Redis co very of the Elements The Ra re Earth s–The Con fusing Years

I A gallery of rare earth scientists and a timeline of their research I I

James L. Marshall, Beta Eta 1971 , and Virginia R. Marshall, Beta Eta 2003 , Department of Chemistry, University of North Texas, Denton, TX 76203-5070, [email protected]

The rare earths after Mosander. In the pre - vi ou s HEXAGON “Rediscovery” article, 1p we were introduced to the 17 rare earths, found in the f-block and the Group III chemical family of Figure 1. Important scientists dealing with rare earths through the nineteenth century. Johan Gadolin the Periodic Table. Because of a common (1760 –1852) 1g —discovered yttrium (1794). Jöns Jacob Berzelius (1779 –1848) and Martin Heinrich valence electron configuration, the rare earths Klaproth (1743 –1817) 1d —discovered cerium (1803). Carl Gustaf Mosander (1787 –1858) 1p —discovered have similar chemical properties, and their lanthanum (1839), didymium (1840), terbium, and erbium (1843). Jean-Charles deGalissard Marignac chemical separation from one another can be (1817 –1894) 1o —discovered ytterbium (1878) and gadolinium (1880). Per Teodor Cleve (1840 –1905) 1n — difficult. From preparations of the first two rare discovered holmium and thulium (1879). Lars Fredrik Nilson (1840 –1899) 1n —discovered scandium earth element s—yttrium and ceriu m—the (1879). Paul-Émile Lecoq de Boisbaudran (1838 –1912) —discovered samarium (1879) and dysprosium Swedish chemist Carl Gustaf Mosander (Figure (1886). 1b Carl Auer von Welsbach (1858 –1929) 1c —discovered praseodymium and neodymium (1885); 1, 2) was able to separate four additional ele - co-discovered lutetium (1907). Eugène-Anatole Demarçay (1852 –1903 )—discovered europium (1901). 1e ments during 1839 –1842: lanthanum, didymi - William Crookes (1832 –1919) 1m —spectral techniques; proposed “meta-elements.” Marc Delafontaine um, erbium, and terbium. 1p (1837 –1911 )—co-discovered holmium (1879). Charles James (1880 –1928) 1k—co-discovered lutetium Mosander’s discoveries signaled the possi - (1907). Georges Urbain (1872 –1938) 1k — co-discovered lutetium (1907). Bohuslav Brauner bility of yet more elements hidden in the parent (1855 –1935 )—predicted element 61. yttrium and cerium. However, it was three and a half decades before the next rare earth was isolated. Mosander’s successes had been rela - Table 1: Crustal abundances of rare earths, ppm [ref 2] tively “easy pickings,” because abundant lan - thanum (see Table 1) could be quickly and Sc Y La Ce Pr* Nd* Pm Sm Eu Gd Tb** Dy Ho Er** Tm Yb Lu quantitatively separated as the soluble trivalent salt (La +3 ) from insoluble tetravalent cerium 22 33 30 60 8.2 28 trace 6 1.2 5.4 0.9 3.0 1.2 2.2 0.5 3.0 0.5 (Ce +4 ); and the v ivid colors of didymium *Mosander’s didymium was a mixture of Pr and Nd. (amethyst), erbium (orange), and terbium (rose) **Tb and Er are now reversed from the original assignments of Mosander. allowed visual tracking of their separation dur - ing repeated recrystallizations. By contrast, the remaining rare earth oxides all generally exhibit

