee when ſalts are diſſolved in water; (for folu-

A P P E N D I X.
181
tion is faid to be owing to the ſame cauſe;) for
example, nitre, when finely powdered, diſſolves
very rapidly, and muſt of conſequence be at-
tended with great motion, but we are ſo far from
generating heat, that the mixture becomes cold-
er than the air, as we find by its finking the mer-
cury in the thermometer.
4th. Sugar diſſolves very rapidly in water,
but without producing any heat, although at the
inſtant of ſolution there muſt have been both mo-
tion, and the deſtruction of the attraction of co-
heſion If the mixture is ſuffered to ſtand, it
will ferment and generate heat, even when there
is no attraction of coheſion to overcome, that we
can be ſenſible of.
The heat occurring in fermentation muſt, I
think, be explained upon the theory of Doctor
Black, reſpecting latent heat: it ſeems proba-
ble, that beat is a body, or fluid, ſui generis, in-
herent in all matter, and eſſential to its exiſtence;
that it enters into different bodies, in different
proportions, as an ingredient in their compofi-
tions, in the ſame manner as electricity is fup-
poſed to exiſt in iron in contact with the earth;
whilft a certain quantity of heat is attached to all
bodies, and if I may be allowed the expreſſion,
mechanically mixed with them, in contradiſtinction
to the other mode of union of heat with bodies,
which is then chemically combined with them, or
is in a latent ſtate. When the heat is in this ſtate,
it is called ſenſible heat; becauſe it is capable of
exciting a certain ſenſation, and of raiſing the
mercury in the thermometer. It is alſo govern-
able by certain laws, by this time pretty well aſ-
certained.

182
A P P E N D I X.
When heat enters into bodies as a principle,
it is moſt probably in different quantities in of
ferent bodies, and it is very remarkable, that a
change in the common chemical qualities of bo-
dies alters very much the capacity of bodies to
contain heat as a principle, or in a latent ſtate ;
hence it happens, that in almoſt all our chemical
proceſſes, an alteration of temperature takes
place. In fermentation, we ſuppoſe that the in-
flammable part or principle of the fermenting bo-
dy, has a tendency to combine with pure air, and
I ſhall juſt remark in this place, that the com-
buſtibility of all bodies, is by ſome chemiſts fup-
poſed to be owing to one homogeneous princi-
ple called the principle of inflammability or phlo-
gifton; this theory has had very powerful oppo-
nents, but I think we have reaſon to believe, that
with certain modifications, it is true; and it is
moſt probable that this principle is inflammable
air. It is alſo known, from direct experiments,
particularly of Dr. Prieſtly and Mr. Kirwan, that
pure air and inflammable air form what Doctor
Black calls fixed air, and Mr. Bergman the aerial
acid, which is preciſely the ſame elaſtic fluid
thrown out in fermentation. The pure air we
may juſtly ſuppoſe was derived from that great
ſource the atmoſphere, and for ſeveral reaſons
we may conclude, that the inflammable air was
furniſhed by the fermenting vegetable, but we
by no means ſuppoſe that the fixed air was for-
mally preſent in the fermenting maſs, or that
it afforded all the materials to form it; now let
us ſuppoſe that the quantity of heat in the two
airs before combination, was in each as ten, or
in other words, that they were capable of con-
taining that quantity in a latent fate, eſſential to

