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      Surgeon General's Office



         NoA/.tJL/         : 
 
 
 OBSERVATIONS
              ON  THE
         DOCTRINE
                OF
     PHLOGISTON,
                AND
 7/fe  Decompofition  of Water.
              Part II.

By JOSEPH PRIESTLEY, LL. D. F. R. S. CsV. &c
      Sed revocare gradum ■
      Hk labor hoc opus eft.       Virgil.

         '': .;s/U'X<v
        PHILADELPHIA;
PRINTED BY THOMAS DOBSON, AT THE STONE-HOUSE,
       N° 4!, SOUTH SECOND-STREET.
1797. 
 
■ \
 OBSERVATIONS

                ON  THE

     DoSirine  of Pblogijlon,

                AND THE

DECOMPOSITION of  WATER*
                PART II.
       THE  INTRODUCTION.

1  TH'NK myfelf happy in having already
drawn a confiderable degree of attention to
the two oppofite theories of chemiftry by my
late publication on  the fubject, and I  am
therefore encouraged to endeavour to keep
up this attention a little longer, and, if poffi-
ble, till the queftion now  depending  be de-
cided to general fatisfa&ion.   At prefent I
am fenfible that I mall be confidered as very
obftinate,  in not admitting the new theory,
when the old  one  is almoft univerfally aban-
doned ;  though it is not true,  that I am the
                   A %             only 
4           THE DOCTRINE
only perfon who adheres to it.  Mr. Kir-
wan informs me,  that MefTrs.  Crell  Wer-
trumb, Gmelin, and Mayer, men of confi-
derable reputation in Germany, frill  main-
tain the doctrine of phlogifton.  So,  I  alfo
hear, do my friends of the Lunar Society of
Birmingham, among whom Mr.  Keir  has
given as much evidence  of his judgment in
thefe fubjects as any other perfon  whatever.
And I fee by the advertifements of  books,
that there is in  France itfelf a recent publi-
cation againft the  new theory.

  As truth  can  never fuffer, but muft  always
gain, by investigation, I  mall not offend any
rational advocate  for the antiphlogiftic the-
ory, if I endeavour to point out in what re-
fpe&s the replies  that I  have already heard
of to my late publication appear to me to be
unfatisfadtory;  and though I have given as
much attention to them as I can,  they ap-
pear to me far from unexceptionable.  But
my diftance from  the centre of philofopbical
information  lays  me under great  difadvan-
tages in this refpecl, as well as many others.
                                      All 
           OF PHLOGISTON.          5
All the anfwers to my book that I have  yet
heard of are that of Mr. Adet in  French,
the Monthly and  Analytical Reviews of it-
in England, and that of Dr. Maclean, Pro-
feflbr of Mathematics and Natural 1 hilofo-
phy in the  College of New Jerfey.  But as
all thefe writers agree,  as far as they go, to-
gether, I may prefume that other anfwera will
go  on the fame general principles ;  fo that
in replying  to them  I  may be  replying  to
others alio.  I mail not, however, think the
controverfy clofed, till I hear from Mr. Ber-
thollet and the  other  French  chemifts, to
whom my  Treatife was addreffed.

   In  matters of much nicety,  as the fubje&s
of many of my numerous experiments are,
I do not  always expert to efcape the charge
of inaccuracy, and perhaps  of inconfiftency.
Perfons who, from  a  want of experience,
are not  fufficiently aware of the difficulties,
will not have the candour that the circum-
ftanccs call for.   From fuch I  mufl appeal
to the judgment of thofe who have the re-
quisite experience and qualifications.  I will,
                                however, 
6           THE DOCTRINE
however, venture to fay, that no perfon who
has made near fo many experiments as I
have, has made fo few miftakes.   I do not
mean with refped: to opinion*, but in my re-
ports oifafts.   But after all our care, errors
will  fometimes arife from a  want of atten-
tion to fmall differences of circumftances ;
and  no perfon can  keep his  eyes open  to
every thing  that is before  him at the fame
time.
             SECTION  I.
    Of the Solution of Iron in the Vitriolic and
              Marine Acids,

 lHE moft fimple of  the experiments that
I have propofed for difcuffion, with a view
to decide concerning  the merits of the two
theories in queftion, is that of the folution
of iron in the vitriolic and marine acids.
Here the  queftion  to  be  folved  is,  from
which of the fubftances prefent comes the
inflammable air that  is  procured in  the pro-
                                     cefs. 
           OF PHLOGISTON.           7
cefs. The phlogiflians fay it comes from the
iron, and the antiphlogiftians from the wa-
ter.  But to this 1 have obje&ed that, fince,
according to their own hypothecs,  water
confifts of  about fix times as much oxygen
as it does of hydrogen, there muft be a large
depofit of oxygen in the veffel, and that I
cannot find it there.   That  it is not in the
acid appears, as the antiphlogiftians  them-
felves  fay,  by its  faturating no more alkali
after the procefs than before.   They,  there-
fore, fay,  and there is no other alternative,
that this addition of oxygen  is in the iron.

