The Radiochemistry of Selenium

Rt?v.1965

NUCLEARSCIENCESERIES

National Academy of Sciences-National Research Council Pubtished $3y: United States Atomic Energ Commission COMMITTEEON NUCLEARSCIENCE S.K.Allison,Chairman f?.D. Evans,Vice Chairman UniversityofChicago Mass.InstituteofTechnology

LewisSlack,Secretary NationalResearchCouncil

E. C.Anderson BerndKahn Los Alamos Sci.Laboratory TaftSanitaryEngineeringCenter

N. E. Ballou JerryB. Marion U.S.NavalRadiologicalDefenseLaboratory UniversityofMaryland

MartinJ.Berger R. L.Platzman NationalBureauofStandards ArgonneNationalLaboratory

C. J.Borkowski ErnestC.Pollard Oak RidgeNatl.Laboratory PennsylvaniaStateUniversity

RobertG. Cochran KatherineWay A & M CollegeofTexas Oak RidgeNationallaboratory

HerbertGoldstein GeorgeW. Wetherill ColumbiaUniversity UniversityofCalifornia(LosAngeles)

LIAISONMEMBERS

PaulC.Aebersold RalphG. Allen AtomicEnergyCommission AirForceOfficeofScientificReeearch

J.HowardMcMillen NationalScienceFoundation

SUBCOMMITTEEON NAOIOCHEMISTRY N. E. Ballou,Chairman W. E. Nervik U. S.NavalRadiologicalDefense LawrenceRadiationLaboratory Laboratory J.M. Nielsen G. R. Choppin GeneralElectricCompany (Richfand) FloridaStateUniversity G. D. O’Kelley H. M. Clark Oak RidgeNationalLaboratory RensselaerPolytechnicInstitute R. P. Schuman R. M. Diamond AtomicEnergyDivision LawrenceRadiationLaboratory PhillipsPetroleumCompany (IdahoFalls)

A. W. Fairhall E. P. Steinberg UniversityofWashington ArgonneNationalLaboratory

Jerome Hudie D. N. Sunderman BrookhavenNationalLaboratory BattelleMemorialInstitute

J.D. Knight J.W. Winchester Los Alamos ScientificLaboratory MassachusettsInstituteofTechnology Radiochemistry of Selenium

V. J. Molinski and G. W. Leddicotte

Ismed,November1966

Union Crmbide Co@oration Mining and Metals Division Research Center Tuxedo, New Yoyk

Subcommitteeon RadiOchemiStry NationalAcademy ofSciences— NationalResearch Councfl

PrintedinUSA. Price$1.00.AvailablefromtbeClearinghoussforFederal ScientificandTechnicalInfmmaticqNationalBureauofStandards,U. S. DepnrunentofCommerce,Springfield,Virginia22151 FOREWORD

The Subcommitteeon Radiochemistry is one of a number of subcommittees working under the Comni.tteeon Nuclear Science within the National Academy of Sciences - National Research council. Its members represent government, industrial, and university laboratories in the areas of radlochemistry and nuclear chemistry. Support for the activities of this and other subcommittees of the Committee on Nuclear Science is provided by a grant from the National Science Foundation.

The subcommittee has concerned itself wi’thpreparation of publications, encouraghg and supporting ac%ivlties in nuclear education, sponsoring symposia on selected current topics in radiochemistry and nuclear chemistry, and investigating special problems as they arise. A series of monographs on the radiochemi.sta?yof?essentiallyall %he elements and on radiochemical techniquesis being published. Initiationand encouragement of publication of articles on nuclear education In %rious subjec% areas of chemistry have occurred, and development and improvement of certain education activities (e.g., laboratory and demonstration experiments with radioactivity] have been encouraged and assisted. Radioactive Contamination of reagents and materials has been investigated and specific recommendations made.

This series of monographshas resulted from the need for comprehensivecompilationsof radiochemicaland nuclear chemical information. Each monograph collects in one volume the pertinent informationrequired for radiochemicalwork with an individual element or with a specializedtechnique. ‘IkeU. S. Atomic Energy Commissionhas sponsoredthe printing of the series.

Comments and suggestionsfor ~her publicationsand activitiesof value to persons working with radioactivityare welccmed by the Subcommittee.

N. E. lhllOU, Clwuknan Subcommitteeon Mdiochemistry

iii INTRODUCTION

This monograph on the radiochemistmy of selenium is one series covering %he rad%ochemis%ry of essentially all the elements. It Ls a revised and expanded version of an earlier monograph. In it are included reviews of nuclear and chemical properties of selenium, discussionsof methods of sample dissolution and of separationreactions,descriptionsof couuting techniques,and a compilationof radiochemicalseparation procedures ~or seleniumas found in the literature.

As new informationaccumulateson chemicaland nuclear propertiesof seleniumand on separationand measurementtech- niques, considerationwill be given to further revision OI?this monograph. Consequently as additional information hcomes available in Ixsthpublished and unpublished form, readers are encouraged to bring it.to the a’thent%onof the author for possible inclusion i.nfuture editions of %his monograph.

iv CONTENTS

I. GENERAL REIFHENCESON THE INORMNIC Am M’?ALY!HCALCHEMISTRY OF SEMNTO’M ...... 1

II. GENERAL REFERENCES CONTAININGINI’ORMK!ZONON THE RAIIB CHEMISTRYOF SELENIUM ...... 2

III. TAELEOF ISOT~S OF SELENIUM ...... 2

rv. IE4TURES OF SELENIUM CHEKK3TRYOF CKCEF INTEREST !IU THE RADIOCHEMIST...... 6

1. INE30DUCTION ...... 6 2. THE NmrALIrc SANE ...... 6 3. m Oxmzs ...... 6 4. 0= DATZONSTA3XS ...... 8 5. Sacs...... 8 6. COMPLEX IONS ...... 10 7. cEEtuTEs...... 10 8. voLAmLEcoMPoLmnx...... U 9. PRINCIPAL ANALYTICALM3THOIJ5...... J-1

v. SELENIUMSEPAFWIONREAC!ITONS ...... 32

1. SEPARATIONEYPRECIPITJWCON...... 12 2. SEPAEtATZONBY SOLVENTEXZ’RACTTON...... u 3. SEPARMZONBYVOLATILITY...... 16 4. ELECI’ROLYTICSEE’ARATION...... 16 5. SEFAMTIONBY IONEXCHKNGE.HHCNS...... 16 6. SEPARATIONEY PAPER CHROMATOGFWWY ...... 17

VI. DISSOLUTIONOF SAMPLES CON’IMININGFZLR%WM...... 17

1. MEmsmonms...... 18

2. SALTS...... 18 3. oFm...... 18 4. BIOCHEMICALSAMPLES...... 18 5. 0-...... - ...... 18

v VII. HKZANXAND PRWAU1210NS...... I-0

VIII. co~TEcHNIms...... ● 19

lx SEPARATIONPROCEIY.JRESlWR SELEWOM ...... 26

x. INIJEXOF SEPARATIONPROCEDURES...... 27

Xt. KEFEKENCES...... : ...... 46

LIST OF TABLES

I. TABLE OF TEE ISOTOPES OF SELEWUM...... 3 11. CHEMICAL ANDPSYSICAL PROPERTIES OF ~ ...... 7 III . VOLUBILITY OF SFLENIUMCOMPOUNES...... 9 Iv. SOLWENT EXCRACTTON SYSTEMS FOR SELENTW ...... 14 v. CALCULATEDWECIFTC SATURATIONMZCTVITICES FOR SELIWUM RADIONUCIJXEWPRODUCED BY T!HERMALNEUTRON CKPrUR3...... 20

LIST OF FIGURES

1. PARTIAL CHMKCOFTHENUCLIEES SHOWING~ ...... 5 2. GAMMA-RAY SPECTRUMOF 7.1-HOUR Sea= ...... 21 3. GAMMA-FWi SPECITIUMOFl.21-D.&iSe75...... 22 4. GAMMA-RAY SPECTRUMOF 17.5-SEC Se- ...... 23 5. GAbWA-RM SPE~OF56.&MIN Seam ...... 24 6. Gw-MsPEcIcurJd oF25-~N Se- ...... 25

vi Radiochemistry of Selenium

V. J. Molineki and G. W. Leddicotte

Union Cmbide Corporation Mining and Metals Dim’sion Research Center Tuxedo, New York

r. GENERAL REFERENCESOH INORGANICAND ANALYTIC cBIM13TRYOF SELEMIUM

1. J. W. Keller, A C rehensiveT!reatiseon Inor anic and Theoretical (Lon~% Green and Co., Inc., New fork, 1960), VO1. x, =2.

2. W. F. Hlllebrand,G. E. F. LundeU, H. A. Bfi@t, ~d J. I. ~f~, APPlied Inorganic Analysis (JohnWiley and Sons, Inc., New York, 1955), Chapt. 19, p. 327-338.

3. W. R. Schoeller end A. R. Powell, The Analysis of .~,n~ralsand Ores of the Rarer Elements (Hsf’nerPublishing Company,New York, 1955)~ Chapt. XIX, p. 8-254.

Robert C. Brasted, ComprehensiveInorganic Chemlst~, Sulfux, Selenium,TelluriuuI,Polonium and O~g en (D. Van Nostrand Co., Inc., Princeton,New Jersey, 1%1 ).

5. H. Remy, Treatise on Inorganic Chemlst~ (Elsevier,Amsterdam,1956), Vol. I, p. 741-752.

6. J. ~einberg, W. J. Argersinger,and E. Griswold, InorUanic Chemistry (Heath, Boston, 1960), P. 434-455.

7. C, L. Wilson and D. W. Wilson, Comprehenslve Analytical Chemistry Elsevier, Amaterdmz, 1959).

8. G. Chariot and D. Bezier, @antltatlve Inorganic ATIalysis (John Wiley and Sons, Inc., New York, 1957).

1 9. N. V. Sidgwick, The Cheml.cslElements and Their Cmp2uudB (University Press, oxford, 1951) .

10. B. S. HopkinB, Chapters in the ChemiEtryof the Less FamiliarElements (StipesPublishing Co., Illinois,1939), Chapt. 19.

11. Selenium amd Tellurium Abstracts,prepared for the Selenium-TelJ.urium DevelopmentAssociation,Inc. by Battelle Memorial Institute,1959-1964.

II. CXNEML FEIERENCES CONTAININGINFORMAITOIV ON THE RADIOCHSTRY OF SELENIUM

1. w. w. Meinke, “Nucleonics”,hal. Chein.~, 104R (1960).

2. G. W. Leddlcotte,“NucleonIce”,Anal, Chem. ~, 143R (1962).

3. G. W, Leddicotte,“Nucleonlcs”,Anal. them. ~, 419R (lg64).

4. H. L. Finstin and J, Miskel, “RadiochemicalSeparationTechniques”, hnual Review of Nuclear Sciencej, 269 (1955);

5. H. J. M. Bowen and D. Gibbons, RadiosctivationAn- 16 (oxford UniversityPress, Herd, 1963).

6. G, W. Leddicotte,cd., “The Radiochemi8tryof Selenium”,Natl. Acad. Sci. - Natl. Research Council Rept. NAS-NS-3030 (1961).