A P P E N D I X.
183
their exiſtence as matter in that form: when
they unite, they form a very different kind of
air, which is not capable of combining with fo
much heat, and perhaps quite foreign to its ex-
iſtence as that kind of matter; we will fuppoſe
then that it can combine with but a quantity of
that heat as five, the conſequence then muſt be
that there is a quantity of redundant heat as fif
teen, and there being no bodies at hand undergo-
ing any changes in their properties, by which
their capacity to unite with heat as a principle,
is increaſed, it becomes mechanically diffuſed a-
mong thoſe bodies which are neareſt to it, it
gives the redundant heat to the feeling hand, to
the atmoſphere, to the thermometer and to the
fermenting fluid, by that law of ſenſible heat
which proves that it is equally diffuſed through
all bodies; and as the cauſe of heat continues to
act, fo the effect muſt continue to enſue until the
fermentation is completed. With the escape of
the elaſtic fluid there is an hilling noiſe, and of
conſequence an inteſtine motion; theſe phenomena
have had more attention paid to them than they
deſerve, and they have been ſuppoſed to be the
moft infallible ſigns that this proceſs is going on;
theſe we know are called the working of liquors,
but they are very fallacious, and have been the
ſource of much error, as I apprehend, and I be-
lieve, that even the great fir John Pringle, truſt-
ing to ſuch appearances, has fupponed that putri-
faction had taken place in experiments, where
there really was no putrifaction, but I am ſtill
more firm in the belief, that he was in fome in-
ſtances wrong in attempting to determine the de-
gree of putrifaction from the degree of theſe ap-
pearances; we ſhall illuſtrate theie remarks in

184
APPENDIX.
the fourth ſection. An alteration of the fenfible
qualities of the fermented body is a more certain
and univerſal circumſtance than any other, there-
fore I think I am ſafe in aſſerting that we can
have no certainty of fermentation having taken
place in any cafe without it, for when an animal
fubftance putrifies it is changed from an inodor-
ous body to one that is very rank and fetid, and
fugar when fermented, is capable of yielding a
highly intoxicating fpirit, and if fermented long-
er becomes highly acid, as we know from the
formation of vinegar, which we ſuppoſe is QW--
ing to the loſs of its phlogiſton.

A PP E N D I X.
185
SECTION III.
A
Produits of Fermentation.
FTER all the phenomena above mentioned
have continued for ſome time, which is
longer or ſhorter, according as the exciting
cautes of the proceſs have been more or leſs ap-
plied, the fermentation becomes for a while fta-
tionary, and the vegetable fluid receives different
names according to the nature of the vegetable
itſelf: the fermented juices of grapes are called
wines, and the juices of almoſt all fruits which
are ſweet when ripe, are capable of affording
analagous liquors when fermented, ſuch as the
juices of currants, apples, peaches, pears, &c. cer-
tain grains may alſo be fermented by ſimilar pro-
ceſſes, as barley, wheat, rye, and ſome others :
all theſe when firſt fermented, and then diſtilled,
yield ardent. fpirit, which by repeated diſtilla-
tions will afford alcohol.
Brandy is the ardent
ſpirit obtained by diſtilling the fermented juice
of the grape, whilft rum or ſpirit, are the liquors
diſtilled from molaffes and water; beer is the
fermented extract of barley, to which is added
a decoction of hops, which as a bitter is an an-
tizymic, and prevents it from haſtening on to
the acid ſtage of fermentation.
There is a conſiderable variety in wines whichi
does not depend ſo much upon any difference in
them as fermented liquors, but in noft cales,
upon fome addition not eſſential to them as
wines, for inſtance, fome have a peculiar flavor
which cannot be analized, and may be but in
very {mall quantities in thein, for who can ana-
Bb

186
A P P E N D I X.
lize the flavor of the peach others differ only
in being weaker, that is, in having a larger quan-
tity of water; others again have the aſtringent
acid combined with them, hence are called
rough wines; fome from being weak foon be-
come four, before a due degree of fermentation
has taken place in the whole maſs, and as for the
difference in colour, it is ſometimes owing to
cauſes which neither influence the qualities of
the wine, nor the fermentation it underwent,
but the moſt material difference in the qualities
of rich wines, ſuch I mean as have a proper quan-
tity of water, is their age; this excellence ſeems
eſpecially to be owing to the more perfect fer-
mentation and aſſimilation of the different parts
of the wine, for then the unfermented faccha-
rine part becomes perfectly vinous, whilſt the
vinous part already generated is ſo ſtrongly an-
tizymic as not to ſuffer any part to become acid.
Wines ſomewhat diluted and expoſed to the
neceſſary conditions of fermentation go on to the
Second ſtage, which is called the acetous or acid
fermentation, and the chief difference between
this and the vinous is, that all the phenomena
are in a leſs degree: the reſult of this fermenta-
tion is vinegar; the explanation of ſome of the
varieties of vinegar, may be underſtood from
what we have faid above.