   But  I now afk, How does this appear ? If
there be any addition of oxygen in this cafe,
it muft fhew itfelf either by an addition to
the acid,  or by its  being exhibited in the
form of dephlogifticated air, called by them
oxygenous gas. The former is not pretended;
and fo far is the latter from being true, that
if the  precipitate be expofed to  a red heat,
it yields much lefs pure air than  the fame
quantity of the acid  without the iron would
have done.
                                      For 
s
THE DOCTRINE
   For this purpofe  I took as much vitriolic
ax id as I had found in the experiment reci-
ted in Vol. III. p.  i 97. of my Obfervations
on Air, (in three vols.) to have yielded 130
ounce  meafures of dephlogifticated air,  of
the ftandard of .15,  which is extremely pure,
and faturated it with iron.   But after this it
yielded  only 52  ounce  meafures  of air,  of
the ftandard of .55, which is much lefs pure.
This fbews that'this precipitate is  fo far from
containing more oxygen, that it contains lefs
than the acid.   It  is in reality poffeffed  of
the oppofite principle, which is agreeable  to
the phlogiftic theory.   For fince much more
inflammable air is  procured from  iron  by
means of  fleam only, than by its  folution  in
any acid, more of the principle of which in-
flammable air confifts,  viz. phlogifton, muft
adhere to this calx of iron than to the other.

   Dr.  Maclean fays, p. 19,  Cl There isth e
" moft fatisfaclory evidence  that  iron, after
" its folution  in  fulphuric acid is in a ftate
" like that of the black oxyd, or  finery cin-
u der."   But the dephlogifticated air which
        4                              is 
        "  OF'PHLOGISTON.          3
is yielded by this precipitate is all procured
before it comes to this form of a calx„ After
it becomes black, in which ftate it ought to
contain more oxygen in proportion to its
bulk than  before, it yields no oxygenous gas
at all.   Alfo,  neither in  this, nor in any
other ftate,  will it oxygenate muriatic acid,
which  however eafily diffolves it.  It there-
fore fhews no fign of its containing any ox-
ygen at all.   The new theory, however, re-
quires  that it be dignified  with the appella-
tion of the  black oxyd of iron.  The black
oxyd  of manganefe gives mofe evidence of
its right to the name they have given to it.

  I have  no great objection to admitting
that this precipitate from the folution  of iron
in the vitriolic acid, when it is burned black,
js the  fame  fubftance with finery  cinder.
Both in this  form,  and in that of a brown
powder,  this precipitate has feveral of the
fame properties with thofe of finery cinder.
They neither of them either gain or lofe any
weight by  expofure to  the greateft heat.
When  heated in atmofpheric air,  they both
                     b               dimir 
 **         THE  DOCTRINE
 <dimini(h and, as 1 ufually fay,  phlogifticate
 it, though  very flowly.  They alfo  equally
 imbibe  inflammable air when heated in it,
 but with this difference, that the production
 of water feemed to  be  greater in the reduc-
 tion of finery cinder than in that of this pre-
 cipitate.  But  the  experiment  being of no
 great confequence, 1 did not give much at-
 tention  to this circumftance,

   There is fbmething very extraordinary in
 the theory  of  this oxygen attaching itfelf to
 the iron on its  folution in  an  acid.   Mr.
 Adet fays, p. 6o, " Experiments prove  that
 "  metals,  in order to be combined with an
 "  acid,  require to be united with oxygen ;"
 and explaining himfelf farther, he fays, " In
 ,c  reality,  a metal not combining with acids
V but when it  js in a ftate of oxide, and not
ct  paffmg  into  this ftate but by its  union
" with oxygen,  muft neceffarily abforb ox-
'.'  ygen  in order to unite with the acid.  But
" this oxygen can only be fupplied by one
»'  of  thcfe two fubftances, the acid itfelf, or
5* the water which it contains. If the oxygen
                                   "  h^.d 
            tiF PrILOGISTOtt.-         ti
it
" had been given by the acid, it would have
" been  in  part decompofed, and  would  irf
" confequence have- faturated lefs alkali. But
" fince it faturates the fame quantity of al-
u kali, it has not been decompofed."

