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Oximidobenzotetronic acid: a new reagent for the gravimetric determination of cobalt.
128
SHORTCOMMUNICATIONS
spcctrophotometer, converter and recorder The absorption spectrum of each solution was taken repetitively, and the results for the standard deviation m the absorbance produced at the wavelength of maximum absorbance are shown In Table I The concentrations of the nickel solutions were selected to produce absorbance values at the two extremities, and at the centre, of the range of values for which good photometric accuracy is obtamed, and which are normally encountered in caltbratlon curves m quantitative solution sl~ectropl~otometry
The umt clescrlhed permits rapid and reproducible presentation of absorbance at recorders fitted with linear shdc-wires The device stabihses immediately and remains stable during many hours contmuous use Changes m laboratory temperature up to 5” cause less than ION,variatron in output voltage. Dcviatlon from linear response at high ahsorbancc values results from the lnablllty of the Zcner diode to respond strictly logarithrmcally to extremely low currents. The upper limit of linearity of absorbance may be found to vary very shghtly from diode to diode (manufacturers tolerance is 79C ) Logartthm~c scale contraction IS avoided, and it IS possible to read an absorbance of o 7 with the same accurncy as an absorbance of o I On the recorder used it is possible to read absorbances to &-0 oar at any value without difficulty Clremcstry Llefiartment, Jntheraal College, l_ov&n, C W 7 (Gveut Brstatn)
D ALCER G I; KIRKBRIGHT M. D MAYHEW T
1
A
15 ‘1 IIOMI’SON,
z S C 13
DAVIIY,
(Received
U,ZLLUm
(I
5) (I@h)
WlSSl
7
, 8 (1963) 2, 30
FlzlgerJ
February
“,S~l’Ctt’OV~SlO,l”,
s
xrtll, 1907)
Oximidobenzotetronic acid: a new reagent for the gravimetric determination of cobalt The most commonly used reagents for the gravimetric determmatlon of cobalt are anthranihc acicll, os-nitroso-/3-naplitliolz, ammonium phosphates and potassium and more recently FOS-~IX AND WILLIAMSO critIcally re-mvesnitrite4 WILLIIUM tlgated these reagents m order to asse$s their relative values as quantitative precipitanis for cobalt; they recommended the phosphate method with certain modrfications, including a rapid spectrophotometric detcrmmation of cobalt m the filtrate with mtroso-R salt. LINGANE~ has improved the potassium cobaltirntrlte method by the use of bollmg solutions for the precipitation of I
Cktm
Acfn, 39 (rgG7)
128-131
SHORT COMMUNICATIONS
I29
a brownish-red precrpitate is formed, with an excess of sodium hydroxide a deep red solution IS formed, so that a spectrophotometrrc determination is possible. In the present work, rt was found that the precipitation of the cobalt-oximtdobenzotetroruc acid complex was quantrtative between PH 3 o and G o, the precipitate could be weghed after drying or converted to cobalt sulphate. The complex contained a metal : ligand ratio of I ‘3 Preparatzon
of oxa?ntdobe,tzotetrolttc
acad
Of the various methods available for the synthesis of +hydroxycoumarm, that recommended by SrAHnIANN etaI 10 was used The coumarm was readrly converted to a-isomtrosobenzotetromc acrd by the method dcscrrbed by ANSCH~JTZ~~and was further crystallrsed from cold chloroform A I 5-2 ocl/osolution of the reagent m ethanol was used
Cobalt sull>hate solutron was prepared from CoS04.7HaO (RDH, AnalaR) and standarcllsed by means of anthramhc acid1 as well as by conversron to CoSOa after precipitation with n-nltroso-P-naphtliol~ All other salts were of either 13DH AnalalC or lMerck Pro Analyst quality. Drlute solutions of hydrochlorrc acid and ammonium hydroxrde were used for the acllustment of pH The pR measurements were made wrth a 13eckman pR-meter &de! H-2 usmg a suitable glass electrode.
