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Resorcinol as a reagent for the spectrophotometric determination of ferric iron
ANALYTICA
564
RESOKCINOL
CH f&f ICA
VOL. 21 (x959)
ACTA
AS A REAGENT FOR THE SPECTROPHOTOMETRIC DETER~~~NATrON OF FERRIC IRON c;. S. RAO Dcparbnerrl
of Clromistry.
Uuiversity
In a recent communication the use of resorcinol metric determination of uranium has been rcportcd with ferric ions, which is unaffectctl by ferrous ions. the preparation of the reagent is simple. The use spcctrophotometric determination of ferric iron is
of
Suugnr
(Indiu)
as a reagent for the spectrophoto1. Resorcinol gives a violet colour In contrast to existing methods+6 of resorcinol as a reagent for the described in this paper.
EXPERIMENTAL
Absorption mcasurcmcnts were made on Coleman’s Univcrval Spcctrophotomcter, Motlei 14. A Marconi prr mctcr was cmplaycd for pi mcasurcn1unts. A frcuhly prcprrrctl solution of rcvorcinol (Mcrclr’za pure quality) was used for the tncasurcmcnts. Solutions of ferric chloride (Andali) were frcsllly prcparcd anti tttc iron content was dctcrmiuccl gravimctricaily :W f:q&k~. Suitable AnaIaR saits were uvcd for testing the intcrfercncc of cations and anions.
DISCWSSIDN
The absorption spectra of the coloured species (0.004 M ferric chloride and 0.4 A# resorcinol, Curve A, and 0.008 M ferric chloride and 0.08 Ad rcsorcinol, Curve B, in aqueous media) in presence of excess of resorcinol is shown in Fig. I along with that of the pure reagent of the same concentration, Curve C. The coloured product has an appreciable absorption at 450 rnp while the reagent has negligible absorption. The wavelength m/Cwas sclccted to study the various factors clcscribcd below.
The pn of the solution has a considerable effect on the colour intensity. Solutions containing the same amounts of ferric cfiloride and rcsorcinol (in excess) were prepared at different PH values and their absorption was measured. The results (Fig. z) indicate that the colour intensity reaches a maximum at pls 2.9. Excess of reagent, even more than a ten-fold excess, has no influcncc on the colour intensity.
The solution attains its m‘aximum intensity immediately after the addition of reagent. The colour is stable for about fi\% hours at room temperature and then fades slowly. The reagent solution is initially slightly brown and slowly darkens on fieferenccs
ip. 565
VOL.
21 frS)59)
SPECTROPHOTOMETRY
OF
Fe
5%
standing for several days. On heating, the colour decreases appreciably and disappears completely at about 75”. The corrected optical densities of solutions containing 0.5, 0.8, x.0 and 2.0 p.p.m. of ferric chloride showed that the smallest am.ount of ferric ion that can be detected is 1.0 p.p.m.
a3 I.60 2 al =
l.40-
8 $ 1.20 1.0 -
0.60 0.404jo =
&I ,’ ;::‘%O Wavelength
in m,a
- 6&I
0.20 -
Fig. i. Crtrvc <;: absorption of :tn aipcous soltrtion c>f rcyorcinol (0.0,; M). Curve 13: abaorpion of in mixture of ferric cl~loridc (0.008 Af) ilnd rcsorcinol (0.08 M). Curve A: absorption of s mixture of ferric cflloridc (0.00~ M) zind rcsorcinol (0.04 M).
Fig. 2, Vdntion of opticd tlcnsity with pH of n mixture of fcrriccldoridc (0.004 M) and rcsorcinol (0.04 M).
