Table
Sample No. 1
2 3 4 5
6 7 8
Average Standard deviation Concentration (in yo)in arc sample Concentration (in parts per million) in milk
II.
Repeatability of Analytical Procedure Zn 2771 Fe 2723.6 Mn 2605.7
Ge 2829 0.74 0.69 0.67 0.70 0.73 0.71 0.69 0.69
Mo 3158.2 Ge 2829 1.37 1.34 1.29 I .40 1.36 1.34 1.34 1.30 1.34 10.036
0.96 0.90 0.96 A0 ,048
Ge 2829 0.70 0.69 0.70 0.75 0.72 0.73 0.73 0.72 0.72 10.020
0.74
0.047
0.0032
0.0072
3.7
0.23
0.016
0.036
0.70
= k O . 023
When all the trace elements have been absorbed on the filter paper, the paper is transferred to an 18-ml. silica crucible, heated for 1 hour a t 100' C. and then ashed a t 450' to 500' C. The loose ash (approximately 1 mg.) is mixed with sufficient buffer to make 100 mg. The buffer consists of one-half graphite powder (Yational Carbon SP-2 Grade), one-quarter anhydrous aluminum sulfate, and one-quarter potassium sulfate. I n addition the sample contains 1.4% Ge as Ge02. A Wig-L-Bug with polyethylene capsules is used for mixing. Spectrography is carried out with d.c. current as described elsewhere (4). No rotating sector is used. Each sample is arced in triplicate. No background correction is necessary.
Ge 2829 0.96 0.96 0.95 1.04 0.91
Mo 3158, and the line Zn 3345, twenty times as sensitive as Zn 2771, were not
1.02
The analytical lines are shown in Table I. The standard curves are prepared by adding known amounts of each element under consideration to solutions of milk ash from which the trace elements have been extracted. The extraction is repeated, and three different concentrations are taken for each element. The standard line used is Ge 2829. The standard curves are plotted on log-log paper. A 2000-fold concentration of trace elements is obtained. The completeness of extraction was checked by repeating the analytical procedure on a sample of milk ash solution starting with the extraction. The sample was found to contain 0.008% Fe and 0.0002% Mn in the arc sample. The line Mo 3132, twice as sensitive as
detected in the spectra. The Fe and hln found are more probably the result of contamination than incomplete extraction. Standard curves were also prepared for Cu, Sn, Pb, and Co using as analytical lines Cu 2824, P b 2833, 2614, 2663, and Co 2521. I n most samples, however, the above lines for Cu, Sn, and Co were too faint to be detected. The line Cu 3274 was too dense for measurement. The results for P b were too erratic. possibly due to ashing losses
(6).
To get some measure of the reproducibility of the procedure, eight samples of milk of 200 grams each were analyzed by the described method. These samples all came from the same half gallon of milk purchased in a local super market. The results are shown in Table I1 in the form of intensity ratios of the analytical line and the standard line for each element. LITERATURE CITED
(1) Gleu, K., Schwab, R., Angew. Chemie
62, 320 (1950). (2) Gysuch, T. T., Analyst 84, 135 (1909'). (31 S c h k e r , K., Judel, G. K., Zeit. Anal. Chemie 156, 340 (1957). (4) Voth, J. L., ANAL. CHEK 31, 1094 (1959).
RECEIVEDfor review April 25, 1963. Accepted July 18, 1963.
Analysis of Ammonia-Hydrazine Mixtures for Both Components STANLEY S. YAMAMURA and JOHN H. SlKES Afomic Energy Division, Phillips Petroleum
b A reliable oxidimetric titration method is presented for the determination of ammonia and hydrazine in ammonia-hydrazine mixtures. Hydrazine is determined by bromination and ammonia is determined by oxidation in alkaline medium with hypobromite. In the analysis of ammoniahydrazine samples, hydrazine is oxidized in acid medium with excess bromine. The residual bromine then is converted to hypobromite with base for the oxidation of ammonia. The relative standard deviations for the determination of hydrazine and ammonia are less than 0.3670.
