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Studies in the rare earths. The fractional crystallization of the rare earth double magnesium nitrates.… Taylor, Arthur E. 1946

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L€% thy STUDIES IN THE RARE EARTHS THE FRACTIONAL CRYSTALLIZATION OF THE RARE EARTH DOUBLE MAGNESIUM NITRATES THE PREPARATION AND FRACTIONAL CRYSTALLIZATION OF THE RARE EARTH BROMATES by Arthur E. Taylor B. A. A Thesis Submitted In P a r t i a l Fulfilment of The Requirements f o r the Degree of Master of Arts i n The Department of Chemistry The University of B r i t i s h Columbia October 1946 ACKNQICLEDGEMENT May I express my sincere thanks to Dr. J. A l l e n Harris f o r the active i n -terest which he has shown i n t h i s study. Ab-s t r a c t STUDIES IN THE RARE EARTHS Analysis of the Basic Residues from a series of rare earth double magnesium n i t r a t e s indicated the p o s s i b i l i t y of the presence of I I i n the material. A new method of preparation of rare earth bromates proposed by Moeller & Kremers (18) was proved s a t i s f a c t o r y . A. E. Taylor f TABLE OF CONTENTS Page I. Introduction 1 I I . Summary of Data Concerning the Rare Earths 5 1. Properties of the Rare Earths 5 2, Valence j> 3# Rare Earth Double Nitrates j? 4. The Absorption Spectra of the Rare Earths j> 5. The Method of Fract i o n a l C r y s t a l l i z a t i o n 7 6. Preparation of Rare Earth Solutions f o r Spectrophotography 7 I I I . Apparatus 9 IV. Studies i n the Rare Earths 12 1. Rare Earth Double Magnesium Nitrates 12 2. Analysis of the Basic Residues from Series DJ 16 3. Preparation and Fractionation of Rare Earth Bromates 21 4. Analysis of the F i l t r a t e from Series DJ 24 V. Discussion of These Studies i n The Rare Earths 26 1. Rare Earth Double Magnesium Nitrates 26 2. The Basic Residues from DJ 1-6 27 3. Analysis of the F i l t r a t e from the DJ Series 28 4. Rare Earth Bromates 28 VI. Suggestions for Further Studies J>0 VII. Conclusion 21 VXTI. Bibliography 32 TABLES, PRINTS AND SKETCHES Page I. Tables 1. Properties of the Rare Earths 3 2. Differences i n Properties of the Rare Earths 4 3 . The Absorption Spectra of the Rare Earths 6 4 . Observations on DJ 1-6 1 4 3 . Observations on DJ" I-VIII 1 4 6. Observations on the Basic Residues 20 7. Observations on the K Series- 23 8. Common Metals Impurities i n the DJ" Series 2 4 9 . Observations on Rare Earths not P r e c i p i -tated by Oxalic Acid i n Presence of N i t r i c Acid , 23 I I . Prints" 1. Apparatus 9 2. Series DJ 1-6 13 3 . Series DJ I-VIII 13 4 . Basic Residues from DJ 1-6 20 3 . Series K 1 - 9 23 6. Spectrograms of Rare Earths not P r e c i p i -tated by Oxalic Acid i n Presence of N i t r i c A c i d 23 I I I . Sketches 1. The Optical Path f o r Obtaining Absorption Spectra 10 2. The Optical Path f o r Obtaining Comparison Spectra 10 3 . The Mirror and Mounting 11 1* STUDIES IN THE RARE EARTHS I. Introduction: Studies i n the rare earths commenced i n 1794 with the discovery of " y t t e r b i a " by Gadolin and with the subsequent separation of thi s mineral into " y t t r i a " and "glucina" by Ekeberg (1). In 1926, the presence of the element i l l i n i u m was reported by Harris and Hopkins from the x-ray spectrogram of neodymium and samarium fr a c t i o n s (2). The period of i d e n t i f i c a t i o n of the elements i n the rare earth group was ended with t h i s research. ^Elements 37 - 71 (the true rare earths) were found to be present i n r e l a t i v e amounts, varying according to the source of the ore (1). In addition to these elements, e l e -ments 21 and 39 are often found i n the ores. These elements remain associated with the rare earths i n many chemical r e-actions and so they are sometimes included i n the rare earth group. The separation of the members of the rare earth group has proved one of the most d i f f i c u l t problems i n analy-t i c a l chemistry. The elements 37 - 71 each d i f f e r i n o r b i t a l electron configuration by one electron. However t h i s electron is*introduced i n the N l e v e l . The valence electrons are located i n the P l e v e l , which i s two l e v e l s removed from the N l e v e l ( 3 ) . Thus t h i s difference has very l i t t l e e f f e c t on the chemical properties of the members of the group. The most sati s f a c t o r y method of separation involves f r a c t i o n a l c r y s t a l l i z a t i o n of various s a l t s of the rare earths. Since rare earth s a l t s are isomorphous, f r a c t i o n a l c r y s t a l l i z a t i o n has additional advantages. F i r s t , there i s no eutectic point i n t h e i r s o l u b i l i t y curves so that eutectic mixtures are avoided. Second, the less soluble of a pair of isomorphous s a l t s i s insoluble i n a saturated solution of the more soluble s a l t (1). Observations on the f r a c t i o n a t i o n of the rare earth double magnesium n i t r a t e s and of the rare earth bromates are included i n t h i s thesis. Also an examination of the basic residues of the former series was conducted. 