III. TABLE OF THE ISOTUPES OF SEUKHJM

The radioactivenuclldea of selenium of interest in the radiochemiatryof 8elenium are given in Table I. This table has been ccunpiledfrcm information (1) (2) appearingin reporte by Strominger,et al. and in the Nuclear Data Sheets . ltLgure1 shows the seleniumportion of the chart of Nuclides(3) including the adjacent elements. TABLE I

TA8LE OF ISOTOPES OF SELENIUM

Isotopic Type of Pa-title Reactions - * ‘f-life = w

se70 &m B+ As75(d,7n)Se70 %71 4.5 m ~+ p: 3.4 &75 (ti, 6n]se71 7, 0.16

8.4 a EC,~+ 7, 0.046 A.e75(d,5n)Se72 se7m 44m ~+ p: 1.7 AS75(d,k )Se7m; 7, 0.88 *74(y, n)Se73m., Se74 (n,2n )Se73m *73 7,1 h ~:EC ~; 1.29,1.65 As75(d,k) Se7m; y, 0.36,0.066 Se74(y,n)Se7s; Se74(n,2n)Se7= ~74 0.87$

a?? 5 121 d EC 7, 0.265,0.136 Se74(n,y)Se75; no 9+ 0,28 ,0.405 As75(p,n )Se75; As75(d,2n)Se75

se7e 9.@ *77 7.584

se- 17.5 s IT Y, 0.162 Se7s(n,7)Se77m; U fission ~7e 23.52$ *7em 3.9 m IT y, 0.096 Se7e (n,7 )Se7m; Se=(n,2n)Se7m; Br7g(n,p)Se7m; U fission

3 TABLE I (Continued)

Iflotoplc Type of Particle Ener Reactions = w ‘f-life ~ HMeV

se7e 6.5x104 y B- P; 0.16 Se7e(n,7)Se7g; U fission

*SO 49,82$ ~Slm 56,8 m IT y, 0.103 SeeO(n,~)Seslm; Slm Brel(n,p)Se ; SeeO(d,p)Seam; U fission Se.sl 18.2 m B- P; 1.38 Sem(n,7)Seal; SeeO(d,p)SeaL; Se=(7,n)See1; BraL(n,p)Seel; U fission

.&2 9.1*

@3m S3m. 70 s B- ~; 1.5, 3.4 *=(n,7)Se , 7, 1.01, 2.02, U fission 0,65, 0,35 *B3 25 m B- p; 1. Se=(n,7)Se=; 7, 0.35 Se=(d,p)Se=; U fission and Th fission

3.3 m B- U fission

40 s B- U fission @6 17 s @- U fission

4 U

FIGURE 1: Partial chart of the nuclides showing selenium. IV. F!EJ4TUFCZSOF SELENIUM CWSTRY OF CHG3F INTEWIST TO TBE RADIO-ST

1. INTROIXJCTTON

Selenium is found associatedwith sulfur aud sulfides. The usual sources are the native sulfides such ss p~te, chalcop~ite, and zinc blende. Flue dusts from the roasting of seleniferousores, and the sludge formed in the lead chambersused In sulftudc-acidmanufacturingprocesses are also highly enriched sources. Selenium in these material~ is usually brought into solution by treatmentwith sulfuric acid and sodiuq nitrate. In this treatment, It is convertedinto selenious acid (%SeOS) and selenic acid (H&eOa) and fintiy precipitatedas elemental seleniumwhen sulfux dioxide is p-seal through the solution. Some of the chemlcsl and physical properties of elemental selenium are (4) summarizedin Table 11. Data have been com@led from publicationsby Hopkins and by Latimer(5).

2. TSE METALLIC STA!171

Selenium, like sulfur, exists in at least three allotropicforms, or modifications: crystsJllne,metalllc, and amorphous. Cmly the crystalline and metallic fores have been well ch=acterized. The crystallineform ( a loose powder ccmposed of at least two varieties of red, monoclinic,c~stals) is prep=ed by crystfiization from carbon disulfide,in which it is soluble. Gray, metallic seleniumis the most stable modificationand forms hexagonal crystals. It is relativelyinsoluble in carbon dlaulfide,is a good conduc- tor of electricity,and ia less active chemicallythan the other fores. Gray selenium is prepared by heating sny of the other forms at temperaturesof frcm 200 to 230”c. Amorphous selenium is obtained in two forms: (1) red powder produced by reducing a selenite in an acid solutionwith sulfur dioxide; end (2) vitreous or glassy selenium,black in color and described SE a super-cooledllquid. Both amorphousfomns are soluble in carbon disulfide. Seleniumwill burn with a characteristicodor, and will combine directly with hydrogen, oxygen, the hslogens, and many other metals. It is not attacked by non-oxidizingacids; but nhen heated, it will dissolve in concentratedsul- furic acid, nitric acid, or caustic alJralis.Nitric acid oxidizes selenium to H&eO~.

3. TBE O~DES

The most stable ccmpound of Se (and its only well-definedoxide) is selenium diotide (Se02) produced by burning selenim in oxygen or sir, Pure Se02 is composed of brilliantwhite needles, It sublimesreadily but can be melted

6 TABLE II

CHEMICAL AND PHYSICAL PROPERTIES OF SELENIUM

Atomic Weight 78.96

SpecificGravity (solid) 4.26-4.79

Color (solid) dark red

Melting Point 170-217°C

Boiling Point 688°c

Atomic Volume (approx.) MC

Heat 01’Fozmation, ~X (Csls.) -25.1

Atomic R8diuS 1.5 Augstrom

Ionization Potentials

—Ion volts I 9.751 II 21.514 III 30,079 IV 42,902 v 73.1C9

OxidationPotentials (volts)at 25’c (a) Acid solution

E&e —0.40 Se .-0.74 H#e03 -1.15 Se04= (b) Base solution

%= 0.92 se 0.366 Seoa= -0.05 seed= without decomposition. In the vapor state, it has a yellow-greencolor. Sele- nium diotide will dissolve in water, concentratedsul-c acid, or alcohol. It can combinewith hydrogen chloride to form Se02.2HCl,and will form similar double compoundswith other substances. It can easily be reduced to elemental selenium. (6) to The characteristicbuznlng odor of selenium is reportedby Berzelius be due to the formationof a suboxide,SeO. It is also reported that a mitiure of SeOz and SeOg is producedwhen selenium reacts”withoxygen In an electrical discharge, Selenium triotide is decomposedTn water to form selenic acid, and is stable to 185”c, at which temperatureit decomposesto oxygen and SeOz.

7 4. OIZDATION STATES

Selenium cam form compounds havl~ oxidation states of -2 (the aelenidea), +4 (the selenites),and +6 (the selenates). Polyaelenides,such as Nasez end NaSe3 are known, but they are leaa stable than the polysulfides. Selenium IB electronegativelybivalent towards hydrogen and the metals. In its electropoaitlvebehavior, selenium has a valence of +4 in compounds formed with most elements;but in combinationwith fluorine it has a valence of +6. In general, the compoundsof selenium,sulfur, and tellurlum,behave similarlyand are analogousto each other. The principal differenceis in the lower stability of the selenium (and tellurium)compounds,which are easily decomposedto the element by heat or reducing agents.

5. SALTS

~.1 Soluble Salts

Selenium dioxide 18 a true anhydride,five parts disaoltingin one part of water. In combinationwith water, Se02 will form seleniousacid (H&o, ). The alkali selenites.(Li2Se03,Na&e03, &Se03, Rb2Se03j Cs#3e03) are all soluble in water, as are the acid selenitesor hydro- selenltes of the type MHSe03, Table III lists some of the more inpor- tant soluble compoundsof selenium.

5.2 Insoluble Salts

The selenate compounds of lead, barium and calcium, like the corres- ponding sulfates, -e insoluble; however, they are leas stable to heat than the sulfates. Hydrogen seletide can form both acid selenides (M%Se) and neutral selenides (&zSe). The alkali and alkaline earth metals can combine with additionalselenium to form polyselenides (~lSex) in the same way that these metals form polysulfideswith sulfur. Pure alkali selenides are colorless. Heavy metal selenidesprepared by the action of hydrogen selenide on solutionsof the heavy metal salts are more or leas strongly colored. Like the heavy metal sulfides,they exe insolublein water, and some are insoluble in acids. Selenium can combine directlywith nitrogen to form seleniumnitride (Se~4), which is insoluble in water, and only slightly soluble in benzene, acetone, acids, and carbon disulfide. Selenium combineswith sulfur to fomn seleniummonosulfide, (SeS) and selenium tisulfide (SeS2). Seleniummonosulfideis insolublein water and ether, but very soluble in carbon disulfide. Selenium disulfide

8 TABLE III

VOLUBILITYOF SELENIUMCOMPOUNDS

Water Volubility CompOund Formula Cold —Hot Other Solvent8 Bromide@ Se2Br2 decomposes decomposes Decomposes In alcohol; (Se + H#e03 + HBr) solublein CS2, chloroform, C&.Br. SeBr4 deccmpoaea decomposes Soluble in CS2, chloroform, (SeOBr2+ HBr) C2~Br, HC1. SeBrC13 Insolublein CSZ. SeBr3Cl Se$2Br inBoluble decompoEe6 Slightly solublein CS2.

Chlorides Se2.C12 decomposes decompoaem Decomposesin alcoholand (Se+ H#e03 + HC1) ether;solublein CS2, CC14 chloroform,benzene. SeC14 decomposes decompoae8 Decomposes in acids and (SeOC12+ HC1) alkelia; slightly soluble In CS2.

Fluorides SeF4 decompoae8 decomposes (*OF.+ SF) SeF8 dec~oses– dec~oses

Iodides Ss212 decomposes decomposes (Se+ H#e03+ BI) SeI~ decomposes decomposes (SeOI=+ =)

Nitfldes se4N4 insoluble insoluble Insoluble in alcohol and ether; slightly soluble In benzene, acetic acid end CS2.

Oxides Se02 soluble soluble Soluble in alcohol, acetone, benzene, acetic acid. Seog decomposes decomposes Soluble in alcohol and fiS04; slightly sligktly insoluble in ether, benzene, (SeO~+ Se) chloroform, CCL4. seso~ deCOnIp08eE decomposes Soluble in ~S04; ineoluble (Se02+ S02) in SOS.

Oxy-sslts SeOBr2 decomposes decomposes Soluble in CS2, CC14, chloro- (H#eO~+ HBr) form, B@34, benzene SeOC12 decomposes decomposes Soluble in CS2, CC14, chloro- (H@e03+ HC1) form, benzene. Seol?z insoluble insoluble Soluble in alcohol, CC14

Sulfides SeS insoluble insoluble Insoluble in ether; soluble in CS2. SeS2 inBoluble insoluble Decm.poses in BN03, aqua regia; soluble in (NH4)fi.

9 ia Insoluble Tn water amd will decompose only in aqua regia or nitric acid. Table III lists Borneof the more Important Insoluble compounds of selenium. Additional information on solubilities appe-s in the “Handboak of Chemistry and Physics” (7),

5.3 Non-isotopicCarriers

In some cases, a hfgh specific activity selenium source must be prepared. A non-isotopiccarrier, chemicallysimilar to selenium,must be used rather than inactive selenium. Telluriummeets these requirements aud can be used to sep=ate small quantitiesof radioactiveselenium High-purity (99.999$)tellufiumia availablecmmnercially. Total helo- gena, sulfur, and selenium do not exceed 5 ppm by chemical analysis. (8) Garrison, et al. re’potieda procedure in which they separatedradio- active selenium from an eraenic target using telluroua acid, precipi- tating telluriumwith sulfur diotide. They reported that 95* of the selenium c=fes, and can then be aeperatedfrom telluriumby distillation.