  On this I Would obfef ve, rhdt if the fepa-
ration of the oxygen from the  water, in or-
der to  its attaching itfelf to the iron,  take
place prior to its folution in the acid,  that
folution is not neceffary to its producing in-
flammable air ;  and this  effect would in all
cafes be produced by fome affinity between
the iron and the oxygen in the water only.
If the affinity be between the  iron and the
oxygen univerfally, what could prevent the
iron from  faturating itfelf in  the firft in-
ftance with that which  belongs to the acid,
as well as with that which was  a conftituent
part of the water, in which  it is  at leaft
much lefs evident.  I would alfo afk,  if an
acid will not diffolve  iron till it be oxyda-
ted, but will  do when it is, why will not_
the acid of vitriol diffolve the black oxyd  of
iVon,  or finery cinder, more readily than it
                  B ?,                does 
12
THE DOCTRINE
does iron ; fince in this fubftance it finds the
iron already abundantly  oxyda:ed;  and yet
the reverfe of this is the cafe.
            SECTION  I*,
             Of Finery Cinder.

 1 HE great queftion between the advocates
for phlogifton and their opponents is, whe-
ther the fubftance that has ufually been call-
ed finery cinder, which is formed by the con-
tact of fteam with iron  when  it  is red hot,
be a proper oxide of iron y that  is,  whether it
contain any principle which can be exhibited
either in the form of an acid,  or of dephlo-
gifticated  air;  and yet this,  which is the
only proper evidence in the cafe, has not
been given.  To  fay that it  forms water
when heated in inflammable air, and that
water cannot be formed without oxygen, is-
taking for granted the very  thing to  be
proved; fince the water fo procured, I fay,
is that which was  imbibed by the iron, and
                                       is 
          OF PHLOGISTON.          13
rt now expelled on the introduction of the
f>hlogifton with which it had parted.

  One of my arguments to prove that finery
cinder contains  no oxygen is, that when it
is diffolved in marine acid, it does oxygenate
it.  Let us, however,  hear the account that
my  opponents  give  of this  circumftance.
Mr. Adet fays, p. 55. " The nonoxygena-
" tion of the muriatic acid by the folution
" of finery cinder is  owing to the latter re-
" taining the oxygen  fo ftrongly,  as not to
•* be difengaged by the action of heat,  aided
" by  the attraction  of the muriatic acid."
To this I anfwer, that if the  acid had not
been able to diffolve this fubftance, this might
have been faid with fome degree of plaufibi-
lity;  but fince it does diffolve it  completely,
fo volatile a thing as oxygenous gas, of which
it is fuppofed to contain fo large a quantity,
and with which this acid has  fo  ftrong an
affinity, could hardly  efcape being  evolved.

  Dr. Maclean makes very light of this, as
indeed  he does  of every other  difficulty.
                                      M It 
 r4         THE DOCTRINE
"It certainly" he  fays, p. 10, "does nol
ct follow that becaufe  muriatic acid  can fe-
" parate a certain quantity of  oxygen from
" lead, when this is combined with a great
4C quantity of that  fubftance,  that it fhould
" likewife feparate oxygen from iron, when
*' this  is united to  a comparatively  fmall
" quantity."   But  finery cinder, if, as all
antiphlogiftians fay, it owes all its additional
weight to the pure oxygen, which it gained
from the water  which it had  decompofed,
muft contain much more of it than  lead in
any ftate, or indeed  than any known  fub-
ftance in nature.  For the  addition to its
weight is nearly  one third ; whereas the ad-
dition  to the weight of lead  by making it
into minium, is only about one tenth of its
weight.  Can this  be all pure oxygen,  that
the iron acquires,  and  yet not  oxygenate
muriatic acid ?

   He farther fays,  p. 24. " The antiphlo-
" giftians fuppofe  the addition  made to
" iron to be  oxygen, becaufe the compound
ft refembles in every refpect, as Dr. Prieftley
                                " himfelf 
           OF PHLOGISTON.          15
ft himfelf allows,  that  fubftance which is
.** formed by burning iron in oxygenous gas,
ic or in atmofpheric air.  And this they con-
" fider as an oxyd, becaufe while it is form-
*' ing the oxygenous gas difappears,  and its
•' weight is exactly equal to that of the iron
*' and oxygen confumed."

  But it is evident to  me, that  though the
pure air,  or oxygen, difappears in this pro-
cefs, it is not imbibed by  the iron, but only
the water which was its bafe,  and  which
formed  at leaft  the principal part  of  its
weight;  the'pure air, or oxygen, ferving  to
form the fixed air which is always found in
this procefs,  and  which  cannot  have any
other  origin.  Confequently, the calx  of iron
fo formed  when  heated in inflammable air.
gives out nothing but water.   The quantity
of fixed  air produced in this procefs appears
to me to be quite  fufficient to take  all the
pure air that difappears in it.   It is poflible,
however, that a fmall  quantity  of oxygen
may enter the iron along with the water  to
ivhich it  wfis united ; as few  fubftances are
                                 perfectly
• 
t6         JHE DOCTRINE
perfectly feparated from each other by any
chemical affinity.

