substance to be analyzed was dissolved in 0.5 ml. of dimethylformamide, 5 to 10 mg. of potassium borohydride was added, and the test tube was heated to a vigorous boil, when the color developed. Then the mixture was cooled with tap or ice water, while being vigorously shaken. The heating and cooling procedure was repeated several times, with the color noted each time a t the boiling and a t the cold stages. For a positive test a red, violet, blue, or green color is obtained a t the boiling point and a pale yellow, orange, or pink color upon cooling. I n the few cases which were investigated, the thermochromic reaction could be reversibly repeated a dozen times. Sensitivities and concentration limits are reported for various p-quinones in Table I. DISCUSSION
OF
RESULTS
Investigation of various types of compounds has disclosed that many polynuclear aromatic compounds containing the quinonoid structure, I 0
‘V’ /I 0
I show a reversible, thermochromic reaction in the color test. The only compounds not containing structure I, but giving a positive (but less sensitive) test, were fluorenone and 2,3-benzofluorenone. The fluorenone structure resembles that of structure I. These results suggest the possibility that the test may also be of some value for polycyclic fluorenones. All the tested un-
substituted polynuclear p-quinones containing structure I were found to give the reaction. Many derivatives of anthraquinones exhibit the color reaction; however, a few do not. Anthraquinone and its derivatives give red to violet colors in this reaction. The higher molecular weight polynuclear p-quinones give blue colors. Several heterocyclic p-quinones and 1-hydroxyanthraquinone underwent reversible thermochromic color reactions, wherein an intense red to violet color was present a t room temperature and a pale yellow to orange color a t the boiling point. il very large number of compounds gave negative reactions under the conditions of the test-e.g., pyranthrone, violanthrone, flavanthrone, dibenzo[a,h]pyrene-7,14-dione, 9,lO-phenanthraquinone, chrysene-5,6-dione, 1,42 - methylnaphthonaphthoquinone, quinone, 2,3-dichloronaphthoquinone, tetrachloro - p - benzoquinone, 2hydroxy - 9,lO - anthraquinone, 1,4diamino-9,lO-anthraquinone, 6,l l-dihydroxy-5,12-naphthacenedione, 5,6, 11,12-naphthacenetetrone, benzil, 9acetylanthracene, benzophenone, 2-hydroxycarbazole, Zaminobenzophenone, pyrene, 2-naphthol, anthracene, dianisylideneacetone, diphenyl sulfide, 1nitropyrene, 1-carboxyfluorenone, and 2,5-dinitrofluorenone. APPLICATIONS
Aliphatic, neutral oxygenated, and acid fractions gave negative results in the test. As 10 y of anthraquinone could be detected in the presence of 2000 y of the oxygenated fraction, this fraction must contain less than 0.5% of the p-quinonic compounds. The
intense absorption of the carbonyl band in the infrared spectrum of neutral oxygenated fractions must be due to the presence of other types of carbonyl derivatives. This fact is to be investigated. On the other hand, a minimum amount of 1.0 mg. of neutral aromatic fractions from a San Francisco air particulate sample gave a reversibly green, thermochromic reaction. Assuming a sensitivity of 10 y, this aromatic fraction would contain approximately 1% of the polynuclear p-quinonic compounds. Under the same conditions a minimum amount of 2.5 mg. of a Charleston neutral aromatic fraction gave a positive green color, while 3 mg. of a rural aromatic fraction from Tonka Bay, Minn., gave a negative reaction. From the green color it would appear that the compound or compounds giving the test must have a t least four fused rings. ACKNOWLEDGMENT
The authors gratefully acknowledge the gift of a sample of dibenzo[a,h]pyrene-7,14-dione from B. L. Van Duuren of New York University. LITERATURE CITED
(1) \ , Graebe. C.. Liebermann. C.. Ann. Chem. Liebigs 160, 127 (1871). ’ (2) Meyer, H., Ibid., 379, 37 (1911). (3) Sawicki, E., Stanley, T. W., Miller, R. R., Hauser, T. R., ANAL. CHEM. 30, 1130 (1958). (4) Stanley, T. W., Sawicki, E., unpub-
lished research.
(5) Tabor, E. C., Hauser, T. R., Lodge,
J. P., Jr., Burttschell, R. H., A . M . A . Arch. Ind. Health 17, 58 (1958).
RECEIVED for review March 19, 1958. Accepted July 29, 1958.
