Hydrogen Peroxide Determination in the Presence of Chromate JOSEPH RYNASIEWICZ Knolls Atomic Power Laboratory, General Electric Co., Schenectady,
A novel procedure employing ion exchange resins was developed to separate hydrogen peroxide from chromate ions, thus permitting the subsequent analysis of peroxide to determine its decomposition rate in sodium chromate solutions. At high pH, peroxide was adsorbed anionically on the ion exchange resins along with chromate. By selecting a resin which would be effective at nearly neutral conditions, the chromate was adsorbed and satisfactorily separated from peroxide. The hydrogen peroxide was determined colorimetrically by the pertitanic acid method. It was found that the rate of peroxide decomposition in slightly alkaline sodium chromate solutions was dependent on temperature, pH, and chromate concentration.
N. Y.
tral range as the triiodide ion.” I t was believed necessary either to find a more reliable method for peroxide in the presence of foreign constituents or to remove the interferences. EXPERIMENTAL PROCEDURES
iissuming that relatively pure solutions would be analyzed for peroxide, the titanium sulfate colorimetric procedure described by Eisenberg ( 4 ) seemed to be a simple and sufficiently sensitive method. This procedure was tested on solutions buffered to pH 9 which contained silicate, molybdate, tungstate, or chromate inhibitors present in the ratio of 10 parts of inhibitor to 1 part of peroxide. The results are given in Table I and show that as little as 8 p.p.m. (10-4111)of peroxide was determined with the usual accuracy of colorimetric work, except where the chromate inhibitor was present. The colorimetric determination of hydrogen peroxide with titanium sulfate after removing chromate by precipitation or solvent extraction methods was unsuccessful. Although Nachod ( 1 0 ) reported the recovery of chromium as chromate from electroplating solutions using an anion exchange resin, Kunin (6-0) in annual summaries on ion exchange resins made no mention of peroxide separations. Consequently the following method was developed whereby peroxide was effectivelyseparated from chromate which was absorbed on an ion exchange resin. All of the ion exchange resins used in this work were manufactured by the Rohm 8: Haas Co., Philadelphia, Pa.
H E X water is subjected to intense gamma and neutron radiation, one of the products formed is hydrogen peroxide, which is believed to be corrosive to steel, especially during the radiation period ( 2 ) . Therefore, to correlate corrosion rates with hydrogen peroxide concentrations, it was necessary to measure the level of peroxide under different conditions and in the presence of various corrosion inhibitors, especially sodium chromate Furthermore, it was desired to measure the decomposition rate of peroxide to note any steady state level. Most of the methods described in the literature for the determination of hydrogen perovide depend on oxidation or reduction reactions (1,3-5,11,13, 1 4 ) , since hydrogen peroxidecan be either an oxidizing or a reducing agent. However, it was suspected that some of the inhibitors or corrosion products would interfere by reacting with the peroxide under the conditions of the analytical procedure. Allen and Bowman ( 1 ) found that l O - S J I hydrogen peroxide could be determined in the presence of lO-4.lI dichromate by measuring the iodine formed from the reaction of potassium iodide and peroxide catalyzed by molybdic acid. On the other hand, Patrick and Wagner (11) stated that the method is “limited to solutions which do not contain other constituents that either oxidize iodide ion or absorb in the same spec-
METHOD
This procedure applies to the determination of peroxide in unbuffered, neutral, or slightly alkaline solutions containing up to 10-331 sodium chromate.
Table 11. Determination of Hydrogen Peroxide in Chromate Solutions Using IRA-400 pesin KazCroc Present, M OR
~ z 0 2 present
.M X 10 4 2
0
Table I. Determination of Hydrogen Peroxide in Presence of Various Corrosion Inhibitors by the Titanium Sulfate Method Inhibitor 10 -3.11 NanCrOc
10-3Jf NazSiOz
HzOa Added, P.P.M. 2.6
%
13.1 26.2 131 .O
P.p.m. 9,2 8 4 7.8 5.2 85.0
theory 350 160 60 20 65
2.6 5.2 13.1 26.2 131 .O
2.7 5.3 13.0 26.0 130.0
104 102
5.2
10-2
Hn02 Found __
2.6 5.2 13.1 26.2 131 .O
in
14 7.1
1
2.6
4
2
14 7.1
1
2.6
4 2
14 7.1
1
2.6
HaOz Found Absorbance 70theory 0.590 100 0.305 100 0.110 100 0.570
97
0.300 0.108
98 98
0.496 (0.495)
84 ( 8 4 ) b
0 . 2 2 8 (0.240bb 0.06 (0.09)
75 (79); 54 (82)
91
97
98
100 4 Standard HzOz solutions were not brought in contact with ion exchange resin b Values in parentheses were obtained a f t e r contact of solution with 4 grams of resin for 10 minutes, decanting of solution into fresh resin, and contact f o r a n additional 5 minutes.