   When fpirit of fait is diftilled over a quan-
tity of fcales of iron, which, being made in
the open air,  are moft likely to have  fome
of this principle attached to  them, it  has
fomething ©f  that faint fmell which a very
fmall  quantity of dephlogifticated air will
give it.   But  it is  the more  evident  from
this, that if this fpecies of finery cinder had
contained any confiderahje quantity of oxy-*
gen, it would have been  extricated in this
procefs.  That a Lttle, and not  more,  ap-
peared, I confider as a proof that it contained
no  more;  whereas, according  to the new
theory, it muft contain more than any  other
fubftance.

   A comparifon of the effects  of the appli-
cation  of fpirit of fait to finery  cinder, and
to red  precipitate, is much in  favour of the
former containing no fenfible  quantity  of
oxygen.   This  acid prefently  deprives  the
precipitate  of its colour 5  during which  a
           1                         great
• 
            OF PHLOGISTON.        Vf
great  degree of heat is produced,  and the
fmell of the dephlogifticated  acid is  pretty
pungent,  though  it  foon becomes faint.
When, after this,  it is expofed  to the heat
of a burning lens  in confined air, the veffel
is filled with denfe white fumes; but when
the fubftance becomes dry, it recovers its red
colour, and the air is increafed.  But when
the acid is applied to  finery cinder, there is
no  heat, and little or no fmell;  and when it
is heated in confined air, the air is diminish-
ed.  Can  both thefe fubftances, which when
treated in the fame  manner exhibit  fuch dif-
ferent phenomena, be equally oxyds ?

   That a very fmall quantity of oxygen is
attached to the fcales of iron, I have thought
probable from a barely perceivable quantity
of fixed air which I have found when they
are revived in inflammable air.  But fo fmall
a  quantity  as this makes  nothing for the'
new theory.

   Dr. Maclean farther fays, p. 28, " The
"  quantity  of carbonic acid  formed  by the
•' combuftion of iron in oxygenous gas ig
                    c              " verv 
i*         THE  DOCTRINE
" very trifling,  and this is owing partly to
" the gas containing fome before the opera-
" tion, and partly to the plumbago  contain-
" ed in the iron."  Now this, I will  venture
to fay, cannot  poflibly be the fource of the
fixed air which appears in  this procefs.  If
the air before the procefs contained any fen-
fible quantity of fixed air,  it could  not fail
to appear on its tranfmiffion through lime-
water.  I appeal to the experience of any
unbiaffed experimenter in this cafe againft
the declaration  of Mr.  Berthollet, or any of
the  defenders  of  the  antiphlogiftic fyftem
whatever; and  Dr. Maclean, I prefume, only
writes after them;  for he never once refers
to any experiments of his own.

   The quantity of plumbago in the iron that
is ufed in this experiment, and which this
procefs could not  difengage  from  it, could
not, if it was wholly fixed air, yield a hun-
dredth part of that which is produced. There
is nothing  whatever,  concerning which, I
am, from much experience,  better  fatisfied
than I am of the truth  of thefe obfervations.
What 
OF PHLOGISTON.         r$
   What makes it almoft a certainty'that the
water which is found on the revival of finery
cinder in inflammable air has not the fource
that the antiphlogiftians fuppofe, is the great
difference in the quantity which is found  in
this cafe, and  that  of the  revival  of other
calces  in it.   Dr.  Maclean  fays, p.  n.
 ' When oxyd of mercury is reduced in hy-
" drogen gas, that difappears, no oxygen gas
" is obtained,  but a quantity of water may
" be collected.''  Now I am confident that
no perfon who had  ever feen  the  experi-
ment could have written  this.   The quantity
of water that appears in this cafe is  barely
perceivable, being no more  than fufficient to
conftitute the  bafe  of  the  inflammable air
imbibed by the calx, or  that  might have
been  concealed  in the fubftance  operated
upon ; whereas  when finery cinder is revi-
ved in  the fame circumftances, the water
forms  itfelf into hundreds of fmall drops,
which unite, and run down the infide of the
veffel in all directions.

   Now if this water was  really formed  by
the union of the inflammable air in the  vef-
                   c 2                 &1 
*e>         THE DOCTRINE
 fel with the oxygen expelled from the calx,
 they ought furely to unite in the fame pro-
 portions, to form the fame thing.  The an-
 tiphlogiftians themfelves always fay, that the
 proportion of hydrogen and oxygen in wa-
 ter is univerfaliy i ; parts (*f the former to
 85 of the latter.   Here,  therefore, is much
 more water produced  than their  principles
 can account for.  The fame quantity of in*
 flammable air difappears, but the fame quarr-
 tity of water is by  no  means formed.  The
•obvious conclufibn  therefore is, that in the
 cafe of the calx of iron,  the great quantity
'of water produced was fimply expelled from
 the calx when  the inflammable air was im-
 bibed ; whereas the  calx of mercury contains
 little or no Water to be expelled,  and only
 unites with the phlogifton  in the inflamma-
 ble air that difappears.