The composition of the colourcd product was determined by following Job’s continuous variation method6 as modified by Vosm~acr~ AND COOPER’. Solutions of M/Go ferric chloride and M/30 rcsorcinol were mixed in different proportions in a total volume of 20 ml. The optical densities at different wavelengths, e.g. 450 and 540 my&,were plotted against the composition of the solution, i.e., ._- [RI __._.. ^__._
[R]
+ [rQ+]
(Fig. 3). Both curves show maxima at a composition corresponding to 0.75, thus indicating tbc formation of a I : 3 product bctwcen ferric ion and resorcinol : FCC13 -t_ 3 CnC_tr(Otf)2 -
I;‘C(C&I&O&
f
3 Ef.CI.
An attempt to determine the composition by conductivity and pi titration methods failed to give conclusive results possibly- because one of the reaction products is a . I free acid. ibferences
#J.568
566
VOL.
c. s. RAO
21 (1959)
Beer’s law The validity of Reer’s law for the system was investigated by the usual method at 450 rnp (Fig. 4) .The system obeys Beer’s law in the concentration range 0.25.10-3 M to 1.416.10-3 M.
~ 0.6 .+ 2 0 ; 0.4 .y 0" 0.2
0.0 0.0
0.2
0.4
0.6
0.6
1.0
22) ‘%5--L--
3. Curves
showing tlia cornposition of the colourecl product formed from ferric cllloridc and rcsorcinol at 450 m/Asnd 540 m/r. Fig.
Fig.
‘-76~--J I6.0
Q__-~~~___*~~___.;~;~.-i~~.__.~~*
ml of
ferric
2oa
chloride
4. Curve showing the validity of 13cor’s law for the system ferric cldoridc-rcsorcinol.
of 0Lhcr ions
Inlarference
The cffcct of certain ions that are likely to interfere with tlreestimation of ferric iron was tested (Table I). The amount of an ion (in p.p.m.) that will produce a j= 2% change in optical density was taken as the tolerance limit.
TABLE E.PFlSCT
Ferric
1CCl I
ion o.oor25
OB
SOME
M (69.8 p.p.m.)
ClNOoSO,$-” ]:-‘r 13rLO,13r03-
I
CATIONS
AND
nntl rcsorcinol
0.0125 M. Temp.
-2.2
10,000 12,400
4,800
I .goo
30 8,000 6.350 835 320
-2.0
-58.5 -23.5 -I- 2.0 -1.8 -1-2.3 :I:
krrgc CXCCSY 4,soo 8,000 6,500 835
g
12
-I-
7’
I
-I-
89
280
25-2~~
IO,000
clinngc
no
200
KlOn NaNOa NaaSaOa
ANLONS
280
SI’ECTROPZIOTOME’kRY TABLE
IC2S20e
szoe-2
567
Or: T;e
I (continued)
192
IO
-‘7 -t- 22
2
2
-i-*.5 +30 -+ I2
a
-t 56 -!- 65.5
1c1-i31=04
iUn04Cr04-2 Cr207-2 Fc(CN)~-~ Fc(CN)~-~ AsO4-3 l?o4-3
(NH&iMo04
MQ,o4-2
I<.$%207 NazLv04
%.JO~-~ wo4-”
I<-formatc Na-ncctatc Nn-oxdlatc Na-l<-tartratc
HCOOCI-l~C00CaO4-2 C~Fl4Oo-”
: 3 I 5 2 II I.50 3
Nn-succinatc
C4I’i404-2
2
Na2C03 ICCNS l
co3-2 CNS-
IO
5 4 1 II 72 25
37
25 22
Nn-salicylatc Na-citrate AgN’& CuSO4
col~I~(oH)CooCnIIG07-3 Af3+ C”+!