Α Ρ Ρ Ε Ν D Y Xe
187
S E C ΤΙ Ο Ν
IV.
F.
Diſlinčtion between a mere Eſcape of Air, and a
true Fermentation.
ERMENTATION is ſuppoſed to take place
in another proceſs, I mean in making bread,
but I think we ought to be very cautious in ad-
mitting that a true fermentation takes place, or
is even neceſſary in its preparation: I ſhall per-
haps, in the courſe of this ſection, uſe the com-
mon language, but when the word fermentation
is applied to the making of bread, I wiſh it would
be underſtood to expreſs nothing more than the
effect produced on flour by yeaſt or leaven.
Of the origin of fermented bread we have no
certain account: I cannot however omit relating
the very elegant conjecture reſpecting it, given
us by our late chemical profeſſor. He ſuppoſes
that ſome careful houſewife had mixed the un-
baked ſcraps of a former mixture with ſome
freſh dough, and he imagines her ſurpriſe at
finding the bread improved by this proceſs of
economy; what gives greater plauſibility to the
conjecture is, that it is certain that leaven was
the firſt ferment uſed for raiſing bread; but ſince
later experiments have taught us that ſeveral
fubſtances in the act of fermentation will raiſe
bread, leaven has gone out of uſe, and yeaſt,
where it can be had, has almoſt univerſally fup-
plied its place. The common idea of a ferment
is, that it is capable of aſſimilating ſubſtances to
its own nature : this is cutting the knot, for we
fee no reaſon why particular ſubſtances ſhould
have ſuch power, whilſt others have not, and in
fact it explains nothing. In many ſuppoſed caſes

788
Α Ρ Ρ Ε Ν Ο Ι Χ.
o
any true
of affimilation, we ſee ſources of fallacy and er-
ror, in others we muſt ftill affent to the common
opinion. In the making of bread, we deny the
idea of any ſuch aſlimilation, or even of
fermentation ; * but let us attend to the proceſs
itſelf, and the phenomena attending it. A quan-
tity of flour is mixed with a certain proportion
of yeaſt and water, and made of the confiftence
of dough ; it is then baked in a manner too ſim-
ple to be deſcribed, and in one hour from the be-
ginning to the end of the proceſs, the bread is
made, and is perfectly good. We are juſtly ſur-
priſed at the ſhort time required to ferment the
bread, eſpecially when we conſider that ſugar
and water, the moſt fermentable mixture known,
requires twenty four hours before fermentation
proceeds to any great degree in it; this reflec-
tion firſt fuggested the idea that the fermentation
of bread is not analagous to the fermentation of
fugar and water, in conſequence of which the
following experiments were made in December,
1788, in the preſence of A. J. De Roſſet, and
two other gentlemen at that time ſtudents of me-
dicine.
* This opinion, ſupported by experiments, was communicated to ſeveral
gentlemen, and eſpecially to DOC OR Rush, ſo early as January 1789.
When I fubmitted this diſſertation to the Doctor for his approbation as a
profeſſor of the college, he was pleaſed to interline a compliment upon this
diſcovery. He did me the honour to declare, that he readily adopted it,
es and afterwards publicly taught it, with acknowledgments to the author,
"s in his Lectures on the application of Philoſophy, Chemiflry, Medicine and Economy
6 to domeſtic and culinary purpoſes.”
T have made no acknowledgments for the idea to any body, but claim it
as original, although the ſame ſentiments were afterwards publiſhed in this
city. The diſcovery may perhaps be but of liitie importance, I have, how-
ever, inſerted this note to obviate any charges of plagiariſm that might be
offered againſt nie