B
ECAUSE of
the demand for hydrazine, the technology and economics of the production of hydrazine from ammonia by bombardment w-ith fission products are being investigated ( I S ) . To evaluate this process, liquid ammonia
1958
e
ANALYTICAL CHEMISTRY
Co.,Idaho Falls,
Idaho
a t 1000 p.s.i., containing suspended unclad uranium dioxide particles, is to be circulated in an in-pile loop through the Materials Testing Reactor. In support of the project, methods are required for the determination of ammonia and hydrazine in filtered 1-cc. loop samples which contain 5 to 10 weight % hydrazine and the ammonia-soluble fission products, mainly iodine. These methods are necessary to establish the efficiency of the fissiochemical process for the conversion of ammonia to hydrazine. An accuracy of 1 t o 2% is required for both components. Because of expected high levels of radioactivity, adaptability to remote analysis is necessary. After a comprehensive study of available methods for the determination of ammonia, hydrazine, and ammoniahydrazine mixtures, oxidation-reduction titrimetry, easily adaptable to remote
analysis, was selected for evaluation Spectrophotometric methods, applicable generally to very low concentrations of ammonia and hydrazine, and acid-base titration methods, requiring a distillation separation of the ammonia (6, 16), were considered unsuitable. Numerous oxidants have been proposed for the determination of hydrazine including bromate (9, 10, 18), bromine (19), cerium(1V) (Q), chloramine T (6), ferricyanide (16), iodate (1, 9, 10, 14), iodine (IO), iodine monochloride ( 4 ) , mercury(1) (S), permanganate ( 9 ) , selenite (60),and silver(1) (17). Of these, bromine, iodate, and iodine, which quantitatively oxidize hydrazine t o nitrogen, appeared most reliable. Bromate, though widely used, has been reported t o produce small amounts of ammonia in addition to nitrogen (16). Hypobromite added as a neutral or alkaline solution (8, 11) or developed in
situ with hypochlorite ( 1 2 )has been used extensively for the (determination of ammonia. The rapid oxidation of hydrazine by bromine and the easy conversion of bromine to hypobromite with base suggested a method for both components based on the bromination of hydrazine in acid medium followed by the oxidation of ammonia in alkaline medium with hypobromite gtnerated in situ. This proved feasible with a relative standard deviation of less than 0.36% for both hydrazine and ammonia. EXPERIMENTAL
Apparatus. Vacuum-type bromination flasks (7) are the most suitable, b u t with appropriatcb caution, standard iodine flasks can be used. Reagents. Reagent grade chemicals were used throughout. Hydrazine sulfate, obtained from both J. T. Baker Chemical Co. and from Eastman Organic Chemicals, was used without purification. Standard bromate solutions, 0.00333M (0.0500Ar) and 0.0200M (0.1200W), were prepared with 2.7864 and 6.6873 grams, respectively, of 99.9%) assay potassium bromate per 2 liters of water solution. The thiosulfate soluldons, 0.05N and 0.12N, were prepared with 24.82 and 60 grams, respectively, of sodium thiosulfate pentahydrate per 2 liters of solution and mere standardized against the bromate solutions iodometrically. For the thiosulfate sclutions, preboiled distilled water containing 0.1 gram of sodium carbonate per liter was used. The aniline sulfate solution was prepared by neutralizing 9 ml. {of freshly distilled aniline with an excess of sulfuric acid and diluting to 500 ml. Determination of Hydrazine. Pipet 5.00 ml. of the 0.0500N potassium bromate solution into a bromination flask. Evacuate the flask. Add 3 ml. of 6 M sulfuric acid and 5 ml. of 20% (w./v.) potassium xomide. Rinse the reagents througl- with water and stir to generate the bi*omine. For convenience, use a magnetic stirrer. Transfer a sample containing 0.05 to 0.20 meq. of hydrazine t o the flask. Wash the sample into the flask quantitatively with water. React for 2 minutes, then add 5 ml. of 20% (w./v.) potassium iodide. Titrate the liberated iodine with 0.05N sodium thiosulfate to a starch or potentiometric (platinumcalomel electrode system) end point. Compute the hydrazine concentration from the difference between the milliequivalents of bromate originally added and the milliequivalents of oxidant determined as iodine after oxidation of the sample. One mole of hydrazine is equivalent to 4 equivalents of bromate. Determination of Ammonia or the Sum of Ammonia Plus Hydrazine. Pipet 15.00 ml. of the 0.12OOAVpotassium bromate solution to the bromination flask, e v a c u a k , and admit 5 ml. of 20% (w./v.) potas:ium bromide and 2 ml. of 6M sulfuric: acid. Mix the reagents with a magnetic stirrer, then traiisfer a sample cojitaining between