5 2 I
3 2
H&la SnCI,j BiC13 UC12
Hg+2 Sn+4 Hi+3 cd+2
Ala(SO4)3
Al+3
CrCla
cl-+3
Co(NOo)a
co+2
NiCla
NW
56 03 ‘3 .5 3 2 I 2
Cc(N03)3 ncso4 ‘1’11(N0~)~
C&3 DC+2
I I ‘2
T-h+4
50 59 2 22s I I2
7 1
ACKNOWLED_G,EMZI’jT
+45.G -t_82.3 _1- f8.5 +9 -37.5 -12 -1.3 +*3 -22.0 + 2.5 .-I- 3 -1-2.1 -t_ 20 -2.H
_
2
3 I 2
‘50
+5*7 -t-40 +s.7 +30 -+- 17.6 + I.9 -I- Go f 2.0 -p 20.7 + 3.4 -t-2.3 i-4 -8 +51.3 -f- 4 i-3.1 -j- 2.81 -2.3 i-10 +4 -t I.9
+3 3-l-5 +7 i-3.1 +3
2
50 03
3
I I I
-+-2.0
2
$_8 +1.7
I
:,
:, ;,,
The’ author expresses’his ‘grateful th&nl@to;Prof. ‘A.. K. BHATTACHARY’A for his king interest in’the.presenti:work,i:and:F!i.~~~~~~~. JAI& for.his,valuable assistance.
VOL.
C. S. RAO
gs3 .
(1959)
21
SUMMARY A zq>cctrophotomctric method for a rapid determination scribctl. Ferrous iron h;zu no effect.
Unc m&hock ypcctrophotom~trique rlc rdsorcinc. Lc fcr(If) nc gkic prrs,
cst clkritc
of ferric iron with
pour Ie dosage rapicic du fcr(IiI),
1% win1 cinc spel~troyhotomctrischc Schncllmcthodc Eison(I1) mit I-Iilfc von IZevorcin bcuchricbcn.
zur Bxtimmung
1’. C. JAIN AND G. Se RAO, f?mil. Cfiim. Ada, 20 (195~)) 171. S. M, P~rmtr, Andysl, 8t (1956) 37t. M, ZBIINILR, And. Chcnr., 28 (rggb) lg8, E. I% IhKHANAN AND w. WENCIt;K, A~?Zd. CkCm., 29 (1957) 754. A. L. Uiun~woon, Aad Glut., 30 (1958) 45. P.Jotr, Ana. CXim,, 9 (~928) 113. w. c. VOSIXURGH AND It. J. COOPER, f. .d?ttrr. C!Mt% SOL, 63 ($941)
J 2 3 4 fi S 7
von
SCHNELLE
PAPIERCHROMATOGRAPHISCME Ba, Ca, Sr UND Mg
is de-
BU moyen
I%scn(III)
n&en
437.
Received
.
rmorcinol
July roth,
TRENNUNG
rgsg
VON
EINLBITUNG It1 kkr systematischcn qualitativen Analyst dcr Kationen mitt& Trennungen auf nasscm Wcge bietct bckanntlich die Gruppc der Erdalkalimctalle Schwicrigkeiten, die durch die grossc Ahnlichkeit im chcmischen Verhaltcn diescr Ioncn vcrursacht werdcn. Eine sorgf%ltige Analyse dicscr Gruppc erfordert denri such rclativ grossen Aufwand un Zeit und Miihc. Namentlich die Trcnnung von Ca und Sr ist gewijhnlich unbefriedigend. Fi.ir die beziiglichen Arbeitsmethoden sci auf die zahlrcichen Uiichcr .. iibcr qualitative Analyst verwiescn, Die MGglichkeit einer papierchromatographischcn Trcnnung w-urdc bcreits von mehreren Autoren gczeigt. Die verschicdenen Arbcitsweisen unterschciden sich ?$,a. mit Bezug auf die Papicrsorte, das geradlinigc oder radialc Laufcn dcr mobilen Phase, die Zusamrncnsetzung dicser Phase, die Zeitdauer vom Akklimatisiercn des Papiers, die Dauer dcs Fliissigkeitsstromes und die Wahl der Nachweisreagenzien. Auf dcr Suche nach einer Arbcitsweise die sich sowohl zum Untcrrichtspraktikum als au allgemeinen &alytischen Zwecken eignen tirdc, stellten wir der zu wghlenden
Literatuv
S. 571
564
RESOKCINOL
CH f&f ICA
VOL. 21 (x959)
ACTA
AS A REAGENT FOR THE SPECTROPHOTOMETRIC DETER~~~NATrON OF FERRIC IRON c;. S. RAO Dcparbnerrl
of Clromistry.