   Before I conclude this feet ion concerning
 finery cinder,  I  muft take notice of  what
 Dr.  Maclean too confidendy advances about
 it.   " The Doctor,"  he  fays, p. 26, <€ is
" " certainly miftaken in fuppofmg that finery
 " cinder cannot ruft.   Mr. Fourcroy fays it
                                   " rufts 
           OF PHLOGISTON.         ai
«' ruffs fooner than common iron, and every
" apothecary knows  it does  fo.  If the ruft
" of iron be  made  red  hot in  a retort,  ;t
" quantity of carbonic  acid  is  difengaged
u from it, and the iron remains in  a ftate
" of black oxyd.  The ruft, therefore, is  a
" carbonate of iron, and muft contain all the
" principles which compofe the black  oxyd,
" and therefore can contain  nothing capable
" of excluding that which would convert  it
" into ruff."  This  very confident affeition
would aftoniih me if it  were not too much
of a piece with the reft  of the Doctor's per-
formance,  Indirect contradiction to what
he afferts, I ftill fay that finery cinder is not
-fubject to ruft.  In  England no  ufe  having
been made of it before it was attended to by
my brother-in-law,   Mr. John  Wilkinfon,
(one of the moft intelligent and fuccefsful  cf
all  tlie iron-mafters  in that  or any country),
but to mend the roads,  it has lain in heaps
for years, I may even fay ages,  without ac-
quiring  the lead tinge  of brown.  All my
specimens have ever remained free from ruft,
 wd the phyficians,  who arc  alfo apotheca-
                                      ries, 
THE DOCTRINE
ries, in this place, affure me they never faw
or heard of any fuch thing.  They get it
from the blackfmiths in the form oi fcales of
irony and the blackfmiths fay the fame.   It
muft, therefore, as I have obferved, be fatu-
rated with fome principle very different from
that of the common ruft  of iron, and is by
no means the fame thing,  notwithftanding
what Dr. Maclean  fays to prove the con^
trary.

  He  alfo confiders  the ruft of iron  as con-
taining more  oxygen  than finery  cinder.
But, though I do not know  exactly what
addition  of weight iron  acquires by being
converted into ruft, it cannot, I am confi-
dent, be near fo much as it acquires by paus-
ing into the ftate of finery cinder. If, there-
fore, as the antiphlogiftians affert, all the ad»
ditional weight  be oxygen, finery  cinder
muft contain more of it than the ruft.   But
neither of thefe fubftances, whether they
contain more or lefs of oxygen, will oxyge-
nate muriatic acid.   Nor what I think of no
lefs confequence, will finery^ cinder (which,
                                       if 
           OF PHLOGISTON.         *$
if it contain any oxygen, contains the moft
of it) when revived in inflammable air, pro-
duce any fixed air,  as the revival of minium,
which contains  much  lefs oxygen,  in  the
fame circumfiances does.
             SECTION  III.
         Of the Calces of Mercury*

 1 HE phlogiftic theory, I readily acknow-
ledge, is moft preffed  by the phenomena of
the calces of mercury.   Bat in forming any
general theory we muft content  ourfelves
with the feweft difficulties.   It will hardly
be pretended  by the greateft admirers of the
antiphlogiftic theory, that it is attended with
none.   Thofe which attend the phlogiftic
with  refpect  to thefe calces I do not think
to be infuperable, and  farther experiments
may throw more light upon them.

   It is always afferted by the antiphlogiftians
that the calces  of mercury  are revived not
                                     only 
24         THE DOCTRINE
only  without  addition,  but without  lofs.
This, however, I have never found to be the
ea-fe,  and after many trials, often affifted by
ether perfons,  1  have concluded  that,  after
the folution of mercury in the nitrous  acid,
there is a lofs of one twentieth of the whole.
And I muft ftill fay that there are calces of
mercury which certainly imbibe inflammable
air, and therefore that this fubftance, or the
bafe of it,  phlogifton, exifts in  that metal as
an element.   This is true both with refpect
to red precipitate, and turbith mineral.

