 elastic fluid. To this I have given the name of _fixed
air_, and perhaps very improperly; but I thought it better to use a
word already familiar in philosophy than to invent a new name, before
we be more fully acquainted with the nature and properties of this
substance, which will probably be the subject of my further inquiry.”

The next proceeding was to render “mild alkali” caustic by means of
lime, and to determine that nearly the same amount of acid is required
to saturate the caustic alkali as to saturate the mild alkali from
which the caustic alkali had been prepared. On exposure to air for
a fortnight, the caustic alkali again became mild, owing to its
absorption of fixed air. Careful experiments were made to prove that
such caustic alkali contains no lime, and does not therefore owe its
causticity and corrosive properties to the presence of that ingredient.
The volatile alkali (ammonium carbonate) was also rendered caustic, and
Black “obtained an exceedingly volatile and acrid spirit, which neither
effervesced with acids nor altered in the least the transparency of
lime-water; and although very strong was lighter than water, and
floated upon it like spirit of wine.”

After a description of some unsuccessful attempts to render mild
alkalies caustic by heat alone (_i.e._ to expel carbon dioxide from
potassium carbonate), Black examines the action of the “sedative salt”
or boracic acid on mild alkalies, by rubbing them together in presence
of some water. At first there is no effervescence, but on adding
successive quantities of boracic acid, brisk effervescence finally
takes place, borax being formed. “This phenomenon may be explained by
considering the fixed alkalis as not perfectly saturated with air...
if they expel a small quantity of air from some of the salt, this air
is at the same time absorbed by such of the contiguous particles as are
destitute of it.” And on “exposing a small quantity of a pure vegetable
fixed alkali (carbonate of soda) to the air, in a broad and shallow
vessel, for the space of two months,” crystals were obtained, which
possessed a milder taste than that of ordinary salt of tartar, which
effervesced with acids more violently
elastic fluid. To this I have given the name of _ fixed 
 air _, and perhaps very improperly; but I think it well to use a 
 word already familiar in doctrine than to invent a new name, before 
 we be more fully introduce with the nature and properties of this 
 substance, which will credibly be the national of my further inquiry. ” 

 The future proceeding was to render “ mild base ” caustic by means of 
 birdlime, and to determine that nearly the like amount of acid is required 
 to saturate the acerb alkali as to saturate the mild alkali from 
 which the caustic base had been prepared. On photograph to air for 
 a fortnight, the caustic alkali again become mild, owing to its 
 absorption of fixed air. Careful experiments were made to prove that 
 such caustic alkali contains no lime, and does not therefore owe its 
 causticity and corrosive properties to the presence of that ingredient. 
 The explosive alkali (ammonium carbonate) was also rendered acerb, and 
 Black “ prevail an extremely volatile and acrid spirit, which neither 
 effervesced with acids nor altered in the least the transparency of 
 lime - water; and although very firm was lighter than water, and 
 floated upon it like spirit of wine. ” 

 After a description of some unsuccessful attack to render mild 
 alkalies caustic by heating system alone (_ i.e. _ to oust carbon dioxide from 
 potassium carbonate), Black examines the action of the “ sedative salt ” 
 or boracic acid on meek alkalies, by rubbing them together in bearing 
 of some water. At foremost there is no effervescence, but on adding 
 successive quantities of boracic acid, bracing effervescence finally 
 learn place, borax being form. “ This phenomenon may be explained by 
 consider the fixed alkalis as not absolutely saturated with air... 
 if they expel a small quantity of air from some of the strategic arms limitation talks, this air 
 is at the same time absorb by such of the contiguous particles as are 
 destitute of it. ” And on “ debunk a minor quantity of a pure vegetable 
 repair alkali (carbonate of soda) to the air, in a broad and shallow 
 vessel, for the space of two months, ” crystal were obtained, which 
 possessed a milder taste than that of ordinary salt of tartar, which 
 effervesced with acids more violently
 elwstic fluid. To this I haye given the namg if _fixxd
air_, ahd perhaos very improperly; but I thonght it btnter to use a
word alrdady famipiar in philiwophy than to invekc a nsa nakx, before
we be mpre fully dcquainted witv ghz nature and properties of this
substwnce, whocj will probabli be uhe subnvcu of my further inquiry.”