Uuiversity
In a recent communication the use of resorcinol metric determination of uranium has been rcportcd with ferric ions, which is unaffectctl by ferrous ions. the preparation of the reagent is simple. The use spcctrophotometric determination of ferric iron is
of
Suugnr
(Indiu)
as a reagent for the spectrophoto1. Resorcinol gives a violet colour In contrast to existing methods+6 of resorcinol as a reagent for the described in this paper.
EXPERIMENTAL
Absorption mcasurcmcnts were made on Coleman’s Univcrval Spcctrophotomcter, Motlei 14. A Marconi prr mctcr was cmplaycd for pi mcasurcn1unts. A frcuhly prcprrrctl solution of rcvorcinol (Mcrclr’za pure quality) was used for the tncasurcmcnts. Solutions of ferric chloride (Andali) were frcsllly prcparcd anti tttc iron content was dctcrmiuccl gravimctricaily :W f:q&k~. Suitable AnaIaR saits were uvcd for testing the intcrfercncc of cations and anions.
DISCWSSIDN
The absorption spectra of the coloured species (0.004 M ferric chloride and 0.4 A# resorcinol, Curve A, and 0.008 M ferric chloride and 0.08 Ad rcsorcinol, Curve B, in aqueous media) in presence of excess of resorcinol is shown in Fig. I along with that of the pure reagent of the same concentration, Curve C. The coloured product has an appreciable absorption at 450 rnp while the reagent has negligible absorption. The wavelength m/Cwas sclccted to study the various factors clcscribcd below.
The pn of the solution has a considerable effect on the colour intensity. Solutions containing the same amounts of ferric cfiloride and rcsorcinol (in excess) were prepared at different PH values and their absorption was measured. The results (Fig. z) indicate that the colour intensity reaches a maximum at pls 2.9. Excess of reagent, even more than a ten-fold excess, has no influcncc on the colour intensity.
The solution attains its m‘aximum intensity immediately after the addition of reagent. The colour is stable for about fi\% hours at room temperature and then fades slowly. The reagent solution is initially slightly brown and slowly darkens on fieferenccs
ip. 565
VOL.
21 frS)59)
SPECTROPHOTOMETRY
OF
Fe
5%
standing for several days. On heating, the colour decreases appreciably and disappears completely at about 75”. The corrected optical densities of solutions containing 0.5, 0.8, x.0 and 2.0 p.p.m. of ferric chloride showed that the smallest am.ount of ferric ion that can be detected is 1.0 p.p.m.
a3 I.60 2 al =
l.40-
8 $ 1.20 1.0 -
0.60 0.404jo =
&I ,’ ;::‘%O Wavelength
in m,a
- 6&I
0.20 -
Fig. i. Crtrvc <;: absorption of :tn aipcous soltrtion c>f rcyorcinol (0.0,; M). Curve 13: abaorpion of in mixture of ferric cl~loridc (0.008 Af) ilnd rcsorcinol (0.08 M). Curve A: absorption of s mixture of ferric cflloridc (0.00~ M) zind rcsorcinol (0.04 M).
Fig. 2, Vdntion of opticd tlcnsity with pH of n mixture of fcrriccldoridc (0.004 M) and rcsorcinol (0.04 M).
