1000000030

H E

Though fixed alkalis, when dry. fufiain the utmofi

~ioltnct

01'

Gre without lIyillg off in ...Ip'lurs, it is re·

nwkabl. thar, hein;: boiled wilh IVm r in .Inopen ..ellel,

conGdmblc quanriti.:s of them rife \Vith the Ik.Iln ; an

clfeé! \Vhieh mllll be artributed

Ihe greal allinity he'

IIVeen Ihefe IWO fubUanees, by means whereof waler

commlloicms (omc r'" of ilS I'olalilit)' ro rhe Gxed falr.

Alkalis Creed of their fuperlluous humidity hy c.!cioa–

tion atmé! Ihe moiflure of the air, but oOt fo Urongly

as acids: fo

th.lt

it iseaGer to procureand prefer"e them

in a foliJ form.

They

il~w

in the Gre, and are then capable of uniting

with ritriG. blc eanhs, and of forming Ihcrewilh

trile

glafs; which. however, will .pamke of their propenies,

if they be ufeo inruilieient quantity.

As the)' melt more readily than vitriGableearrh, they

faci litare ," fu"on; ro th.\[ a we.k<r fire wllI reduce it

to glafs. when a li Ked

alk.li

is joined with it, than IVill

md t it without that addition.

Alkalis are knolVn by.their tafie, whieh is acrid and

fiery; aod by the,J'fopertics they puffers of turning blue

or violet I'egetables green; panicularly ryrup of riolels.

Their affini ty IVith acids is grearer than that of abfor–

bent earrhs; Ir"nce, if analkdli be pr&nted toa eombi–

pation of an acid IVirh an abforbent eanh, the cartb will

be (eparateJ from the acid by the llkali, anoa ncw unioo

between the acid afld the alkali lVill Idke place. This is

both aninllaoce aod a proof o( our fi¡'th propofilion con:

cerning affi oities.

If a pure alkali

prefented to a pure acid, Ihey mfh

togelher wilh violeoce, and produce Ihe fame

phen~

meña as IVereobférveo io Ihe uoioo of an abforben¡ earrh

\Vith ao aeid, but io a greater an.1 more rcmarkable de–

gree.

Fixed . Ib lis may

gentral be dil'ided inroIWO

(OrlS :

one of Ihefe h. lh

,11

the above reciled properties; bm

the other poll'effcs (ome

tlJat

are peculiar tOilfelf. \Ve

fhall conGder Ihis laner (on more panieularly under Ihe

hcad of fea-fJIt.

N[U TRAL SA LT! .

aeid and the alkali 'thus unitiog,

mutu~lIy

rob

eaelr olher of Iheir cluraéleriaie propcnies ; lo that Ihe

compouod reful ting (romtheir unioo

proJu~~s

no change

io the bluc colours of I'egelables, ..nd has

rane whicb

js oeilher (OUI' nor acrid, bUI f.ltifh .

lidin.: combina

1;00 of Ihis kind is for Ih,t reaCoo oamed

¡a/ ¡U!jIlIlJ , fui

nudiuIII,

or a "(//11'. /

(a/I.

mua be obferved, Ihat io order

make Ihe(e Calts

perfeélly oeulral, it is oecendry thal oei.her uf Ihe IWO

f. lioe principies of which Ihey are compounded be pre·

dominant ovcr Ihe olher ; for in rhar ca(e they wdl have

Ihe propcrties of Ihe prel'ailing

princi~le.

The rea(uo is

Ihis: neither of Ihe(e (.Iine Cubll.oces can IInile ,. ith Ihe

other but io a limiled !'ropo.lion bcyond whieh Ihere

n o be 00 fUrlher oalilion belIVeen Ihem Thc ,élion

by IVhieh tilis per(e, uoi" n is accomplilhcd is IcrmedI a.

tllra/i,n:

and Ihe inflant when fu eh pro!,"'li"ns' of the

two (aline fubllaoces ,1I'e mixcJ wgelher, Ih.1I the ooe is

inrorporal.J \Vith a'· mudl of Ihe olher .s 1 can roflibly

w e up, is c.

'lll.cd

Ihe

poilll

fi/lara/ioll.