A PP E N D I X.
189
t
Experiment Firſt.
Part of a quantity of dough which had been
Taiſed in three quarters of an hour, was put in-
a retort, and the proceſs of diſtillation per-
formed upon it; ſome liquid came over into the
recipient, which was not inflammable, and as
taiteleſs as pure water. It is allowed by all che-
miſts that vegetables, in the firſt ſtage of fermen-
tation, yield a vinous fpirit in diſtillation; here
then we muſt conclude, either that the dough had
not fermented, or that fermented wheat flour
will not yield a vinous fpirit, but the practice of
this country proves that wheat will ferment, and
yield a vinos Spirit, when diſtilled, therefore I
conclude that the dough had not fermented.
Experiment Second.
The other parcel of the ſame dough was bak-
ed, and yielded a perfectly fermented bread.
Experiment Third.
The ſame dough remaining in the retort uſed
in Exp 1. was rendered inore fluid by the ad-
dition of a little water, and kept in a warm
room ; in nine hours there were no appearances
of fermentation ; in fixteen hours an eſcape of
air, a hiſſling noiſe, &c. feemed to indicate that
the proceſs had proceeded fome time : it was
now diſtilled again, and yielded a little acid
fluid, and a ſmall quantity of a weak vinous Spi-
rit.
Does it not ſeem true, therefore, from theſe
experiments, that flour requires even more than
nine hours before it ferments, and if bread can

190
A P P E N D I X. N
be made in one hour, it amounts almoſt to a de.
monſtration, that the fermentation of bread is
not analagous to the vinous fermentation, or
even the fermentation of flour.
From a variety of facts, I am induced to give
the following explanation of the proceſs : Yeaft
is a huid containing a large quantity of fixed air,
or aerial acid, and the proportion is greater in
proportion as the fluid is colder: as ſoon as the
yeast is mixed with the dough, heat is applied ;
this extricates the air in an elaſtic ſtate, and as
it is now diffuſed through every particle of
dough, every particle muſt be raiſed; the vif-
cidity of the ma's retains it : it is now baked,
and a ſtill greater quantity of air is extricated
by the increaſed heat, and as the cruſt forms,
the air is prevented from eſcaping ; the water is
diſlipated ; the loaf is rendered ſomewhat dry
and folid, and between every particle of bread
we find a particle of air, as appears from the
Spongy appearance of the bread, owing to the
apparent vacancies which the air had made, by
inſinuating itſelf into it.
But let us attend to another fact, which thoſe
who ſupport the doctrine of fermentation will
find a great difficulty in explaining: if the
dough be kept longer than the proper time,
without baking, it falls again as it is termed, or
as I would expreſs it, all the fixed air which
raiſed it is diffipated, and then being baked we
get heavy bread, exactly like the bread made
with flour and water, and haſtily baked, which
we know is taſteleſs. Some will perhaps ſay the
fermentation is over, but this cannot be admit-

A P P E N D I X.
197
ted; for after the vinous comes the acetous fer-
mentation, but in this inſtance we have no ſigns
of acidity, neither can we fuppoſe that any ſub-
ſtance is fo fermentable as to finiſh the vinous
ſtage of fermentation in nine hours, for we
found that the ſame materials in more favour-
able circumſtances, required ſixteen hours before
the proceſs began; fonietimes, however, we do
find heavy bread that is acid, but in ſuch cales I
conclude that the acid came from the yeait,
which had proceeded to that ſtage.
Another fact I would wiſh to be attended to
is, that fermentation alters the eſſential proper-
ties of bodies, as we have ſhewn in Se&. 2d.
and 3d. but bread is not chemically nor effenti-
ally different from flour, for we can actually ſe-
parate the different conſtituent principles of
flour from bread, beſides, bread itſelf infuſed in
water, and expoſed to the neceſſary cauſes of
fermentation, will actually ferment, and no
doubt yield a vinous fpirit in diſtillation.
If we might be allowed to reaſon from fir Iſaac
Newton's axiom, “ that no more cauſes of na-
" tural phenomena are to be admitted than are
* fufficient to explain them,” we can produce
three facts that will prove clearly, that fermen-
tation is not neceſſary to make bread; from which
I infer, that it does not take place. The bakers
in this city find much difficulty in getting good
yeaſt in fummer, for fermentation goes on fo
rapidly in the warm weather, that it grows four
in a ſhort time; they can, however, make it
anſwer their purpoſe. They diffolve a ſmall
quantity of pot-aſh in as much water as is necef