99 99
99
Prepare a quantity of a neutral anion exchange resin as follows. Stir the strongly basic resin, IRA4-400(R,NOH), with a concentrated sodium chloride solution. Decant the solution and wash out the residual sodium chloride with water. Repeat this treatment until a suspension of the resin in water gives a pH of 7.0 to 7.3 v,.ith the glass electrode.
108 106
13.3 27.0 130.0
Pp
93 89
10-3M NanMoOc
10-3M NazWO,
4
102 103 99
355
356
ANALYTICAL CHEMISTRY
Stir about 20 ml. of the unknown peroxide-chromate solution with 2 grams of the neutral anion exchange resin for 10 minutes. Allow the resin to settle and centrifuge about 15 ml. of the supernatant solution. Withdraw about 10 ml. of the centrifuged solution with a transfer pipet. Add the solution to the mark of a 10-ml. volumetric flask containing 1 ml. of 0.02% titanium suIfate-20% sulfuric acid solution and mix well. Allow the color to develop for a few minutes and read the absorbance a t 420 mp using a 25-mm. cell. A standard curve prepared from a measured amount of a peroxide solution standardized with potassium permanganate ( 5 ) may be used to obtain the peroxide concentration in the unknown solution. The concentration of peroxide in the solution taken for analysis should be multiplied by l0/8, since a 9-ml. aliquot was diluted to a 10-ml. volume. For solutions containing between 10-3 and 10-*M sodium chromate, stir 4 grams of the resin with 20 ml. of solution until the solution becomes colorless. Decant the supernatant solution into a beaker containing 2 grams of fresh resin, stir for 10 minutes, and proceed as previously described. RESULTS
Table I1 shows that as little as 2.6 p.p.m. of peroxide could be determined in and 10-4iZI chromate solutions with a precision of +2 relative % and with an apparent accuracy of 82, 91, and 98%, respectively. In fact, the accuracy was better than the data in Table I1 would indicate because of the effect of chromate on peroxide decomposition. Table 111shows that in 10-4M peroxide solutions, only 1 p.p.m. of chromium as sodium chromate for every 30 p.p.m. of peroxide gave a negative error of 4% peroxide by the titanium sulfate method. However, all except 0.1 p.p.m. of chromium was removed from the peroxide solutions containing 10-3 and 10-'M chromate using the ion exchange resin under the conditione of the analytical procedure. A single contact with 4 grams of resin removed all but 4 p.p.m. of chromium from a 10-2M chromate
pH va. TIME DURING EXCHANGE
OF CrO; WITH AS RECEIVED XE-81 RESIN
A
k4hOpFOUNDvS.X SATURATW OF XE-81 RESIN WI n 0.IM NozCrO, */a
pH
K :1
MINUTES
4 6 8 M 40 60 80 % RESIN SATURATED WITH 0.1 M NopGrO, 2
I2
UNSATURATED RESIN t 10% No,CfO,
IO
P"
0
-
"
O A
I
+
UNSATURATED RESIN
HeO
B
. 2
RESIN S A T U ~ ~ E ~ ~ NaCP I T t H 1 6 % NOECQ
.
4
.
