Rapid, Economical and Selective Complexometric Determination of Iron (III) in its synthetic alloys using 3 hydroxy-3 phenyl-1-(2,4,6-tribromophenyl) triazene

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Rapid, Economical and Selective Complexometric
Determination of Iron (III) in its synthetic alloys
using 3 hydroxy-3 phenyl-1-(2,4,6-tribromophenyl)
triazene.
Ombaka, O., Musundi, S. W., Gitonga, L. K., Kibara, D., and Olivia, A. N.
Abstract
The present study describes a simple, selective, rapid and economical method for the determination of iron (III)
in its synthetic alloys using 3-hydroxy -3- phenyl-1- (2,4,6- tribromophenyl) triazene as metallochromic
indicator in the  and temperature range of 2.5-3.0 and 20 60 respectively. The colour and shape of the
synthesized indicator was light yellow shinning needles having melting point of 59. It was crystallized from
ethanol. The results of elemental study showed that, the values of C, H, N obtained experimentally agrees very
well with those obtained theoretically. The colour at the end point changes from violet to light yellow using
EDTA as a titrant. There is no interference in either determination from common metal and anion ions other
than Pb(II), Cr(II), Mo(VI), Mn(II), U(vI), Cu(II), Cd(II), , 
, 
, 
. Reproducible and
accurate results are obtained for 5.59 -1.12mg of Iron with relative error less than ±1.79% and standard
deviation not more than 0.10%. The results of the test method and reference method (Atomic absorption
spectrophotometric) showed that, there is no statistical difference in the results by the two methods.
Index terms – Hydroxytriazenes, Metallochromic indicator, Complexmetric titration, Iron (III), EDTA,
Foreign ions, Selective.
1.0 INTRODUCTION
Hydroxytriazenes have the general structure
R – N – N = N – ′
OH
Where R and ′ is alkyl or aryl group [1], [2].
Hydroxytriazenes are widely used as ligands to
coordinate different transition or inner transition
metal ions due to their good solubility of their
complexes [3]. They coordinate with the metal ions
via the N-OH and the –N-N=N- group [4]. For
example it was reported that complexometric
determination of Zn(II) using three
hydroxytriazeness as metallochromic indicators in
three medicines-zivinal-CD, Becozine, and Vi-
syneral Z [5].
Complexometry is a very useful method for the
determination of major quantities of metals present
in various combinations [6], [7], [8]. The indicators
used in complexometric titrations are as follows;
Mordant black II, Eriochrome black T, Solochrome
black T (Ca, Ba, Mg, Zn, Cd, Mn, Pb, Hg),
Murexide, Ammonium Purpurate (Ca, Cu, Co),
Catechol-Violet (Mn, Mg, Fe, Co, Pb), Methyl blue,
Thymol blue (Pb, Zn, Cd, Hg), Alizarin (Pb, Zn,
Co, Mg, Cu), Sodium Alizarin Sulphonate (Al, Th),
Xylenol Orange (Bi, Th, Pb, Zn, Cd, Hg) [9]. In all
these procedures the quantity of the element
determined is hampered by the presence of some
cations and anions [10]. For example, Cu, Ni, Co,
Cr, Al, even in traces, must be absent when
conducting titration of Iron (III) with EDTA using
Eriochrome black T as indicator [11].
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In the present study the possibility of using
hydroxytriazenes as indicators for Iron (III) - EDTA
titration has been extensively explored. The effects
of foreign ions are studied and application of the
method in the determination of iron (III) in its
synthetic alloys is also reported in this paper.
2.0 MATERIALS AND METHODS
All chemicals used in the analysis were of analytical
reagent grade (merk) and used without further
purification and in all of the steps redistilled water
was used. The atomic absorption spectro-
photometer (Varian spect-AA-10-model) was used
for measurements.
2.1 PREPARATION OF HYDROXYTRIAZENE.
The synthesis of the new hydroxytriazene described
in this study proceeded as follows:
2.1.1 Preparation of aryl hydroxylamine
Nitrobenzene (0.25mol), ammonium chloride (15g),
water (400ml) and rectified spirit (100ml) were
mixed and stirred mechanically at 40°C zinc dust
(40g) was subsequently added in small quantities
until the temperature reached 60°C and maintained
for 15 minutes. The resultant mixture was filtered at
the pump and the residue washed with 100ml of
warm water (40°C). The filtrate was left to cool in a
freezer at 0°C.
2.1.2 Preparation of aryldiazonium salts.
Aromatic primary amine (0.2ml) was dissolved in a
warm mixture of concentrated R
(60ml) and
water (10ml) with vigorous stirring. It was them
kept in freezer to cool. In a separate beaker sodium
nitrite (13.9g) was dissolved in water (40ml) and
left in the same freezer. After three hours the
aromatic amine Sulphate solution was transferred to
an ice bath and the sodium nitrite solution slowly
added with stirring. The temperature of the reaction
mixture was maintained at well below 5°c, which
favoured the formation of the aryldiazonium salt.