0.5 and 1.6 meq. total of ammonia or ammonia plus hydrazine to the flask. Wash the sample into the flask quantitatively with small w:iter rinses Let stand for 2 minutes with continuous stirring. Convert the bromine to hypobromite by adding 6-11sodium hydroxide until the color of the solution changes from orange to pale yellow. This conversion requires approximately 5 ml. of 6 M sodium hydroxide. React for 5 minutes with continuous stirring; then add 5 ml. of 20% (u../v.) potassium iodide and 5 ml. of 6-11 .ulfuric acid. Immediately add 2 ml. of 0.2M aniline sulfate solution and titrate the liberated iodide with standard 0.12,\' thiosulfate to a starch or potentiometric end point. Process a reagent blank on 15.00 ml. of the bromate reagent using the procedure recommended above. Determine the total milliequivalents of ammonia or ammonia plus hydrazine from the difference between the two titrations. When samples contain both ammonia and hydrazine, measure the hydrazine as described above and determine the ammonia by difference. Special Modifications for Analyses with Iodine Flasks. \Tlicn a i i a l ~scs are performed with iodine fluslis rathcr than bromin:ition A d s , minor niodifications are necessary to minimize bromine loss. I n the analysis of hydrazine, pipet the sample into the iodine flask and dilute to about 15 ml. 171th water. Add 3 ml. of 6-11 sulfuric acid and exactly 5.00 ml. of the 0.05OO.Y potassium bromate reagent. Add 5 inl. of 20% (w./v.) potassium bromide rapidly and stopper immediately. Add 5 ml. of 20% (w./v.) potassium iodide to the well and allow 2 minutes for the bromine to react with the hydrazine. Loosen the stopper and drain the iodide solution into the flask slowly. Continue with the determination as described above. I n the analysis of ammonia, transfer the sample to the flask and dilute with water to approximately 15 ml. Pipet exactly 15.00 ml. of the 0.1200N bromate reagent; then acidify with 2 ml. of 6 V sulfuric acid. Generate the bromine by adding 5 ml. of 20% potassium bromide rapidly, and immediately stopper the flask. Transfer 6 ml. of the 6M sodium hydroxide to the well and allow 2 minutes for the oxidation of hydrazine. Drain the sodium hydroxide into the flask cautiously to convert the bromine t o hypobromite. Continue with the determination as described above. RESULTS AND DISCUSSION
Oxidation of Hydrazine. The ouidation of hydrazine in an acidic medium with Cxces bromine is rapid and quantitative yielding nitrogen as the ouithtion protluct. I n a basic riiediurn, air oxidation of 1ij-dr:uinP and noristoicliiuriietric reactions iiitly be encountered (2, 14). Thus, to determine the sum of hydrazine and ammonia, the bromine is allowed to oxidize the hydrazine completely before it is converted to hypobromite with base. The
production of small amounts of ammonia by bromate oxidation (16) is prevented by converting the bromate to bromine prior t'o the introduction of the sample. With iodine flasks, preliminary generation of bromine is not feasible because of loss of bromine during the pipetting of the sample. In the procedure with iodine flasks, the sample is diluted with 11-ater prior to the addition of the Iironiate reagent t o minimize the ammonia production side reaction. Oxidation of Ammonia. The reaction of ammonia and hypobromite, usually descrihcd :is 2SH3
+ 3SnOUr
--+
K?+ 3SaBr
+ 3Hz0 (1)
varies slightly with alkalinity as shown in Table I. In wakl?. basic solut'ions a t pH 8 buffered with bicarbonate, reaction 1 is reported to br quantitat'ive (11, 12). With a phosphate-buffered medium a t pH 8.5 f 0.5, we obtained a slight positive bias increasing to about 2% at pH 10 (Table I). This h a s is attribut'ed to a partial Oxidation of ammonia to nitric oxide. The evidence for the formation of nitric oxide is a gradual release of iodine following the iodometric determination of the excess hypobromite. The iodine release is observed in the presence of oxygen only after t'he hypobromite oxidation of ammonia samples in strongly basic medium. Khen ammonia is excluded or when oxygen is expelled from the sample solution by a carbon dioxide gas purge, no post end point iodine formation occurs. The proposed mechanism for the gradual release of iodine is