   In reviving red precipitate in inflammable
*ir, 1 find no fenfible quantity of water, of
which there  appears abundance during the
 revival of finery cinder in the fame  eireuna-
 ftances, but I fbmetimes get fixed air.   Mr.
 Adet fays, p. 64, " The fixed air which  is
 " generally obtained by  the  revival of red
 11 precipitate in inflammable air, comes from
 " the carbone held in folution  in that air."
 But it cannot be proved that this kind of air
 ever  holds any carbone, or any element  of
 fixed air, in folution.   That which fome-
       1                              times 
           * OF PHLOGISTON*         '•£$
 times appears  on the decompofition of  it,
 when it is fired with  dephlogifticated air,  is
 in fome cafes certainly, and therefore in all
 the others probably, formed by their union
 in the explofion.   For in fome cafes, I  have
 fhewn,  that the  quantity produced  is  fo
 great, as to exceed the weight of all  the in-
 flammable air employed ;  fo  that  its being
 fuppofed to  confift wholly of fixed air  will
 not folve the difficulty*

   As to the  calx of mercury  from the acid
 of vitriol, Mr. BeaUme *, I find, agrees with
 me in the  obfervation, though I did not
 know it at the time, that it is not completely
 reducible by mere heat.  But  " later obfer-
 *' vations," Dr. Maclean fays,  p. 11,  " fhew
 " that  the turbith mineral,  or any other:
 u fubftance into which it may be converted

  * With Mr.  Beaume I  was  a little acquainted. Mr.
Macquer introduced me to him in his laboratory in Paris*
and though he was an avowed opponent of the whole of
the pneumatic chemiftry, he was a gaod operator  m the
oLi way, and his fires, I am perfua.led, were as hot as any
raited by the perfons mentioned by Mr. Adet, or thole  by
Dr. Mope.
                      D                «• by 
3<?         THE DOCTRINE
" by a red heat, does not require any addi-
" tion to conftitute it a metal."  And Mr.
Adet  fays, p. 43 > " that the yellow  °xide
" of mercury has been revived without ad-
" dition by Meffrs.  Monnet, Bouquet,  La-
" voifier, and Fourcroy."

   To this I can only fay, that  I have never
been  able to reduce  the  whole of this calx
by any heat that I  could  apply, not even
that of a burning lens of fixteen inches dia-
meter ; and this, I am  confident, is a greater
heat than can be raifed by any furnace what-
ever.  From being  a red friable fubftance,
this heat converts  it into a yellowifti glafs,
with the lofs  of about three-tenths of its
weight; but after this, no continuance of the
fame heat makes any farther  change in it.
Yet after this, when it is heated in inflam-
mable air, the air is imbibed,  and it is  co-
vered with a black powder, evidently ethi-
'cps mineral, into which mercury,  with all
 its component  parts,  whatever they be,  is
 known to enter.  This fubftance alfo,  and
 not directly running mercury, was frequently
                                       the 
           OF PHLOGISTON.         27
the refult of my experiments on this precipi-
tate before 1 left England.

   I wifti that Dr. Maclean would repeat this
experiment himfelf,  as well as others which
are differently related by myfelf and my op-
ponents.  Whatever is afferted by any anti-
phlogiftian he never hefitates to admit; but
he makes no  difficulty  of difregarding any
thing that I affert to the contrary.   This is
certainly an experiment of confiderable con-
fequence.  For if it be true that inflammable
air b& really imbibed by any  calx of  mer-
cury, that it is revived by it, and cannot be
revived without it, we are authorized to fay
univerfally, that fome  element of which  it
confifts, and no doubt phlogifton, is a necei-
fary component part of that metal, and there-
fore of all the other  metals alfo.

   In contradiction to what I and Dr. Wi-
thering have  faid of mere heat not.  being
able to feparate  fixed air from the aerated
barytes, Dr.  Maclean  fays, p.  50,   " Dr.
.•* Hope  has  difcovered that it can be done
                     D 2             4t by 
aS          THE DOCTRINE
" by fuch a temperature as can be raifed in
" a fmith's forge."   This,  however, 1 will
venture to fav  could  not be done  in  Bir-
mingham, where the forges  and furnaces are
as good as thofe of Edinburgh.

  In reply to what I have obferved of water
being effential to  this  kind of air,  becaufe
readily procured with it, and not at all with-
out it; he fays, p. 50, •' He has  entirely
" overlooked the property  which carbonic
" acid gas has  of diffolving water.   -Every
" chemift knows it has this property  and
u in a greater degree at a high than  at a low
" temperature.   But water is  not  neceffary
" to the conftitution of this gas, becaufe it
" exifts before the folution of the water,
" and may be deprived of water by the ful-
" phuric acid, or any deliquefcent fubftance,
" and ftill remain carbonic acid gas."

   Whether Dr. Maclean  will allow me to
know what every chemift knows,  or not, I
was not ignorant of, nor did I overlook, the
property of fixed air,  or of any kind of air,
                                diffolvinjr
                                        is 
           OF PHLOGISTON.         3$
diffolving water.  But that vitriolic acid, or
any other fubftance, will deprive that, or any
kind of air, of all the water which it only
holds in folution, is more than any chemift
can pretend to know.   But this is nothing,
to the purpofe.  I find no air at all, nothing
in the form of air, without the application of
water, a great quantity of which difappears
in the procefs, and can only remain in the
air.  I therefore conclude that water is effen-f
tial  to this kind of air.  I  fpeak from my
own  obfervations, and I only wiili that Dr.
Maclean would fpeak from his.  If he have
no aerated barytes, I will  fupply him  with
fome for the  experiment.
SECTION 
3*
THE DOCTRINE
            SECTION IV.
  Of the Compofition and Decompofition of Water.