Estimation of Boron-1 0 Burnup by Flame Photometric Lithium Determination DRAGOMIR DUTINA
Co., Schenectady, N. Y
Knolls Atomic Power laborafory, General Electric
b In connection with the burnable poison and control rod program, it became necessary to estimate the burnup of neutron-irradiated steel, zirconium, and Zircaloy alloyed with boron-10. A method is described in which the burnup is measured by determining with a flame photometer the lithium produced by means of the boron-1 0 (n,cu) lithium-7 reaction. An ammonia precipitation of the hydrolyz-
2006
ANALYTICAL CHEMISTRY
able radioactive materials is carried out remotely and reduces the radioactivity sufficiently to permit the lithium analysis of the filtrate with ordinary laboratory handling methods.
T
o
TEST the effect of neutron bombardment on burnable poison and control rod materials such as alloys of zirconium-boron-10, Zircaloy-boron-10,
and steel-boron-10, accurate burnup values were required. As the neutron flux values were not known with sufficient accuracy t o permit calculation of boron-10 burnup, an empirical determination became necessary. Several methods of determination based on the boron-10 (n,a) lithium-7 reaction were possible. For example, mass spectrometric determination of the boron-11-boron-10 ratios before
and after irradiation was used as a measure of boron-10 burnup. A second method involved the vacuum fusion of the sample with the consequent evolution of the helium produced by the %,a reaction. The composition of evolved gases was determined by mass spectrometric analysis. A thiid approach depended on the estimation of the actual lithium produced. The determination of boron-10 burnup in boron carbide has been made in this laboratory by each of the methods described, and the results are compared in Table I. The data indicate that compatible results were obtained by each of the methods. The last method, lithium determination, was chosen because it appeared most readily adaptable to the highly radioactive samples being considered. The use of flame photometry for the determination of lithium in a variety of materials is well established (2, 4 ) . Direct determination of lithium in the solution of the dissolved alloys by this technique was considered. However, because of limited space in the Radioactive Materials Laboratory, it was impractical to install a remotely operated flame photometer. It was necessary, therefore, to reduce the radioactivity t o safe handling levels prior to the "cold lab" lithium determination. For this purpose, a single precipitation of the hydrolyzable metal ions-Le., iron, zirconium, etc.-by ammonia proved satisfactory in scavenging the radioactive species. The experimental results show that the supernatant solutions, after the precipitation, contain the lithium being sought and, in addition, are sufficiently low in activity to permit routine handling. The precipitation step by the remote operation is simple. Filtration is unnecessary because an aliquot may be taken from the supernatant solution without prior removal of the precipitate.
of the hood in which the instrument was located. The tube was loosely packed with glass wool near its upper end to provide a surface for collection of the vaporized particles.
REAGENTS AND APPARATUS
Flame Photometric Reference Curve. Interferences to flame photometric analysis arise from the excess ammonia and the ammonium salts of the dissolution acids present in the supernatant solutions from the precipitation. I n addition, interferences may be expected from materials not removed by the precipitation, and, to a minor extent, from reagent impurities. There is the additional consideration of lithium impurity in the alloys being studied and in the reagents. No attempt was made to evaluate the extent of interference of each of the possible factors. Instead, both the interference and the blank problems were solved by the preparation of a separate reference curve to correspond to each alloy tested. This was done
Lithium nitrate (stock solution), 1 mg. of lithium per ml. Dissolve 9.935 grams of dry (110" C., 4 hours), reagent grade salt per liter of water. The flame photometer was a PerkinElmer Alodel 52C. All determinations n-ere made a t an air pressure of 10 pounds and acetylene pressure of 4 pounds. The atomizer funnel permitted a flow of 10 nil. per minute. A didymium filter, Corning Catalog KO. 5120 ( I ) , was placed before the entrance slit to filter out the sodium emission resulting from the production of small amounts of sodium by hydrofluoric acid attack on glassware. As a safety precaution against radioactive spray, a length of borosilicate glass tubing was used t o extend the photometer's chimney from the existing height to the top
PROCEDURE
Carry out dissolution and aliquoting remotely. Dissolve a 1- to 2-gram sample of zirconium-boron-10 or Zirc-
Table II.