-
E
I
6
MINUTES
8
Ir)
I2
Figure 2. pH Transitions during Chromate Exchange with XE-81 Resin
solution, and an additional contact with 2 grams of resin removed all but 0.5 p.p.m. of chromium. I t was believed that cationic corrosion products such as iron, nickel, and chromium, as well as some anions such as chroni:itc, would interfere with the titanium sulfate method for peroxide. Consequently an anion-cation exchange resin (mixed-bed type) was sought which would remove the relatively small amounts of interfering cations along with chromate. An amino-sulfonic acid (R,NHTR,SOaH) type of resin, SI:-81, was substituted in the analyt,ical procedure, but a negativv test for peroxide was obtained. When the resin from the previous test was re-used to repeat the experiment,, a positive qualitative test for peroxide was found. Apparently the positive peroxidc test was associated with the partial saturation of the resin with sodium chromate. I t wap found empirically (Figure 1) that 1 part by weight (grams) of resin equilibrated with 3 parts (milliliters) of 0.1M sodium chromate gave an ion exchange material (60% saturated) which would separate all but 0.6 p.p.m. of chromium. Table IV, column B, shows that 87 f 1% of the added peroxide (2 to 59 p.p.m.) waa found using the 60% saturated resin. The 87 =k 1% peroxide found appears to be low, largely as B result of peroxide decomposition during the analysis aa will be shown later. The mechanism effecting the successful analysis of peroxide using the chromate-treated resin was not fully understood, but it was believed that it was partially dependent on pH. Figure 1 shows that during the separation of chromate with the *received resin, a pH-transition curve waa obtained which closely followed the curve made by plotting per cent peroxide found against the degree of saturation of the chromate-treated rclsin.
IO
IO0
Figure 1. pH Dependence of Hydrogen Peroxide Chromate Separation with XE-81 Ion Exchange Resin
Table 111. Effect of Sodium Chromate on Pertitanic Acid Complex (10-'M HLOP,15 p . p . m . ) 10-3.w NsrCrOh Added P.p.m. M1. Cr 1 0.5 5
10
20
0
a
b I R - 4 8 , %NH2 TYPE ANION EXCHANGE RESIN
HlOn/Cr Ratio 30
2.5
5.0 10.0
0
A
B"
A-B
"0
- 4 - 23
...
0.34 0.17 0.56
0,005 0.02 0.04
0.54
6
0.54 0.45
0.00
0.56
3 1.5
'
0.08
0.43 0.30 0.09
- 46 - 84 0
No peroxide present -~
MB?, ~ O , H - ~ O TYPE H EXCHANGE RESIN
Relative Error,
Absorbance
- __
14
6.0 5.6 MINUTES
Figure 3. pH Transition Curve for Differen1 Resins with 10-SM Sodium Dichromate
V O L U M E 2 6 , NO. 2, F E B R U A R Y 1 9 5 4
357
Table IV. Determination of Hydrogen Peroxide in 1O-aM Sodium Chromate Solutions Using Chromate-Treated XE-81 Resin [One part (grams) of resin was equilibrated with 3 parts (milliliters) of 0.1M NazCrO,]
tion used to wash the resin. It wa3 concluded that at high pH conditions, hydrogen peroxide was adsorbed anionically on the R,NH2 portion of the mixed-bed resin. Since the successful performance of the mixed-bed resin depended on pH, the resin was equilibrated with a concentrated
IItOz Founda
A
HzOz ridded,
P .P.M. I .92 2.94 3.83 5.88 Y.60 11.5 14.7 17.6 19.2 "9.4 58,8
P.p.m.
...
1.32
...
3.71
...
70
theory
B P.p.m.
..
1.67
87
..
3.29
86
46 63
... 11.1 ...
76
22.8 47.0
74
... ...
8.35 10.2
...
15.2
16.3
80
Av. = 87
...
n.7
%
loot
10
theory
.. 87 89
..
86 85
qY KH
50
0 0
* 1%
A . Chromate-peroxide solutions were allowed to stand for about 10 minutes before analysis; B . Chromate-peroxide solutions were analyzed immediately after being prepared. -~ .
OH 8.5
:iv, 10
5 5
1
#
IO
HOURS
,
20
, ,
30 ,
25
Figure 5. pH Effect on Decomposition of lO-4M Hydrogen Peroxide in M Sodium Dichromate at 40" C.
sodium chloride solution in an effort to obtain a neutral material, probably RGNH3C1-R803Na. However, an aqueous slurry of this resin had a pH of 4.0. The ion exchange material removed chromate over a p H range of 7 . 2 to 4.5 (Figure 2), permitting an 85% recovery of peroxide (Table V). Two other commercial resins (besides IRA-400 and XE-81) were tested to see if a chromate-peroxide separation could be effected. The p H transition curves for these resins with lO-3M chromate are shown in Figure 3. IR-4B resin, the R,NH2-type anion exchanger, was buffered over a pH range of 8.3 to 8.1 but failed to remove chromate. According t o the Rohm 8: Haas sales literature ( l a ) ,this material is effective only below a pH of 7. By making the chromate-peroxide solution slightly acid, it may be possible to separate the t r o constituents with this resin.