2.1.3 Coupling and crystallization
To aryl hydroxylamine (step I) in an ice bath was
slowly added till aryldiazonium salt (step II) in
small portions with continuous stirring. The  was
maintained at 5-6 using sodium acetate and
temperature at  5°. Fifteen minutes later the
resultant mixture was filtered at the pump, and the
residue washed with ice cold water. The crude
hydroxytriazene product was treated with activated
charcoal and crystallized from ethanol.
2.2 REAGENTS
2.2.1 EDTA solution
A stock solution (0.01M) of disodium salt of EDTA
was prepared by dissolving requisite quantity of the
salt in water and standardized against zinc sulphate
solution (0.01M) using xylenol orange as indicator
at  6-7 [12].
2.2.2 Zinc sulphate solution
Prepared by dissolving a known amount of zinc
sulphate in water and standardize gravimetrically by
oxinate method [13], [14].
2.2.3 Solution of diverse ions
Solution of various cations and anions were
prepared by dissolving calculated amount of
appropriate salts in water or in suitable dilute acid
and making up to a known volume.
2.2.4 Xylenol orange indicator (0.5%)
A freshly prepared solution of xylenol orange in
water was used [15].
2.2.5 Iron (III) stock solution (0.01m)
Prepared by dissolving 1.2055g of ammonium iron
(III) sulphate dodecahydrate in water containing
concentrated sulphuric acid (5ml) in a calibrated
flask [16].
2.3 PROCEDURE FOR COMPLEXOMETRIC
TITRATION
All the freshly prepared hydroxytriazene (0.1% in
ethanol) solutions were screened as metallochromic
indicators for iron (III) determination. Iron (III)
solution (5.0 x 10-3M) was titrated in the  range
2.0- 4.0.
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2.4 EFFECT OF  AND TEMPARATURE
 metric studies were carried out by performing
the titration of iron (III) using a 1.0% sodium
acetate-acetic buffer in the presence of a 1.0%
perchloric acid solution. For synthesized
hydroxytriazene the optimal  (2.5 – 3.0) and
temperature (20 -60°c) ranges were determined in
which the colour change at the end point was sharp
and most perceptible. Interference by 35 different
ions was also investigated.
2.5 TITRATION PROCEDURE.
A general titration procedure for ion (III) using
hydroxytriazene as indicator was developed. Iron
(III) solution (10ml) was diluted to 30ml with an
ethanol-water mixture. Five to six drops of
hydroxyzene were added, which usually resulted in
instantaneous development of a blue colouration.
The solution was at this point titrated very slowly
with equimolar EDTA solution. The point where
there was a sharp yellow colour change was taken
as the end point in all the cases. The results were
further augmented by atomic absorption
spectophotometry.
3.0 RESULTS AND DISCUSSION
The physical characteristics, crystalline shape,
colour, melting point etc, for the synthesized
hydroxytriazene are displayed in table 1, together
with the crystallization solvent and the elemental
analyses.
Table 1: Physical characteristic and elemental
analysis of 3-hydroxy-3-phenyl-1- (2, 4, 6-
tribromophenyl) triazene.
The titration of iron (III) in the concentration range
of 0.002-0.010 mol/L (1.12-5.59mg) was carried out
under optimized experimental conditions. These
results are presented in table 2.
The results indicates that the relative error ranges
between +1.19% to -1.79% and the standard
deviation ranges from 0.02 to 0.10. These results
revealed that iron (III) could be accurately
determined using this hydroxytriazene down to
values as low as 0.002M. Further, the tabulated t
value (2.365) at the 95% confidence level exceeds
the calculated t value (0.036) and this shows that,
there is no significant difference between the
amount taken and that which was found. Hence the
proposed method is precise and accurate.
Table 2: Determination of iron in iron (III)
nitrate solution (n=5)
 range = 2.5 -3.0
Temperature range = 20-60°c
End point: violet to light yellow
Iron/mg
Relative
error %
Standard
deviation
+ value at
95%
confidence
level
Taken
Found
5.59
5.03
4.47
3.91
3.35
2.80
1.68
5.62
5.06
4.50
3.93
3.34
2.81
1.70
+0.54
+0.60
+0.67
+0.51
-0.30
+0.36
+1.19
0.06
0.07
0.10
0.03
0.03
0.04
0.03
Calculated
= 0.036
Tabulated
= 2.365
Physical
characteristics
Elemental
Analysis
Molecular
Formula
Th
Exp
Colour and
sharp of
crystals
Light
yellow
shinnin
g
needle
21.6
6
21.4
7
C
12
H
8
N
3
OBr
3
Crystallize
d from
Ethanol
1.55
1.08
M.P
59
10.8
3
11.0
7
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1.12
1.10
-1.79
0.02
* Average of five determination
In order to establish the possibility of using the
proposed method for the quantitative determination
of iron (III), the effect of diverse ions was studied.