0 2
S O -+ NO1 (slow reaction) NO2
2HXOs + "01
(3)
(4)
I- +IZ (rapid reaction) NO2
(5)
As indicated by the positive bias and the rapid generation of iodine, the formation of nitric oxide via Reaction 2 is quite significant a t pH values greater than 10. This reaction appears to be less significant in solutions buffered with phosphate a t pH 8.5. The results still are biased positively in the order of 0.5 to 1%, but there is no measurable formation of iodine. Although solutions buffered a t pH 8.0 to 8.5 with phosphate or bicarbonate appear most suitable for the oxidation of ammonia with hypobromite, the vapor pressure of bromine in this pH region is appreciable. Thus, with iodine flasks, Oxidation a t pH greater than 10 i q advantageous. As shown in Table I, the precision is excellent even under strongly basic conditions enabling the use of a simple correction. Masking of Nitrous Acid with Aromatic Amines. The nitrous acid formed via Reaction 4 is masked comVOL. 35, NO. 12, NOVEMBER 1963
e
1959
Table 1.
Effect of p H on Oxidation of Ammonia with Hypobromite and Reliability of Ammonia Determination
Approx. pH of Results Mmolea reaction No. of Mmole % Rel. std. taken medium detn. found recovery dev., % 0.2500 10 2 0. 255gb 102.3 0.4000 10 3 0.4069 101.7 0.27% ~0.5000 10 15 0.5078* 101.6 0.28% 8.5 4 0.502gC 100.6 0.17% Reagent grade ammonium sulfate. * 0.2 mmole of aniline added to prevent post end point formation of iodine. No aniline added. KO iodine release observed. Table II.
Reliability of Hydrazine Procedure
Results Rel. std. Mmole tal‘en detn. Mmole found 70Recovery0 dev., % 0.0250 6 0.02492 99.68 0.20 0.0500 7 0.04988 99.76 0.15 5 0.1496 99.73 0.21 0.1500 Analysis of the hydrazine sulfate reagent by direct acid-base titrimetry gave a purity of 99.7%. S o . of
deviations for the determination of hydrazine and ammonia are less than 0.36y0. The ammonium ion even a t a 393 to 1 molar ratio to hydrazine does not interfere in the determination of hydrazine (Table TV). Fission product levels of iodine also do not interfere in either determination. This method for the analysis of ammonia, hydrazine, and ammoniahydrazine mixtures is simple and reliable and offers several advantages. The potassium bromate reagent is stable for months and is converted rapidly and quantitatively to bromine in acidic bromide medium. 41~0, the in situ conversion of bromine to hypobromite with sodium hydroxide is accomplished readily and the effective oxidizing strength of the reagent remains constant. The gradual conversion of hypobromite to bromate, characteristic of alkaline hypobromite reagents (81, is not encountered. LITERATURE CITED
Table 111.
Analysis of Synthetic Ammonia-Hydrazine Samples
Results Ammonifi Make-up concn., Sam- -~ mol&^^ %-Re- Rel. std. ple Ammonia Hydrazine Molarity covery dev., 7 0 hIolarity A 0 9000 0 04009 0 ‘3150“ I01 7 0 23 0 03992” 0 6395 0.02005 0 6466* 101 1 0 22 0 0l99ti0 B a Average of 5 determinations. * Average of 4 determinations.
Table IV. Effect of Ammonium Ion Concentration on the Determination of Hydrazine
AmmoAmmo- nium ionnium hydra- Hydrazine zine Hydrazine sulfate found, added, mole taken, mmoles mmolee ratio %” 0.0500 0.67 25 99.62 2.70 100 99.68 - .. ~. . 100 99.92 0.0250 1.35 393 99.67 0.1500 59.0 Average of two or more determinations. 0
pletely by the addition of a primary aromatic amine t o the sample solution immediately after the conversion of the excess hypobromite reagent t o iodine. Both aniline and amino-G (7-amino1,a-naphthalene disulfonic acid) effectively prevent post end point release of iodine through a diazotization reaction. Aniline and amino-G are equally satisfactory when titrating to a potentiometric end point, but for visual titrations with starch indicator, aniline, which is nearly colorless, is preferred. The
1960
ANALYTICAL CHEMISTRY
(1) Bapat, M. G., Sharma, B., Z. Anal. Chem. 157, 258 (1957).
