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I* Carrike 7Rse Separation 07 Cobalt Ii I* CARRIKE 7RSE SEPARATION 07 COBALT II. THE DISINTEGRATION 07 THE RADIOACTIVE ISOTOPES Co54, Co57, and Co5* III. CHEMICAL AHALTSIS BT CICLOTROH ACTIVATION DISSERTATION Freaented In Partial Fulfillment of the Requireaenta for tha Dagroa of Doctor of Philoaophy in the Graduate School of Tha Ohio Stata UnlTeraitjr JAMES L. DICE, B. So., M. Sc. Tha Ohio Stata Uniaereitjr 1953 Approved by* / / A * i,V / - u . i./r V - Adviaera 1 ACKHOULXDGHEIT The writer wishes to express his sincere appreci­ ation to Professors J. D, and M. H. Kurbatov for suggesting this rasoareh and for their continuing advice and encouragement throughout the course of this work; to Mr* Mitsuo Sakai and Lieutenant Willis Anderson for their assistance in Spectroscopic studies; and to my wife, Marie, for her patience and encouragement* 11 TABLE OF CONTENTS I. Carrier Free Separation of Cobalt**. 1 Separation of Carrier Free Cobalt from a Manganese Target........... .....* 1 1* Introduction....... 1 2* Experimental Procedure and Results. *......................... 5 3# Discussion*.................. .*...*•* 20 4* Summary . ............................ 2U Separation of Carrier Free Cobalt from Enriched Isotopes of Iron in Iron Oxide •••*•..•... ................. 26 1* Introduction*........................ 26 2* Preliminary Investigation and Results............................ 28 3* The Chemical Procedure....... *...... 33 4* Summary ............................. 36 II. The Disintegration of the Radio— c 4 gj active Isotopes Co , Co f and Co'’** ....................... 37 Instrumentation* ...................... 37 1* Thick Lens Spectrometer.......... 37 2* Solenoidal Spectrometer *••••••*.•• 53 3* Scintillation Spectrometer •••••..* 55 ill TABLE 07 CONTENTS (coat.) JEa e a B* Spectroscopic Studies....................... 58 1. Introduction*. ................... 58 2. Sample Preparation • •................ 60 3. The Iaotope C o ^ ............ ....... 64 a. The Continuous Positron Spectrum of Co^® 6 4 b. The Photoelectron Spectrum of C o 5 6 ................ .. 70 c* The Internal Conversion Elec­ tron Spectrumof Co56 ........ 77 d« The Gamma Ray Energies and Relative Intensities Measured with 0 Scintillation Spectro- notor.............................. 79 e. Summary of Results and Discussion • •..... 87 4* The Isotope C o ^ ...... .. 93 a* The Continuous Positron Spectrum of C o " •..*••••••••• 93 b. The Internal Conversion Electron Spectrum of Co^" .... 95 o. Summary of Results and Discussion ......................97 5. The Isotope 98 a. The Continuous Positron Spectrum of Co^8 . ........ 98 b* The Internal Conversion Electron Spectrum ofCo56,58 101 o. Summary of Results and Discussion. ...... 101 ir TABLE OF CONTENTS (cont,) Eagft CHAPTER III. Chemical Analysis by Cyclotron Activation................... 106 A. Introduction.......... 106 B. The Beryllium—Copper Alloy.............. 109 1. Experimental Procedure and Results...................... ............ 109 2. Discussion. ... ........................ 113 3. S u m m a r y ............................. 114 C. The Nickel Ore .................... 115 1. Experimental Procedure and Results .................. 115 2. Discussion .................. 123 3. Summary ................................. 12 5 Bibliography ..................................... 126 Autobiography ................... 129 X, CARR HR FREE SEPARATION OF COBALT A . CARRIER FREE SEPARATION OF COBALT FROM A MANGANESE TARGET 1. INTRODUCTION The bombardment of a unganese target by alpha particles yields several cobalt Isotopes according to the following reactions* Mn55 (a, n) G e 58 Mn55 (a,2n) Co57 Mn55 (a,3n) Co56 In order to study the disintegration schemes of the cobalt Isotopes formed it is necessary to separate them from the target material* If the nuclear spectroscopic investi­ gation is to be limited to a study of the gamma emissions carrier may be added to assist in the separation. In this case the absorption effect of the residue on the energy of the gamma emission is insignificant. However, the usual conditions require a thorough investigation of both gamma and beta emissions. The presence of carrier decreases the specific activity, alters the observed energies of the beta emissions and Increases scattering especially in the low energy region of the beta spectrum* To avoid this not only must the final sample be free of reagent Impurities which tend to accumulate during the processing, but the specific activity, the ratio of the radioactive atoms to the total isotoplc atoms present, Must be high. Therefore the study of the behavior of cobalt iaotopca in concentrations of tho order of 10“^ 1C v«i undertaken for the purpose of preparing a carrier free sample of the radioactive isotopes of cobalt from a manganese target* After