70
z 60 u)
50 40
'
30 20 10
0
Figure 4. Temperature Effect on Decomposition of 1.6 X 10-'M Hydrogen Peroxide in 10-3M Sodium Dichromate pII 8.5 solution
The highest value (90yo) for peroxide was obtained using a resin whivh was 50% saturated with chromate-Le., 1 part (grams) of resin to 2.5 parts (milliliters) of 0.1M chromate solution. The decrease in the peroxide found using resins which were more than 70% saturated may be ascribed to the insufficient exchange caparity of the resin, causing an incomplete removal of chromate. The changes in pH during equilibration of the partially saturated and of the unsaturated resin (XE-81) with 10-aM sodium chroniate and with water are shown in Figure 2. The exchange of chromate started a t a p H of about 10.5 with the unsaturated rcssin, and under slightly acid conditions with the partially satur:ttetl resin. Curve C (Figure 2 ) , in effect, is thetailendofthepHtime curve in Figure 1. It was desirable to know If the peroxide was destroyed or adsorbed when the unsaturated resin was used. Aft P a chromatefree peroxide solution was slurried with XE-81 resin (R,XH211.803H type) for 10 minutes, the supernatant solution gave a negative test for hydrogen peroxide. When the solution was decanted, the resin was washed with water and then with 1% sulfuric acid. The acid solution contained 78% of theperoxideadded. The experiment was repeated using IR-100-H cation resin (R,S03H type). This time, 78% of the peroxide was found in the supernatant solution, whereas none could be detected in the acid solu-
Table V. Ion Exchange Resins Used to Separate Chromate from Peroxide Resin h-0. IRA-400 (lot 2606) XE-81 (MB-1) XE-81 (MB-I), NazCrOl buffered e XE-81 (LIB-1) KaC1 bufferldd IR-4R MB-3
*
HaOr Found,
pH Rangea 7 . 1 to 5 . 8 1 0 . 5 to 1 1 . 0 7.Oto 6 . 3
% Theory
...
7 . 2 to 4 . 5
85
RAH2 RSOIH-RzOH
8 . 3 to 8 . 4 7 . 2 to 9 . 3
0 9
Type RzNOH RZSOIH-RSNH~
....
91 0 90
MB-3 (R.S03H-R.0H type), an anion-cation exchanger, removed chromate over a p H range of 7.2 to 9.3, but only 9% of the added peroxide was recovered. However, IRA-400 resin, the chloride form of the R,NOH-type anion exchanger, removed the chromate between a pH of 7.1 and 5.8, permitting a 91% recovery of the added peroxide (Table 11). Table V summarizes the data obtained with the different resins. Although slightly more peroxide was recovered using the anionic IRA-400 resin than with the buffered (neutral) XE-81 anion-cation resin, the latter material is recommended where cationic corrosion products are present in the solutions to be analyzed.
ANALYTICAL CHEMISTRY
358 100
90
i5 8 0
: g
70
60
*
50 40 0
30
10%
NoECrO,
X IO-% NOICrOI
A 16% NolGrO,
20 10
0 0
0.5
Figure 6.
30
20
1.5
I
50
40
60
MOURS
Effect of Chromate on Decomposition of lO-'M Peroxide at 24' C.
DECOMPOSITION OF HYDROGEN PEROXIDE
The effects of temperature, pH, and chromate concentration on the decomposition of hydrogen peroxide in sodium chromate solutions were determined. The peroxide analyses were made by the titanium sulfate method after separating chromate with the chloride form of IRA400 resin. The stock solution used for this work was Baker's 3% hydrogen peroxide. At the time of the experiment it was not realized that this solution contained a small amount of acetanilide added as an inhibitor. The following data, therefore, represent the minimum amount of decomposition under the conditions studied. Figure 4 shows the rate of decomposition of l O - 4 M hydrogen peroxide in 10-331 sodium chromate, pH of 8.5, at 24. 40, 57.5, and 67.5" C. The data show that the rate of peroxide decomposition increases with increasing temperature; a t 67.5 ' C., the peroxide decomposition was complete at 3.5 hours. 4 t 57.5' C., the peroxide was destroyed in 28 hours. After 72 hours a t 40' and 24" C., 87 and 3275, r r s p ~ + i v e l yof , the peroxide decomposed.
