Selective Determination of Ferrous Ion, Sulfamate Ion, and Hydrazine E. KENNETH DUKES Savannah River laboratory, E. I.du Pont de Nemours & Co., Aiken, S. C.
b A method was developed to deter-
a method \ \ a i dcidopcd which depends
mine, separately, the concentrations of ferrous ion, sulfamate ion, and hydrazine in solutions of nitric acid containing all three components. The method incorporates a ceric titration of ferrous ion, a spectrophotometric determination of hydrazine, and a photometric titration to determine the total concentration of sulfamate ion plus hydrazine.
on reaction of sodium nitrite n i t h sulfamate ion and hydrazine. The sum of the hydrazine and sulfamate eoncentrations \vas obtained by backtitrating excess sodium nitrite photometrically. The sulfamate concentration i~ as then obtained by difference. Ferrous ion reacts with sodium nitrite; therefore, it was osidized with the stoichiometric amount of ceric ion prior to the hydrazine-sulfamate analysis. The analytical sequence involves the follon ing reactions:
S
~ L U I IO K ~of
ierrous ~ u l h m : i t c and ~ h ~ d r a z i n ein nitric acicl arc coninionly used in thr chc.miral y r o c e s z i n g of nuclear fuels, to control the valence state's of various actinitk c>leincnts (6). Thv adjustment and coiitrol of valence statm are often dependent to a large mtrmt on the concentrations of ferrous ion, sulfamate ion, and hydrazine. For studies of valence control in chemical Ixocesses, methods were needed to dctermine the concentration of each of these components in solution< containing all three components. A spcctrophotornetric method described in the literaturc nas suitable for the determination of hydrazine in solutions of interest (4, 8 ) . Determination of the ferrous ion by a standard ceric titration was not considered feasible because hydrazine reacts with both ceric and ferric ions (1, 5 ) . Howc\ er, initial studies showed that this method could be used for samples containing less than 0.05il1 hydrazine, and could be applied a t any concentration of hydrazine if the titration were performed in cold 5 X sulfuric acid. The maximum concentration of hydrazine in this medium is less than 0.03X because of the low solubility of hydrazine sulfate (1).
An acceptable determination of sulfamate ion was not availahle; therefore,
Table 1.
Determination of Ferrous Ion in Presence of NzH,
Sample NZH4,
M 0.05 0.11 0.23 0.34
1304
Fe+2, M 0.0495 0.0495 0.0495 0.0495
Fe+*Found, M 1M 5M HzSO~ H2SO4 (5" C.) 0.0506 0.0494 0.052'7 0.049i 0.0543 0.0497 0.0576 0.0494
ANALYTICAL CHEMISTRY
+ Fe+* NH2S03- + HXOs Ce+4
+
+ Fe+3 (1) S04-2 + NP +
Ce+3
-t
H+
+ HzO
(2)
N?H,-+ HIYO, + HIY3 + H + + 2H2O
+ "02 Fe'3 + HN3
HS,
+
+
$
(3)
+ H?O (4) FeS3TZ+ H + (5)
S?
N20
.Iftcr the ferrous determination, Reaction 1, a measured quantity of sodium nitrit? is added to react with the sulfamate and hydrazine by Reactions 2, 3, and 4. The excess nitrite is then back-titrated with sodium azide according to Reaction 4. The end point of this titration is indicated by formation of thc red complex, Fe?;J+Z ( 2 , 7 ) , according to Reaction 5. EXPERIMENTAL
Reagents. Hydrazine nitrate used in this study was a n aqueous solution produced by the Fairmont Chemical Co. All other solutions were prepared from reagent-grade chemicals. Apparatus. A Beckman D U spectrophotometer and matched 1.0-cm. Corex cells were used for absorbance measurements in t h e hydrazine analysis. T h e cell compartment was controlled t o 0.3" C. Photometric titrations were performed with a Beckman Model B spectrophotometer and a n attachment described by Goddu and Hume (S). The attachment consisted of a holder for a 100-ml. beaker and a magnetic stirrer located in the cell compartment. The titrant was delivered through a n opening in a specially constructed, light-tight cover.