5.4 Coprecipitation

Microgrmn quantitiesof selenium can be collectedby coprecipitation on ferric hydrotide. The weight of the iron present should be 30 times that of the selenium(9). The Iron Is precipitatedwith an excess of ammonium hydroxide. A method(lo) for separatingsmall amounts of selenite and selenate ions ia baaed on the copreclpitationof the selenite ion with iron hydrotide at pH 8.4-8.6. Under these conditions,

the selenate ion Is not coprecipitated.

6. COMPLEX IONS

Several of the selenium halogen compounds can form complex acids by adding on hydrogen halide ions. For example, SeBr4 will combinewith H& to form hexabromoaelenicacid (B#eBre). Hexabromoselenatesand hexachloro- selenates have been formed by the reaction of al12mlihalide salts upon these ccmplex acids. Their aolubilitiesresemble those of the selenates.

7. CHELATES

Selenium forma a chelate In an acid solutionwith sodium dlethldithio- c=bamate that can be extracted (pH 3) with ethyl acetate‘U)W). The c~- (13) plex can be extracted into carbon tetrachloride , end telluriumis also extracted.

10 Bode WI. Aanswold(’4)reported the quantitativeextraction of the SeIV chelate of dlet~ldltblophosphatefrom 10~ HCl into CC4, only 40$ of the te~urium being extracted. che*(’5) has shown that a 5$ aqueouB dlanrlnobezitinehydrochloride solutionvIIJ.form a selenium complex In a fotic acid-watersystem that can be extracted into toluene at pH 6-7. Although Fe+=, CU+2, @5 and other oxi- danta Interferes,the Fe+g and CU+2 interferencescan be eliminatedby EDT.A completingat pH 2-3. TelluzYum forms a cmuplex that is extractedbut doet3 not Interfere in the colorlmetricanalysis.

8. VOIJICILECcwourms

The distillationof neutral or acid alkali selenldeswith potassium alkyl sulfatesproduces sJ@l selenldessew (whereR=the alkyl group) and alkyl selenomercaptansSeFH. The a.lkylseletides are volatile liquidswith pungent, repulsiveodors. They readily combinewith, or add on, halogens or oxygen to fomn such compoundsas (C41S)&eC12 or (C2%)@e0. In addition,they can add on alkyl iodl.desto form such compoundsas eJ.kylselenonium, e.g. (C2~)@eI. These compoundsam strong bases and, when treated with moist silver otide, form the correspondinghydroxide.

9. PFLIIKXPAL AIwlYTrcAL m.!EHoDS

9.1 Gravimetric

The gravimetricdeterminationof selenium is csrrled out byweigb- ing the element after it has been precipitatedby reduction in strong (16). acid solutionwith either sulfur dioxide or hydro~lemine hydrochloride

,.2 vohnnetric(’6)

9.2.1 Selenic acid is reduced by hydrochloricor hydrobrmnic acid. The halogen is caught in a Bolution of potassium iodide and titratedwith arsenlte and thiosulfate.

9.2.2 Selenious acid is reduced by hydriodic acid followedby titration of the liberated Iodinewith thiosulfate.

9.2.3 Seleniousacid in hydrochloricacid solution Is reduced by a brown excess of sodium thiosulfate. The excess thiosulfate Is then titratedwith stand- iodine solution.

9.2.4 2eleniousacid is oxldlzed by an excess of standardper- manganate solution in sulfuric acid solution. The excess permauga- nate Is titratedwith ferrous sulfate or oxalic acid solution.

n 9.3 Colorlmetric

9.3,1 3,3’-rn~nObe~iUne reacts with Se to form an intenee yellow compound (piazselenol).~eng(15) reported a procedure for determiningtraces of Se by extractingthis ccmpound into toluene and measuring the color apectrophotcanetricaldyat a wave length of 420 m. 9.3.2 2,3-DiaminonaphthaLenealso reacts with Se to fomn a piaaselenolwhich 1s a reddish precipitate. It may be extracted into toluene and measured spectrophotometricallyat a wave length of 380 UP(17).

9.3.3 Selenious acid liberates iodine quantitativelyby ofida- tion of iodide ion. The blue color is developedwith a cadmium- iodide starch reagent and measued spectrophot~etricallyat a wave length of 615 mI(18).

v. SELENIUM SKPARA’ITON~ACTIONS

1. SEPARATIONBY P~CIPITATION

Selenium ia separatedfrom moat elements by the use of reducing agents (16) in acid solutions. EH.llebrand,et al.. report that Se (and Te) can be initially separatedfrcnnmost elementsby reductionwith S02 in 3.7 to 4,~ HC1 solution. Gold, Pd, and small mounts of Sb, Bi, Cu, and other elements are also reduced under the same conditons. Gold can be separatedby filtration after the mixed metal precipitatehas been digested for some times in a dilute HN03 solution. The selenium C= then be separatedby precipitation with E&03 or hydroxylamlnehydrochloride. Quadrivalentselenium or telltium can be separatedfrom other elements (19), by saturatingau acid solutionwith H# Sexivalentselenium and tellu-

rium can be completelyprecipitatedfrom 122 HC1 solution at room tempera- tul-e(20).Sulfides of the copper subgroupmay interfereunder the same conditions. (21) In their studies, Seath and Besmiah end Noakes(22) showed that nitrates of CU+2 and Au+= interferedin the reductionof Se (or Te) to elemental Se (or Te). The nitrateswere removed by evaporationwith HCl and NaCl, and CU+2 and Au+= were separatedbefore the reductionwith hydroqui- none(23,24). Selenium (and tellurium)may be separatedfrom many elementsby reduction of an acid solutionwith stannous chloride. Selenium and telluriumare precipitatedand can be sep=ated by a brcminatedHCl dissolutionof the (25)0 metals followed by a precipitationof Se with S&

12 Bode(26) has shown that a separationof Se from Te can be effected in a 51 HC1 solution using a solution of tetraphenylarsoniumchloride.Telluium+8 will precipitate and bromide, iodide, fluoride,nitrate,Mo+e, and tie will interfere. Ripen-Tilici(27)Snd SPQCU(28) have shown that Se can be detetined as lead selenate. To obtain this form, Se must be oxidized to the hexavalent state with *02 and precipitatedby a lead salt solution.

2. SEPARATIONBY SOLVENT EXTRACTION

Solvent extractionmethods, used as wparation methods for other analysis techniques,can often be adapted for use in radiochemistry. They can be quite useful in separatingthe desired radionuclidefrcm .&sample by either (29) a carrier-freeor carrier rsdiochemist~ method. Morrison and Freiser have reviewed the applicationsof ion-associationand chelate-complexsys- tems to the detehnation of most of the elements. Some of these are applicablesa separationprocesses in the radiochemistryof selenium. Table IV gives a few of the solvent extractionsystems that could be used for the separationof selenium. Few epecific solvenbextraction methods for seleniumhave been developed,but many could be adapted.

2.1 Ion-AssociationSystems

Kitahar.(3°)has reported that Sn+2 and Sn+4 can be completely extractedwhile Se+4 (md As+’, %+’, mdMo+’) iS 01dyp3.I’ti-y extracted (about L%) from HF solutions of varying concentrations by ethyl ether and a 4:1 volume ratio of organic-to-aqueous phase. (31) Using equal volumes of IIFand ethyl ether, Bock and Herman have shown that only Nb+5, Ta+5, and Re+7 were extracted in amounts greater than 5*; Se+4 (aawell as Sn+2, Sn+4, As+3, As+5, Te+4, Ge+4, ~5, @3, @?, h!o+eaud Sb+3) was only partially extracted. However, the extract- ions of Se+4 and the other ions Incresaedwith increasingHF concentr- tion. These two studies show differentextractionvalues; however, these differencesmay be due to the manner in which the metel fluorideswere (32) prep-ed. Stevensonand Hicks report that Se+e (ss well aa Te+8, Fe+3, Ga+3, sb+5, and Aa‘s) canbe quantitativelyextractedbytiis~ propyl ketone from anlneral acid-hydrofluoticacid (6E HC1 - O.% HF) aqueous system. Se+4 (aa well as Sb+3, As+5 and Te+4) is only slightly extractedunder the8e conditions. In this same study, it was shown that Se+4 (and Te+e ~d Ta+5) co~d be extractedby diisopropylketone frcnna 6~ H2s04 - O.bg m’ Systemp At least 3C$ Se+4 can be etiracted from a mixture of metal bromides

13 mHLE Iv

SoLsm’rmcmoN sYs-JEMs FOR slImNIuM *

Oxidation % Skate Extraction Reference IV 4.6ME? ethyl ether 4.0 30 IV 20M HI? ethyl ether 12.9 31

VI @ Hcl-o.g HF diimpropyl ketone 100 32

Iv 4-% HBr ethyl ether 31 33

IV I.METJog o.ca-o.6M dibutylphophoricBCid <5 34

IV HC1 methylisobutylketone 100 35 (4-methyl-2-pentanone)

r? 30-35$HBr di-iaobutyl ketone 90 36 (2,6-dlmethyl-~heptanone)

rv Na-tiethyldlthio- ethyl acetate 100 11,12,13 c-bamate

IV Pi=selenol- t oluene 100 15 complex of 3,3 ~tinobenzitine hydrochloride

rv Complex of 2,3 toluene 100 17 diamino-naphthalene

Iv Complex with mixtureethylene 100 37 toluene- chloride- ccl~ 3-~dlthiol and 10~ HCl

* All of theee ❑ol.ventextraction system - also applicable to tellurium. The Na-dietbyldithiocarbamatesystem is the only practical method for separating Te from Se. Tellurium can be extracted from thiB ayatem into carbon tetrachloride atpH 8.5 - 8.7; selenium ia not extracted,

14 (~ to @ E&) into ethyl ether(33). AU+3, Ga+3, In+3, T1+3, Sb+5, Sn+2, Sn+4, and Fe+= qU8ntit8tiVely extract from thie ByBtem; As+3, sb+3 and Mo+e extract slightly;Cu+2 and Zn+2 do not extract. (34) Scsdden and Ballou have shown that leas than 5$ Se+4 (and Te+4) till extract Into O.@ or O.@ di-n-butylphosphoric acid (DBPA) frm a

1# HN03 solution. A 1:1 orgamlc-lio-aqueouavolume ratio was used In

these studies. Yttrium, Sn, Mo, Nb, Ta, Zr, and In me extractedIn concentration v~ng from 5 to more than 95$ fram the same system. Selenium (es weu as Tej Fe, Ge, Sn, As, and Sb) can be quantit- tively extracted into methyl iBobutyl ketone I’rcnnvarious concentratlon8 of HC1(35). This study determined the approximate ranges of extract- ability for metallic Baits of the~e and other elementB. Kuroda(%) used a HBz=dllsobutylketone Bystem for the rapid radlo- chemicel separationof Se7sm. Selenium (8s well aa As, Sn, Hg and Au) can be quantitativelyextrhcted into dilsobutylketone frmn 30 to 35$ HBr. The interferingelements can be strippedby shakingwithED’TA ~d sodium t-rate, or with sodium hydroxide solution.