192
A P P E N D I X.
ſary to make their bread; this they mix with
their yeaſt and four: in leſs than ten minutes
their bread is fit to bake, and has every proper-
ty of what is called the beſt fermented bread.
We need fcarcely explain this fact; every per-
fon moderately acquainted with the fubject,
knows that pot-aſh is an alkali united to much
fixed air, and we think the acid in the yeaft ſets
it at liberty, which is the cauſe of the raiſing of
the bread, as before explained.
A fecond fact that I ſhall mention, was given
us by our late chemical profeſſor Doctor Ruſh,
in the courſe of lectures which he delivered in
the winter of 1788-9; he informs us, that near
Saratoga, there are two mineral ſprings, the
waters of which have all the properties of the
famous Pyrmont water, in other words they are
highly impregnated with fixed air. This water
when mixed with flour into dough, is ſufficient
without yeaſt, to make a very light and pala-
table bread.
A third fact appears deciſive; we know that a
little falt is added to the bread by our bakers;
this ſuggeſted the idea of ſupplying it in the fol-
lowing manner, which I confeſs is rather fanci-
ful: I procured ſome nice chryſtals of the falt
formed by the foſſil alkali and fixed air, and
diffolved them in water fufficient to make a ſmall
loaf of bread, to this I added a little of the ma-
rine acid commonly called ſpirit of fea-falt; fix-
ed air was generated, but was abſorbed by the
cold water; it was then mixed with flour, fet in
a warm place to riſe, and ſhortly after baked ;
and I had the exquiſite pleaſure to obtain a toler-

A P P E N D I X.
193
ably light loaf of bread, fuch as any one would
have ſuppoſed to have been fermented, which
was ſeaſoned by the ſea-falt, formed by the uni-
on of the fofiil and the ſpirit of fea-falt; whilſt
the fixed air of the foffil alkali was diſengaged
in order to raiſe it.

194
A P P E N D I X.
S E C Τ Ι Ο Ν
V.
Zymics and Antizymics.
HIS is by far the moſt difficult part of the
fubject ; that many ſubſtances have the
power of exciting fermentation and others of re-
tarding it, cannot be denied ; but I am far from
believing that chemiſts are quite correct upon
this ſubject; whilſt the one phenomenon, the
eſcape of air, is fo much attended to as the diſtin-
guiſhing character of fermentation, we can ne-
ver be accurate ; thus I ſuſpect that when a ſmall
quantity of an alkaline ſalt is ſaid to be an anti-zy-
mic, with reſpect to milk, it abforbs the acid that
is generated in the fermentation, ſo that it can-
not be taſted, and hence preſerves the milk
fweet; chalk on the other hand is ſaid to be zy-
mic, and to accelerate the vinous fermentation ;
but is it not probable that in ſuch caſes a ſmall
quantity of acid is generated in the vinous li-
quor, which unites to the chalk, ſets the fixed
air at liberty, and it then eſcapes by mere effer-
veſcence ?
Subſtances that have fermented, yield a mat-
ter that is ſuppoſed to poffeſs the properties of
exciting fermentation in other bodies; for in-
ſtance yeaſt, and ſuch ſubſtances as are faid to
poffefs a power of aſſimilation ; but we cannot ac-
count for the operation of the yeaſt in theſe
caſes, for we by no means know why they tend
to diſſipate the phlogiſton of ſuch ſubſtances,
neither do we ſee any fimilarity in the chemical
compoſition of different zymics and antizymics;
that yeaſt excites the vinous fermentation in li-
quors I muſt not deny. I cannot, however, omit