preliminary investigation of some of the more common analytical methods of separation, it was decided to attempt the preparation of a carrier free sample of the cobalt isotopes using an organic complexlng reagent* By nature of their structure, many complexlng agents exhibit considerable selectivity in their reactions* Alpha-nitroso beta-naphthol, one of the better known reagents in this category, was favorably considered for separating the cobalt isotopes from the manganese target material. It is best known for its separation of cobalt from large quantities of nickel. It is also applicable for quantitative separation of oobalt from mercury, anti­ mony, aluminum, sine, manganese, calcium, barium, strontium, chromium, lead, cadmium, beryllium, and arsenic (l)* Sil­ ver, tin and bismuth interfere with this reaction. Alpha- nitroso beta-naphthol exists in two Isomeric forms which react with oobalt salts to form inner complex oompounde of the following composltieht Thi purple-red oobaltie salt ii Insoluble In aeldi, but Is successfully precipitated only from s weakly sold, aautralf or ammonlacal solution, sines tbs eobsltie sslt is derived from tbs tautomeric quinoxlme form of tbs ra- agent* Both forms exist together In equilibrium, but in strongly sold solution tbs equilibrium shifts to tbs phsnol form; tbs quinoxlme form prsdomlnates In s weakly acid solution (2). Illnskl and Knorrs (3) first observed that alpha-nitroso beta—napbthol rsaetad with solutions of eobalt salts to form a brisk rad precipitate* Tbs com­ position of tbs prseipitata formed in tbs reaction between oobalt salta and alpba-nltroso beta—napbthol corresponds to tbs formula (C^qH^0 2 M)^Go*2 H2 0 in which cobalt exists in tbs trlvalont state* The exact composition remains somewhat in doubt. The reagent commonly employed for precipitating oobalt is prepared by dissolving alpba- nltroso beta—napbthol in ethyl alcohol, acetone or $0% acetic acid* Hydrochloric acid is the usual medium In which the precipitation of cobalt la carried out, but may be replaced by nitric a d d so long as it contains no oxides of nitrogen* Tamlc and ooworkers (4.) have studied the effect of pH upon the precipitation of cobalt, iron, vanadium, palladium, and uranium* Their report is as follows s UmImI pB fll Sfllailgfl Co less than 8.74 Cu 3*96 to 13*2 To .95 to 2*00 ▼ 2*05 to 3*21 Pd loss than 11*82 U 4.05 to 9.38 Thoao studies vtrt nodo uolng macro quantities of the elements in question* For application in the field of nuclear spectroscopy it was necessary to extend this investigation to quantities on the order of 10“^ M* The effect of a number of variables on the percent of oobalt operated from manganese have been studied and a satisfactory method of separation of oarrler free cobalt from a manganese target has been developed. 2. EXPERIMENTAL PR OCX DUES AND RESULTS a. SAMPLE PREPARATION A sample of manganese (99*9 pareant purity) ob— taluad from Battalia Maaorial Inatltuta vaa machined to fit tha targat mount of tha cyclotron at Ohio Stata Uni­ versity, This sample, valghlng 2,34 grama, vaa bombardad six hour# with alpha partlelaa of anarglaa from alghtaan to twenty Mar. Tha aampla vaa earafully removed and atorad for approxlmataly thraa waaka during vhleh tlma any abort lived lmpuritlaa disintegrated, Tha raaotlona expected by bombarding tha manganasa targat with alpha partlelaa of tha energy ranga alghtaan to twenty Mar arai (a, n) Ce58 Mn55 (g,2m) Co57 following tha waiting period in which tha ahort lived activities disintegrated, tha aampla vaa dissolved in 25 ml, of 6N hydroohloric acid and evaporated to dryness, Tha residua vaa than redissolved In 250 ml, of 3N hydrochloric acid and atorad In a 250 ml, volumetrle flask. This solu­ tion became tha parent material rrom which all experimental aaaplaa vara taken. For purposes of establishing a con­ venient oounting rata and later to aid in determining tha loss on glassware during the procedure, five 2 ml, portions of tha parent solution ware placed in individual counting dishes and slowly evaporated to dryness using a hast lamp. These five aaaplaa yielded an average counting rata of 1440116 counts per minute. b. GENERAL TESTING PROCEDURE KOB ESTABLISH­ ING CONDITIONS OP CARRIER PEEK SEPARATION OP COBALT A 2 ml. sample of the solution containing tba activated targat vaa plpatted into a 50 ml. beaker and dllutad to 12 nl. with triple diatilled vater and dilute hydrochloric acid of auch atrength to give the deaired acidity to the aolution. The pH deterilnatlom vere made with a Leeda and Morthrup pH Meter. The aolution vaa then heated to approximately eighty degreee centigrade and 4 ml. of alpha—nltroao beta-naphthol aolution vere gradually added vhlle stirring. The aolution of alpha—nltroao beta-naphthol oontalned .5 grama of alpha-nltroao
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