To about xoo ml of an aclueous solutton of cobalt(II) sulphate (contammg about 3 75 mg of cobalt(II)), add 2-3 g of ammomum chloride or nitrate and heat to 40-50”. Add the reagent solutron slowly with constant strrrmg. The mltrally dark green solution graclually changes ancl a greemsh brown precipitate is formed Add the reagent unto! no more precrpitate forms, then add a shght excess (the total amount of the reagent requn-cd is 2-3 times the theoretrcal amount) Leave the solution for 10-15 mm at room temperature so that the supernate becomes clear yellow-green Falter through a weighed G3 smtered glass crucible and wash with hot 1% NHdNOs solutron until the washings are free from chloride and sulphate, then wash with hot water untrl the washmgs give no color with Nessler’s reagent Dry the complex at 140~ and weigh as Co(CuH4NO& TAULE
I
DI
01’
DIFPEI~lSNT
QUANTITICS
OF
COI3ALT
UbING
OYIhIIDOI3l3N/.O~ETItONIC
ACID
c-0
(by
taken
a-rrilroso-~l-~raplrtlroC
mc!lrodj (nw1 1 3 7 15 18
733 768 536 07 84
Co found
D?/fcrc~lcc
Dy m?w
(w!)
1 3 7 I4
0 0 0 0 o
ntclhod (nv)
18
723 758 496 97 7G
010 010 040 IO 08 Alsal
Chatn Acfa, 3g (xgG7)
128-131
130
SHORT COMMUNICATIONS
TABLE
II
EIVECT
Of’ PR
(Wwght
ON
P”
Co found
TABLE
THE
of cobalt
PRECIPITATION
taken=3 06 I 985
(mg)
OX’ COBALT-OXIMIDOB&N2OTETRONlC
ACID
COMPLEX
768 mg) 20 2 970
25 3 I3I
40
50
3 754
3 758
GO
3.750
66 2 093
78 -
III
DETERMINATION
OF COBALT Foreign
IN PRESENC&
OP POREIGN
aon
A rnounl
added (Wl
added
NI 2+ .IY N1SO4.71irO
3 460
IONS
%nz+ as ZnSO4
+71-120
I 3 3 5 7 4
61
3 454 3 474
0 or2 o 008
3 454 3 474 3 459
0 0x2 0 008 0 007 0 0x2 o 008 0 002
4 28 IG 18
3 65 8 65
454 464 474 264 657
0
0x2
0
002
o 008 I 202 I 8og
35 90
3 454 7 474 3 464
Cr3+ as cliromc
alum
3 58 I705 34 38
3 459 3 445 3 469
0 007 0 021 0 003
CIA=+ as CuS04 Tartrntc
* 5H&
4 52 5 69 I909 39 65
4 3 3 3
I o 0 0
12 21
3 062
0 404
8 78
3 075
o 391
4 52 22 21 44 2I
4 540 4 540 4 536
o 028 o 028 0 024
4 65 43 23
4 931 4.540
o 4x9 o 028
24 08 22 76 21 61
2.261
0 005
Oxalatc Phosphate
as (NI&)~HPOQ
Mn’J+ as MnSO4
Acctntc Zn2+
r7c1&SO4
7HaO
cda+
2 256
( WTl
3 3 3 2 I
39 70
4.5’2
Error
875 750 750 525 50
7.86
cc12+ as CclCln~2Hz0
co
$ound (W)
Zna+
Ala+ Cr3+ Mna+
809 633 656 676
343 167 190 2x0
20 79 22 IO
The complex 1s quite stable in the temperature range x20--170’. It 1s soluble m organic solvents such as ethanol, ether and chloroform, but is insoluble in acetone, dilute hydrochloric acid or nitric acid (PH >3), hot water or hot water containing not more than xo”/ ethanol, A#nZ
Chanr
Ada,
3g (IgG7)
128-131
SHORT
COMMUNICATIONS
131
Effect
of $ki on the precapatatson of the complex As can be seen from Table II, cobalt can be accurately estimated m the PH range 3 o to 6 o At lower PH the precipitation is incomplete while at pH 7.8 and above, the complex 1s soluble Sefiaratzon of cobalt from other metal sons With oximldobenzotetromc acid, cobalt could be separated and determined m presence of zmc(II), cadmmm(I1). manganese(II), alumm~um(II1) and chromlum(III) even when these were present rn quantities IO times that of cobalt(I1) (see Table III) Iron(I1) at the p.p m level gives a deep blue water-soluble complex with the reagent, m larger amounts It was precipitated and thus interfered. Copper(I1) was copreclpltated while nickel(I1) Interfered m amounts more than equal to that of cobalt Blsmuth(II1) salts were hydrolysed at the PH used and hence interfered Anions such as phosphate, tartrate, citrate, oxalate and acetate interfered. Further studies regarding complex are in progress.