7 X 10-5 to 3 X 10 milliiiiolc~ oJ hydrazine \\as placed in a 2c5-ni1. volumctric flask containing 10 ml. of p-dimethylaminobenzaldehyde rengc,iit. The solution was diluted to the mark with 1.11 hydrochloric acid, mixed, and allowed to stand 15 minutes bcforc the absorbance \\as measured a t 458 m p . F E R R OION. U ~ An aliquot D l sanililr containing ferrous sulfamate and hydrazine was placed in a 100-ml. beaker containing about 25 ml. of 521 sulfuric acid cooled to about 5" C. The minimum amount of ferroin indicator required to give adequate visible coloration was added, and thr. solution was then titrated n i t h a standard solution of ceric ammonium sulfate. HIDRAZIiiE
-451)
sULFA\lATC
ION.
An aliquot of sample was added to a 100-ml. beaker containing about 50 nil. of 1J1 nitric acid and 3 ml. of 131 ferric nitrate. The stoichiometric amount of ceric ion, as determined in the ferrous analysis, was added to o\idize the ierrous ion. Addition of R standard solution of sodium nitrite (0.05-I!) ivas started immediately. The nitrite was added slowly (10 ml. in 1 minute) beneath the surface of the solution, with gentle agitation to avoid loss of nitrous acid. The beaker \\as transferred to the cell compartment of a modified spectrophotometer, and the q c e s s nitrous acid was titrated photometrically, n ith a standard solution of sodium azide, using the absorbance of F e S l r 2 a t 460 mp as the indicator. .bide \\as added in small increments a t a slow ratc to pemiit completion oi the
Table 11.
Determination of Fe+2, "2sos-, and NzH4
Added, Found,a Std. Dev., M M III FP+ 2 o 0482 n nom ._ _ ~ o 0479 %H4 0 0515 0 0514 0 0003 NH2SO3- 0.0512 0 0509 0 0012 Fe +2 0.192 0.192 0,0012 N2H4 0.0515 0.0514 0.0001 XH2S03- 0.419 0.408 0,0110 Fe +2 0.0482 0.0482 0.0004 0,209 0.0030 0.206 NJL NHnS03- 0.0512 0.0512 0.0018 Analytical Procedures. HYDRAa .4verage of five determinations. ZINE. An aliquot of sample containing Coinponent
this nay the at)sorIxint~~ thcx solution incrcwwd, t h t ~ n doTable 111. Interference by HN, in twasetl to the original reading \\ ith c w h Determination of Fe+2 incroint~ntof azide. .it the vnd point a (Ceric titration in 5M H&O, at 5’ C.) pcrmanent increase in absorl)anccI \+as Fe+2,d l o l w n ed and succeeding incrcnients of “3, M Added Found n zidc increased t hc absorbance linearly. 0.0025 0,0495 0.0495 l‘hc true end point was obtaincd by 0.0062 0,0495 0.0495 plottiiig the absorbancy against thc 0,0125 0,0495 0.0499 azide concentration and c\tral)olating 0.0250 0.0495 0,0503 thr straight-line portion of the curve to ~01’0 absorbancy. Attempts to determine the end point visually gavc poorer procedure is e\;trcrndy sensitive and precision. large dilutions are necessary. The sulfamate concentration is obtaincd by RESULTS AND DISCUSSION difference from the hydrazine and The satisfactory results of the dcltcrsulfamate-hydrazine determinations; mination of ferrous ion in the prcscnce therefore, the precidion of the sulfamate 01 hydrazine are given in Table I. Data determination depends greatly on the for analyses of solutions containing precision of the hydrazine determination known concentrations of ferrous ion, and the ratio of hydrazine to sulfamate. sulfsniatc ion, and hydrazine are preI n nitric acid solution the hydrazinescntrd iii Table 11. Larger errors occur nitrous acid reaction produces low conin thtl hydrazine determinat,ion a t high centrations of hydrazoic acid that react conccntrations of hydrazine because the with ceric ion anti interfere in the I ~ Y I ~ I ~ I I111 .