72 THE HEXAGON/ WINTER 2015 the same valence state (+3), are colorless, and exist in low concentrations in nature.

The advent of spectroscopy. During 1860 –1861 Robert Wilhelm Bunsen (1811 –1899) and Gustav Robert Kirchhoff (1824 –1887) of the University of Heidelberg discovered the elements cesium and rubidium (1860 –1861) in Dürkheim Spa mineral waters with their newly invented emission spectro - scope. 1h This spectral tool was immediately adopted by William Crookes 1m in London to discover thallium (1861) from Harz Mountain mines of Germany; and then by Hieronymus Theodor Richter (1824 –1898) and Ferdinand Reich (1799 –1882) of the Freiberg Mining School in Saxony to discover indium (1863) from the neighboring Himmelfürst Mine. 1a,h Spectral analysis was quickly recognized as a possible solution to untangle the confusing rare earth mixtures. With the simultaneous develop - ment of more sophisticated chemical separa - tion techniques, rare earth research experi - enced a surge during the last quarter of the nineteenth century. Figure 2. On the left is the building housing the Royal Swedish Academy of Sciences (second site), Wallingatan 2 (N59° 20.26 E18° 03.52), where Mosander lived and worked. Here he prepared lanthanum, Spectral analysis —the situation becomes didymium, erbium, and terbium. 1p The building is now used for general offices. The church at the end of the complicated. One might expect that the new street is Adolf Fredriks Kyrka [Church], inaugurated in 1774. The view looked the same in Mosander’s method of emission spectroscopy might time. “Father Moses,” as Mosander was affectionately called by his friends, proudly told Berzelius prompt immediate discoveries of rare earths. (co-discoverer of cerium) that in this building was prepared the only pure sample of ceric oxide in the Ironically, spectral analysis initially complicated world — “white, slightly yellowish” (1842). 4 the situation, because thousands of spectral lines now had to be separated and identified. Figure 3. Historically important rare earth minerals. Gadolinite, (Y, RE) FeBeSi O , from the Ytterby Mine, These lines arose not only from mixtures of rare 2 2 10 Sweden; source of the first rare earth discovered, yttrium, and named for the element’s discoverer, Johan earths themselves, but also from many other Gadolin; analyzes (%) for Y/Tb/Tb/Dy/Tm/Yb 16/2/2/2/5/3. Cerite, (Ce,RE,Ca) Fe(SiO ) (SiO OH)(OH) , elemental impurities such as iron, strontium, 10 4 6 3 3 from the Bastnäs Mine; source of the first lanthanide; by Klaproth, Hisinger, and Klaproth, analyzes (%) for barium, etc., with which rare earths were chem - La/Ce/Pr/Nd/Sm 12/26/3/11/2. Bastnäsite, (RE)CO F, the main source of rare earths both in the U.S. and ically bound in the original minerals. Further 3 China. This sample from Mountain Pass, complicating the situation, different source CA, analyzes (%) for La/Ce/Pr/Nd/Sm minerals would have different relative compo - 33/49/4/12/1. Samarskite sitions of the rare earths (Figure 3), rendering (RE,U,Th,Fe)(Nb,Ta,Ti) O , resembling corroboration difficult by other s—it was even 5 16 “black obsidian,” has wildly variable possible that a mineral specimen would be compositions; this very radioactive lacking one of the rare earths which would be sample from Jefferson County, CO, present in abundance in a sample from a differ - analyzes for (%) U/Th/Dy/Er/Yb/Lu ent geological site. Furthermore, different 10/10/3/3/6/1. researchers would use different recrystallization All mineral photographs in these conditions (concentration, temperature, etc.), figures are taken of specimens in the resulting in subtle composition differences and private collection of the authors; all different spectral appearances for the “same” specimens possessed lesser (<1%) element preparations. Announcements soon quantities of the remaining rare appeared of philipium, decipium, mosandrium, earths which are not listed. rogerium, glaucodymium, russium, 3a carolini - um, berzelium, 3c celtium, 3e denebium, dubhium, welsium, 3d terbium-II and terbium-III, neo- holmium and neo-erbium, 3d thulium-II and thulium-III, 3e etc., etc. Known rare earths with samarskite (Figure 3); Er ␣ and Er ␤ in erbium; invention of the spectroscope, no less than confusing manifold spectra led hasty chemists, Tm ␣ and Tm ␤ in thulium; Sm ␣ and Sm ␤ in ninety-four (94) spurious claims were made for eager to win the glory of new discoveries, to samarium; and Di ␣, Di ␤, Di ␥, Di ␦, Di ⑀, Di ␨, new rare earths! 3 announce even more complex mixtures, e.g., Di ␩, Di ␽, and Di ␫ in didymium! 3a In fact, during Sometimes, in the hands of two indepen - X␣, X␤, X␥, X␦, X⑀, X␨, X␩, in “element X” from the half century after Bunsen and Kirchhoff’s dent researchers, different but “similar” ele -

