QT AST IT ATI YE DKTKltMlSATlOSX «>4«>

solution which, In turn, is .standardized by the method usrd In
the preceding exercise*. A.s tluit standardisation was, in rflVct,
an analysis of the* acid solution no further experimental work
should be necessary. But because of the fact that potassium
hydroxide and sodium hydroxide solutions have* a wider applica-
bility than do carbonate solutions, serving for the tit ration of a,
great variety of strong and weak acids as well an of acid salts,
the base solutions are more often kept as standards and, us such,
may be conveniently used for the determination of hydrochloric
acid in solutions.

Volumetric Determination: I'otnxxiuin /Ij/fln^idc Mt'thml.- Calculate tin*
weight <»f nolid potassium hydroxide necmsary for 1UIMJ er of fifth 'normal
.solution. Acid I per rent fnr water and other implicit JCM arid di^olve fit**
calculated quantity in recently boiled mid cooled diMtiHcd wafer. Th«* 'io|td
bane need not be weighed on the nimlytical balance. Dilute the ;<oluf ion to
about 12fM)cc-, mix and allow to cool to 20'*.

Prepare att approximately fifth-normal solution of hydrochloric acid and
tifrnf'e nguinsf fifth-normal *odittm carbonate, JUH directed in thr preceding
exiifine, AM flit* acid in merely an intermediate, in Ihi* prociw^ jt:-» ft<»rttudify
need not be calculated. Measure out 25 c<" of the ba^e ?tolufi<Mt from ji
hurette, add a drop of inethyl nntngf* or methyl red uttd tit nil** !*•» a faint
pink color with the acid solution, f Methyl red should not br* u?>«»d if fhe
base cotitaiiiHi nion* than very liiimll <|ttnntitit'M of pot/^Ntum c./irbouatc, |
Thin IM nimply uri in<lir«*ct cdidpuriMon of fiie noniiiilsf ii*fi of haw and car-
horuite .solutions, aii(2 flit* voliuiw* of acifl iioi*« not enter info flu* final *'»1«'U^
Intions if e.qiifil voiumeN of lui-Be mid nirhouaf (^ W«T<* uwd, iw i« ;n»cii from f-hii
following:

Lei I*,, •• volume of acid equivalent to 2.ri cc of earbotitite Motuttofi and
Pfl ..... ' voluiin* iM|utvnIifftt, to 25 cc of luw. Then the Mormitltty *»f tlie

. I", N

hnwir •- ,. • . -
I .-» »'»

Titration.- -The «fn»d»rd b.jn«* jiwt. prcfuired will Hcrve for tl»r tit rut ion
of hydrochloric arid nnd of other strong nttd w«»nk ncid^f nt«o of mutiy »fid
wilfH, «ncli lih jirid !4iilplii4tcii, The t ?f rat toft i^ ffirrii'd <mt »•>» in «f mtd:»rd>/tn^
the lm««% i'Xccpi I hut fihettolphthjiiein IM iifii'd iw ifidfciifof for the wr?iti*"f
acidn. In any **H,HI* th** uriwr inrli4'ttfar mu«t. he tw*«d when titmttfig fit*'
hiisc ngiiirtMt flic iiifmiiciliiife »cid in i*tiiftdnriIi/Jii|i:, ^in*fe tip* j|i%-iiri»J#I*'
presence of it HHiiiil aiiiiiiiiit of cnrhoitnh* in tin* biwicwiliitniti given a wfiglitlv
ciiffcr<'nt noriiiiiiify, an niimliitcd from iilriitinfin in jirrj«»itc*« of diffwnf.

Titi* tifnitioiiH miiy 1»<* carri«4cl cmt in either direction, l»{w bcinj? jyiil*-il f*»
licidorai'id tolmn*, pn.tvi.«!f»d that thermite color tint t*tuk**fifuifh«*f«i!dpt»inf.
indicntum in nil cit^fH with u icivi*tt ttt«licntor, II«»wi«v««r it m u^iiuHv ftu*«
timf it iMt»HMJf*r to judgr' tli** firnt it|ijM«itrii!ir«' of fiiiik tliiin it-* liiinl i\iwn\*'-;.it*