the nature of cobalt-oxlmldobenzotetromc
G. S MANKU A. N BHAT B D JAIN
Department of Chemtstry, Unzverszty of Delha, Delha-7 (Indaa) I
L 3 4 5 G 7 8 9 IO II
acid
A I VOGEL, A Tcrl Book of Qttaulttattve InorRanrc .~wzlysrs tncfudtrag A nalysrs, 3rd IGIn , Lotigrnrrns, Green CQCo , r9G2, p 550 N H FURMAN. Scoff’s Starrdnrd Methods of Chemrcnl Analysts, Vol York. 1959. p 3r4 N H FURMAN, Scoll'sStandard Methods of Chon~cal Analysts, Vol. York, 1959. p 330 N H FURMAN, Scott’s Sfandard Mcfhods of Cltemrcal Analysis, Vol York. 1959. p 312 W J WILI-IAMS, Talanta. I (1958) 88 W J WILLIAMS AND A G FOSTER, AttczlChrnr Attn. 24 (1961) 20 J J LINGANP,, Anal Churn A&a, 31 (1964) 3x5 A N BHAT AND I3 D TAIN, Anal C/arm Acla, 25 (1gGr) 343 h N BIIAT AND I3 D JAIN, J Ind Chm Sot , 38 (19G1) 779 M A STAHMANN, I WOLF AND I< I? LINK, J Am. Chem Sot, 65 R ANSCHOTZ, Awa C/rem, 3G7 (1909) 169
ECentortnry Instrroncnfal I, D
Van Nostrand,
New
I, D
Van Nostrand,
New
I. D
Van Nostrand,
New
(1943)
2285
(Received November zSth, 1966) Anal. C/rim Acta.
39 (1967) 128-131
SHORTCOMMUNICATIONS
spcctrophotometer, converter and recorder The absorption spectrum of each solution was taken repetitively, and the results for the standard deviation m the absorbance produced at the wavelength of maximum absorbance are shown In Table I The concentrations of the nickel solutions were selected to produce absorbance values at the two extremities, and at the centre, of the range of values for which good photometric accuracy is obtamed, and which are normally encountered in caltbratlon curves m quantitative solution sl~ectropl~otometry
The umt clescrlhed permits rapid and reproducible presentation of absorbance at recorders fitted with linear shdc-wires The device stabihses immediately and remains stable during many hours contmuous use Changes m laboratory temperature up to 5” cause less than ION,variatron in output voltage. Dcviatlon from linear response at high ahsorbancc values results from the lnablllty of the Zcner diode to respond strictly logarithrmcally to extremely low currents. The upper limit of linearity of absorbance may be found to vary very shghtly from diode to diode (manufacturers tolerance is 79C ) Logartthm~c scale contraction IS avoided, and it IS possible to read an absorbance of o 7 with the same accurncy as an absorbance of o I On the recorder used it is possible to read absorbances to &-0 oar at any value without difficulty Clremcstry Llefiartment, Jntheraal College, l_ov&n, C W 7 (Gveut Brstatn)
D ALCER G I; KIRKBRIGHT M. D MAYHEW T
1
A
15 ‘1 IIOMI’SON,
z S C 13
DAVIIY,
(Received
U,ZLLUm
(I
5) (I@h)
WlSSl
7
, 8 (1963) 2, 30
FlzlgerJ
February
“,S~l’Ctt’OV~SlO,l”,
s
xrtll, 1907)