3 . I I . Summary of Data Concerning the Rare Earths Table 1. Properties of the Rare Earths (4 and 5 ) . atomic Number Symbol Name of Element Oxides Known Color of Oxide Colors of s a l t s 21 S© Scandium SC2O3 White Colorless 39 Y Yttrium Y 2 0 3 White Colorless 51 La Lanthanum La20^ White Colorless 58 Ce Cerium 0620^ Ce O2 Yellow Colorless Orange to red 59 Pr Praseodymium Pr203 1*4.07 Green Black Green 60 Nd Neodymium Nd203 Pink Red, red v i o l e t 61 11 I l l i n i u m 62 Sm) Sa) Samarium Sm203 Cream Topaz yellow 63 Eu Europium EU2O3 Pale Rose 1?ale Rose 64 Gd Gadolinium Gd2°3 White Colorless 65 Tb Terbium Tb203 ^307 White Brown Colorless 66 Dy Dysprosium Dy203 White Bright green 67 Ho Holmium H02O3 Pale yellov J Yellow to orange 68 Er Erbium Er203 Rose Deep Rose 69 Tm Thulium Tm203 Green Blue green 70 Yb Ytterbium Yb^Oj White Colorless 71 Lu Lutecium LU2O3 White Colorless Chemical separation of the rare earths i s based on s l i g h t differences i n properties between members of the group. Some of these differences are given i n Table 2. In each of the columns, the rare earths are arranged i n order of increasing s o l u b i l i t y of the various s a l t s . In the f i r s t column the elements are arranged i n order of decreasing b a s i -c i t y . A reference to each property i s found below the heading. Regarding the simple n i t r a t e s , i t has been found (7>9) that .the. s o l u b i l i t y decreases with increasing atomic weight to a minimum at Gd, af t e r which the s o l u b i l i t y becomes d i r e c t l y proportional to the atomic weight and reaches a maximum at Yh>. Table 2. Differences i n Properties of the Rare Earths. B a s i c i t y (5) Double Mgv Nitrates (6) A l k a l i Sulfates (7) Bromates (7) Acetates (8) 57 La 57 La 58 Ce 62 Sa 68 Br 58 Ce+3 59 Pr 57 La 63 Eu 67 Ho 59 Pr 60 Nd 59 Pr 64 Gd 65 Tb 60 Nd excess Mg 60 Nd. 65 Tb 64 Gd 39 Y 62 Sa 62 Sa 62 Sa 63 Eu 63 Eu 63 Eu 60 Nd 64 Gd 68 Er 64 Gd 66 Dy 62 Sa 64 Gd Tb 67 Ho 65 Tb 39 Y 66 Dy 39 Y 66 Dy yttrium 67 Ho 68 Er 67 Ho group 39 Y 69 Tm 68 Er 68 E r 70 Yh 69 Tm 69 Tm 70 Yb> 70 Yb 71 Lu 71 Lu 21 Sc • 58 Ce+4 '5. 2. Valence A l l elements i n the rare earth group have a valence of three. Cerium also has a higher valence of four. Pra-seodymium may possibly possess a,valence of four, according to Daudel who has given a wave mechanic treatment of the rare earths (10). Also, according to t h i s a r t i c l e , no other rare earth may possess a valence of four. A lower valence of two i s known f o r 62, 63, and 70 (1). j?8, 62, 63 and 70 may be separated from the other rare earths by taking advantage of t h i s difference i n valence (12 ,13) . 3. Rare Earth Double Nitrates The rare earths form double n i t r a t e s of the form 2R(N03)^ • 3M(N02)2 • 24H"20 where R i s the rare earth element and M i s a divalent metal (6) . Series have been f r a c t i o n a l l y c r y s t a l l i z e d using various divalent ions such as Cd, Zn, N i , Mn, Pb, Mg, Co, and Cu (13,14). Results show the same order of s o l u b i l i t y given i n Table 2, page 4. Fractionation with these various divalent ions has been done to determine i f any of them would serve as an "element separateur". The f i r s t element of t h i s type was bismuth which was used by Urbain to separate Sm from Eu and Gd from Tb (1). 4. The Absorption Spectra of the Rare Earths The most convenient method of i d e n t i f y i n g the rare earths i s the study of the absorption spectrogram i n the v i s i b l e region. Each of the rare earths has d i s t i n c t absorp-t i o n l i n e s i n the v i s i b l e with the exception of Lu, Yb, and 6. Gd. A table of the absorption bands f o r each of the rare earths has been composed from the data given by Yntema (15). A comparison between the absorption spectrograms obtained and the absorption bands i n Table 3 w i l l allow rapid conclusions regarding the rare earths present i n the various f r a c t i o n s . 7. 5. The Method of Fract i o n a l C r y s t a l l i z a t i o n The solution of s a l t s i s evaporated to such an ex-tent that, on cooling and a t t a i n i n g equilibrium at room tem-perature ( 2 j j degrees C), the volume of mother l i q u o r i s about one t h i r d that of the c r y s t a l s . The mother l i q u o r i s allowed to drain thoroughly from the c r y s t a l s . This comprizes the f i r s t pouring. Water 3 6 i s then added to the cr y s t a l s i n a volume approximately equal to that of the mother l i q u o r . This mixture i s heated u n t i l a l l but a small f r a c t i o n of the cry s t a l s has dissolved. On cooling and at t a i n i n g equilibrium, the second pouring i s made. This process repeated u n t i l f i v e pourings have been made. The c r y s t a l residue i s the f i r s t f r a c t i o n . A second f r a c t i o n i s begun by evaporation of the combined mother liquo r s from the f i r s t f r a c t i o n . As many as eight f r a c t i o n s may be obtained i n t h i s manner. 