WINTER 2015 /THE HEXAGON 73 t l h i g i s h

t f e i g r s u . r

T e

h i e s e t M a h

a r r e o a n t

s h r m

a e a s

n i

m e n ( d a w e e e r r t i r t a h t , h

h l y b B m

(

5 d s c e e a r t o f o 6 i u a d - o d m d / c r z m r 0

e o o i e n p l . r l p

i , 4 o o o

n t x i i / h t s r u t

l 1

i e u l e e f m t u . d l o y r i 0 e s o e

r

b / c f H s K t w i m b d n 0 T i K t r y e s l e r

u

. a t e

p h e

a i 2 ( o e t e a

b l t r r % a e h n s n u / i r e e o n y 2

o r o

s e

i

t m n ) o a

k i . m c s

III i

t u 0 n t l

r u

t e i o h i i t h d t o e n / p

p n t z f o e 0 e t d e r

e e i u a e

h

, t t .

, v

i d (

h r h r 1 s a p e t m

p S i a a

u h

e i

/ p c h 7 D F F F t u

h 3 n s l t

p a e e h p

o e i i i

b 4 r . a o e s

h i a l g g g s e e 0 d s p c l d

w . r

b a u u u

a r i a

p s o /

l T d

y n n a t 0 m b e e s r r r r s h l

i m e h d o c

a ,

e e e y

. h n

o c u 1 p l w o r

i e Z n

a a r r i a 6 5 4 n W

n n l . s u c

y

l o e t a r r . . . e g

y i d u e e

d

m s f y R n T i

C M e

i l

a s t r m n y s y

w b t d l

a i u e

v r r s h c

g e , e s e i o , l L i

y y b a o o o

s l e s a f h ) x b n a l

s o a

l a c , l l s

f e o e

t h o u c l d t a

o ) r e c / ( : y d i w a c a r , C y

e n Y t v h i z n

o

S

d l y n

i i d h e u e

t ,

s e g e p s t c R g

y h e i r l r

/ e i r s

g h c p e o l P l e m g o a p a , o u E e

a l m

e d u f h t o a n r y l ( s v a

) r r h i f

R / i p i r

s r -

u e e i

l m N l o a e

i s s a o r

r i n

E m i m n m r n e i o m i a p

o d o t o c m , s c f

g s s h T n

n p / h i n

t , e o ( c e

B S i

n m o a o - o a h n w

R t u w

r o m d

a o e e s r r l y z ) t d s n o

E e c r

i t i d i u P i i p s a ( c t l

a y a s r t r t s ) s t t 2 r b h O

s e r n t e e b n m l ( e a o a y r

o l

s 8 e

h N t d n o u t s a l r i 4 c t n

c n i i / s

c h a . l i p f e o o

u i u 5 , e i

4 d a O

l s t

g

“ s n n n i t s c

l n t

w 2 m d )— A

M t h l s u i i h s o g d s s a e o /

n

r .

a s l l e i 4 e

r s r s s n c a ( l ( s i d (

( t . r e

a s

e u s /

S o “ s A “ r F g

n a v o 1 e d S

( . c m c g r a a i u r n s % i m r f e f . t 3 i a h e O e g e t t

e r e e e s s e e p i B o ) / r e

i d u ) d n e

d n a 2

4 , m w e c a n l

a

a r d Y p

p ) o t r r r g a . P

r a a b ) s

2 m e

e s

g ” r

/ . a r

i b

e t z y

(

t t N k a

a n i t i T s w r O t x i a h e C c

m h s i i n 3 l i a

a M t t h d a l t a ; n n s e e i u e H h , r ) d

e ” m n m l e / e t c t

g l g n , o e

“ (

y S

,

o i h

a ) o m

”

l N n r f n s c d s a m 2 m s t e e s a n l i

a i m o ) h t e i a s F c e

a l y t v e d

c

n r o e n e l o /

r u ( e n c h o s 5 r m

e E e , c c l p u d F t x c t

p h R t , , e d l d r

u n a ” e

t

g o u h e y y a o d i e e

m f y b a b w i E e i e g n p n i r e i u r a / s r

m m e e n s n n r u , u y G b o i ) u — m t e o

d o t r .