The composition of the colourcd product was determined by following Job’s continuous variation method6 as modified by Vosm~acr~ AND COOPER’. Solutions of M/Go ferric chloride and M/30 rcsorcinol were mixed in different proportions in a total volume of 20 ml. The optical densities at different wavelengths, e.g. 450 and 540 my&,were plotted against the composition of the solution, i.e., ._- [RI __._.. ^__._
[R]
+ [rQ+]
(Fig. 3). Both curves show maxima at a composition corresponding to 0.75, thus indicating tbc formation of a I : 3 product bctwcen ferric ion and resorcinol : FCC13 -t_ 3 CnC_tr(Otf)2 -
I;‘C(C&I&O&
f
3 Ef.CI.
An attempt to determine the composition by conductivity and pi titration methods failed to give conclusive results possibly- because one of the reaction products is a . I free acid. ibferences
#J.568
566
VOL.
c. s. RAO
21 (1959)
Beer’s law The validity of Reer’s law for the system was investigated by the usual method at 450 rnp (Fig. 4) .The system obeys Beer’s law in the concentration range 0.25.10-3 M to 1.416.10-3 M.
~ 0.6 .+ 2 0 ; 0.4 .y 0" 0.2
0.0 0.0
0.2
0.4
0.6
0.6
1.0
22) ‘%5--L--
3. Curves
showing tlia cornposition of the colourecl product formed from ferric cllloridc and rcsorcinol at 450 m/Asnd 540 m/r. Fig.
Fig.
‘-76~--J I6.0
Q__-~~~___*~~___.;~;~.-i~~.__.~~*
ml of
ferric
2oa
chloride
4. Curve showing the validity of 13cor’s law for the system ferric cldoridc-rcsorcinol.
of 0Lhcr ions
Inlarference
The cffcct of certain ions that are likely to interfere with tlreestimation of ferric iron was tested (Table I). The amount of an ion (in p.p.m.) that will produce a j= 2% change in optical density was taken as the tolerance limit.
TABLE E.PFlSCT
Ferric
1CCl I
ion o.oor25
OB
SOME
M (69.8 p.p.m.)
ClNOoSO,$-” ]:-‘r 13rLO,13r03-
I
CATIONS
AND
nntl rcsorcinol
0.0125 M. Temp.
-2.2
10,000 12,400
4,800
I .goo
30 8,000 6.350 835 320
-2.0
-58.5 -23.5 -I- 2.0 -1.8 -1-2.3 :I:
krrgc CXCCSY 4,soo 8,000 6,500 835
g
12
-I-
7’
I
-I-
89
280
25-2~~
IO,000
clinngc
no
200
KlOn NaNOa NaaSaOa
ANLONS
280
SI’ECTROPZIOTOME’kRY TABLE
IC2S20e
szoe-2
567
Or: T;e
I (continued)
192
IO
-‘7 -t- 22
2
2
-i-*.5 +30 -+ I2
a
-t 56 -!- 65.5
1c1-i31=04
iUn04Cr04-2 Cr207-2 Fc(CN)~-~ Fc(CN)~-~ AsO4-3 l?o4-3
(NH&iMo04
MQ,o4-2
I<.$%207 NazLv04
%.JO~-~ wo4-”
I<-formatc Na-ncctatc Nn-oxdlatc Na-l<-tartratc
HCOOCI-l~C00CaO4-2 C~Fl4Oo-”
: 3 I 5 2 II I.50 3
Nn-succinatc
C4I’i404-2
2
Na2C03 ICCNS l
co3-2 CNS-
IO
5 4 1 II 72 25
37
25 22
Nn-salicylatc Na-citrate AgN’& CuSO4
col~I~(oH)CooCnIIG07-3 Af3+ C”+!