2 As the soluble end of the double magnesium n i t r a t e series i s approached, the rare earth s a l t s become les s basic and tend to hydrolyze when water i s added. In order to pre-vent the formation of large basic residues i t was found ad-visable to add small quantities of concentrated n i t r i c acid to the l a t t e r f r a c t i o n s of t h i s s e r i e s . 6. Preparation of Rare Earth Solutions f o r Spectrophotography Metal l i c ions and acids have a marked e f f e c t on the rare earth absorption spectra (16). As noted by Hopkins, Q u i l l and Selwood (16), n i t r i c acdd cannot be expelled com-pl e t e l y from samples containing the less basic rare earths, without hydrolysis occurring. However the small concentration 8. of acid l e f t i n these solutions does not a f f e c t the p o s i t i o n or width of the absorption bands obtained from a spectrograph with small dispersion. The spectrograph used i s a Hilger D77 o constant deviation model with a dispersion of about lA/mm. Except where otherwise noted, a l l solutions f o r spectrophotography were prepared i n the following manner. The c r y s t a l f r a c t i o n i s r e c r y s t a l l i z e d and 10 ml of mother l i q u o r pipetted out at 25 degrees C. The solution i s dil u t e d to 50 ml, heated to b o i l i n g and the rare earth oxalates precipitated with saturated oxalic acid s o l u t i o n . The p r e c i p i t a t e i s digested f o r half an hour, f i l t e r e d and washed f i v e times to insure removal of occluded ions. The oxalates are ignited at 800°C for one hour and at 900°C f o r an a d d i t i o n a l h a l f hour. The rare earth oxides, a f t e r cooling, are moistened with JO per cent hydrogen peroxide, then 1 ml. of 16 normal n i t r i c acid i s added. 2 The solution i s d i l u t e d and evaporated three or four times to remove excess aci d . F i n a l l y 10 ml. of acid f r e e * ( l l ) rare earth n i t r a t e solution i s obtained* This solution i s suitable f o r absorption spectrophotography. s I f solution i s incomplete, care should be taken to maintain an excess of hydrogen peroxide. This method was found to produce immediate solut i o n of the oxides. I t i s more rapid than the method used by Pearce (15), i n which the oxides are f i r s t moistened with water. * The sharp odor of n i t r i c acid fumes served to detect the presence of excess acid. 9. I I I . Apparatus I t was found necessary to construct a Hartmann diaphram for the Hilger D77 model spectrogaph used i n ob-taining the absorption spectrograms of the rare earth f r a c t i o n s . E l e c t r i c heating elements were made f o r the steam bath. These allowed c a r e f u l temperature control during the f r a c t i o n a -t i o n of the bromates. A new o p t i c a l arrangement was devised to overcome the former d i f f i c u l t y of recording both absorption spectra and comparison spectra on the same photographic plate. This arrangement i s shown i n pr i n t 1, page.?. 10. Sketches 1 and 2, page 10, indicate the o p t i c a l paths used. A p o i n t o l i t e lamp was the source of continuous spectrum. Sketch 1. The Optical Path f o r Obtaining Absorption Spectra. Spectroscopic Absorption S l i t C e l l Condensing Lens Light Source Condensing Lens Aperture Sketch 2. The Optical Path f o r Obtaining Comparison Spectra. Spectroscopic S l i t 1 1 . An improvement on the optics of recording the com-parison spectrum has been devised. This i s a provision f o r rapid removal of the mirror and f o r rapid, accurate replace-ment. Sketch 3. The Mirror and Mounting. D, A . B B i c A - hollow c y l i n d r i c a l mount B - s p i r a l s l o t f o r lug B ± - lug C - mirror holder D - arms f o r f i r m support of mirror E - mirror The entire assembly i s f i r s t adjusted i n such a manner that either the lower or upper portion of the mirror r e f l e c t s the l i g h t along the optic axis of the spectrograph when the lug B i i s f u l l y inserted i n the mount. Then the mount i s fi r m l y clamped i n t h i s p o s i t i o n . Rotation of the mirror holder through 90 degrees w i l l now allow absorption spectrograms to be taken. To record comparison spectra, the mirror holder i s merely rotated back to i t s i n i t i a l p o s i t i o n . 12. IV. Studies i n the Rare Eartlis : The studies confronted at t h i s time resolved them-selves into several d i s t i n c t problems. 1. Extension of f r a c t i o n a t i o n of a double magnesium n i t r a t e series referred to as DJ serie s . 2. Examination of the basic residues produced during the f r a c t i o n a t i o n of the DJ ser i e s . 3. Conversion of the soluble end of the DJ series to bromates and the f r a c t i o n a t i o n of these s a l t s . 