m t d o ( e i r a

m y m

e t n i m t a

r p s d c l C

a u

u h p a n r o

e d t l m i w o

M

W i 5 i l

t ( e l m , h g b ( n b O

s

t n

1 g x e t

i i % . d r

“ 6 ) s— a c h

o s n i o y e e s t 4 i i

.

o t e i f g a ) u n n

r c g t t e e

( c ) h s o / l 1 . i o e l s m r

a

1

d r

s F t

t h a i Y D l l o r

K s F t e 8 g o

n r a e l b e l 2 d u t r t o

m

a e r a

/ i r f

f e o 8 d t e w a u n e o b i a G s / b e o

i

a s m h

u g t n 8 5

e r f c l a e i l m l “ u t f d e s s p o a f e t i d

u

a h b /

i b t

d g p e

h o e u t

t 7 n t n h t e f e a

/ t r

v i l

n w h h o i k l w o r D s s i / t

t g o g e s

o r d s e e a e s 1 M o

e a m

e a t i , n

l M n

p s a

g R y m i d y l

s t r h i n i

3 u f ) m n s e i g t n s l t s i d s i r m e

/ e i i i g i . u t s , w i o a a

o H m s o

s i v ” d h e

g v s

w c e t p g O u n b i m a i l i c m n v s s e ) h a a t y w d n t e h v n u o h e l l

h n a l r u h e m e e l b i t n m e a f

/ e e , e

m w o a t i , n t l e

n a a t b E i d r i

c d M v ” c s n e

o n

K r

s

c r n w x s

e y v t t s c m i d r e

” c i

a h a p

n h

d a e

s a u t i

o o n T

e / i

t a d ( r o i x o d s b e

t o s ( T

n g

s o n n u

l 1 a m s e s h r e h a w h t .

e

m n a y f r p e i l r

w c m y y a s r

s s s 8 d t t

t a i ’ r a s N t d x e k

i r ) a e y s t e a l s y f h

h e s

s e e p b d 7 s p . g y e h h i u

/ w

o

v o r

o t l 3

e s e s Y e r i e r d i w 7 r , i G

p o d o o c e i e l ) c o u o t b d t d b a n t f w e i n c

r i

3 ) b

h m e s p

h a i

d h d

l b a e i b r y t m i i y h i

d i o

• / u i d e t n s n a t u e h r e e y h n

l s a L a l - m p s m l i w

t y , y 1 a a

l c r s h e s

s

m c a m c e e e t o

u y e r w c m b

h e i . u n i

m a

e i e e i f i i o

a h r 5 p s a s

r e a o s u i s n u d o s i r l e l i n t . ,

i

i e r u c v H i u c i a

o n

a a n

a s e c n i e t m m a i

g r u t i o d s— p t t e m

n , D h r l

m l n h

m r m t t n w

h 2 l s f s u a c t a m n a n d m h i a n R s e i u g

O

e o a

s n s f e t a e a o t r

h e m a h

a f o

f u

i s e p l

l . l i d n a i , l l i m r a t 1 c

t

f l

c r r

v l o a t i i x r a l r s d p u e o s h u , f t

t t i a I o e o y

t n o i

m s s t e r j n n f i e e t p b r

d h u r s a o m r e e t u t

n i

n

o t r o

u d r p n e e

i v u a e e h o

d w e n l m a

f h e p m r t b g . n e t

w v l

f u e

t .

c

t c u e o r i i t o w d

r M d t e L a

s r

/ e t e d e n t o e d l n

t e b

i i d h s l a e e w e f

a

d r

i e a o s n r e y n o

f m

i

b t t a 1 a l e o t r g w , s f e e o i s f t r r

e p p s s x

m i t o m w

t i n b e f l e

l s h a t a s t n c a s b h t o w r : d i t e p p a i b h h .

e r i

e d e r

a l t

r e s e i

e a n t e r u w ) r e e

a o t u f h u h t d s e l

o c n e h e r

t e h l n o a

e .