Oximidobenzotetronic acid: a new reagent for the gravimetric determination of cobalt The most commonly used reagents for the gravimetric determmatlon of cobalt are anthranihc acicll, os-nitroso-/3-naplitliolz, ammonium phosphates and potassium and more recently FOS-~IX AND WILLIAMSO critIcally re-mvesnitrite4 WILLIIUM tlgated these reagents m order to asse$s their relative values as quantitative precipitanis for cobalt; they recommended the phosphate method with certain modrfications, including a rapid spectrophotometric detcrmmation of cobalt m the filtrate with mtroso-R salt. LINGANE~ has improved the potassium cobaltirntrlte method by the use of bollmg solutions for the precipitation of I
Cktm
Acfn, 39 (rgG7)
128-131
SHORT COMMUNICATIONS
I29
a brownish-red precrpitate is formed, with an excess of sodium hydroxide a deep red solution IS formed, so that a spectrophotometrrc determination is possible. In the present work, rt was found that the precipitation of the cobalt-oximtdobenzotetroruc acid complex was quantrtative between PH 3 o and G o, the precipitate could be weghed after drying or converted to cobalt sulphate. The complex contained a metal : ligand ratio of I ‘3 Preparatzon
of oxa?ntdobe,tzotetrolttc
acad
Of the various methods available for the synthesis of +hydroxycoumarm, that recommended by SrAHnIANN etaI 10 was used The coumarm was readrly converted to a-isomtrosobenzotetromc acrd by the method dcscrrbed by ANSCH~JTZ~~and was further crystallrsed from cold chloroform A I 5-2 ocl/osolution of the reagent m ethanol was used
Cobalt sull>hate solutron was prepared from CoS04.7HaO (RDH, AnalaR) and standarcllsed by means of anthramhc acid1 as well as by conversron to CoSOa after precipitation with n-nltroso-P-naphtliol~ All other salts were of either 13DH AnalalC or lMerck Pro Analyst quality. Drlute solutions of hydrochlorrc acid and ammonium hydroxrde were used for the acllustment of pH The pR measurements were made wrth a 13eckman pR-meter &de! H-2 usmg a suitable glass electrode.
To about xoo ml of an aclueous solutton of cobalt(II) sulphate (contammg about 3 75 mg of cobalt(II)), add 2-3 g of ammomum chloride or nitrate and heat to 40-50”. Add the reagent solutron slowly with constant strrrmg. The mltrally dark green solution graclually changes ancl a greemsh brown precipitate is formed Add the reagent unto! no more precrpitate forms, then add a shght excess (the total amount of the reagent requn-cd is 2-3 times the theoretrcal amount) Leave the solution for 10-15 mm at room temperature so that the supernate becomes clear yellow-green Falter through a weighed G3 smtered glass crucible and wash with hot 1% NHdNOs solutron until the washings are free from chloride and sulphate, then wash with hot water untrl the washmgs give no color with Nessler’s reagent Dry the complex at 140~ and weigh as Co(CuH4NO& TAULE
I
DI
01’
DIFPEI~lSNT
QUANTITICS
OF
COI3ALT
UbING
OYIhIIDOI3l3N/.O~ETItONIC
ACID
c-0
(by
taken
a-rrilroso-~l-~raplrtlroC
mc!lrodj (nw1 1 3 7 15 18
733 768 536 07 84
Co found
D?/fcrc~lcc
Dy m?w
(w!)