4. A report on the f r a c t i o n a t i o n of the rare earth double magnesium n i t r a t e s could scarcely be complete without a report on other common ion impurities. Therefore an analy-s i s f o r the common cations was conducted and reported i n part 4. 1. Rare Earth Double Magnesium Nitrates Monazite sand residues from the Lindsay Light Com-pany formed the source of rare earth material f o r t h i s s e r i e s . A f t e r removal of cerium and thorium, 2.4 Kg of rare earth oxides were obtained. 417 g- of magnesium oxide were added to s a t i s f y the formula 3MgO • 2R2°3» The oxides were d i s -solved i n n i t r i c acid and the s a l t s fractionated to 5 f r a c -tions, a r b i t r a r i l y designated as series J. Fractions J 1-2-3 were further fractionated to 7 f r a c t i o n s noted as series AJ. Fractions J4-5 were further fractionated to 12 fra c t i o n s noted as series BJ 1-11 and 11a. Series CJ was formed from AJ 5-6-7 with BJ 1-2-3.and was fractionated to 11 f r a c t i o n s . Series DJ was formed from BJ 8-9-10-11 and 11a ulth 13. CJ 8-9-10-11 and fractionated to 6 f r a c t i o n s by 18 f r a c t i o n a -t i o n s . Each of these f r a c t i o n s were r e c r y s t a l l i z e d and 10 ml. samples prepared f o r spectroscopic analysis i n the manner outlined on page 7« S a t i s f a c t o r y absorption spectrograms were obtained with a four second exposure. Eive seconds were required to record a s a t i s f a c t o r y i r o n arc comparison spec-trum. P r i n t 2 shows the extent of separation at t h i s stage. Table 4 i s a record of the colors of the rare earth n i t r a t e solutions obtained from each of the s i x f r a c t i o n s . In t h i s manner the i n i t i a l separation i n the DJ series was determined. The s i x f r a c t i o n s , DJ 1-6, were then extended by an additional 30 fractionations to eight f r a c t i o n s noted as DJ I-vTII. During the f r a c t i o n a t i o n of DJ V, a very large pro-portion of cr y s t a l s tended to form a super saturated solution. This material c r y s t a l l i z e d out when the mother l i q u o r was poured. These l a t t e r c r y s t a l s were returned to DJ Y f o r ad-d i t i o n a l f r a c t i o n a t i o n except i n the l a s t case, when they were kept separate from DJ V and noted DJ VB. A spectrogram of t h i s f r a c t i o n i s included i n the pr i n t s of the extended DJ series. The object of t h i s separation i s to determine whether there i s a marked difference between DJ V, VB and VI. The DJ series now consists of 8 f r a c t i o n s , plus a sub-fraction, and a quantity of s a l t s which w i l l not c r y s t a l -l i z e as double magnesium n i t r a t e s by the method used. Treat-ment of these soluble s a l t s i s recorded i n part 3, "Prepara-t i o n and Fractionation of Rare Earth Bromates". 14". A spectrogram of each of the fra c t i o n s and of the soluble material was obtained i n the usual manner, as des-cribed on page 7. Pr i n t 3 was made from the1 spectrograms. Table 5 i s a record of the colors of the c r y s t a l s , mother liq u o r and of the n i t r a t e solutions. This completes the experimental portion on the DJ series at t h i s time. Table 4. Observations on DJ 1-6. Fraction Color of Nitr a t e Solution DJ-1 Light brown & green 2 Light brown & pink 3 Brownish pink 4 Brownish rose 5 Rose & f a i n t brown 6 Mauve Table 5. Observations on DJ I-VIII. Fraction Color of Color of Mother Color of Nitr a t e Crystals Liquor Solution DJ-I Colorless Yellow green Yellow green II . Colorless Tan Tan & green I l l C olorless Tan Tan ( s l i g h t pink) IV Light Mauve Light pink Brown & pink V Mauve Pink Brown & pink VB Mauve & rose Rose Brown & pink • -VI Mauve & rose Rose Rose & brown VII Deep rose Deep rose Rose & f a i n t brown VIII Deep rose & Red & mauve Mauve some l i g h t color. 16. 2. Analysis-of the Basic Residues from Series DJ In the i n i t i a l f r a c t i o n a t i o n of the DJ series, a basic residue separated from each of the f i r s t f i v e f r a c t i o n s . Residues from DJ1 and 2 were small and were combined to give a t o t a l of four residues to be analysed. These four residues were noted as follows: Rl - residues from DJ 1 & 2 R2 - » » DJ J> R3 - " " DJ 4 R4 - " " DJ 5 Each of these residues was ig n i t e d at 800°G f o r one hour to remove carbon and to convert most of the material to oxides. The ig n i t e d material proved to be refractory. The usual treatment with n i t r i c acid and hydrogen peroxide ap-peared to dissolve j? per cent or less of the residue. Hydrochloric acid and hydrogen peroxide produced no change. Perchloric acid and aqua regia were also i n e f f e c t i v e . Before resorting to fusion methods, i t was decided to t r y a powerful reducing agent. The residues were attacked with aqua regia and mossy zinc to give s a t i s f a c t o r y solutions. The