Per Cent of Boron-1 0 Burnup of Boron Carbide (5) B-11-B-10 Ratio Helium Method Using Lithium Analysis Mass Spectrometer Analysis 18.1 15.4 15.7 15.8 18.3 18.3 14.8 18.8 14.4
Table 1.
Separation of Lithium Added to Zirconium, Zircaloy, and Stainless SteelBoron-1 0 Samples
Material Zircaloy-B-10 Zirconium-B-10
Sample Kt., Grams 1.00 2.00
3.00 Zircaloy-B-10
4.00 5.00
Stainless steel-B-10
1.00 3.00
aloy-boron-10 with a solution of 3 nil. of hydrofluoric acid, 15 ml. of nitric acid, and 4 ml. of water. Dissolve a 1- to 2gram sample of stainless steel-boron-10 with a solution of 10 ml. of nitric acid, 20 ml. of hydrochloric acid, and 40 ml. of water. Heat a t 50" C. for 1hour. After the reaction is completed, add 1.5 ml. of hydrogen peroxide (30%) and heat for a n additional 0.5 hour. Dilute the acid dissolver in all cases with 7 5 ml. of water and add 50 ml. of ammonium hydroxide. Dilute to 200 ml., shake, and let settle for a t least 4 hours. Remove a 10- to 20-ml. aliquot. I n the cold laboratory, dilute the aliquot to the 0- to 10-p.p.m. lithium range (based on estimated burnup). Determine lithium flame photometrically. EXPERIMENTAL
Lithium Added, Mg. 1.00
5.00 2.00
3.00
5.00 1.00 2.00
6.00
3.00 10.00 1.00 4- .. 0.0-
1.00 4.00
Lithium Found % 1.03 103 5.07 101 04 2.09 96.0 2.88 04 5.19 95.0 0.95 1.91 95.3 00 6.02 95.3 2.86 99.0 9.90 98.3 0.983 96.7 3.87 98.0 0.980 02 4.09 Mg.
Table 111. Comparison of Calculated and Experimental Burnup Values for Burnable Poison Elements
Sample Zirconium-B-10 Stainless steel-B-10
Burnup, % Exptl. (Li Calcd. analysis) 41 33.8 52
99 98
Zircaloy-B-10
70 65
47.7
100.0 99.0 78.6 72.0
by treating samples of the unirradiated, but otherwise representative, metals as described under Procedure through step 4, the settling of the gel. Aliquots of the supernate were removed and lithium nitrate was added to them to give lithium concentrations, after dilution, of 0, 2, 4, 6, 8, and 10 p.p.m. The volume of aliquot chosen was such as to give a concentration of supernatant constituents in these standard solutions identical to that obtained for a given size of actual sample. The photometric gain settings were adjusted to give galvanometer readings of 0 for the 0-p.p.m. and 100 for the 10-p.p.m. standard (3). Galvanometer readings for 2-, 4-, 6-, and 8-p.p.m. standards were then obtained. The readings were plotted against lithium concentration to give the reference curve, which, when obtained in this fashion, will compensate for both the interferences and lithium blanks to be encountered in an irradiated sample. Efficiency of Lithium-Hydrous Oxide Separation. The ammonia preVOL. 30, NO. 12, DECEMBER 1958
2007
cipitation produced a voluminous gel which could have occluded the lithium. The results in Table 11, however, indicate a clean-cut separation of the lithium from the hydrous oxides and give the over-all accuracy of the method. The results were obtained by adding a solution of lithium nitrate t o tabs of the various metals under consideration. The metal tabs were dissolved and the lithium was analyzed as described under Procedure. The concentrations of lithium relative to sample size shown in the tables were chosen to cover the expected ranges of boron-10 concentration (0.2 to 1.5%) and burnup ranges (30 to 100%) expected for the radioactive samples. The accuracy of the complete procedure could not be established, as no irradiated samples of accurately known burnup were available. Although the neutron fluxes maintained during the radiation period n‘ere not known exactly, a n approximate burnup value could be calculated for the samples submitted for lithium analysis. These calculated values along with the values obtained experimentally are shown in Table 111. The compatibility of the two sets of results indicates that no gross errors are included in the experimental procedures. Effect of Boron on Lithium Flame. A standard lithium curve was prepared with a sample devoid of its hydrolyzable ions, corrected for all interferences except boron. Because of the burnup process, the boron concentration in a sample may decrease from 2% in an unirradiated