I  WISH I could fay that I have  met with
any thing in Dr. Maclean's Obfervations on
my Experiments relating to the Compofition
and Decompofition of Water, befides general
exclamations, fome falfe affertions, and much
boafting  of the fuperior accuracy  of  the
French chemifts.   " In what  refpects," fays
he, p. 45, " his experiments were lefs liable
" to  exception than thofe  of the French
" chemifts,  is what I do  not comprehend.
" Theirs  were performed on a very exten*
" five fcale, great care was taken to afcertain
" the degree of purity of the gaffes before
" combuftion, and the apparatus was  fo con-
"  ftructed, that the refults could be determi-
"  ned  with the greateft nicety.   The Doc-
"  tor's, on the contrary, were made with
" very trifling quantities of materials,  their
(<  purity was not tried, and their weight not
"  accurately determined."
Let 
           OF PHLOGISTON.          51
  Let us now confider what thefe high found-
ing words amount to.    Experiments made
with a great quantity of materials are not, al-
ways on that account, the moft accurate, efpe-
cially where, as in this cafe, the thing to be
determined  is limply the  quality of the re-
fult.  When I  can produce but a few drops
of a  ftrong acid, and as  often as I pleafe,
from the very fame  materials  from which I
am told that I ought to get only pure water,
what is it to me whether they produce gal-
lons ?
                             t
   Great care, he fays, was taken to afcertain
the purity of the gaffes, wherein with refpect
to me,  he  fays, the. purity was  not  tried.
Now that of mine was not only tried, with
as great accuracy  as they could  try theirs,
but the dephlogifticated air that I ufed was
purer than any that I believe they  ever pre-
tended to have  made.  For with  two equal
meafures of  nitrous air,  the  refiduum was
only four hundredth parts of a meafure, and
this flight impurity was certainly not in the
dephlogifticated, but in the nitrous air, which
                                       is 
32          THE DOCTRINE
is very apt to vary in its quality, and very
difficult to  obtain pure.   And  yet with this
very pure dephlogifticated air, and a  propor-
tion, exactly defined,  of the pureft poffible
inflammable air,  I got drops  of a  ftronger
acid than can be  procured  by means of air
lefs pure.   To this impurity, viz, a  mixture
of phlogifticated  air, the antiphlogiftians al-
ways  afcribe  the production  of the acid,
though if the air be  purpofely lefs  pure,  I
never fail to find that impurity, viz. the phlo-
gifticated air, unaffected by the procefs ;  fo
that it could not poflibly have contributed
to the production of the acid.

   With the  greateit, confidence, however,
Dr. Maclean fays, p. 53,  «' the denfe acid
" vapour  that I  produced by the explofion
" of the two  kinds of air was occafioned by
4t the azote contained in the oxygenous gas
" that I employed."  He might as well have
faid it was occafioned by that which I did
not employ.  If tQii  times the quantity of
azote in the air  I ufed had  been wholly de-
compofed, it would not have amounted to
      1                                the 
            OF PHLOGISTON.         33
the hundredth part of the weight of the acid
that I procured.

   Their apparatus, he fays, was fo conftruct-
ed, that the refult could be determh vd with
the greateft nicety.  On the contrary, it was
extremely complex, as a view of their plates
will fhew, and mine was perfectly fimple, fo
that nothing can  be imagined to be lefs lia-
ble to be a fource of error.   How, indeed,
was this poffible ? I ufe only one large veffel,
of glafs, or copper.  I put into it  at once a
certain  proportion of the two kinds of air,
the purity of which, when it is neceffary, I
can afcertain as well as other perfons. From
the fimplicity of the apparatus no other fub-
ftance can poffibly mix  with them, and I
then  explode the whole at once by an elec-
tric fpark.   After this I  prefently find the
refult by examining the liquor that is drain-
ed from the veffel.   Though I  have not
gallons of this liquor, I  have fome ounces,
which  no antiphlogiftian  would  care  to
drink.  Will Dr. Maclean fay that my pro-
cefs is lefs accurate than that of the French,
                    £             becaufe 
34          THE DOCTRINE
becaufe it  can be finifhed  in lefs than five
minutes, and theirs requires the afliduous at-
tendance of fome days.