The next pdoceediig was to rendet “mild alkali” caustic by mfans of
lime, and to detfrmine that neawoy the same xmount of acid is requjred
to saturate the caustic alkxli ax to saturqtw tjg mild alkalm from
rhich the camxtic ankali hsd been preparcd. On exposure to air for
a foctnight, the caustic wlkali agdiu became mild, owing ti uts
abvorpdion if wixtd eir. Carefkl xxperiments were made ro prove that
such csufnoc alkali cohtains nj lime, and does not therefore owe its
calstidity and corrosive propwrties to the presencg of that yngredient.
The volatile alkali (ammonium carbonate) fas amro xckderde faustic, and
Black “obtained an exceedingly volaejlt akd acrid spirit, chich neither
effrrgexsed with acidr nor cmtsred in the least hhe tragsparwncy of
liie-wayer; and although very stront was lighteg thqn water, and
floateb upon it liye skirit pf wine.”

After a descriptnon of some unsucfessful afgempts to render mikd
dlkalies caustic by heat ajone (_i.e._ ti ex'el carbun dooxide from
potasdium gdrbonate), Black exalines tve action lf the “sedative salt”
or boracic erid on mild akkdlivs, by rubying tmem together in presence
of soke watex. At fkrst there is no xffervescencq, but on addith
successive xuantitiqs od boeacic azkd, brisk efferfescence ynnally
takws place, borax beikg fotmsd. “This phenomeuub may be explaimed by
sojsmderigc the fixed dlkauis ss nog perfectly ratutated with air...
if thef exlel a small quantiyy of air drom somq of the salt, this air
is at the same tioe abxorfed by such of the contiguous larticles as are
destitutq of it.” And on “erposing a small quantity of a pure vegeteble
fixed alkali (carbonqte of soda) to the civ, in a broad and fhallow
vevsel, for the space od two months,” crysuals were obtained, whicg
possevsed w milder taste than that of ordinary salt of tartar, which
effervesced with acids more violenfly
elastic fluid. To this I have given of air_, and very improperly; but use word already familiar philosophy than to a new name, before we be fully acquainted with the nature and properties of this substance, which will probably the subject of my further inquiry.” The next proceeding was to render “mild caustic means lime, to determine that nearly the same amount of acid is required to saturate the caustic alkali to saturate the mild alkali from which the alkali had been prepared. exposure to air for a the alkali again mild, to absorption of fixed Careful experiments were made to prove that such caustic alkali contains no lime, and does not therefore its causticity properties to presence that The volatile alkali was also rendered caustic, and Black volatile and acrid spirit, which neither effervesced with nor altered the least the transparency of lime-water; although very strong was lighter than water, and upon it like spirit of wine.” After a description of some unsuccessful attempts to render caustic by heat alone to expel carbon from carbonate), examines action of “sedative salt” or boracic acid on mild alkalies, by rubbing them in presence of some water. At first there is no on successive quantities of acid, brisk effervescence finally place, being formed. “This phenomenon explained considering as perfectly with air... if they a small quantity of air some of the salt, same time absorbed by such of the contiguous as are destitute of it.” And on a small quantity of a pure vegetable fixed alkali (carbonate of soda) the air, broad and shallow vessel, for the space of months,” crystals were obtained, possessed a milder taste than that of ordinary salt tartar, effervesced with more violently
 elastic fluid. To this I have giVen the name Of _fixEd
aIr_, aNd PerhAps vEry improperly; bUT I thOught it better to use a
worD alreAdY FamiLIaR in phIlosophY ThAN To iNvEnT a nEw NAmE, befoRe
wE be more Fully acquaIntEd With the naturE AnD propertieS of This
substancE, whIch wilL pRobABly be The SubjeCt of my FUrther Inquiry.”