5 2 I
3 2
H&la SnCI,j BiC13 UC12
Hg+2 Sn+4 Hi+3 cd+2
Ala(SO4)3
Al+3
CrCla
cl-+3
Co(NOo)a
co+2
NiCla
NW
56 03 ‘3 .5 3 2 I 2
Cc(N03)3 ncso4 ‘1’11(N0~)~
C&3 DC+2
I I ‘2
T-h+4
50 59 2 22s I I2
7 1
ACKNOWLED_G,EMZI’jT
+45.G -t_82.3 _1- f8.5 +9 -37.5 -12 -1.3 +*3 -22.0 + 2.5 .-I- 3 -1-2.1 -t_ 20 -2.H
_
2
3 I 2
‘50
+5*7 -t-40 +s.7 +30 -+- 17.6 + I.9 -I- Go f 2.0 -p 20.7 + 3.4 -t-2.3 i-4 -8 +51.3 -f- 4 i-3.1 -j- 2.81 -2.3 i-10 +4 -t I.9
+3 3-l-5 +7 i-3.1 +3
2
50 03
3
I I I
-+-2.0
2
$_8 +1.7
I
:,
:, ;,,
The’ author expresses’his ‘grateful th&nl@to;Prof. ‘A.. K. BHATTACHARY’A for his king interest in’the.presenti:work,i:and:F!i.~~~~~~~. JAI& for.his,valuable assistance.
VOL.
C. S. RAO
gs3 .
(1959)
21
SUMMARY A zq>cctrophotomctric method for a rapid determination scribctl. Ferrous iron h;zu no effect.
Unc m&hock ypcctrophotom~trique rlc rdsorcinc. Lc fcr(If) nc gkic prrs,
cst clkritc
of ferric iron with
pour Ie dosage rapicic du fcr(IiI),
1% win1 cinc spel~troyhotomctrischc Schncllmcthodc Eison(I1) mit I-Iilfc von IZevorcin bcuchricbcn.
zur Bxtimmung
1’. C. JAIN AND G. Se RAO, f?mil. Cfiim. Ada, 20 (195~)) 171. S. M, P~rmtr, Andysl, 8t (1956) 37t. M, ZBIINILR, And. Chcnr., 28 (rggb) lg8, E. I% IhKHANAN AND w. WENCIt;K, A~?Zd. CkCm., 29 (1957) 754. A. L. Uiun~woon, Aad Glut., 30 (1958) 45. P.Jotr, Ana. CXim,, 9 (~928) 113. w. c. VOSIXURGH AND It. J. COOPER, f. .d?ttrr. C!Mt% SOL, 63 ($941)
J 2 3 4 fi S 7
von
SCHNELLE
PAPIERCHROMATOGRAPHISCME Ba, Ca, Sr UND Mg
is de-
BU moyen
I%scn(III)
n&en
437.
Received
.
rmorcinol
July roth,
TRENNUNG
rgsg
VON
EINLBITUNG It1 kkr systematischcn qualitativen Analyst dcr Kationen mitt& Trennungen auf nasscm Wcge bietct bckanntlich die Gruppc der Erdalkalimctalle Schwicrigkeiten, die durch die grossc Ahnlichkeit im chcmischen Verhaltcn diescr Ioncn vcrursacht werdcn. Eine sorgf%ltige Analyse dicscr Gruppc erfordert denri such rclativ grossen Aufwand un Zeit und Miihc. Namentlich die Trcnnung von Ca und Sr ist gewijhnlich unbefriedigend. Fi.ir die beziiglichen Arbeitsmethoden sci auf die zahlrcichen Uiichcr .. iibcr qualitative Analyst verwiescn, Die MGglichkeit einer papierchromatographischcn Trcnnung w-urdc bcreits von mehreren Autoren gczeigt. Die verschicdenen Arbcitsweisen unterschciden sich ?$,a. mit Bezug auf die Papicrsorte, das geradlinigc oder radialc Laufcn dcr mobilen Phase, die Zusamrncnsetzung dicser Phase, die Zeitdauer vom Akklimatisiercn des Papiers, die Dauer dcs Fliissigkeitsstromes und die Wahl der Nachweisreagenzien. Auf dcr Suche nach einer Arbcitsweise die sich sowohl zum Untcrrichtspraktikum als au allgemeinen &alytischen Zwecken eignen tirdc, stellten wir der zu wghlenden
Literatuv
S. 571