d m a

s l s r e i h i m p

( o

i , i r n d n e i n c i h m s

c t f n y l F i r e B e t

t n o e l a t s o t e r l d

t c b u a t , h e t

h e t a e s i e i i h x

g o c i e t e m r c x o r

h i b n s o e g t s l u o l r t r a t

h o i

n o e t i

y

a i e d a a f

u ’ e s e a n m s a u n a c g , h d t t n s s f o r c e i v g e t

d

r m t e u

h d n i m a s t n d e t i r

d i

o l o e r

s r e n n n u o u p

s p r e O y h l c

d d e s o e

e A m

i w r t p l n v s g b i , s o a r r m

i v i e o e c e t h i

t q i

f t z n e t e l i . n

u y c s n . t d l i i a e w c d

d s e i i n

e g h e u l g n m e h d g t e ,

c

d

A W m t u i y s r n a v

i e e z a a d e “ a

l o

a

e s O

5 n i

c w i t u d a t t a b u w l n r e f c t - d M

. e s m u t e

x u s h W c t o

a f e

a j d c o n e l f ( d p n s t h i a

o l

H e e s a e a r l e f l

i d “ s ( s s e f e i r a w a c e e e

g s

e e r s r 6 o s x s s f F i

b s

R e a e

e d e e

m

o n g i s c d , U l s a

c

a

u i e y

m 3 s r a s s

r

s o E f n t

d i g h r i r 5 i

i m h ) b i e b u c r u t

t r . g w o a c n e f -

t e a m f ” 3 S u t t t e h

o

a p a e i o a h t

l c

h u h

r t s T a p n u

= h

s . h r l l s o t l m c c i ( o c l

p

g

r e t e i u l e e 5 m c o C H w m 1 i e

e a h h s z e a e r i 2 r c h r

r p o

p m D 5 v e i t s

t e e 4 p , s o n l a c T e h a N n E i

a b t p i j s r

e a u

g o d t r ) o g l c s r

i e h o y

o

e n o t a m e h i e ,

r H q i n m

r g H

h b

c h g e l f m c e r l a m y f

t t a t e u

t n a l a a a a e

l t u o

e h

4 h U t a s h , E o f i e p n l o t e n l N r a a i i a

n r t r o l s e

e a z X e w r s o r y e a e

f e e r r n a t s i .

r n e d

t b O t y n

r l n

w c d p e

A l e

a s h l d f t s t

a

y l i v t g

o

e d h e d l 3 d a a o z

h i G a t e e t p n a e r c i

r a 4 v a m a i n i e n e i n n

s l i c s i f b a , a t O n s t e s f

-

f c

c t i a t w e o

t r y 5 n r w i a o m

e r h o o a o c a b i l

N i n a c i c g r n h

i r n v h t n

l e o b e e n r e i i a r

i h

i e s s n / g e n i o i e n n n c e d

z n W o t

q c r t m

s g

h g f t t i c e e t 1 f u g h o o t

) u n c

h

e

c r e . s

a s s r I e l t n e

o h e t D v N e i

e e h h n o m h d s t t e n p

d e i ( - f e r

. e e T p

C F

a i a

e l t a n q

a g s a i r R h t E s l g

u , e a g t e f e r

R i e i o u d t s a v e t a c n a i o n

a s e s r

o r q e l 2 e e n t l

i n r u . z a 0

i i a s i t e i A 1 5 n n l r o s l i 5 ) n g y e c - - , TOP RIGHT: Figure 7. Crookes moved to this house in 1880 at 7 Kensington Park Gardens in Notting Hill (N51° 30.69 W00° 12.16.) where he spent the remainder of his life. Crookes was never formally associated with any university; instead, he worked in his home and at the editor’s office of his The Chemical News . Figure 8. The laboratory inside Crookes home. It was here where terrestrial helium was first spectro - scopically verified. 1n At the end of the laboratory is his spiral Periodic Table, prepared to show his theory of an electrical oscillation phenomenon that created the elements out of a primordial material. Crookes’ imagination took him to many places, including spiritualism, which he seriously explored for a large portion of his life.