1 3 7 I4
0 0 0 0 o
ntclhod (nv)
18
723 758 496 97 7G
010 010 040 IO 08 Alsal
Chatn Acfa, 3g (xgG7)
128-131
130
SHORT COMMUNICATIONS
TABLE
II
EIVECT
Of’ PR
(Wwght
ON
P”
Co found
TABLE
THE
of cobalt
PRECIPITATION
taken=3 06 I 985
(mg)
OX’ COBALT-OXIMIDOB&N2OTETRONlC
ACID
COMPLEX
768 mg) 20 2 970
25 3 I3I
40
50
3 754
3 758
GO
3.750
66 2 093
78 -
III
DETERMINATION
OF COBALT Foreign
IN PRESENC&
OP POREIGN
aon
A rnounl
added (Wl
added
NI 2+ .IY N1SO4.71irO
3 460
IONS
%nz+ as ZnSO4
+71-120
I 3 3 5 7 4
61
3 454 3 474
0 or2 o 008
3 454 3 474 3 459
0 0x2 0 008 0 007 0 0x2 o 008 0 002
4 28 IG 18
3 65 8 65
454 464 474 264 657
0
0x2
0
002
o 008 I 202 I 8og
35 90
3 454 7 474 3 464
Cr3+ as cliromc
alum
3 58 I705 34 38
3 459 3 445 3 469
0 007 0 021 0 003
CIA=+ as CuS04 Tartrntc
* 5H&
4 52 5 69 I909 39 65
4 3 3 3
I o 0 0
12 21
3 062
0 404
8 78
3 075
o 391
4 52 22 21 44 2I
4 540 4 540 4 536
o 028 o 028 0 024
4 65 43 23
4 931 4.540
o 4x9 o 028
24 08 22 76 21 61
2.261
0 005
Oxalatc Phosphate
as (NI&)~HPOQ
Mn’J+ as MnSO4
Acctntc Zn2+
r7c1&SO4
7HaO
cda+
2 256
( WTl
3 3 3 2 I
39 70
4.5’2
Error
875 750 750 525 50
7.86
cc12+ as CclCln~2Hz0
co
$ound (W)
Zna+
Ala+ Cr3+ Mna+
809 633 656 676
343 167 190 2x0
20 79 22 IO
The complex 1s quite stable in the temperature range x20--170’. It 1s soluble m organic solvents such as ethanol, ether and chloroform, but is insoluble in acetone, dilute hydrochloric acid or nitric acid (PH >3), hot water or hot water containing not more than xo”/ ethanol, A#nZ
Chanr
Ada,
3g (IgG7)
128-131
SHORT
COMMUNICATIONS
131
Effect
of $ki on the precapatatson of the complex As can be seen from Table II, cobalt can be accurately estimated m the PH range 3 o to 6 o At lower PH the precipitation is incomplete while at pH 7.8 and above, the complex 1s soluble Sefiaratzon of cobalt from other metal sons With oximldobenzotetromc acid, cobalt could be separated and determined m presence of zmc(II), cadmmm(I1). manganese(II), alumm~um(II1) and chromlum(III) even when these were present rn quantities IO times that of cobalt(I1) (see Table III) Iron(I1) at the p.p m level gives a deep blue water-soluble complex with the reagent, m larger amounts It was precipitated and thus interfered. Copper(I1) was copreclpltated while nickel(I1) Interfered m amounts more than equal to that of cobalt Blsmuth(II1) salts were hydrolysed at the PH used and hence interfered Anions such as phosphate, tartrate, citrate, oxalate and acetate interfered. Further studies regarding complex are in progress.
the nature of cobalt-oxlmldobenzotetromc
G. S MANKU A. N BHAT B D JAIN
Department of Chemtstry, Unzverszty of Delha, Delha-7 (Indaa) I
L 3 4 5 G 7 8 9 IO II
acid
A I VOGEL, A Tcrl Book of Qttaulttattve InorRanrc .~wzlysrs tncfudtrag A nalysrs, 3rd IGIn , Lotigrnrrns, Green CQCo , r9G2, p 550 N H FURMAN. Scoff’s Starrdnrd Methods of Chemrcnl Analysts, Vol York. 1959. p 3r4 N H FURMAN, Scoll'sStandard Methods of Chon~cal Analysts, Vol. York, 1959. p 330 N H FURMAN, Scott’s Sfandard Mcfhods of Cltemrcal Analysis, Vol York. 1959. p 312 W J WILI-IAMS, Talanta. I (1958) 88 W J WILLIAMS AND A G FOSTER, AttczlChrnr Attn. 24 (1961) 20 J J LINGANP,, Anal Churn A&a, 31 (1964) 3x5 A N BHAT AND I3 D TAIN, Anal C/arm Acla, 25 (1gGr) 343 h N BIIAT AND I3 D JAIN, J Ind Chm Sot , 38 (19G1) 779 M A STAHMANN, I WOLF AND I< I? LINK, J Am. Chem Sot, 65 R ANSCHOTZ, Awa C/rem, 3G7 (1909) 169
ECentortnry Instrroncnfal I, D
Van Nostrand,
New
I, D
Van Nostrand,
New
I. D
Van Nostrand,
New
(1943)
2285
(Received November zSth, 1966) Anal. C/rim Acta.
39 (1967) 128-131