2.2 Chelate Complex Systems

Selenim can be extractedfrcm an acid solution (PH 3) as the Bodlum diethyldlthiocarbamatesalt with ethyl acetate (U,M) . Se+4 (and Te+4) will also forma complexin an acid solu~~ (pH 5-6) by use of O.~ solution of Bodium diethyldithiocarbamate . The conplex can be extracted into CC14. The addition of a 5$ solution of EDIM to the s stem assists in masking out other extractableelements. ,hew(15$ haB 8hown that a 5$ aqueous diaminobenzidlnehydro- chloride solutiontill fozm a piazselen@ cmnplex in a fomnic acid- water systm that can be extractedat pH 6-7 by toluene. Fe+3, Cu+2, @5j and other ofidants interfere;however, the Fe+3 and Cu+2 inte~ ferences can be eliminatedbyEDTA ccxuplexingat pH 2-3. Vanadium (V) otidizes diaudnobenzidlnepreventing the fomaticm of the cmnplex, but traces of vanadium have Httle effect. Tellurlum is extractedbut does not interferecolorimetricalJ.y. Lott, et al.(17) used a similar 8yetem for extractingSe. A l? aqueoue (0.~ HC1) solution of 2,3-dieminonaphthalene was used to complex Se; and the complex was extracted, at pH 1.5 to 2.5, into toluene. hlmking agents were used to prevent interferences. Watkinson(37) etimcted Se from strong HC1 solutions (QO~) 8s the Se (IV) complexwith toluene-3,~dithiol into a mixture of ethy- lene chloride and carbon tetrachloride. Elements that also react with toluene-3,&dithiol are Te (~), Pd, Au, W (VI), andRe (VII).

15 3. SEPARMICONBY VOLATUITY

Selenium (or tellurium)in the selenide (or telltide ) fom can be sepwated fran metalm whose chlortdes- nonvolatileby pasdng C12 gas (38) into a hot aqueous solution . Hydrochloricacid gas csnbe used instead of C~ to sep=ate either”Se+4or Se+e. Selenim can be 8epua- ted from telluriumby a distillationmethod in which HC1 gas is passed into a H#04 solution. The distillateis caught in cold water, and Se+e 18 precipitatedby adding S02. Either Se+4 or Se+e can be quanti- tatively~eparated fran te~urium by passing C02 gas into a l@Tobromlc- (40) phosphoric acid solution . Selenium o~chloride and SeOBr2 ( as well (41) as TeOC~ and TeOBr2) are volatile from 61 HC1 0, 6~ ~(@-44)SOk tiong at temperaturesabove 100”C. Arsenic, antimony, tti and germanium are also volatile under these conditions.

4, ELlmImLrmc sEPARA!tToN

Electroseparationand electrogravlmetrymethods for seleniumme not extensivelyreported. Only a few electroanalysistechniquesexist for the determinationof seleniumby amperometryand coulometry;however, a consi- deration of these ml t be profitablefor use in rediochemistry. For example, F45) +4 with CUpfic COPper Lingane and Niedrach report on the titration of Se in an mnmonicslmedium. Se+4 is reduced to Se+2, and cupric selenide is only slightly soluble in thi6 medium. The potential of the dropping elec- trode is such that the tetreazdnocupricions and the eelenite ions are reducible;its value will increasewhen excess cupric ion is added. Rowley and swift(~) have used a coulometrictitration of thiosulfatefor the determinationof Se+4. The back-titrationprocedureswere followed. In one, en excess of iodide is added to a strong seleniousacid solution and iodine iB liberated and reducedwith sodium thiosulfatesolution,the excess thiosulfate being detemined by coulometrictitration. In the second procedure, excess thiosulfateis added so that the selenlousacid is reduced to sele- nopentathionate(SeS40e),and the excess thiosulfateis dete?.minedby coulo- metric titrationwith iodine. More accurate results (YO.1~for several hun- dred micrograms)were obtainedby use of the second method.

5. HEFAB-ATIONBY ION EXCHANGE RESINS

Kraus aud Nelson(47) report that selenite (Se+4) and telluriteshow good adsorptionon an anion resin column as chloride complexes. As en example, this behavior of Se+4 ha de it poesible tO Sepwate ‘t ‘rm As+a ~d Br- by use Of solutions of various N&Cl concentrations. AS+3 ie removed by elutionwith O.01# ~Cl; Se+4 with 0.5CljNI&Cl; and Br

16 (49) with 5.OFJ~C1. Attebury,et al. , and Aoki(’g) report that se can be sep=ated from Te by adsorptionupon an anion resfi column from ~ HC1, A mlxlmre of ~ HC1 and ~ NH&NS was used as the eluant. (50) Lederer and Kertes used selenite end tellu%te ions in a study concernedwith the use of a Ibwex-re,ein-lmpre&ate& paper. Optimum conditions for wepsxationwere calculatedby consideringthe relationship of the ion adsorptionwith the pH of the aqueou6 acid used as elusnt.

6. SEPARATIONBY PAPER CHROMMIWRAPHY

Levi and Banon(5’)have used paper chrczaatographyto separatemixtures of BI=o, pb=o, Po, Se, and Te in ~Os BOlUtiOn8. A butanol-propanolmix- ture was used as the solvent and a good separatlonof each elementwea (52) obtdned. Crouthameland Gatrousis also report on a similar separation of Se, Te, Po, and Bi by peqer chromatography. Specific separationsof Se (ss se+4) from teU&5~ (SS Te+4) in HCl, ~03, and HBr have been studied by Bursta12, et al. , Lederer(54), md Weatherley(55). Solvents such as mixtures of butanol-methanol,butanol-water,and butanol-HClwere uOed to effect the separation.

VI. DISSOLU’ITONOF SAMPLES CONTAININGSELENIUM

When dissolvingselenium-contairihgseanpleO,it is necessary to use (56) techniquesthat will minimize the 10BS of Se by volatilization . Sele- nium is easily volatilizedas Se02S2HClfrom strong HC1 solutionsby heating. Very little Se is lost by heating dilute HCl solutionsat temperat~s” below 100”C. The presence of alJmli salts do not prevent the volatilizationof Se. The volatile monochlorideof selenium (Se2C12)can be formed in strong HC1 solutionsby the action of reducing agents. The neductionof Se Bhould be performed rapidly,with an excess of reducing agent, to reduce the Se to the element. No loss of Se occurs if sulfuric acid or perchloric acid solutionsof seleniousacid - evaporatedto dense fulnes(s~)unlees there are chlotidesor bromides present. Some selenidesattack platinum during a fusion process. The fusion can be done with N@2 or a mixture of N&C03 and KN@ in a nickel or zir- conium crucible. Fbion with KCN may cause sane loss due to volatili~ation. The addition of inactive selenium cexrier to the mixture before dissolution begins wild assist in achieving an exchmge of the radlonuclide with the carrier atom. The chmical states of the hradlated selenium and the carrier selenium should be the same dting the dissolutionprocedm so that any losses that occur will be accountedfor in the chemicalyield determinationof the added inactive carrier.

17 1. MEmLs AND O.xJIIEs

Acid dissolution18 TeC~ ded for the asBay of metals and oxides. For exszuple,copper metal can be dissolvedin nitric acid; iron and steels may be dissolvedin HN03, HC1 and HC104; lead muat be fused with N~COg and Na#OS in a nickel crucible. Insoluble oxides maybe fuse~=~th N@Oz or sodium carbonateand potassim nitrate in a nickel crucible’>”).

2. QXG!rs

Nitric acid and HCl will decmpose most selts. C= should be taken that no selenium is volatilized.

3. =

Ore samples can be fused with N@2 or a ml- . of sodium carbonate and sodium nitrate in an iron or nickel crucible(59J. Some ores can be decomposedwith 1:3 BN03 followed by funbg with s~ic acid to remove BN03. Ores containingselenidescan be deccmrposedby heating at dull red- ness h a current of C~ and catching the volatile chloridesof selenium in 1:1 dilute HC1.

4. BIOCHEMICALSAMPLES

Biochemicalsamples can be &ccrmposedby destroyingthe organicmatter with a 1:1 aahing mixture of nitric end perchloricacids(60). Tissues can (61) be decaposed by fusing with N@@ . SmsJl amounts of Se in vegetation, grains, and anhal matter have been z=eleaaedfrom these materials by distilling with HSr(62). Organic or biological samples cam be decomposedIn a SchUnige~type ~gen-combustion flask; the gases are absorbed in a HC1 solution containinga selenium carrier. Gorsuch(63), in a series of ra&Lo- chemicalinvestigationsconcernedwith the recovery of trace elements from organic matter, has evaluateda number of dissolutionmethcds for recover- ing trace Se frmn similarmaterials. The results of these studies showed that Se was lost by volatilization.

5. mm

Glass samplesmay be taken into solutionwith hydrofluoricand nitric acida(64). Rubber is deccnnposedby a fusion with a mixture of Ns20z, NaNOs, and Sll@r.

VTI . HAZAFUM AND PRECAUTIONS

No matter what method is used to decompose a sample, adequate safety

18 precautions should be followed. The toxicologyof most elemental compounds (65) has been reportedby Pieters and Creyghton , and It should be consulted for infonuatlonon handling selenium-containingmaterials safely. Due to the volatile nature of some of the selenium compounti,radiochemicalRepa- rations requiringheat should be carried out in a well-ventilatedhood. Safety practices are always importantin rSdiOChemi6try. The disch=ge of radioactivityby explosion or evolutioninto a laboratoryarea can be hazardous and can result in wide-spre.%iradioactivecontamination. Thus, some souxce of informationon safe-handlingpractices in processing radioactive samples should be consultedbefore a rsdiochemlcalanalysis Is undertaken. One such source is the Oak Ridge National Laboratory’sMsster AnalyticalMsmual(66). Other similar sources of informationexist and should be consulted.

VIII. COUNTING TECHNIQUES

The analysis of smple materials containingselenium rsdionuclidesmay be completedeither by a direct (non-destmctive)measurementof the radioactivity of the particular radionuclideor by obttining the radionuclldein some form by radiochemicallyprocessing the radioactives.mple. The choice of techniquedepends upon the selenium radionuclidesbeing measured, and such characteristicsas half-life, type of radiationemitted, and the ener&y of the radiations. An excellent source for counting techniquesis the monograph by OrKelly entitled,Detection and Measurement of Nuclear Radiation(67). Table I shows the nuclear characteristicsof each of the known radioactive isotopea of selenium. Those usually encountered by the radiochemist are Se75 (121 d), Se77m (17.5 see), Seem (56.8m), Sesl (18.2m) sndse= (25 m). These isotopes are produced as a result of a number of nuclear reactions on stable isotopes, either of selenium or other elements. Se=m decays to Seel by ismnerlc transition; Se= decays further to stable Br81 by the endssion of 1.3@-MeV beta radiation. Se= decays with the half life of Seelm (56.8m), stice the two states are intransigentequllibtium. “The measurement of Se= must be completedby beta counting,using 4 rror 2 n Geiger-MuelJeror proportional-betacounters. The other isotopea decay by means of gamma radiationsand can be measured with a gamma scintillationcounter or gsmna scintillationspectrometer. Figures 2 through 6 give gamma-ray spectra of the ss7s(87), Se7s(87), ~mn(~), See1rn(89 ~~ sem(90) radioisotopes. Although a number of radionuclidesof selenium are formed by radiative capture in stable selenlunisotopes,L21-day Se75 and 3.g-minuteSe79m have been most extensivelyused as the analyticalindicatorsfor the activation analysis of selenium. However, these are not the most sensitiveindicators