ThE nEXt procEEding waS TO rEndeR “mild alkali” caustiC By MEans of
lime, and tO deterMiNE tHAT neArlY the same amOuNt of aCId is reqUIrED
TO saTUrate the caustIc alkali as tO SatUrate tHe MilD Alkali From
wHiCH thE caustic alkAli hAd been prePared. ON ExposurE To air foR
a fortNigHt, tHe caUStIc AlkAlI AgaIN bEcaME miLd, owing tO iTs
AbsorPtioN OF FIxed Air. careFul exPeriments were MadE to pROve That
sUch caUstiC aLkali ContaiNs no lImE, and does not therEforE owe its
caUstIcIty AnD corrOSive prOpeRtiEs to the PresencE Of tHaT INGrEdient.
The volatile aLkALI (aMmonium cArbonaTE) wAs ALso rendeReD caUstiC, ANd
BlaCk “obTAiNed an excEedingLY vOlAtile anD aCrid spIrIt, wHicH neitHEr
efFervesCed with aCids nOR altered in the lEAst the transpaREnCY Of
LIme-wAteR; and althougH verY StroNg waS LiGhtER than Water, AnD
FlOAted upon it like spiriT oF wine.”

AFter a Description of Some unsuccESSFul attemPts tO ReNDer mild
alkalieS causTic by heat aLOne (_i.e._ to eXpel cArbon dioXide from
pOTAssium caRboNatE), BlAck EXAmInes the action OF The “sEdAtive saLt”
oR boraciC acId oN miLd aLkAlies, by ruBbing theM tOgEtHeR in PreseNCe
of some WaTer. at FirSt theRE is no eFfervEsceNcE, bUT on Adding
sUCcESSive QuAnTitiEs oF bOraciC aciD, BriSk efferVescence fInaLLy
taKeS pLace, borAx being formed. “thIs phenomenOn May Be explAINed by
conSidering the fixed alkalis AS not perFecTly saTuraTed with aiR...
if They exPel A Small qUantitY of aiR fRom SOMe of tHE SaLt, tHiS air
is at thE SAme Time aBsOrbeD by such Of the contiguous parTIclEs as are
destitUte Of it.” aND oN “exPOsINg a SmALl qUANtity of a pure vegEtable
fixeD aLKaLi (carbonatE Of sOdA) to the aIr, in a brOad anD Shallow
Vessel, for The space oF tWo moNTHs,” cRystals werE obtaineD, which
posSEssed A MiLder tAstE than tHaT of OrdinAry salT Of tArtar, Which
eFfErvescEd witH aCids more Violently
 elastic fluid. To this Ihave given  thenam e o f_fix ed
a ir_, and perha p s ve ry improperly; but I t hough ti t be t te r touse a
w o rd a lre ad yfam il i ar  in p hil osophythan to in ven ta new name,b ef ore
we bemor e fully acqu ain ted wi th  th e  natu reand p ropert i es ofthis
subs ta n ce, wh i ch will p ro babl y be the subjecto fm y further inqu iry.”
T h en e xtpro ceeding wa sto re n der “mi l da l k ali ”  caustic by m eans of
lim e , a nd tode ter m ine th at ne ar l y t he same amo untof acid i s requ i red
tos aturate  the c aus tic  alk a li  a s t os atu r at e t h e m ild alka li  f rom
w hich t h e  cau sti c al kalihad been prep are d. O n  ex posur e toairfo r
a f ortnig ht, t he  caustic alkali  aga in became  mi ld , o wi ng to its
ab sor pti on of f ixed ai r . C ar e f u lexperiments were m ad e to  prove t hat
su c hca u stic alk al i c onta i n s nolime ,  a nd doesnot th e re fo re oweit s
caus ti cit y a nd co r rosi ve pro pertiesto th e  presence of t h at ingredient . 
T h e  v o lati lealkali (amm oniu m  car bona t e)  wa s  also  rend er e dc austic, and
Black “ ob tained  an e xceedingly vo latile and a c rid spir it,w hi c h neither
effe rvesc ed with ac i ds nor a ltere d in the  least th e transpar enc y o f
l ime - w at er; and altho u g h ve ry  strong  wa s light ertha n w ate r,  and
floa ted upon  i tli ke  sp irito f wine.” 
Aft er  adescr i ptionof so me u ns uc c ess ful att e mp t s  tore nd er m ild 
a lkali es c a ust ic by h eat alone  (_ i .e._  t oexpel c arbon dioxide  f rom
potass iu m c arbona t e ), Black  examines the action of the “se dat ive s alt” 
or borac icacid o n m i ld alk alies,  by r ub bin g themt o ge the rin presenc e ofsomewa ter.  At fir st there is no eff e rve scence, but o n a ddin g su cce s si v e q ua n tit i e s of boracic ac id, briskef f er vescence f i nal ly 
takesplace,borax being f ormed. “T his pheno me nonm a y b e explaine d by
con sideringt he fi x ed  alka lis  as no tper fectl y satu r ate d wit h air. .. 
if th ey ex pe l a smal l quantity of air fromsome o f the  sa lt, thisair isat the sa me t ime absorb edbysuchoft he co ntig u ou s p a rticl es a s  are
dest i tu teo f  i t.” And on“ e x pos ing a  sm a ll qua ntit y of a pure veget a ble
fixed alka li ( c a rbo nat e  ofso da) to the air , i na broad an dshallow
ves sel, for  t h e spa ce oftwo mo nths,”c r ys t als we re o bta ined, whi chpo s sessedami l der ta steth an tha t of o r dina r y  salt of tartar,  whic h effer v esc ed wi th  acidsm oreviolently
 elastic_fluid. To_this I have given_the name_of__fixed
air_, and_perhaps_very improperly; but_I thought it_better to use a
word_already familiar in_philosophy_than to invent a new name, before
we be more fully acquainted with the nature_and_properties of_this
substance,_which_will probably be the subject_of my further inquiry.”