rare earths were pr e c i p i t a t e d as the hydroxides from hot solutions with ammonium hydroxide . Levy (5) noted that a basic s a l t is-, produced when ammonia i s added to cold or concentrated solutions of the rare earths. After washing out some of the impurities, the hydroxides were dissolved i n n i t r i c acid and some of the excess acid removed by evaporation. P r i n t 4 indicates the r e s u l t s obtained from the absorption 17. spectrograms of these solutions. The gelatinous rare earth hydroxides w i l l occlude other ions to a considerable extent and these ions w i l l a f f e c t the absorption spectrogram (16). Also i t was found impossible to concentrate these f i n a l solutions without hydrolysis except i n the presence of a large excess of n i t r i c acid. Thus p r i n t 4 can be regarded only i n a q u a l i t a t i v e manner. 18. EXPERIMENTAL PROCEDURE As mentioned previously, the residues were f i r s t i g n i t e d f o r one hour at 800 degrees C, followed hy treatment with n i t r i c acid and hydrogen peroxide, which appeared to d i s -solve 5 per cent or l e s s . The solution was f i l t e r e d and evaporated. I t was observed that quantities of material pre-c i p i t a t e d out continuously during evaporation. This material did not appear c r y s t a l l i n e , but strongly resembled the undis-solved material. I t was suspected that a f i n e suspension or a c o l l o i d , rather than a true solution, had been obtained. The Tyndall effect was very noticeable i n these "solutions". Treatment with aqua regia and zinc produced solution of about 70 per cent of the material i n two hours, almost complete solut i o n was obtained i n three hours. Each solution was f i l t e r e d three times to insure removal of the f i n e sus-pended p a r t i c l e s . The small residues remaining were set aside for future reference. The f i l t r a t e contains a number of impurities, chief of which are Zn, Mg, and possible traces of Mn and Fe. The usual procedure f o r removal of impurities and f o r preparation of samples for spectrophotometry as given on page 7, was not attempted to avoid the d i f f i c u l t l y soluble oxides. 50 ml of f i l t r a t e s Rl-3 and 25 ml of R4 were made approximately neutral with 6 normal ammonium hydroxide and then made alk a l i n e with 15 normal ammonium hydroxide. No external heating was re-quired due to the high heat of ne u t r a l i z a t i o n . The hydroxides were f i l t e r e d and washed twice with 6 normal ammonium hydro-19. xide and three times with water and then taken up i n the le a s t amount of 6 normal n i t r i c acid (12 - 15 ml). The r e s u l t i n g solutions were cautiously evaporated to 5 - 10 ml to remove some excess n i t r i c acid and to concentrate the solutions. The absorption spectra of the solutions was then obtained. In t h i s case, an exposure of three seconds was s u f f i c i e n t . T heoretically, t h i s method should free the rare earths from a l l the above mentioned impurities except i r o n , which i s preci p i t a t e d as f e r r i c hydroxide. Zinc remains i n solution as the ammonia complex while magnesium hydroxide and manganous hydroxide are not pre c i p i t a t e d by ammonium hydroxide unless a very high concentration of the metal ions i s present. However major contamination of the hydroxides i s caused by occlusion of ions. These fo r e i g n ions cannot be washed free from the gelatinous p r e c i p i t a t e and so they r e-main to contaminate l a t e r solutions. Pr i n t 4 concludes the report on the rare earths pre-sent i n the basic residues. However i t would be advisable to determine which common metals, i f any, were present In the solutions used to obtain the spectrograms. With t h i s i n mind, these solutions, Rl-4, have been reserved f o r analysis at a l a t e r date. Table 6. Observations on the Basic Residues 20. Sample Color oride Color hydroxide Color n i t r a t e s o l u t i o n Inference Rl white red brown f a i n t yellow green Pr R2 grey red brown & white rose Nd,Sr,Eu R3 mauve red brown & white rose Gd,Nd,Er,Eu R4 purple red brown & pink rose Gd,Nd,Er,Eu P r i n t 4. Basic Residues from DJ 1-6 21. 