combination of double magnesium nitrates (RE)(NO 3)3l 3Mg(NO 3)2 and isomorphous bismuth nitrates. In this elaborate procedure, he separated the rare earth mixture into light and heavy fractions. Bismuth nitrate was extremely useful here, as its solubility lay between those of samarium and europium. The bismuth could be removed with hydrogen sul - fide, and then the remaining two fractions could be further separated and purified by employing double magnesium nitrate salts. By this method, Urbain was able to refute many of the spurious rare earth discoveries of others. 7 Charles James, professor at the University of New Hampshire and member of 〈⌾ ⌺’s Mu Chapter, 8 is credited 4 with developing the best and most efficient overall scheme for separating the rare earths. In his complex flow chart, he used a large variety of rare earth salts, including oxalates, bromates, sulfates, ethylsulfates, and double nitrate salts of the rare earth and mag - nesium, ammonium, sodium, bismuth, and nickel —each specific step carefully chosen after trying out all possible systems. Even with his grand achievement, he admitted that it was not perfect, warning the reader that there is simply “no quantitative method of separation of any of the rare earths.” 8

Crookes, phosphorescence spectroscopy, and the meta-elements —anticipating the concept of isotopes? The complexity of the rare earths and confusion in their separation could engender unusual ideas. The classic example was the hypothesis of “meta-ele - ments,” spawned in the imaginative mind of William Crookes during his spectroscopic study of yttrium. Crookes is perhaps best known for his invention of the “Crookes tube” in 1875, the original cathode ray tube which eventually led to the discovery of electrons in 1897 by Joseph John Thomson (1856 –1940). Crookes also

WINTER 2015 /THE HEXAGON 75 invented the radiometer, a popular scientific toy to this day. Another creation of his was the spinthariscope, which was popularized in the 1940s as the “Atomic Bomb Ring” displayed proudly by schoolboys who ordered them from breakfast cereal box advertisements. 1m Crookes split his activities between his home laboratory in east London (Figures 7 –9) and the offices of The Chemical News . He founded and served as the editor of this “bumptious, gos - sipy” 9 journal in which he recounted the daily chemical discoveries (including his own, of