A P P E N D I X.
195
relating a ſolitary experiment; I took a quantity
of ſugar and water, and divided it into two
equal parts, I put them into two veſſels of the
fame ſize and ſhape, and expoſed them to the
ſame temperature of heat ; to‘one I added yeaſt,
to the other none; after ſome time they had both
become conſiderably acid ; they were then both
faturated with an alkali, and the quantity re-
quired for that purpoſe was almoſt exactly alike
in each. Here then it would ſeem that the
yeaſt was entirely paſſive. I can make no re-
marks
upon this experiment; I leave it to be
confirmed or rejected as future fa&s ſhall dictate.
Mr. Henry of Mancheſter, in a very elegant
memoir, preſented to their Philoſophical and
Literary Society, on the ſubject of fermentation,
afferts, that " It is a well known fact to the
brewers of malt liquor, that wort cannot be
brought into the vinous fermentation, without
the addition of a ferment.” But when we conſi-
der the analogy between beer and other vinous
fluids, and that all wines, cyder, perry, &c. fer-
ment without any addition : I think we have
great reaſon to doubt the fact. But I cannot as
yet diſprove his idea by experiment.
In the memoir above mentioned, the author
ſeems to think that fixed air is the true cauſe of
fermentation in vinous liquors, and he tells us of
the excellent taſte afforded to punch by being im-
pregnated with it. Fixed air, it is well known, ,
improves the taſte of liquors, but we cannot
fufpect that it made the punch ferment in his ex-
periment; but he tells us that he made an arti-
ficiol yeaſt by impregnating flour and water with
fixed air, that with this yeaſt he made beer (per-

396
A PP E N D I X.
haps he might have made it without it) and vi-
negar, and that he fermented bread with it: as
for its fermenting bread, we might readily al-
low that it would raiſe bread upon the principles
already laid down in Section 4. and when he
he tells us how quick the fermentation takes
place in his liquors, when expoſed to a gentle
heat, may we not juſtly ſuppoſe that the warmth
extricated the fixed air, that he had artificially
combined with it, and that from this phenome-
non alone he had ſuppoſed fermentation to be
going on in them? Fixed air, as we have already
faid, is the cauſe of the briſkneſs, pungent taſte,
and ſparkling appearance of vinous liquors; and
it is remarkable that in equal circumſtances the
colder they are the more air they contain: I
have been told as an argument againſt me in fup-
poſing that bread does not ferment becauſe it is
raiſed fo quickly; that a barrel of beer may be
kept in a vault in the ſummer, without ferment-
ing, but if it is hoiſted up into the air it will fer-
ment in two or three hours. But may I not
juſtly conclude that this apparent fermentation
was only owing to the eſcape of fixed air; but,
ſay ſome, there is alſo a change of properties;
the beer becomes fat and vapid; but this is the
natural conſequence of looſing its fixed air which
is the cauſe of its briſkneſs. It is alſo a curious
fact that the fixed air in liquors muſt be in a pe-
culiar ſtate, otherwiſe they do not poffefs that
briſkneſs or pungency we ſpoke of: in fact it
muſt be on the point of aſſuming its elaſtic form:
hence liquors are pot fo brifk in cold as in warm
weather, and a connoiffeur in porter for inſtance
will tell you, that a bottle ihall open very brills

Α Ρ Ρ Ε Ν Ο Ι Χ. .
197
in a warm day, and upon the coming on of cold
weather, all the reſt fhall be flat and dead; but
let them be corked up, and kept in a warm room
for a few days, they will all recover their briſk-
neſs, nay, I have ſeen a bottle opened in a cold
day that has been quite vapid, which was made
briſk and lively by corking it up tight again, and
ſetting it for ten or twelve minutes in a baſon of
water little more than milk-warm.