____ ___._( 2 ) Booman. G. L.. Holbrook. W. B.. Hydrazine
% Re- Rel. std. covery dev., % 99 58 99 55
0 25 0.36
effects of aniline and amino-G on the thiosulfate titration of iodinc were investigated by titrating known amounts of iodine containing added amino-G or aniline sulfate. At the 0.5mmole level, neither amino-G nor aniline interferes. Analysis of Ammonia, Hydrazine, and Synthetic Ammonia-Hydrazine Samples. I n the sampling process, a 1-cc. filtered sample from the loop will be acidified and diluted t o a volume of about 25 ml. Even though the filter efficiency for the UOr particles is expected to be at least 99%, the short cooling time coupled with the solubility of the fission products, iodine, bromine, and ruthenium, probably will require the use of a remote analytical facility. With the available remote pipetter, the maximum aliquot t h a t can be delivered for analysis is 0.9 ml. For samples containing 5% hydrazine, the expected equilibrium level in the loop, this 0.9-ml. aliquot will contain 1.2 mg. of hydrazine. The ammonia content will be about 20 mg. The results of the analyses of ammonia and hydrazine standards arid of synthetic ammonia-hydrazine samples are presented in Tables I, 11, and 111, respectively. The relative standard
‘ ANAL.CHEX 35, 1986 (1963).‘ (3) Burriel, F., Conde, F. L., Jimeno, S. A. ,Anales Real SOC. Espan. Fis. Quirn. Ser. B 50, 303 (1954); C.-4. 48, 9259e (1954). ( 4 ) Cihalik, J., Terebova, K., Chem. Listv 50, 1768 (1956): C.A. 51. 2471a (1957). ’ ( 5 ) Clark, J. D., Naval Air Rocket Teat Station, Rept. No. 9, 1951; C.A. 48, 3692b (1954). (6) Devries, J. E., Gantz, E. St. C., ANAL. CHEM.25,973 (1953). (7) Fritz, J . S., Hammond, G. S., “Quantitative Organic Analysis,” p. 81, Wiley, New York, 1957. (8) Hashmi, M. H., Ali, E., Umar, M., ANAL.CHEM.34,988 (1962). (9) Jilek, A,, Brandstetr, J., Chem. Zvesfi 7, 611 (1953); C.A. 52, 8848d (1958). (10) Kolthoff, I. M., J. A n . Chem. SOC. 46,2009 (1924). (11) Kolthoff, I. M., Stricks, W., Morren, L., Analysf 78,405 (1953). (12) Laitinen, H. A., Woerner, D. E., ANAL.CHEM.27,215 (3955). (13) Pearson, R. L., Standerfer, F. R., Snyder, H. J., Watanabe, H. T., Carpenter, L. G., Miller, R I., U. S. Air Force Rept. ASD-TR-7-840 A (VI), 1962. Available from ASTIA, Document Service Center, Arlington, Va. (14) Penneman, R. A., Audrieth, L. F., ANAL.CHEM.20,1058 (1948). (15) Pugh, W., Heyns, W. K., Analyst 78, 177 (1953). (16) Sant, 6. R., Anal. Chim. Acta 20,
371 (1969).
\ - - - - I
( l 7 ) S a n t , B. R., Rec. Trav. Chim. 77, 400 (1958); C.A. 53, 12091c (1059). ( 1 8 ) Sant, B. R., Mukherji, A. K., Anal. Chim.Acta 20,476 (1959). (19) Siggia, S., “Quantitative Analysis Via Functional Groups,” p. 74, Wiley, Xew York, 1949. (20) Suseela, B., Chem. Ber. 88,23 (1955); C.A. 50, 2366d (1956). RECEIVEDfor review
May 6, 1963. hccepted August 12, 1963. Division of Analytical Chemistry, 145th Meeting, ACS, New York, N. Y., September 1963.