The next_proceeding was_to render “mild alkali” caustic by means of
lime,_and_to determine that_nearly the same amount of acid is required
to saturate_the caustic alkali as to saturate_the mild alkali_from
which_the_caustic alkali had been_prepared. On exposure to air for
a_fortnight, the caustic alkali again became_mild, owing to its
absorption of fixed air._Careful experiments were made to prove_that
such caustic alkali contains no_lime, and_does not therefore owe its
causticity_and corrosive properties_to the_presence of that_ingredient.
The volatile alkali (ammonium carbonate) was_also rendered caustic,_and
Black “obtained an exceedingly volatile and_acrid_spirit, which neither
effervesced_with_acids_nor altered_in the least_the_transparency of
lime-water;_and_although very strong was lighter than_water,_and
floated upon it like spirit of wine.”

After_a description of some_unsuccessful_attempts to render mild
alkalies_caustic by heat alone (_i.e.__to expel carbon dioxide from
potassium carbonate),_Black examines_the action_of the “sedative salt”
or boracic acid on mild alkalies, by rubbing_them together in presence
of some water._At first there is_no effervescence,_but_on adding
successive quantities_of_boracic acid,_brisk effervescence finally
takes place, borax being formed._“This phenomenon_may be explained by
considering the fixed_alkalis as not perfectly_saturated_with air...
if they expel a small_quantity of air from some of_the salt, this air
is at_the_same_time absorbed by such of_the contiguous particles as are
destitute of_it.” And on_“exposing a small quantity of a pure_vegetable
fixed_alkali (carbonate of soda) to the_air,_in a broad and shallow
vessel, for_the_space_of two months,” crystals were_obtained, which
possessed a milder taste than_that of ordinary salt of tartar, which
effervesced with acids_more violently