3. Preparation and Fractionation of Rare Earth Bromates. The soluble end of the DJ series formed the source of rare earth material f o r t h i s project. This material was f i r s t p u r i f i e d by two p r e c i p i t a t i o n s of the rare earth oxalates from hot, d i l u t e s o l u t i o n with hot, d i l u t e o x a l i c a c i d i n the presence of a s l i g h t excess of n i t r i c acid. This procedure, according to Archibald (17), minimizes the quantity of oc-cluded s a l t s , thereby producing a more pure product. The oxaltes were converted to oxides the second time by i g n i t i o n f o r one hour at 800 degrees C, and f o r an additional half hour at 900 degrees C. Ninety grams of rare earth oxides were ob-tained and converted to bromates by the method proposed by Moeller and Kremers (18) with c e r t a i n modifications. The pro-cedure used i s outlined i n the ensuing paragraphs. The oxides are incompletely dissolved by heating with an exactly equivalent amount of 70 per cent perchloric acid, calculated on a mean atomic weight of 150 f o r the rare earths. The s l i g h t residue i s f i l t e r e d out and combined with basic precipitates which are obtained l a t e r i n the procedure. The f i l t r a t e i s an almost neutral s o l u t i o n of rare earth perchlorates (about 0.05N as an a c i d ) . A f t e r d i l u t i o n to twice the volume, powdered potassium bromate i s added slowly to the hot s o l u t i o n u n t i l a s l i g h t excess over the calculated amount i s present. The mixture i s digested f o r one and a h a l f hours on a hot plate, care being taken not to b o i l the mixture. The solution i s allowed to cool to room temperature and i s f i l t e r e d to remove the p r e c i p i t a t e d potas-22. sium perchlorate. Rare earths are leached out of the residue by re-peated washing with small portions of wash water u n t i l the volume of washings i s approximately equal to that of the f i l -t r a t e . The f i l t r a t e and washings are not combined, but are evaporated separately, without b o i l i n g , u n t i l c r y s t a l s begin to form. on.the surface. Fractionation of the f i l t r a t e i s begun at t h i s stage. The c r y s t a l s obtained from the evaporated washings are combined with the appropriate f r a c t i o n of the ser i e s . Basic s a l t s are formed i n varying amounts during f r a c t i o n a t i o n , these are f i l t e r e d out and combined to form one residue. This residue i s dissolved i n n i t r i c a c i d with hydrogen peroxide, the rare earths p r e c i p i t a t e d as oxalates, ignited to oxides and f i n a l l y converted to bromates by the above procedure. The c r y s t a l s obtained from t h i s s o l u t i o n are also added to the appropriate f r a c t i o n s of the se r i e s . The appropriate f r a c t i o n of the series i s determined by v i s u a l comparison of the absorption spectra of the various bromate solutions. The series obtained i n t h i s manner was a r b i t r a r i l y named the K serie s . Since the quantity of rare earth oxides was r e l a t i v e l y small, i t was not p r a c t i c a l to form more than nine f r a c t i o n s i n t h i s s e r i e s . Samples were taken from each of these fract i o n s and prepared f o r absorption spectroscopy i n the manner described on page 7. P r i n t 5 indicates the probable composition of the. 2 3 . various fract i o n s as well as the extent of separation at t h i s time. The colors of the cry s t a l s and of the f i n a l n i t r a t e solutions are given i n table 7. Table 7. Observations on the K Series. Fraction Color of Crystals Color of Mother Liquor Color of Oxides Color of Nitrates Inference K 1 2 3 4 5 6 7 8 9 white white mauve rose rose rose (some l i g h t ) rose pink pink f a i n t pink f a i n t pink pink rose rose rose rose pink & brown pink & brown brown & blue blue and brown gradual change from tan to medium brown mauve mauve mauve & brown gradual increase i n depth of brown KBrOj KBr03 Nd Sm Nd Sm Nd Sm Nd Sm Nd Sm Nd Sm Nd Sm Pri n t 5. Series K 1-9 24. 4. Analysis of the F i l t r a t e from the DJ Series I t was f e l t that a f r a c t i o n a t i o n of double magnesium n i t r a t e s would not be complete without a report on the common .metal impurities which were present during the-fractionation. Therefore an analysis f o r the common cations was conducted on the solution, a f t e r the soluble rare earth double magnesium nit r a t e s had been removed by p r e c i p i t a t i o n with oxalic acid. The method of analysis i s the one devised by Harris and Ure fo r the elementary analysis course at the University of B r i t i s h Columbia. This method has not yet been published. I t was found necessary to introduce one modification to remove some rare earths which had not been prec i p i t a t e d by oxalic acid. These were prec i p i t a t e d as hydroxides, taken up i n n i t r i c acid and reprecip i t a t e d as oxalates with ammonium oxalate. Both f i l t r a t e s were tested f o r group I I I cations. Manganese was found to be quantitatively absorbed by the hydro-xides. Table 8 i s a report on the cations found, with an ind i c a t i o n of the r e l a t i v e amounts of each, compared to magne-sium as 100. Table 8. Pb Cu R.E. Mn Zn Mg 0.1 0.05 10 5 1 100 Three rare earth oxalate precipitates were obtained by successively increasing the pH of the solution with ammonium hydroxide. These were i g n i t e d to oxides and prepared f o r 25 . spectroscopy i n the manner given on page 7. These were a r b i -t r a r i l y named NI, N2, N3 and observations reported i n Table 9 and i n print 6. From