The poiot of (.llIlral;ooiskoowo

be obtaioeo, when,

afler repem d aliur,ons of ao .cid io fm .dl qu,olir'ls 10

an alkali, or aoabCorben¡ cUlh, we Gnd tllII(e

phenom~oa

ce.di:

, whi(h in fuehcafesconfiantlyatteod Ihe couillél of

uoion, oalllely, ¡bullilion, hilling,

&c.

aud we may be

allured Ihe IiHuration is complelew.henIhenewcompouoJ

11:11h neilher ao aeio nor ao acrid tafle, nor io the lean

chaoges the bluc coloul's of vegm bles.

Neulral f:tl ts h,,'e OOt fo sreat ao affioilYwilh waler

as either acids or all;alis halt, be,"ufe Ilhy are more

compounJ~J ;

for lI'e ob(erveJ before, Ihal Ihc aAionies

of the mol! compouodeJ bodics aregencrally II'eal;er thao

thoCe of the moll filOple. In confequcncé hereof (eIV

natural (alls, when dn,d, JttraLl the moiflure of the air;

ano Iho(. Ihal do,

attr.~t

It more1I0wly and in lels quao–

lily thao eilher aeids or alkalis do.

AII neutral (allS are foluble it waler; bUl moreor Icfs

reacLly, aoJ in a gremr or fmaller qua.nmy, aceordlog

10 the nalure of their componcmprincipies.

Water madc boiling hOI dilrohcs a grcatcr quantity of

(hn(e f. hs whieh do 001 attraél Ihe moifl ure 01' Ihe air,

thao when it i, eo!d ; and inoeéd it mufl be botling hot

10 take upas much of them as it is capable of diff.,lving:

bUI as for Iho(e which ruo in lhe air, Ihe differcoce is

imperceplible.

·Some neutral fahs Irave the propeny of 1I100ling into

cryfial" aod others hare it nol.

Tbe oature of cryUalliz3tion is Ihis : Water eanoot

dilloh'e, oor kcep in folutioo, more than a determinate

quantilY of aoy pmieular (alt; IVhen Ihererore (ueh

quaotilY01 water i9 evaporattd from the folulioo of a,

Cah capaWe of cryaallizalioo, Ihat the remainder con·

tains jufl dSmuch (dlt as it can diffoll'e, Ihen by

eo~ti

nuing the eraporaliuo the (all gradually recovers lIS folid

form, and Concretes ioto rever.d little Iran(parent marres

eallerl cryrtals.

Th eCe

cryOals have regular ligures,

,11

differiog from ooeanother according to Ihe fp'-cilS of (Jlt

of which tI>!y are formed. D,ffm nl methuds of evapo–

rating

(~line

1(¡lutioos hare different effeCts 00 Ihe figure

aod regularilYof Ihe er)'nals; and taeh particldar (on

of fal t requires a pceuli,,' merhodof evapotdllOo

make

its cryOals perf<élIy regular.

folulion of (alt defigued for crynallizationisufilalfy

evaporaled by mea05of lire 10

pellicle : tha t is. till

Ihe f,llt besin 10concrete; whieh is perr.,'i'·ed by '1

...d

of Ihin oark Ikin that galhers on Ihe rurl:lce of the li–

quor, and is fOImee!

01'

Ihc cryl!allize,1partidos of (, Ir.

Whcnthis rellicle ,'ppem , Ihefolulion is fulTered

euol,

anJ Ihe

tri

I!,ds

~orm

Ihereio

fal!~r

or 1I0wer aceololnr,

lhe (on of Cdlt

h,rnn. lf tlle evaporarion be e.rrricJ

00 brilkly

perfCl'1 drineC! , no eryn.lls will be f"rmed,

aod ooly aoirrcguldr ma(s or f:dl IVill beoblaincd.

. The r,carons why no cryflalsarpear when Ihe cl'apora–

lion " hafldy performe", and

c~rricJ

on 10 Jrioefs,

.\r~,

úril, dlJt Ihe p;rrtlcles o(

f.dt

bcin~

alll'ays in nllllhn

while, Ihe (OIUlioo is h 1, have 001 lime 10 exCrt their

mUludl illlioili,s, aotl lO unilc logelh. r ,IS

er\'n.dlizilli"~

r~quires :

(cCtlndly, IhH • c<'ruin qll.lnlity

w.lta eo–

ters inlo Ihc ven eomp"lition01' a yll,tls; whieh is dlerc–

fore abfolutcly nec&ll'y

Ihdr fOrlUJlion, ano in a

srCdt~1'