Table VI. Correlation of Hydrogen Peroxide Analysis with Original Chromate and with Residual Chromium Concentrations NanCrOl Present, Jf 10-2
HzOn Present, P.P.M 14 7.1 2.6
Residual Cr,a P.P.RI. 0.5 0.5 0.5
14 7.1
0.1 0.1
HaOi!Cr Ratioa 28
14 5.2
HzOa HzOz Found Expected b , Exptl. i, 7 c Theory % Theory 96 84 90 79 72 82 Av.
10-8
2.6
0.1
140 71 26
=
98 98 98 Av.
82 i 2 93 89 91
=
91 f 2
Left in peroxide solution after treatment with ion exchange resin. Corrected for interference of residual chromium (Table 111). See Table 11.
tion a t the last two pH's wm not noted. At 67.5" C., it would be expected that the effect of increasing pH would be accentuated. The rates of decomposition of 10-lM hydroand l O - 4 M sodium gen peroxide in 10-2. chromate, pH 8.1, a t 24" C. are shown in Figure 6. The decomposition of peroxide was more rapid in 10-2M sodium chromate than in the weaker chromate solutions. After 1.5 hours, there was no significant difference between the decomposition rates of peroxide in 10-3 and lO-4M chromate. The fastest rate of peroxide decomposition occurred within the first hour. However, the greatest differences in the decomposition rates were noted during the first 10 minutes. Were TO these differences real, or could they be ascribed to a deficiency in the analytical method? Hydrogen The only known interference with the analysis was that caused by chromium, but the amounts left after the ion exchange separation were too small to cause the apparently low recoveries reported in Table 11. All but 0.5 and 0.1 p.p.m. of chromium was removed from 10-2 and lO-3Jf chromate solutions, respectively, by the ion exchange resin. Table VI compares the theoretical peroxide recoveries (corrected for the interference of residual chromium, Table 111) with the experimental values for peroxide. The data in Table VI show that the peroxide recoveries are more dependent on the original chromate concentration than on the effect of residual chromium. Therefore, it is more likely that the low recoveries of peroxide from 10-2 and l O - 3 M sodium chromate can be ascribed to peroxide decomposition during the analysis rather than t o a faulty analytical procedure. ACKNOWLEDGMENT
The author wishes to acknowledge the assistance of J. W. Ryan for the data in Table I and of N. G. Mills for part of the literature survey. Acknowledgment is also due to L. P. Pepkowitz. who encouraged this work and reviewed the manuscript. LITERATURE CITED
dllen, A. O., and Bowman, 11.G., Atomic Energy Commission, Classified Rept. N-1129 (1944).
Allen, A. O., Hochanadel, C. J., and Ghormley, J. A., -4tomic Energy Commission, AECU-1413 (1949). Bonet-Maury, P., Compt. rend., 218, 117-19 (1944). Eisenberg, G. M., ANAL. CHEM.,15, 327-8 (1943). Furman, N. H., "Scott's Standard Methods of Chemical Analysis," 5th ed., Vol. 2, pp. 2180-1, New York, D. Van Nostrand Co., 1939. Kunin, R., ANAL.CHEW., 21, 87-96 (1949). Ibid., 22, 64-5 (1950). Ibid., 23, 45-6 (1951). Ibid., 24, 64-5 (1952). Nachod, F. C., "Ion Exchange," p. 247, New York, Academic
Press, 1949. Patrick, W. A., and Wagner, H. B., ANAL.CHEM.,21, 1279-80 (1949).
Figure 5 shows the effect of pH on the decomposition a t 4 0 " C. of l O - 4 M hydrogen peroxide in 10-3-V sodium chromate solutions adjusted to different pH's with sodium hydroxide. The rate of peroxide decomposition increased with higher pH. A t a pH of 10, decomposition was complete in about an hour, but a t pH 9.5 and 8.5 about 10 and 50% peroxide, respectively, was left after 28 hours. The time necessary for the complete decomposi-
Rohm & Haas Co., Philadelphia, Pa., Newsletter, "hmberlita IRA-400'' (May 3, 1948). Schwicker, A , , 2. anal. Chem., 108, 89-96 (1937). Singh, Balwant, and Malik, I. I., J . I n d i a n Chem. Soc., 14, 435-9 (1937). Received for review August 7, 1953. Accepted October 30, 1953. The Knolls Btomic Power Laboratory is operated by the General Electric Co. for the Atomic Energy Commission, The work presented here was carried out under contract Xo. W-31-109 Eng-52.