the color changes i n the solution of the oxides i t i s suspected that manganese i s also present i n these samples. Table 9. Sample Color of Oxide Color of Nitrate NI Grey green pink N2 Tan Faint brown N3 Black Colorless 26. V. Discussion of These Studies i n the Rare E a r t h s 8 1. Rare Earth Double Magnesium Nitrates The r e s u l t s of f r a c t i o n a t i o n of the DJ series are i n agreement with those obtained by other workers. Comparison of prints 2 and 3, page 15, shows Pr to be concentrating i n the head f r a c t i o n s . Continued f r a c t i o n a t i o n of t h i s series should concentrate Pr quite r e a d i l y . I t i s to be noted that DJ IX (the soluble portion) i s p r a c t i c a l l y free from Pr. Nd remains spread over a l l of the fr a c t i o n s but it.seems to be concentra- . ti n g i n DJ IV, VB and VIII. The Sm band (about 4000,8,) appears i n DJ VII and i n subsequent f r a c t i o n s . No conclusive evidence of other rare earths can be observed. The unusual fashion i n which Nd appears to concentrate i s most probably due to the fa c t that the second f r a c t i o n a -t i o n was performed upon an i n i t i a l f r a c t i o n a t i o n i n which Nd concentrated i n DJ 3-6. The s i m i l a r i t y between DJ V and VI i s notable, while DJ VB appears to contain a greater concentra-t i o n of both Nd and Pr. This p e c u l i a r i t y i s probably due to a s l i g h t v a r i a t i o n i n actual concentration of the s a l t s i n the solutions from which the spectrograms were obtained. Also i t may be due to a s l i g h t difference i n time of exposure. I t i s suggested that an investi g a t i o n be conducted on these f r a c t i o n s to f i n d an explanation f o r the supersaturation observed at thi s point. I t i s possible that t h i s would be. a good point at which to s p l i t the ser i e s . A l l observations have been made d i r e c t l y from the negatives and not from the p r i n t s . 27. 2. The Basic Residues from DJ 1-6. The following observations have been made from the •spectrograms recorded i n print 4, page 20. Rl has p r a c t i c a l l y no absorption bands, although traces of Pr and Nd are evident. La may possibly have formed the residue, although t h i s i s not i n accordance with the strongly basic properties of t h i s metal. R2 and R3 contain appreciable amounts of Pr and Nd o as well as Sm, which i s evident by the band at about 4000A. This band has not been recorded c l e a r l y i n p r i n t 4. R4 i s of considerable i n t e r e s t . The Nd band at about o j?800A i s c l e a r l y composed, of two bands. These bands l i e i n the region of absorption bands which may possibly be due to I I (2). They are of s l i g h t l y longer wavelength than the corresponding Nd band at 5750JL In addition, the Nd band at about $220Jt.. has approximately the same i n t e n s i t y as the band at about 5100iL This l a t t e r band i s usually l e s s intense than the. former. This l a t t e r band may possibly belong to I I (2). Other Nd l i n e s are f a i n t . Since R4 was obtained from DJ j> i t would now seem ad-visable to di r e c t close attention to t h i s portion of the DJ series . As has been noted, peculiar behaviour of the s a l t s i n the fr a c t i o n a t i o n of DJ J? had already attracted attention to t h i s member of the ser i e s . I t i s strongly advised that ad-d i t i o n a l examination be made on DJ IV, V, VB, VI i n view of these observations. Caution must be observed regarding t h i s interpreta-28. t i o n , since, as was stated i n the" experimental portion, excess n i t r i c acid i s present and the absence of other cations has not been established. Examination of R 1-4 f o r other cations i s being conducted but has not been completed. 3. Analysis of the E i l t r a t e from the DJ Series. The rare earths were removed and fractionated as bromates. Discussion of these i s recorded i n the next part. Manganese was found to be the only impurity present i n suf-f i c i e n t quantity to a f f e c t f r a c t i o n a t i o n . I t i s possible that some double Mn s a l t s were formed. However the separation ob-tained with Mn double n i t r a t e s i s very s i m i l a r to that obtained with Mg double n i t r a t e s (13). Consequently no change i n the separation could be evident and so the series may be safely assumed to be a double Mg n i t r a t e s e r i e s . P r i n t 6, page 23, i s a record of those rare earths which were not precipitated by oxalic acid i n the presence of n i t r i c a c i d . Eaint Nd bands at about 5800A" and 5220A. are evident i n NI. Each of the spectrograms contains an unidenti-f i e d band at about 6140A. No other bands are evident i n these spectrograms. Thus i t may be concluded that other rare earths are absent from these solutions, excepting Gd, Yb and Lu which have no absorption spectra i n t h i s region. 