19 for a selenium malyais. Table V is a tabulationof the calculatedspeciflc- saturationactivitiesof the nuclides formed by radiative themsl-neutron capture in the stable selenium isotopes. Activation cross sectionswere ccm@led frm Informatim appearing in reports by Eughes and Harvey(Q) ~ by Weigman(70). Krsmer, etal~m) discuss the metastable isaners of eele- nium, emd show that the greatest sensitivitycan be obtainedby using l~.5- second Se7m as the radioactiveindicator. Seleniumm, a metastable isomer of stible Se=, decays with a half- life of 17.5 secondswith the emission of 0.160-Mev gamma ~. Its short ~-life has precluded the use of Se- in an activationanalytical scheme in most laboratories. In fact, there appear to be only two references(61)~) that report quantitativeselenium analyaesbased onthia particularnuclide. With rapid pneumatic-tubesyatems, s~les carIbe transferredfram the irradiationfacillty to the gamma scintillation counter inafew6econd3. OkS&(~) haE recently reported on the use of gamma spectrometryto detect and &tennine t@ radioactivityof Se- (17.5-see.) in nondestructiveanalyses of neutron-imsdiated sulfur, ammonium cmrpounds,end ores for trace selenium. Putman and Taylor(72’73) have reported a techmlquefor ualng Se75 (121 d), for detenuining trace selenium in glass. ‘I’@ made measurements of irradiated sauple & glass, with and without selenlum, simultaneously, with two IieZ(Tl)scintillation

TABLE V

CALCULATEDSPECIFIC SATURATIONACTIVITIESFOR SELENIUM RADIONUCLICESPROEUCED BY THERMAL NEU’ITONCAPTURE

‘~ecific Stable Isotopic Radio- Activation Saturation ll&lll@ nuelide Half-Life Cros8-section Activity (a) T (bma ) *74 0.87 *75 l’ld 26 1.7 x lCP Se77m *7e 9.02 17.5s 22 1.5 x 1o11 %7 s 23.52 Se7m 3.9m 0.40 7.2 Xld Seslm Se* 49.&2 56.&tI 0.030 1.1 x ld

*8O 4$),82 *81 18.2m 0,5 1.9 x ldo

*S2 9.19 70s 0.050 3.5 Xlos

sea2 9.19 25m 0.004 2.8 x 107

(a) dis/sec.g, baaed on a themsl flux of 1 Xldg neutrons/cm2. 8ec.

20 7’.1-hour sir :“KJ”;21 NaI :

Absorber: 1.!8 g/cm2 Be+ 0.51! 0.1 Cu sandwich - mihilotio Source dist.: 10 cm (c) Energy scale: KeV/PHU (Cd -

% .4 e \ e.

I -L o 800 Kx )0 12 10 1400

PULSE HEIGHT

FIGURE 2, Gommwmy spectrum of ‘?.l-hour Se73. — — .2$33, .:

—

(

— -i-

121- day Se75 .410 ) 3“X3*’- 2 N(ll 5/’19/58 Absorber: 2CX3rng/cxnz - 6) source C!istfmce: IOcm(c) - Eh3rgy scale: ~ lKev/PHU

. — — — — 64 — — T

—

l----- I 2( 0 400 6’ )0 1200 PULSE HEIGHT

FIGURE 3, GQmmQ-rQyspectrum of121 -day Se?s.

22 I .16 Mew $7’.!5-sec. SELENIUM 77M

—

$“ ! 1 1 I I ,y%#; I ~. E —,d I tI ~q’d \ &

— Cumulated difference — spectrum showing first W half - minute decay. f1-

I I

23 se“m 56.8 fTtifl. 590 mglcm2 Be (horne?ry: 4070 1W.= !5.5 kev

ENERGY ---+--

FIGURE !5, Gammo-ray spectrum of 56.8 min.SeaB%

24 0A4 Iu I I 1 SELENIUM-83 n Wr@e: Se, 1.0375 grams Gold disc: 15.5mg; !1,053 CX5mir 11/’24?’!59 0. A KY 3

831n 83m Se Se .69 1.01

!02 +se83 .84

I OcL3 0.6 c 3 1.2 1.5 1.8 :

ENERGY, Nlev

FIGURE 6, GammQ-roy spectrwm of Sease

25 counters; the response of the counters can be subtractedto leave only the (75) selenium-75activity. Erion, et al.’74) and Fineman, et al. have also determinedtrace seleniumin sulfur and ore concentratesby a nondestruc- tive analysismethod.

IX. SETJ!RATTONPROCEDURES FOR SELENIUM

The radiochemlcalprocedures describedin the folloVingpages have been divided inta four.cat.egories.In each category,special informationregard- ing the method used, aep=ation time, type of bcunhardment,etc., appems as part of each procedure. Whenever possible, an evaluaticmof the procedure is made concerningits use in the decontaminationof other radioactivespecies from the radioactiveseleniumisotopes. “Activation-analyaisprocedures”deacrib.evarioua methods used to deter- mine microgram and aubmicrogrememounta of selenium in various typea of amplea. In the activation-analyaisprocedu=s cited, a carrier techniquewas used to separate the radionuclidefrcunthe rgioactive mixture. In the procedum,by Kuroda(36) the c~erwas labelledwith Se75. The chemicalyield can be 75 in the find sample wfth ‘he determined by comparing the peak =ea of Se Se75 &ded with the Cufiero

Moat procedures describingthe prep-ation of radioactivetracera use carrier techniquesto aep=ate the radlonuclidefrom the target material. In the prep=ation of smne radionuclides,however, it la neceaaary to separate them without any addition of c~er. These procedures appe=” under a aepsrate classification: carrier-free separation. In addition to the procedures cited, It should be poaaible to uBe ion exchange in the carrler- free sepexationof radioactiveselenium isotopes. Procedures we also included for the emlysia of fission-productacti- vities in plant-process solutions.

26 x. INIEX OF SEPARATIONPROCEDURES

1. ACZEVA!TZOWANALYSIS PROCEDURES

1.1 Metals and Alloys, BiologicalMaterials,Waters ...... 28

1.2 Ore Concentrates,Slags, Waate Gase8...... 32

lm3Stony Meteoritea...... 33

1.4 Fertilizers,Tmnato Tissue, Huron Blood ...... 34

1.5 Sildcate Rocka, Sedhants ...... 35

1.6platinum Met~...... 36

2. TRAcER-PREPARAmoriPROCEDURES

2.1 Frmn Arsenic...... 38

2.2 FrcenBismuth Metal...... 38

2.311rom Uranyl Nitrate...... 39

3. FISSION-PIMXXKTPROCEDURES

3.1 Ilssion-productSolutions ...... 40

3.2 POIYphe~ls ...... 41

4. CARRDZR-= SEPARATION PROC3LIJRES

4.1 FYom Szilard-ChalmereReaction...... 42

4.2 horn Ikuteron Eambardmentof an Arsenic ~get...... 43

4.3 FromumilRll Fls6ion...... 44

5. CARFCtERPREPARATIONAND S~TION...... 45

27 1.1 Metals aud Alloye, Biolo@cal Materials, Waters (76,77-79)

Procedm used in: Activationaualyeis

Method: Volatility and precipitation

ITucle= banb~t: *74 (n,y)s875 *so(n, y)*U S& (n,y)Seel

Procedureby: Leddicotte,G. .W.’76)

Chemical yield of carrier 75-W%

.&pLmationtime: 1.5 hours

I&gree of purification: Btudlemwith radioactivetracers of Aa, W, Sn, Sb, Ha show that decontamrlnatiogiB better than 108 for each

E@paent required: neutron source and stmdard I_ehoratoqequi~nt

1.1.1 Irradiaticmof Smuple Materials

I“madlatebmoun euwunlm of test (Note 1) and comparator (0.C$25to 0.030 g of Se metal to neeze,et0.1 lug)samples (Note2) in a neutron flux of at leaat 5 x @l n/c#. sec for 16 hours. (Note 3). Use mall quartz tubes, polyethylenebottles,.or alu- minuM foil to contadn the s.mples..

1.1.2 Preparatim of Cmp aratar Smnplea

a. After the irradiation,quantitativelytmazmfer”the cmparator omples (Note 2 ) to a MM-ml volmetric flack, dissolve it in a mall meaeured volume”of 6M BHOg, then dilute the solution to 100 ml with water. Mx well, ueing stie-hendmng practices for radioactivemateriels. b. Pipet a 1.OCHul aliquot of this solutioninto a second 10WDI. volumetricfleak; dilute to volume with water and ndx well. c. Pipet a 1.O&nl aliquot of this solution inta a 125-ml @ems distillationflack. By meane of a volumetricpipet, add to the mme distillationflack 2.~ ml of a standard carrier solution of known Se concentration(Note 4). Also add 1 ml each of holdback carriers of k, Cu, Co, Fe, IVa,and Sr (Notes 5 end 6). Con- tinue with Pti 1.1.4 helm.

28 1.1.3 PrepWatlon of Test Ssmples

.9. If the sample is a metel or tioy, quantitat~vely tramfer the irradiatedtest portion frcnzthe qu.&tz tube or slu- minum wrap to a 125-ml glass distillationflask, and then add, by means of a volumetricpipet, to the same distillationflask 2.00 ml of standard cexrler solution of known Se concentration. AhO add 1 ml each of holdback caxriersof Aa, Cu, Co, Fe, Na and Sr (Notes 5 and 6). To this tixture, add dropwise enough concentratedmine- ral acid to dissolve the sample completely. If neceasaxy,heat the mixture to effect solution. Continuewith Part 1.1.4 below. b. If the sample is an aqueous liquid, pipet an aliquot of the irradiatedportion into a 125-ml glass distillationflask. By means of a volumetricpipet,”add to the seinedistillationflask 2.CO ml of a standard carrier solution of known Se concentration. Also add 1 ml each of holdback carriers of As, Cu, Co, Fe, Na, and Sr (Notes 5 and6). Continuewith Part 1.1.4 below. c. If the sample is biologicalmaterial (plant ash, tissue ash, bdy fltid, etc.) or if it is an organic liquid (a petrochemi- cal or one of its derivatives),pipet a luwwn aliquot, or quantita- tively transfer the total amount of solid, to a 125-ml glass distillation flask. Then add (by means of a volumetric pipet) to the same distillation flask 2.00 ml of a standti carrier solution of known Se concentration. Also add 1 ml each of holdback cerrlers of As, Cu, Co, Fe, Na and Sr (Notes 5 and 6). To this mixture add 3 nil of ~0, 1 ml of @ HC1, ,md 15 ml of BN03-HC104mixture. ~SO, put 2 or 3 glass beads into the flask, then heat the solutlon at a nderate temperature (60”C)until all of the HNOg is removed and HC104 condenseson the neck of the flask (Note 7). Digest the mixture in this manner frcun1 to 2 hours. Remove the flask from the hot plate, cool it aud continuewikh Pert 1.1.4 below.