  Ufmg the fame moft fimple apparatus, I
can, by only varying the proportions of the
two kinds  of  air, produce  the refult which
the French chemifts fo much boaft  of.  For
I can  produce water as  free from acid  as
theirs, and with  much greater certainty,  as
I have no attention to give to a flame, left it        t
{hould at any time burn  too  fiercely.  But
in this cafe I always produce  a  quantity  of
phhgifticated air, in which they acknowledge
that the principle of acidity refides.   They
alfo do not deny that they had a furplus of
the fame kind of air; and as to the quantity
of it,  I  cannot  help fuppofing that,  inter*
efted as they were to make it as little as pof-
fible, being men,  and of courfe liable  to the
fciaffes of other men, they may have  repre-
fented it,  by  the allowances  they made  in
their computation,  fomething  lefs than it
really was.  All the infide of my large vef-
fel being, of courfe, wet with the liquor pro-
                                    duced 
           OF PHLOGISTON.         35
duced by the explofion, I could not pretend to
tae/gh that which was drained from it with
much  accuracy.  But  then very little de-
pended upon the  quantity', compared to the
confideration of the quality of the  liquor;
and  this may be as clearly afcertained  by
drops,  as by the largeft quantities;  and till
the French chemifts can make their experi-
ments in a manner lefs  operofe and expen-
five, requiring fewer precautions, and lefs of
computation,  I fhall continue to  think my
refults  more to be  depended  upon than
theirs.

   That phlogifticatel  air can be produced
from the fame materials from which I get
nitrous acid, viz. dephlogifticated and inflam-
mable air, I  have given various and fufficient
proof.  Dr. Maclean, however, fays of them,
and  of  other  of my experiments,  p.  66,
iC As the Doctor has not favoured us with a
" detail of his experiments,  and as they bear
" the moft ftriking marks of not having been
*' performed with accuracy, I will not take
"up your time"  (fpeaking to  his  pupils)
'•' with a review of them."
                   e 2          Thougji 
36         THE DOCTRINE
  Though an account of the experiments to
which he here refers was not inferted in the
pamphlet on  phlogifton, it was printed for
the Tranfactions of the Philofophical Society
at Philadelphia, which  I  expected  would
have been publilhed long ago.  It is evident,
however, that Dr. Maclean had feen a copy
of thofe  articles.   How elfe could he fay
that  they' bear  fuch evident  marks of not
having been  performed  witji accuracy ? He
Ought  certainly  to  have ftiewn how they
could have been made with more  accuracy,
with refpect  to the proper object of them,
and I requeft that he will do it.

  Notwithstanding  this  authoritative con-
demnation of thofe  experiments, on which,
however, till I hear fome good reafon t© the
contrary, I (hall continue to lay fome ftrefs,
1 fhall here give an account of another expe-
riment, though.I  do not pretend to fay that
it is more accurate than the  reft.   Having
made a number of  pieces  of iron rufty by
dipping them in marine acid, I put them
into a glafs veffel, which  I then filled up with
mercury, and I difplaced  this  mercury by
                                  inflam- 
            OF PHLOGISTON.         3F
 inflammable air.  After waiting about eight
 months, I examined the air, and found it to
 be very flightly inflammable, the far greater
 part of it being evidently phlogifticated air.
 The  iron, from being red, which all anti-
 phlogiftians  will fay was owing to its con-
 taining oxygen, was  become black, being
 covered with a kind of foot, which was eafily
 wiped off, ftaining the fingers  and  paper.
 Under this coating the iron was  of its ufual
 colour.

   Whence,  now, came this  phlogifticated
 air, if not from the union of dephlogifticated
 and  inflammable  air?  I  have pretty clear
 proof of the fame elements forming in other
 circumftances fixed air, efpecially  the pro-
 duction of a great quantity of this kind of
 air from heating a mixture of iron  filings
 and red precipitate ; fo that, in contradiction
 to the maxim of Mr. Lavoifier, this carbonic
 acid,  as it is called, is  formed  without car-
 bone.   This  remarkable fact  \ am  told is
 difputed by the antiphlogiftians,  but  I have
 lately repeated the experiment with the fame
refult  as before.
                                    This 
 3$       THE DOCTRINE, &c.
   This experiment  is very  little liable to
 the  objection of  the  Monthly Reviewer,
 p. 371, as the pieces of iron had not been
 expofed to the atmofphere any  great length
 of time, and I am confident that by  no pro-
 cefs  whatever could any phlogifticated  air
 have been extracted from them.

   If the  above-mentioned  black fubftance
 with whioh the pieces  of iron were  coated
 be plumbago  (and of this little doubt can be
 entertained) it will appear to be a calx of
 iron  fuperfaturated with phlogifton, and that
 the whole of the iron might have been eon-
 verted into it, but that plumbago cannot be
 contained  in iron, fo as to yield, on its folu-
tion  in an acid,  the phlogifticated  air of
 which my opponents have  endeavoured to
avail tfyemfelves.

   As to the experiments recited in my third
fection, I fhall not enlarge upon them at this
time, but leave my readers to compare them
with the remarks that have been, or may be
made upon them, and judge for themfelves.
THE EXD. 
 
 
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