I course) and other happenings in the industrial

I world and the professional societies. His

I research was well respected, and he was elect - ed a member of the Royal Society, of which he was president 1913 –1915. Another invention of Crookes was “phos - phorescence spectroscopy,” achieved by irradi - ating samples in his Crookes tube. 10 These spectra were more complex than the usual emission spectra, and he was able to detect variations with samples which otherwise Figure 9. The chemical portion of Crookes’ laboratory. Crookes applied his chemical and spectroscopic skills showed identical spectra in ordinary emission to the study of the rare earths. After radioactivity was discovered in 1896, he studied the radioactive spectroscopy. 7 He announced that “there were elements. probably eight constituents into which yttrium might be split,” 11 and he reported similar Others had doubts as to the usefulness of elled, at the conception of an element having behavior with samarium and gadolinium. the phosphorescence spectroscopy method. atoms of different weight though chemically Thus, he claimed, he had evidence for chemi - Boisbaudran 1b stated that variations would like - identical.” cally identical elements which differed in their ly to be simply due to impurities; and in fact he Although it is frequently mentioned that physical properties. He called these “meta-ele - reported that in an ultra pure sample of yttrium, Crookes “was the first to suggest the existence ments.” And what would cause a difference in he could not observe a phosphorescence spec - of isotopes,” 9 it must be remembered that any physical properties? Obviously, their atomic trum at all, but instead the usual emission spec - similarity between Crookes’ meta-elements weights, he concluded. trum. 7 Marignac 1o argued that since there was (based on a false interpretation of spectral data) This idea of meta-elements held appeal for no experiment to confirm the authenticity of and Soddy’s isotopes (securely founded on a some, particularly those in Great Britain, since meta-elements, the concept was useless. 7 wealth of radioactive and transmutation exper - the idea paralleled Prout’s hypothesis (William Clarification of the phosphorescence spectra imentation) is fortuitou s—although great cred - Prout, 1785 –1850) that all elements were built phenomenon came two decades later. In 1919 it must be given to Crookes’ spectral skill as well up of multiples of hydrogen. 7 Perhaps even a Urbain completed a thorough study showing as his vivid imagination. At his Nobel address better candidate for the universal simple sub - that trace amounts of impurities could drasti - in 1921 —“The Origin of the Conception of stanc e—called protyle 7—might be helium, first cally alter the phosphorescence spectra (antici - Isotopes,” 15 Soddy did not mention Crookes’ spectroscopically observed in the sun in 1868, 1n pating the use of dopants in modern phospho - work nor his meta-elements, but instead con - whose single spectral line (only one was known rs). Urbain could duplicate Crookes data by centrated on the research on radioactive ele - at that time) signaled its simple nature. By con - artificially prepared mixtures of the rare earths ments that provided the evidence for the con - trast, heavier elements, such as iron, exhibited a in the proper ratios. 13 Urbain also worked out cept of isotopes. 16 complex spectrum, consistent with a wide dis - procedures for the fractionation of double salts tribution of meta-elements. 7 Even some organ - of the rare earths (RE/Mg) to prepare pure sam - The last of the natural rare earths. The last ic chemists weighed in with their endorsement; ples of the rare earth s—and he extended naturally occurring rare earth discovered was Jean-Baptist Andre Dumas (1800 –1884) 1f sug - Boisbaudran’s work for yttrium to report that lutetium, in 1907. In The HEXAGON we have gested that elements might be unusually stable for all utterly pure samples of the rare earths, previously visited the convoluted story of this radicals, just as an organic molecule is built up the anomalous phosphorescent spectra ceased discovery. 1k Today the discovery of lutetium is of smaller organic radicals. 7 to exist. 13 credited to three chemists: the opportunistic Crookes expanded his hypothesis to include Utterly unfazed by Urbain’s criticisms, Urbain who published first (and prematurely), genesis of the elements themselves: a cooling Crookes took advantage of his position as pres - Welsbach who presented evidence that he had process of the protyle 7 in star s—he proposed ident of the Royal Society to announce in his discovered the element earlier, and James who the elements condensed into a statistical distri - 1914 President Address to the Royal Society 14 had the only pure sample of lutetium existing at bution of weights but with identical chemical that he had anticipated Soddy’s discovery of that time. Today all three scientists are consid - properties. Thus, while the measured atomic isotopes 1j which had just been announced: ered co-discoverers of lutetium. mass of calcium was 40, actually there might be “[Soddy’s] ‘isotopic’ elements occupy the same At the time of the discovery of lutetium, some 39, 38, and 41, 42 —or perhaps 39.9, 39.8 place in the Periodic Table. He has thus arrived, Urbain was claiming evidence of another ele - and 40.1, 40.2, and so on. 12 by a totally different path from the one I trav - ment beyond lutetium (atomic number 71),