1,1.4 RadiochemicalSeparationof Selenium

a. Add 10 ml of concentratedHC1 and 10 ml of 48$ HBr to the distillationflask and place a 50-ml glass centrifugetube at the end of the distillatetube. Add 10 ml of water (or WmLli solution)to the centrifugetube. cool the tube by placing it in an ice bath. b. Connect the condenserhead to en air flow end begin bubbling alr through the mixture in the distillationflask. Heat

29 the flask (an open fl=e can be used) to boiling. Continue distillation process for at least 5 minutes (Note 8). c. Remove the centrifugetibe containingthe distillate fractidn from the ice bath, then neutralizethe solutionby adding concentrated~OH dropwiae (Note 9). d. Acidify the solutionwith 2 ml of cone. HCL. Add 4 ml of @ H@33 solution, Stir the mixture until the aelenioua acid is reduced to elemental Se. Centrifuge the mixture; tiscti the super- natant liquid. e. wash the precipitate once with 15 ml of hot water. Centrifuge; discard the wash liquid. Add a 10-ml volume of hot water to the tube and stir. f. Rllter off the Se metal thr&gh a weighed filter paper (MunktellsNo. 00 or Whatman No. k?) held in a Hirsch funnel;wash the precipitate twice with 10-ml portions each of &O, 95$ ethyl alcohol, and ether. ~. Dry the precipitatefor 30 tinutea in a dqlng oven at llO”C (Note 10). Weigh the Se metal precipitate (Note 11) and filter paper on am analyticalbalance. Then mount the precipitate for the refkloactititymeaaurements.

1.1.5 Measurementof the Radioactivityfrcm Se75 (and/orSe= or Se-) and Calculationof Inactive Selenium Content of the original SSrQle

a. The analyses involvingthe meaeurement of Sem must be completedby beta counting. S-e= m a ha,lf-ufe of 10.2 tiutea end decays to stible Bra only by the emission of 1.3&Mev beta radiations. These mesaurementa can be made with a Geige~Mueller counter. The analyses involvingthe measurementof Se75 and Se-must be cczzpletedbygamma couuting. Se75 has a half-life of 121 days and dec~ by means of electron capture and @ma radiations of various ener~es (chiefly, o.u1, 0.136, 0.27, 0.28, 0.405 b, plus others). Se- has a half-life of 57 minutes and decays to Sea (18.2m) by isomeric transitionwith the emissim of O.10>Mev gamma radiations. These measurementscan be made by means of a ~ scintmatim comter or a gwma scintillationspectrometer. In the use of the latter, the @or gamma radiationsare measured. b. FolJowing the -oactive messurements, the observed radioactivityis correctedfor loss of carrier during the experi- ment, half-life of the selenium isotope measured, and the weights

30 of the tei3tand cmqxrator semples. A comparisonof these corrected radioactivitiesbecmnes a measure of the stable selenium content of the test ssmple:

Percent stable Se in test = Corrected Se radioactivity: in test smuple sample Oorrected Se radioactivity: in cmnparator ssmple

NOTES:

1. At least O.lGg portions of solid samples (metals,aUoys, tissue, etc.) should be used. Liquid ssnples (water,body fluids, etc.) should be 1 to 20 ml.

2, Compsxatorsample may be either Se metal or a solution of a Se cmpound. If a solution is used, an aliquot of the irmdi- ated solution containingat least 20 micrograms of Se can be pipetted tirectly into the distillationflask.

3. The sensitivityof the method is such that 2 x l~s gm of Se can be determined. The sensitivitycan be improvedby use of higher neutron fluxes.

4. As seleniou2acid (E&3eO~),Se+4 concentration 10 mg/ml.

5. Holdback carriers should be tie up to contain of desired elemental species.

6. Solutions of ions of other elementsmay also be added e.aholdback carrLers.

7. If the biologicalmaterials is a fatty substance,a Wet digestionwith HN09-&S04 mdtiure should be used to effect a solution.

8. Telltium, As, Sb or Ge can follow,wholly or in part, through this distillationprocedure. In most of the materiels analyaedby this method, the radioactivecontaminantswere in minor concentrations,or completelyelhdmated, in the reduction of Se to elementalform.

9. The Br2 color of the solution disappearsduring neutrali- zation.

10. If the Se= or Sem radioactivityis to be measured, this p=t of the procedure cam be completedafter the radioactivity measurements.

31 Il. By ccmpexingthe final weight of the Se-metalprecipi- tate obtainedhere with the theoreticalyield expected for the amount of Se carrier added, it is poaaible to determinethe chemicalyield of the expertient. The chemicalyield correc- tion is then used to determinethe emoumt of Se75 (end/orSee’ or Semm) recovered during the separationprocess.

(75) 1.2 Ore Concentrate, SISRS, Waste Gases

Procedure used in: ActivationanalyBis

Method: Volatility and precipitation

Type of bombardment: Se74(n,7)Se75

Procedureby: Fineman, et al.(75)

Chemicalyield of curler: 50-00$

separationthe: Several houm

Degree of purification: Excellent frmn other volatile impurities

Equipment required: Neutron source and standard laboratory equipment

1.2.1 Procedure:

a. Irradiate samples (0.1 to 1 g) in a nuclear reactor for 14 days at a flux of 4 x ldl n/cm2,sec.

b. Mix a weighed amount of Se (10-100 mg) thoroughly with irradiatedsample and fuse the mixture in a nickel or iron cruciblewith 25 grsonsof Na20z at 9OO-1OOO”C.

c. DLssolve cake In 50 ml of water. Cool solution and neutralizewith “(1:1)H&Q. Add at least 50 ml more of concentrated &S04 to the solution and evaporateto 100 uL. To separate Si02, boil the solution for 15 minutes, then cool to 60 to 70°C. Add 15 ml or 5$ gelatin solution and bubble air through the solution for 30 minutes. Add hot water (50 ml) to the solution and filter the Si02. Evaporate the filtrate to 100 ml, cool, end then transfer to a distillationflask.

d. Add 100 ml of 4~ HBr, contahing 7 ml Br2, to the flask, and distill the mixture into 10 ml of water; collect 40-

50ml distillate.

32 e. Neutr.sJlzedistillatewith N&OH, add 10 ml HC1 and 1-2 g hydrazine sulfate. After a 12-hour digestion,filter, wash with water and ethanol, and dry at 105’C; weigh and mount for the radioactivitymeawuement.

f. Measure the Se75 gmzaa radioactivityby use of a 3“ x 3“ NaI(Tl scintillationcrystal.

g. Irradiate and process compmator s~les in a similar manner to obtain the Se concentrationof the materials being ana- lyzed.

1.3 Stonv Meteorites(m)

Procedure used in: Activationanalysis

Method: Fusion, precipitationand ion exchange

me of nuclear bombardment: Se74(n,7)Se75

Procedure by: Schindewolf’80)

Chemical yield of c=rier: Quantitative

Sep=ation time: Several hours

Degree of purification: Decontaminationof >104 for Ag, Ce, Co, Cs, Hg, Ir, Ru Sb, Sc, Ta, Zn, and Zr.

Equipment required: Neutron source and standard laboratoryequipment

1.3.1 Procedure:

a. Irradiatepowde~d meteorite samples weighing 0.050 to 0.20 grams.

b. Add 0.020 g each of Se and Te to the irradiatedsample and fuse the mixture in a nickel cruciblewith 1-2 grams of NQ02.

c. After cooling, dissolve the cake in 6~ HC1 and boil the mixture. Reduce Se and Te to elemental form with S02 gas.

a. Dissolve precipitatein aqua regla and make the solution basic with N&OH. Scavenge impuritieswith Fe(OH)3.

e. Acidify the solutionwith HC1 and then adsorb Se and Te on a Dcwex-1 (100-200mesh) anion-exchangeresin column. Sele- nium can be sepuated from Te by eluting it from the column with 3 to ~-columnvolumes of 31 HC1.

33 f. heat the acid solutionwith S02 gas to reduce Se to the elemental fem. Collect precipitateby filtration,weigh, and mount for the radioactivitymeasurement.

g. Measure the Se75 gsnma rsdioactititywith a 3“ x 3“ NaI(TL) scintillationcrystal.

h. Irradiate and proces8 comparatorsamples in a similar manner to obtain the Se concentrationof the meteorite.

(60) 1.4 Fertilizer, Tomato Tissues, Human Blood

Procedure used in: Activationanalysia

Method: Volatility and precipitation

Type of nuclem bomb~nt: Sem(n,y)Se= (60) Procedure by: Bowen and Cawse

Chemical yield of carrier: 7@

Separationtime: 40 minutes

Ikgree of purification: Decontaminationfrom sxsenic, bromine, manganese, sodium and zinc was found to be satisfactory

Equipment required: Neutron source and standard laboratoryequipnent

1.4.1 Procedure:

a. Irradiate samples in a nuclear reactor for 18 minutes at a flux of l&2 n/cm2.sec.

b. After irradiationtransfer the sample to a beaker containing 10 ml of asblng mixture (1:1 16~ HNOg-7@ HC104) and-25 mg each of As, P, Mn, and Te carrier solutions.

c. Heat solution until organic is destroyed and fumes of perchloric acid evolve.

d. Transfer acid solution to distillationflask with 5 ml each of HC1 and HBr. Distill for 4 ndnutes using N2 as a cwrier gas,

e. Collect distillatein 50-ml centrifugetube conteini~ 5 ml of HC1, 10 ml water, O.lml of Teepol solution (wettingagent, Shell Chemical Company) and 2 drops of Mn carrier.

34 f. Pass sulfur dioxide through solution for 1 minute end centrifugethe seleniumprecipitate.

8. Dissolve the precipitatein about 0.25 ml of bTT@. Add ten ml of hot water, 0.1 ml of ~02 and 5 ml of HC1, and precipitate the Se again with S02.

h. After separationby centrlfugation,wash the precipitate with water and acetone, and transfer to a weighed eihnnlnum counting tray with acetone.

1. After the sample is C&y, count the beta-actititywith an end-windowGeiger counter. Check radiochemicalpurity by comparing decay curve~ of samples and standards over several half- lives.

il- After counting,weigh the selenium to obtain the chemical yield of the carrier.

k. Irradiate comparatorssn@es and process in a simila manner to obtain the Se concentrationof the materials being ana- lyse~.

Procedure used in: Activation analysis

Method: Solvent extraction

Type of nuclear bombardment: Se7e(n,7)Se7em

Procedure by: Kuroda, R. reportedby Mei*e(36)

Chemical yield of carrier: . 6%

Separationtime: 10 minutes

Ikgree of purification: Good except for iodine radioactivity

Equ@ment required: Neutron source and standard laboratoryequipment

1.5.1 Procedure:

a. Irradiatel-g sample in nuclear reactor for 10 minutes at a neutron flux of 2 x ld2 n/cm2.sec.

b. Fuse the sample with 6 g of N*02 containing 30 mg of Se curier labeled with a lumwn amount of Se75 (121 d).

35 c. Cool the crucible in an ice bath; put the crucibleinto a beaker; and add successively10 ml of &O, 10 ml of formic acid, 35 ml of HC1 end 75 ml of KBr.

d. Filter off the precipitatedsodium salts.

e. Add a few grams of hydroxylemlnehydrocblorldeand 1~ ti of 2,6-dimet~l-4-heptEmoneto the filtrate and stir vigor- ously with a mechanical stirrer.

f. W-h the organic phase with 50ml of water (Note 1).

g. Wash the organic phase again with 20 ml of 5% tartaric acid and then with 40 ml of 5$ ELXCAsolution containingsmall Smounta of ~ NeOH. Diacmiwashinga.

h. ~lute the organic phase to 15 ml with the extractant and measure the Se7- gamma activity.

i. Chemical yield is determinedby compting the peak area of Se75 n- the orgdc phaae from ample with that of se75 in a known amount of carier.