4. Rare Earth Bromates. The.K series bromates, made from the soluble end of the DJ series double Mg n i t r a t e s are shown i n pr i n t 3, page 23. Due to the r e l a t i v e l y large concentrations of Nd, Sm, Pr the spectrograms contain a large number of absorption bands. I t i s consequently very d i f f i c u l t to observe the presence of bands due to Y group elements. V i r t u a l l y a l l of the l i n e s present i n the spectrogram of the K series are also present i n the spectrogram of the DJ series. Thus v i s u a l observation of the K series spectrogram i s li m i t e d to a report on the d i s t r i b u t i o n of Pr, Nd, and Sm. Pr appears to be unaffected by the f r a c -tionation. Nd appears to concentrate i n fr a c t i o n s K6 and 7., while Sm i s concentrating i n f r a c t i o n K7. Tb, Dy, Ho, Er may be present i n t h i s material but no conclusions may be drawn due to the heavy masking by Nd and Sm. Since these f r a c t i o n s are now quite small (the largest being about JO ml) i t i s not suggested that any further work be done with t h i s material. The only s a t i s f a c t o r y method f o r determining the presence of Y group rare earths i n these Lindsay Light residues would be. to commence with a much larger i n i t i a l sample. 30. 71. Suggestions f o r Further Studies. The suggestions made throughout t h i s thesis are c o l -lected under three headings as follows. 1. Double Magnesium Nitrates. The DJ series could be s p l i t s a t i s f a c t o r i l y into three groups. Fractions DJ I-III could be combined and f r a c -tionated to purify Pr. Fractions DJ 17-71 could be combined and fractionated. Pr would again concentrate i n the head fractio n s while the other f r a c t i o n s could be examined f o r an explanation of the supersaturation apparent i n DJ 7. Also the p o s s i b i l i t y of the presence of II could be investigated i n these f r a c t i o n s . Fractions DJ 7II-7III could be combined and fractionated to increase the Nd-Sm separation. 2. Basic Residues. In view of the in t e r e s t i n g spectrogram of R4 (print 4, page 20) i t i s suggested that the examination of subsequent basic residues be conducted and the re s u l t s reported as a part of the studies on any series. Examination of basic residues obtained from DJ I-7III i s being conducted at t h i s time. 3. Bromates. Since the quantity of these s a l t s i s small, i t i s suggested that the K series be combined and set aside u n t i l such time as another series of bromates i s being prepared. These could then be added to such a series i f i t i s so desired. 31. vTI Conclusion. Rare earth double magnesium n i t r a t e s were f r a c t i o n a -ted to eight f r a c t i o n s . The separation obtained agrees with the results of other workers (12). The DJ series was found to be composed c h i e f l y of Pr and Nd, with some Sm i n the l a t t e r f r a c t i o n s . Analysis of the basic residues from the DJ series has indicated the possible presence of II i n t h i s s e r i e s . Also i t was shown that small amounts of Mn, Zn, Pb and Cu were present as impurities i n the DJ s e r i e s . An attempt was made to determine whether any Y group rare earths were present i n the o r i g i n a l J series by examina-ti o n of the soluble end of the DJ s e r i e s . By f r a c t i o n a l c r y s t a l l i z a t i o n of 2400 g. of rare earth oxides as double magnesium nitrates-, a l l but 90 g. (4f.) of oxides were c r y s t a l -l i z e d . Results from the spectrograms of the K series bromates show that t h i s remaining 4% i s composed l a r g e l y of Nd, Sm and Pr. Hence i t can be concluded that very l i t t l e , i f any, Y group rare earths were present i n the o r i g i n a l material. The new method of preparation of rare earth bromates (18) was found s a t i s f a c t o r y . VIII. BIBLIOGRAPHY 1. L o r t i e , Leon Can. Chem. Proc. Ind. 27; 213-16 (1943). 2. Harris, J". A. with Hopkins and Yntema J-.A.C.S. 48; 1585 (1?26). 3. Parkes, G. D. and Mellor, J. W. "Mellor"s Inorganic Chemistry" 1939. 4. Segerblom "Properties of Inorganic Substances", 1926. 5. Levy, S. I. "The Rare Earths", 1924. pp. 106, 111, 114. 6. Muthmann & Weiss Liebigt s Ann. 331; 4 (1904). 7. Vickery, R. C. Metallurgia 30; 130-4, 215-20 (1944). 8. Harris & Cameron Trans. R. Soc. Can. 26; I I I ; 61-2 (1932). 9. Harris & Wylie Trans. R. Soc. Can. 26; .III; 63-8 (1932). 10. Daudel compt. rend. 217; 396-7 (1943). 11. Roberts C. A. 5, 2231 (1911). 12. Marsh J. Chem. Soc. 65; 8-10, 531-5 (1943). 13. Pierce & Harris Trans. R. Soc. Can. 24; I I I ; 145-51 (1930). 14. Jantsch Zeitsch anorg. Chem. 76, 303 (1912). 15. Yntema J.A.C.S. 48; 1598 (1926). 16. Selwood, Q u i l l & Hopkins J.A.C.S. 50; 2929 (1928). 33. 17 . Archibald "Preparation of Pure Inorganic Substances" Chapt. T i l l , (1932). 18. Moeller & Kremers J.A.C.S. 66; 1795 (194-4). 

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