of
ferrous tlt%miiii:ition. The rwults in Table 111 show that thc interference is not significant a t ~ ( J W concentrations of hydrazoic8 acid. LITERATURE CITED
( 1 ) .4udrieth, L. F., Ogg, B. A,, “The Chemistry of Hydrazine,” Wiley, New York, 1951. ( 2 ) Dukes, E. K., Wallace, R. M., L4NAL. CHEM.33,242 (1961). ( 3 ) Goddu, R. F., Hurne, D. N., Ibid., 26, 1740 (1954). ( 4 ) Pesez, hl., Petit, A,, Bull. SOC.Chim. France 1947, 122. (5) Pollard, F. H., Nickless, G., J . Chromatog. 4, 196 (1960). (6) Ryan, J. L., U. 8. At. Energy Comm., Rept. HW-59193 (February 1959). ( 7 ) Wallace, R. M., Dukes, E. K., J . Phys. C‘hem. 65, 2094 (1961). (8) Watt, G. W., Chrisp, J. D., ANAL. CHEM.24,2006 (1952).
RECEIVEDfor review March 20, 1962. Accepted June 14, 1962. Information developed during work under Contract AT(0iT2),-lwith the U. S. Atomic Energy Commission.
Determination of Deuterium Concentration in Heavy Water by the Reaction Oxygen-16 (d, n ) Fluorine-17 Induced by Reactor Neutrons SAADIA AMIEL and MAX PEISACH Israel Atomic Energy Commissionllaboratories, P. 0.Box 527, Rehovoth, Israel
b Recoiling deuterium nuclei from n-d collisions in heavy water react with oxygen. The 66-second fluorine-1 7 resulting from the reaction is measured, and its activity is used as a monitor for the deuterium concentration. In a fission spectrum neutron flux of 1 O I 2 n per cm.Z-sec., 1 gram of 100% D 2 0 produces about 14 pc. of F17 at saturation. The amount of F I 7 produced is proportional to the deuterium content over a wide range.
T
HE APPLICATION of reactions induced by knock-on particles in reactor irradiations has recently drawn considerable attention (7, 10, 11). Proton recoils i n hydrogenous media were used in reactions such as 0 1 8 (p, n)FlS for determining oxygen-18 abundance in hydrogen-normalized water samples (4). Other reactions of the types (P, n), (P, 71, b, 4, etc., with isotopes of light elements have been observed in aqueous solutions irradiated h-ith fast neutrons (7, 10, 11). I n this work the occurrence and applicability of the nuclear reaction 0 I 6 ( d , n)FI7 ini-
tiated by neutron-deuterium recoils were investigated. Fluorine-17 is a pure positron emitter decaying with a half life of 66.0 1 0 . 3 seconds to stable oxygen-17. It can be produced in water irradiated with fast neutrons by the secondary reactions 0 1 6 ( p , 7)F17, and 016(d, n)F17 following n-p or n-d collisions, and has already been identified as a radioactive ?onstituent of the heavy water moderator of some reactors (6). I n the neutron energy range of 1 to 8 m.e.v., the cross sections of n-p and n-d interactions are reported to be about equal, varying from 4.3 to 1.2 barns and from 3.0 to 1.3 barns respectively (9). The production of fluorine-17 as a function of deuterium content was studied as a means of determining the latter. The yields from the competing 0 1 6 ( p , y ) and 016(d, n) reactions, both of which give the same product, were determined for reactor neutrons. The advantage of using fluorine-17 as a monitor for deuterium content lies in the fact that, in the absence of other positron emitters, i t can readily be detected and measured by its positron
.
decay. Using this property, the irradiated water sample does not have to be processed further. among the usual methods for determining deuterium in water are mass spectrometry, interferometry, optical and infrared spectrometry, and density measurements ( 5 ) . The only method utilizing nuclear properties is that based on photoneutron emission (3, 8 ) . EXPERIMENTAL
Samples of 1 gram were prepared for irradiation by mixing known weights of heavy nater containing 94.5% D20 with natural water. It is essential that all samples be normalized with respect to natural oxygen. The DzO content of the prepared samples ranged from about 0.5 to 94.5%. The samples were contained in polyethylene vials which \\ere heat-sealed before use. Natural B ater samples, similarly prepared, were used as blanks. The samples were irradiated in the pneumatic tube system of IRR-1 (The 5 M w Israel Research Reactor No. 1 a t Nahal Soreq) for 66 seconds which produced half-saturation yields of fluorine-1i. Irradiations were carried out VOL. 34, NO. 10, SEPTEMBER 1962
1305