198
A P E N D I X.
S E C T I O N VI.
Some analyſis of Animal Matter, the difference ben
tween Animal and Vegetable Fermentation.
WH
HEN we conſider that almoſt, and perhaps
all animals are ultimately derived from ve-
getables, we muſt be very much ſurpriſed at the
difference that ſubſiſts between the objects of the
two kingdoms. They ſhew their difference ſur
priſingly in the ſpontaneous changes which they
undergo, when expoſed to the neceſſary condi-
tions of fermentation, for animal ſubſtances emit
a fetid diſagreeable ſmell, and the elaſtic fluid
is the vapor of volatile alkali.
If with Doctor Cullen we may believe that
only certain parts of vegetables are alimentary,
we might fuppoſe that the parts of the animal
formed of thoſe alimentary parts, would in fome
meaſure retain their nature;* his idea is, that it
is only the acid, ſ gar and oil of vegetables that
render them nutritious, and if that idea were
juit, we ought to find them in thoſe animal fluids
that are immediately formed of the food; that
an acid is preſent in the blood, at leaſt neutral-
ized by ſome faline baſe, is eaſily demonſtrated,
but it may be doubted whether it is uſeful to the
animal; and we have irrefragable proots that an
* Since the five laſt ſections were printed off, I have met with a fact, that
tends to throw much light on this ſubject, and proves hat animal and veges
table, matters are more allied to each other, than chemifts have heretofore
imagined; in vol. iv. part 2. of the laſt edition of the Encyclopedia Bris
tannica, under the article CHINA. $ 114, we find the following obſerva-
tion nother kind of wine is uſed by the Chineſe, or rather Tartars,
called lamb-wine It is very ſtrong, and has a diſagreeable imell; and the
ſame may be believed of a kind of ſpirit diſtilled from the fleſh of ſheep."
66

A P P E N D I X.
199
oil, or at leaſt the conſtituent principles of an oil
exiſt in the blood, for we obtain it by diſtilla-
tion; the taite of the urine of diabetic patients
proves the preſence of ſugar in the fyftem,
which may have either exiſted formally in the
blood, or been formed by ſecretion, and the
principles of it at leaſt muſt have been afforded
by the vegetable food. I know of no direct ex-
periments to aſcertain the preſence of ſugar in
the blood; I am in poffeffion of one, however,
that would ſeem to give plauſibility to that idea.
As Mr. Bergman had obtained the acid of Jugar
from gum arabic, and from thence concluded
that it contained ſugar; I was ſtruck with the
analogy between gum erabic and the coagulable
lymph of the blood; I treated this laſt mentioned
ſubſtance according to the manner for obtaining
acid of ſugar from fugar, gum arabic, &c. that
is, by boiling it with ſtrong nitrous acid; the
mixture when cold yielded ſome ſmall chryſtals,
which precipitated lime from a folution in lime
water in the fame manner as the acid of ſugar
does. It is true, the blood has not a faccharine
taſte, neither has gum arabic, and perhaps ſome
trifling circumſtances, as an intimate chemical
union of ſugar with an oil, may deſtroy all the
ſenſible qualities of the fugar, yet as gum arabic
yields nearly the ſame reſult in chemical proceſſes
that ſugar does, it would be wrong to aſſert that
it contains no fugar; nay, barley has no fac-
charine or ſweet taſte, yet the trifting circum-
ſtance of malting will make it remarkably ſweet,
and confeffedly faccharine; and who would say
that barley did not contain fugar, before it was
malted, merely becaufe it could not be tafted.

200
A P P E N D I X.
There have been, however, fo few experi-
ments made to determine the cauſes of the dif-
ference of animal and vegetable fermentation,
and the ſubject is in itſelf ſo truly difficult, that
I muſt candidly confeſs it is far beyond my
reach.
FINI S.



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