sample to 0% in a completely burned-up sample. Although the main boron flame emission at 548 mp would not be expected to interfere with lithium a t 671 mp, the effect of boron \%-asnevertheless checked. A known amount of lithium nitrate was added to the appropriate sample of zirconium containing 0, 0.5, and 1.5% of boron-10. After the procedure was carried out as described, the galvanometer readings rrere referred to a standard curve obtained with a zirconium sample containing 2% of boron, The results may be found in Table IV. All samples consisted of 1.0 gram of zirconium containing the specified percentage of boron. The results indicate that boron in the concentrations encountered does not affect the flame photometric determination of lithium within the experimental
2008
e
ANALYTICAL CHEMISTRY
Table IV. Effect of Boron on Flame Photometric Analysis of Lithium
B
~ (7 :0
0 0.5
1.5
Lithium -4dded, ~ ~ Mg. 3.00 3.00 3.00
Lithium ~ , Found hlg. % 2.88 96.0 3.05 102 2.93 97.6
error ( =k35% relative standard deviation). DECONTAMINATION
The efficacy of the ammonia decontamination step may be evaluated by the results shown in Table V. The values in the second column are radiation readings on the flasks containing the ammonia - precipitated samples; those in the third column are readings on the supernatant solution removed from these same flasks. Dilution of this solution to the proper range for lithium analysis affords further reduction of activity. The radiation level of samples analyzed was generally on the order of 5 to 10 mr. per hour.
Table
V.
Decontamination Efficiency by Ammonia Precipitation
Material Zirconium Zircaloy Stainless steel
Activity, Mr./Hr. Pptd. Supersample nate 3,000 50 7,000 55 10,000 100
-4 health physics air sampler was placed at the opening of the hood in which the flame photometry was carried out. Radiation readings on these air filters gave no evidence of contamination, The chimney, funnel, and burner grid suffered some contamination, which m s reduced to negligible levels by acid rinsing. ACCURACY
The accuracy of the burnup determination is probably somewhat below that indicated by the results shown for the lithium recovery, as the burnup value includes errors that may occur in the remote-controlled operations as well as in the estimation of the boron present in the unirradiated sample. It is felt, however, that these errors
are not of great significancr and thc over-all accuracy of the proccdure is on the order of 5%. CALCULATIONS
The calculations can be summarized by means of the formula:
yo burnup
= a x b
x
200 X 1 O ; i X lOO/c
where a = lithium in yl’nil. obtained by referring galvanometer readings to the standard curve b = dilution factor. Correction for any dilutions, exclusii e of the original one to 200 ml., necessary to bring the lithium concentration to the proper range c = weight of B-10, in y , found in a n equal weight of the unirradiated material CONCLUSIONS
A method has been described by n hich the boron-10 burnup in stainless steelboron-10, zirconiuni-boron-IO, and Zircaloy-boron-10 samples may be determined by the flame photometric analysis of the lithium produced by neutron irradiation. For samples containing boron-10 in the range 0.2 to 1.5%, burnup values h a w been de% termined with a precision of ~ 5 rclative standard deviation. ACKNOWLEDGMENT
The author gratefully nckrion ledges the aid of Gene Ste. X i r i e who carried out many of the analyses included in this paper and of Edwird Renzi n h o performed the burnup calculntions \\-hich appear. LITERATURE CITED
(1) Corning Glass Korlis, Optical Bales Department, Corning, S . I-.,’ Glass ~
Color Filters,” 1048.
( 2 ) Horstman, E. L.,
-11.4~
CHEX 28,
1417 (1956). (3) Perkin-Elmer Corp , Son\-alk, Corm, Instruction Manual, Flame Photometer Model 52-4. (4) Strange, E. E., . S A ~ LCHEX . 2 5 , 650 (1953). (5) Valovage, IT. D , KAPL-1403, ‘*Effect of Irradiation on Hot-Pressed Boron Carbide,” p 17, Sol-. 15, 1055. ‘
RECEIVED for revie\\- Ileceniber 19, 1057. Accepted July 25, 1958. Division of Analytical Chemistry, 134th Meeting, .4CS, Chicago, Ill., September 1958.