This was done by adding different amounts of
diverse ions to a solution containing 2-80 mg of
iron (III). The tolerance levels of the non interfering
diverse ions are summarized in table 3. An error of
less than +2% in the recovery was considered to be
tolerable. The diverse ions such as Pb
(II)(51.80mg),Mo (VI)(95.94mg), Mn(II)(13.74mg),
U(VI)(59.51mg),Cu(II)(15.89mg),
Cd(II)(28.10mg),Cr(III)(13.00mg),(4.75mg),

(23.74mg),
(22.05mg),HPO42-
(23.99mg), do interfere with the determination of
iron (III). The results of interferences shows that,
cation interfere causes positive error while anion
causes negative error. The positive error might be
contributed due to iron(III) and interference species
competing for EDTA during titration while negative
error might be due to interfering species forming a
very stable complex with iron (III) leaving a small
amount of uncomplex iron(III) for titration with
EDTA. The interference of Cr (III) and Cu (III) is
mainly due to the deep purple and blue colour of
their EDTA complex respectively which makes the
detection of their end point rather difficult. The
interference of Ni(II) and Co(II) can be obviated by
the addition of excess potassium cyanide prior to
EDTA complexation as masking agent.
Table3: Determination of iron (III) in presence
of diverse metal ions
(Iron taken in solution =2.80mg)
Diverse
ion
Diverse
ion taken
/mg
 
(mg)
Relative
error %
Na(I)
5.75
2.79
-0.36
K(I)
9.78
2.78
-0.71
Mg(II)
6.08
2.76
-1.42
Ca(II)
10.02
2.82
+0.71
Ba(II)
34.34
2.75
-1.79
Sn(II)
29.67
2.76
-1.42
Zr(IV)
22.81
2.81
+0.36
Th (IV)
58.01
2.78
-0.71
W(VI)
45.96
2.81
+0.36
Zn(II)
16.34
2.75
-1.79
Co(II)s
14.73
2.77
-1.07
Hg(II)
50.15
2.77
-1.07
Ni(II)s
14.78
2.82
+0.71
NH4+
4.51
2.79
-0.36
S2-
8.02
2.76
-1.42
SO4 2-
24.02
2.76
-1.42
SO3 2-
20.02
2.78
-0.71
S2 O3 2-
28.03
2.75
-1.79
Cl-
8.86
2.84
+1.43
I –
31.73
2.77
-1.07
NO2-
11.50
2.81
+0.36
NO3-
15.50.
2.85
+1.79
CO3 2-
15.00
2.83
+1.07
CH3Coo-
14.76
2.78
-0.71
*- Average of the five determination
S -Pre masked with potassium cyanide
The utility of the proposed method was explored in
the determination of iron (III) in its synthetic
mixture of iron (III) with alloy compositions. The
analytical results are given in table 4. The
calculated F value (1.020) is less than the tabulated
value (9.28), so the two methods have comparable
standard deviations. Further, the tabulated t for
(+2) at the 95% confidence level is 2.447
and the calculated t value is 0.008, so there is no
statistical difference in the results by the test and
reference method. This indicates that, the test
method would be effective for the analysis of alloy
samples of similar complexity.
Table 4: Determination of iron (III) in synthetic
mixture with alloy composition.
Mixture
Composit
ion%
Test method
Iron
found*
%
Standar
d
Deviati
on
Relative error %
Fe+Ni
58+42
58.65
0.02
+1.12
Fe
+Si+Ca
8+90+2
7.85
0.02
-1.88
Fe
+Ni+Co
54+29+17
53.86
0.04
-0.26
Fe +Co
60+40
60.51
0.04
+0.85
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*Average of five determinations
4.0 CONCLUSION
A new metallochromic indicator for direct
complexometric determination of iron (III) have
been introduced. The results obtained by the
hydroxtriazene are comparable to those using
atomic absorption spectrophotometric method.
Interference studies have shown that direct
complexometric determination of iron (III) can be
satisfactorily performed in the presence of a number
of cations and anions. This reveals that the method
may be suitable for the determination of iron (III) in
its alloys. Readily prepared and in higher yields,
hyroxytriazene exhibit obvious advantages over
some other metallochromic indicators such as
Eriochrome black T, solochrome black T, murexid,
etc.
4.1 ACKNOWLEDGEMENTS
The authors are grateful to Chuka University for
providing the laboratory facilities.
Similar appreciation goes to Prof E.N Njoka, the
Vice Chancellor of Chuka University for the
support and encouragement he gave towards this
research.
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DETAILS ABOUT AUTHORS
Ombaka, O. Department of Chemistry, Chuka
University, Kenya, P.0 BOX 109-60400 Chuka,
Email: ombakaochieng@gmail.com
Musundi, S. W. Department of Mathematics, Chuka
University, Kenya, P.0 BOX 109-60400 Chuka.
Gitonga, L. K. Department of Nursing, Chuka
University, Kenya, P.0 BOX 109-60400 Chuka.
Kibara, D. Department of Biological Sciences,
Chuka University, Kenya, P.0 BOX 109-60400
Chuka.
Olivia, A. N. Department of Biological Sciences,
Chuka University, Kenya, P.0 BOX 109-60400
Chuka.
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