NOTE :

1. If the two layera do not aeperate quickly,add small amounta of formic acid.

1.6 PL5Lthum Metal(84)

Procedure used in: Activation ~yais

Methcii: Ion exchange aad precipitation

Type of nuclear bombardment: Se74(n,~)Se7s (84) Procedure by: Morris and Killick

Chemicalyield of carrier: . 8@

Separationtime: Several hours

Degree of purification: Separationfactor of selenium from tellurium of greater than 104.

Equipment needed: Staatid

1.6.1 Procedure:

a. Irradiate aemple (041 g) in nuclear reactor for E? @a at a flux of l&2 n/cnF.sec.

36 b. Trarmfer sample to a flask attached to a water-cooled reflux condenserthat contains 10 mg of Te and 15 mg of Se carriers. Wash samples into flaak with ~ HNOS and add 5 ml of ~ HC1 and dissolve the platinm by wamhg at 600C on a water bath.

c. Remove HN03 by addjng ~ HC1 and heating. Cool, aud transfer to a centrifuge tube. Dilute to 35 JIJ with water. Place in an ice bath and add 1 g N&Cl to precipitate (~)2 PtCle. Allow to stand 10 minutes and centrifuge.

d. Separate supernate into cleea centrifugetube. Pass S02 rapidly through solction for 2 to 3 minutes. Centrifugeand va9h with water.

e. Dissolve Se and Te in ndnbnnn amount of ~ llNOg. Add

2 mg of Pd carrier and dilute to 20 ml with &.O. Heat to boiling. Neutralizewith ~ NaOH .md add 1 ml more of the reagent. Add 1 to 2 mg Fe+s carrier dropwisewith stirring. Centrifugeand discard the precipitationof Fe(OH)S.

f. Add 1 ml of 6~ EIN03 to supernate and then add, with stirring,1 ml of 1$ solution of dimethylglyoximein 95$ C2HSOH. Allow to stand 10 minutes and filter through a Whatman No. 41 paper. Evaporate the filtrate to dryness, adding a few drops of lC$ KI during the evaporation;then dissolvewith 5 ml of 12M— HClc

g. Pass the solution through a deaciditeFF (100-203 mesh, preequilibratedwith la HC1) anion-exchangecolumn (equiva- lent to Resin Dowex 1-x8), 5 cm in len@h and 1 cm in diameter.

Elute with 20 ml of 31jHC1 into a 50-ml glass centrifugetube.

h. Add 20 ml of l% HC1 to the eluate in a centrifuge tube. Paas S02 through the solution to precipitatethe Se and centrifuge, Wash with water and dissolve in minimum quantity of @ HIT03. Evaporate to dryness. Add 1 ml of 6M— NaOH, then 20 ml of @ HC1, and boil for 15 minutes. After the addition of 10 ml of 2C$ solution of hydroxylsminehydrochloride,centrifuge, then discard supemate. Wash the Se with water and then with C2HSOH. Transfer the precipitatewith a little C2H50H to a weighed aluminum counting tray, and dry at 100”C. Weigh as Se and determinethe chemicalyield.

37 2.1 Arsenic

Procedure used h: Preparationof radioactive tracers

Method: Volatill.tyand precipitation

Type of nuclear bombardment: 194-Mev deuterom

Procedureby: H. Hopkins, Jr., reportedby Mei*e(8’)

Separationtime: 45 minutes

Chemicalyield of carrier: > 90%

Decontamination: RadiocheH&caUy pure by a factor of - 100

Equipment needed: Standard

2.1.1 Procedure:

a. DissolveAa metal in mintium 10~ HN03.

b. Add5mg Se carrier, evaporate to near dryness to remove excess HN03.

c. Make up to 3 ml with ~ HC1, add N& OH,HCl until Se darts to precipitatefrm hot Bolution.

a. Add 1 ml ~ ICI,heat 5 minutes, centrifugeoff mixture of Se and 12.

em Dissolvewith a udnlnmm amount of fuming HTJOS,repeat precipitation.

2.2 Bismuth Metal(81)

Procedu uged in: Preparationof radioactive traceri3

Method: Volatility aud precipitation

Type of nuclear bombardment: 184” cyclotron (388-MeveLphas; 3~Mev protone; 194-Mev deuterons)

Procedure by: Goeckermen,reportedby Mei*e(8’)

Sepexationtime: 1 hour

Chemicalyield of terrier: - 9&

Decontamination: _ 104 from fission and spallation products

Equipment needed: Stsnhrd

38 2.2.1 Procedure:

a. To aliquot of BN03 solution of target, add 10 mg Se

and Te, 10 ml concentratedHBr, sad 0.5 ml liquid Brz in a glass still. Uging en air stream, distill into a centrifugetube containing 5 ml saturatedBr2 water, which is cooled in en ice bath, disti~ until only a >ml residue remains.

b. Keep at ice temperatureand reduce to Se (red)with S02 or N&OH.HCl. Add aerosol and centrifuge.

c. Dissolve Se in a few drops of concentratedHN09, add 10 ml concentratedHC1 and reduce with S02 in am ice bath. Centri- fuge with aerosol.

d. Repeat SeBr4 distillationand Se precipitationsas often as necessuy for desired purity.

e. PrecipitateSe, filter, wash three times with 5 ml ~0, three times with 5 ml ethyl alcohol, three times with 5ml ether, dry 10 minutes at llOUC. Weigh as Se.

(36) 2.3 Uranyl Nitrate

Procedure uBed in: Preparationof radioactive tracers

Method: Solvent extraction

Type of nuclear bombardment: Neutron - 5min. at power level of 1000 Kw. (36) Procedure by: Kuroda, reportedby Meinke

Separationtime: 19 min.

Chemicalyield of carrier: 70%

Decontamination: Radiochemicallypure by gamma spectroscopy

Equipment needed: Neutron source and stand- laboratoryequipment

2.3.1 Procedure:

a. Di8BOlVe 30-50 mg irradiateduanYl nitrate in 20 ti of concentratedHBr containingw 1 mg of Te and 30 mg of Se carriers.

Pass air stream through the solution for 5 minutes to expel fission gases.

39 b. Extract Se with ~ ml of 2,6-dlmethyl-&heptanonefor @ sec. and discard aqueousphase,

c. Shake the organic phase for 30 secondswith 10 ti 10$ tartaric scid; repeatwith 10 ml of ~ NsOH. Dlscti aqueous phases.

d. Wash the organicphase by shaking for 30 secondswith 30 ml of a solution 5$ in EDTA and 5$ in sodium tartrate. Then shake with 20 ml of water.

e. Strip Se from the organic phase by shaking for 20 seconds each with three 10-ml portions of C12-saturatedvater.

f. To the aqueous phase add a few mg of iodide carder and 6 ml of 12 NsOH md shake.

g. Add 20 drOpS Of COnC. HN03 to acidify the solution.

h. Add dropwise a 2* solution of hydroxylamhe hydro- chlorideuntil brown color of iodine appears.

i. Extract iodine with successive5-ml portions of C- bon tetrachlorideuntil the color of the organic phase disappe=s.

J. The organicphase Is discardedeach time and the radle chemicalPurim of the aqueous phase is tested by gemma spectroscopy.

(82) 3.1 Fission-Roduct Solutions

Procedm used in: Determinationof fission- product activitiesin plant process solutions.

Method: Volatility and precipitation

Type of nuclear bombardment: Uranium fission (83) Procedure by: Glendenin snd Winsberg Chemical yield of c~er: M Sepmation the: 1 hour

Degree of purification: Excellent

Equipment reqtired: Standexd laboratoryequipment

3.1.1 Procedure:

a. Place not more than 5 ml of seanple(Note1) in a glass

still and add 2 ml of Se csxrier =d 10 ml of cone. HBr. Distill

40 the Se into ~ HL of water contained in a 50-ml centrifugetube placed in an ice bath. Continue the distillationuntil no more than 2 to 3 ml of Bolutlonremains in the distillationflask (Note 2).

b. Paas S02 rapidly (Note 3) through the distillate (in an ice bath) until the red precipitateof Se is coagulated (2-3 minutes), centrifuge,and wash with 10 ml ofwater (Note 4).

c. Dissolve the Se by heating with 5 to 10 drops of cone. SNO~; evaporatenearly to dryness; and take up In 10 UL of cone. HC1. Place in an ice bath and precipitate the Se with S02 as in step b,

d. Repeat step c.

e. Transfer the Se with 5 to 10,ml of water onto a weighed paper (Note 5) in a small Hirsch Ihumel and filter with suction. Wash three times with 5 ml of ethanol, and three times with 5 ml of ether. Dry at 11O”C for ten minutes, weigh as elemen- t~ se; and munt.

NOTES:

1. If the sample contains a large amount of nitrate, add the Se carrier and boil down to about 1 niibefore distilling with HBr.

2. The distillationof Se is practically complete at this point. The solution should not be taken to drynees.

3. A rapid stream of S02 hastens precipitationand aids in coagulation.

4. A few drops of aerosol solutionprevents scum fomna- tion and aids in centrifugation.

5. The filter paper is washed with ethanol end ether, and dried under the conditionsof the procedurebefore weighing.

(85) 3.2 IrradiatedPolyphenyls

Proceduremed in: Iktemination of fission product activitiesin irradiated polyphenylB

Method: Volatility and precipitation

41 Type of nuclear bombardment: Uranium fission (85) Frocedum by: Felber and Koch

Chemlcel yield of carrier: Wgojt

Ilsgreeof purification: Good

Equipment required: Stand-d laboratoryequipment

3.2.1 Procedure:

a. Aliquots of samples (not exceeding15 grams) and carriers are dissolved in cone. PN03, and perchloricacid is added to deccunposethe organicmaterial. S-ampleis taken to fumes of HC104.

b, Sulfur is sep=ated from the solutionby precipitation of B8S04.

c. Selenium is separatedby reductionwith S02. The Se precipitateis dissolved in cone. HBr containingsulfuric and nitric acids. SeBr4 is distilled in the presence of air into water. Seleniummetal is precipitatedby reductionwith S02.

d. Selenium Is distilleda second time and the metal Is repeatedlyprecipitated,and then weighed as the metal smd the Se75 is counted.

4.1 Szilard-ChalmersReaction

Procedure used in: Carrier-freeseparationof Selenium radioactivity

Radioelement(s)separated: Se=(25m), Se-(5~), Se=(17m), and Se75(121d) (&) Procedure by: Gest and Edwexda

4.1.1 Procedure:

a. One gram of ammonium Eelenite (Note 1) irradiated for 30 minutes.

b. After irradiationdissolve selenite in 31 HC1 and extract with CS2 (Notes2 end 3).

c. Evaporate CS2 fraction to dryness and the take up Se in cone. HNO~.

42 N~S:

1. Anmonl.umseleniteprepmed by neutralizingSe02 solutions with Ii&OH and crystallizingwith acetone.

2. 2C$ of the seleniumactivity faund in CS2 fraction.

3. In a second method, a 62 HC1 solution of the irradiated selenltewas filtered through a fine sinte~d-glaas filter. Much of the radioactivitywas deposited on the filter. 28$ of the original aelenlum radioactivityremoved by passing boiling cone. EUT09through the filter. h.2 Ikuteron lkmbardmentof an Arsenic Tex@

Procedure UBed in: Preparationof carrier-free selenium

Method: Bombardmentof arsenic tiget

Type of bombardment: lg-Mev deuteron bombardment with 60” cyclotron

Time of sepantion: 3-4 hours

Chemical yield: 80-95$ (8) Procedure by: Gartison,Maxwell and Hamilton

Ikgree of purification: At leaat factor of 103

Equipment required: Standard laboratoryequipment

4.2.1 Proceduxe:

a. Dissolve arsenic-powdertarget in aqua regla.

b. Add ~ HC1 to destroy excess HNOS and adjust acidity to yJ.

C. AddlOmg of tellurousacid and precipitateTe with S02; approtitely 95% of Se carries.

d. Diesolve the Te precipitatein cone. BIT03and repre- cipitate from 31 HC1 in presence of As holdback caxrier.

e. Repeat Step d two more times.

f. Wash the Te precipitate,dissolve in minimum volume of 16x HN03, and transfer to distillingflask.

g. Add 141 EBr dropwise whil-ea stream of N2 carrier gas is bubbled through the solution at 200eC. Collect the distill.ate in a water trap cooled w~th ice.

43 h. Remove the HBr with HN03 and evaporate to dryness on 40 mg of NaCl in the presence of excess EC1. Th&actltity, presu- mably as aelenate,is quantitativelysoluble in 5 ml of water.

4.3 Uraulum FYssion

Procedure used in: Prep=ation of carrier-free selenium radioactitities

Type of bombardment! Neutron source

Reikloelement(s)sep=ated: Se7m(17.5 s), Se7m(3.9 m), Se=m(57.5 s), See1(18.2m). (36) Procedure by: Kuroda, reportedbyhleitie

Eegree of purification: Radiochemicallypure by gaunna spectroscopy

Equipment required: Standard

4.3.1 Procedure:

a. Put irradiateduranyl nitrate (40-50mg) into a centrifuge tube. Add 2 or 3 drops of concentratednitric acid md 4ml of water. Pass air streem through solution for 5 minutes.

b. Add- 1 mg of Te c~er and 20 ml of cone. HBr.

c. Extract seleniumwith 5 ml of 2,6-dimethyl-4-heptanone for 40 seconds and discard aqueous phase.

d. Shake the organic phsae for 30 secondswith 10ml l@ tartsric acid; repeat with 10 ml of lliNaOH. Discard aqueous phases.

e. Wash the orgaaicphase by shaking for 30 secondswith 30 ml of a solution 5$ in EETA and 5$ in sodium tartrate,then shake with 20 ml of water.

f. Strip selenium from the organic phase by shaking for 20 seconds each with three 10 ml portions of C12 - saturatedwater.

g, To the aquecrusphase add a few mg of iodide carrier and 6 ml of lIJNaOH and shake.

h. Add 20 drops of cone. HN03 to acidify the solution.

i. Add dropwise a 2C$ solution of hydroxyleminehydro- chlorideuntil brown color of iodine appears. J. Extract iodine with successive5-ml portions of c- bon tetrachlorideuntil the color of the organic phase d.isappeus.

k. The organic phase is discardedeach time, end the mdiochemical purity of the aqueous phase is tested by gamma spectroscopy.

5. CARRIXR PIUZPARATIONAND STANDARDIZATION

1. Prepamti on

Dissolve 16.4 grams of seleniousacid in water and dilute to one Ilter (1 ml ==lCkug Se).

2. Standardization

Pipet 5 ml of carrier solution Into a beaker. Add 100 ml of 5! HC1. Add 10 ml of a 25$ hydroxyleminehydrochloridesolution. Heat for 1-2 hours at 90°C. Filter through a pretreated slntezwd glass crucible, wash with water, and then with alcohol. Dry in an oven et 105-110°C for 20 ndnutes. Cool and weigh as selenlummetal.

wt. of Se metal Mg S+l = 5ml

NOTES:

1. If the red selenium is overheatedit may convert to the crystallinegrey-blackvariety. This may result in high results due to the occlusion of water and oxidation.

2. To prevent oxidation the precipitate can be dried in an atxnosphereof carbon dioxide.

45 REF!EMNCES

1. Strominger,D., Hollander,J. M *J and Seaborg, G, T., “Table of Isotopes,”“Rev: Mod. Physj ~ (2) p. 585-904 (1958).

2. Nuclear Data Sheets, Nat’1 Aced. Sci.-Nat’lResemch Council, Washington,D.C.

3. Chext of Nuclides, General Electric Company, Schenectady,New York, December,71962 ).

4. Hopkins, B. S., ~ti%ch~”trx.— of the Less Familiar Elements, Chapter 19, Stipes, Champaign,Illinoi~l~

5. Latimer, W. M., The CMdation Potentials,2nd Ed., p. 81-9, Prentice HaU, N~Y_2].

6. Berzelius,J. J., Acad. Han&l. Stockholm,~, 13 (1818).

7. Eodgman, C. D., Weaet, R. C., Shankland,R. S., and Selby, S. M., Handbooks Chemist~ and Physics, 44th Ed., 1962-1963,chellliCSl Rubber Publishing Comp~, Cleveland, (1962).

8. GarrisonjW. M., MmWell, R. D., and Hamilton, J. G., USAEC Report AECU-579 (UCRL-450)(1949).

9. Schoeller,W. R., and Powell, A. R., The Anal. is of Minerals and Ores of the Rarer Elements, Chapter ~~ ~&er,p. N. Y=, m5T — —

10. All-UnionMining MetallurgicalScientificReseexch InOtitute of Non-FerrousMetals, ZavodskayaLab., —25, No. 6, 666, (1959). 11. Goto, E. and Kakita, Y., Sci. Repts. Reaemch Insts. Toholm Univ. —7A, 365, (1955), I-2. Chernikov,Y. A., and Dobkina, B. M., ZavodskayaLab., ~, 1143, (1949).

13. Eode, H., Z. Aual. Chem. —143, 182 (1954). 14. Bode, H. and Arnawold,W c, Z. Anal. Chem. 185, 179-201 (1962),

15. Cheng, K. L., kml. Chem. 28, 1738 (1956).

46 16. Hillebrand,W. F., Lundell, G. E. F., Bright, H. A. end Hoffman, J. L., ##~~kI~~IC AntiYaia, chapter 19, p. 327, John Wiley and Sons, Inc., .

17. Lott, P. F., Cukor, P., Moriber, G. and Solga, J., Anal. C&m. ~, 1159 (1963 ). 18. Snell, F. D., Snell, C. I. and Snell, C. A., CalorimetricMethods of Analysis,Vol. 11A, pp. 680, D. Van Nostrand Company,New-9~).

19. Taboury,M. F. and Gray, E., Compt. Rend. ~, 481 (1941).

20. Noyes, A. A. and Bray, T?.C., A System of QualitativeA&lyEIis——for the ——Rarer Elements, p. 272-330, Macmillan,~- York (1937).

21. Seath, J. and Beamlsh, F. E., Ind. Eng. Chem., Anal. Ed. ~, 373 (1937).

22. Noakes, F, D. L., k~yst —76, 542 (1951).

23. Beamish, F, E., Russell, J, J. and Seath, J., Ind. Eng. Chem., Anal. Ed. Q, 174 (193’7).

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Copiesof thefollowingmonographsare availablefrom the ClearinghouseforFedeml Scientificand Teohnioalfnforma- tlon,NationalBureauofStandards,U. S.DepartmentofCom- merce, Springfield,Va.

Alumtium and Gallium,NAS-NS-3032, $0.50 Rubidium, NAS-NS-3053, $0.50 Americium and Curium, NAS-NS-3006, Ruthenium, NAS-NS-3029, $1.00 $0.75 Selenium, NAS-NS-3030, (Rsv.)1965 $1.00 Antimony, NAS-NS-3033, $0.50 Sfliccm, NAS-NS-3049, $0.50 Arserdc,NAS-NS-3002 (Rsv.)1965$1.00 Sflver, NAS-NS-3047, $0.75 Astatine,NAS-NS-3012, $0.50 &xUum, NAS-NS-3055, $0.50 Barlurn,Calcium,and strontium,NAS-NS- Sulfur, NAS-NS-3054, $0.50 3010,$1.25 Technetium, NAS-NS-3021, $0.60 Be@ium, NAS-NS-3013, $0.75 Tellurium, NAS-NS-3038, $0,50 Cadrolum, NAS-NS-3001, $0.75 Thorhun, NAs-Ns-3004, $0.75 Carbon, Nitrogen, and @gen, NAS-NS- Tin,NAS-NS-3023, $0.75 3019, $0.50 TiWunl, NAS-NS-3034, $0.50 Cesium, NAS-NS-3035, $0.75 Tranecurium Elements, NAS-NS-3031P Chromium, NAs-Ns-3007, (Rsv.)1964 $0.7s $0.50 cobalt, NAS-NS-3041, $1.00 Tungsten, NAS-NS-3042, $0.50 Copper, NAS-NS-3027, $0.75 Umrdlml, NAS-NS-3050, $3.50 Fluorine, Cblor5ne, Bromine, and Iodine, Vanadium, NAS-NS-3022, $0.75 NAS-NS-3005. $0.50 Zblc, NAS-NS-3015, $0.75 Franoium, NAS-NS-3003, $0,50 Ziroordum and Hafniurn, NAS-NS- 3011, Germanium, NAS-NS-3043, $0,50 $0.50 Gold, NAS-NS-3036, $0,50 Ind.ium, NAS-NS-3014, $0,50 Iridium, NAS-NS-3045, $0.50 Iron, NAS-NS-3017, $0,50 Applications of Computers to Nuclear and Lead, NAS-NS-3040, $1.75 Radiochemiatry, NAS-NS-3107, $2.50 Magnesium,,NAS-NS-3024, $0,50 Application of Instillation Techniques to _ese, ”NAS-NS-301B, $0.50 Badiochemical Separations, NAS-NS- Mercury, NAS-NS-3026, $0.50 3108, $0.50 Molybdenum, NAS-NS-3009, $0.50 Detection and Measurement of Nuclear Ra- Nickel,NAS-NS-3051, $0,50 diation, NAS-NS-3105, $1,50 Niobium and Tantalum,NAS-NS-3039, $0.75 Liquid-liquid Extinction with Higb- Osmium, NAS-NS-3CM6, $0.50 molecular-weight Amines, NAS-NS- Palladium,NAS-NS-3052, $0.75 3101, $1.00 Phosphome, NAS-NS-3056, $0.50 Low-level Radiochemical Sepamtions, NAS- PIMnum, NAS-NS-3044, $0.50 NS-3103, $0,50 Polonium,NAS-NS-3037, $0.75 Paper Chromatographic and Electromigra- Potassium,NAS-NS-3043, $0.50 tion Techniques in FQdiochemistry, NAS- Protactinium,NAS-NS-3016, $1.00 NS-3106, $0.50 Radium, NAS-NS-305’7,$2.25 Rapid Radiochemical Sepamtions, NAS-NS- Rare Earths— Scandium,Yttrium,and Ac- 31W, $1.25 tirdum,NAS-NS-3020, $3.00 Separations by Solvent Extnmtion with Tri- Rare Gases, NAS-NS-3025, $0.75 n-octylphospbine Oxtde, NAS-NS- 3102, Rhenium, NAS-NS-302S, $0,50 $0.75 Rhodium, NAS-NS-300S, (Rev.)1965 $1.00