76 THE HEXAGON/ WINTER 2015 which he called “celtium.” 1k However, his pre - conceived notion that the next element would be a rare earth was leading him astray (the next “REDISCOVERY” ARTICLES ARE NOW ON-LINE element, atomic number 72, was actually hafni - um 1k , which was not found in rare earth miner - All HEXAGON issues that include “Rediscovery” article s—a series which began in 200 0—are now als but instead in zircon 1k ). Whereas Urbain was on-line at: http://digital.library.unt.edu/explore/collections/HEXA/ claiming he was obtaining purer and purer samples of “celtium” (which he followed by These HEXAGON issues, as a group, are fully searchable and thus are amenable to scholarly magnetic susceptibility measurements 10 ), he research. One can search either for words, Boolean “OR” combinations, or for full phrases (by plac - was actually witnessing purer samples of ing in quotation marks). Not only the original “Rediscovery” articles may be accessed, but also cover lutetium, which others had already prepared. photographs by the authors and other auxiliary articles connected with the “Rediscovery” project. Additionally, the UNT Digital Library has separated out all these individual articles and placed Atomic numbers. By the turn of the century, the major question was: Just how many rare them in the “Scholarly Works” section. These articles may be located and perused at: earths did exist? Even at this late stage, spurious http://digital.library.unt.edu. At the top of the webpage, search for “James L. Marshal l” as “creator” rare earths were being reported; Crookes was and for convenience, “sort” by “Date Created (Oldest).” The “Scholarly Works” articles are not announcing “ionium” and “incognitum” (1906) searchable as a group, but only within each individual article. in his rare earth mixtures; 3f Urbain was stub - born with hi s“celtium” (1907), 3e and there was a smattering of other elements from Demarçay (1900; ⌺, ⌫, ⌬, ⍀, ⌰), Brauner (1900; thorium- ␣ and thorium- ␤), and Welsbach (1911; thulium 3f I, II, III), as well as a few lesser-knowns. References. 7. R. K. DeKosky, “Spectroscopy and the Brauner, professor of chemistry at the Elements in the Late Nineteenth Century: University of Prague (today’s Czech Republic), 1. J. L. and V. R. Marshall, The Hexagon of the Work of Sir William Crookes,” B. Journ. on the basis of the solubility trends of salts of Alpha Chi Sigma , (a) 2001 , 92(2) , 20 –22; Hist. Sci. , 1973 , 6(4) , 400 –423. the known rare earths, as well as the relatively (b) 2002 , 93(4) , 78 –81; (c) 2002 , 93(1) , 9 –11; large difference in the atomic masses of (d) 2003 , 94(1) , 3 –8; (e) 2003 , 94(2) , 19 –21; 8. C. James, Chem. News , 1908 , 97 , 205 –209. neodymium and samarium, in 1902 predicted (f) 2007 , 98(1) , 3 –7; (g) 2008 , 99(1) , 8 –11; 9. S. Kean, The Disappearing Spoon , 2010 , an element between the two. 3b Then in 1914 (h) 2008 , 99(3) , 42 –46; (i) 2010 , 101(3) , Little, Brown, and Company, 255 –259. Henry Gwyn Jeffreys Moseley (1887 –1915), 2010 2011 42 –47; (j) , 101(4) , 68 –71, 74; (k) , 10. J. F. Spencer, The Metals of the Rare Earths , with his X-ray studies, experimentally devel - 102(3) , 36 –41; (m) 2011 , 102(4) , 62-67; 1919 , Longmans, Green and Co. oped the concept of atomic numbers. 1i Moseley (n) 2012 , 103(2) , 20 –24; (o) 2014 , 104(3) , showed that celtium was spurious and that a 46 –51; (p) 2016 , 106(3) , 40 –45. 11. W. Crookes, Report of the British void lay between neodymium (element 60) and Association for the Advancement of 2. J. L. and V. R. Marshall, “Walking Tour of the samarium (element 62), just as Brauner had Science, 1886, (London, 1887). Elements,” in Rediscovery of the Elements , predicted. One would surmise that this would JMC Services, Denton, TX, ISBN 978-0-615- 12. W. Crookes, Chem. News , 1891 , 63 (6 quickly clarify the situation, because scientists 30795. March), 114. would know where to look —in crude prepara - 13. G. Urbain, Comptes rendus , 1908 , 147 , tions of neodymium and samarium —but 3. M. Fontani, M. Costa, M. V. Orna, The Lost 1472 –1474. instead it led to more confusion and con - Elements. The Periodic Table’s Shadow Side , tention, and element 61 was not found until 2015 , Oxford University Press; (a) 119 –127; 14. W. Crookes, Chem. News , 1914 , 110 , three decades later. (b) 175; (c) 192; (d) 202 –215; (e) 235; (11 Dec), 290; Proc. Roy. Soc. , 1915 , 91(625) , (f) 488 –490. 106 –119. In the next issue of The HEXAGON , 4. M. E. Weeks and H. M. Leicester, Discovery the search for element 61. 15. F. Soddy, “The Origin of the Concept of of the Elements , 7th ed., 1968 , 675 –684. Isotopes,” Nobel Lecture, December 12, 5. C. H. Evans, ed., Episodes from the History of 1922 , 371 –399, available at http://www.nobel Acknowledgment. the Rare Earth Elements , Kluwer Academic prize.org/nobel_prizes/chemistry/laureates/ Publishers, 1996 , (a) F. Szabadvary and C. 1921/soddy-lecture.html. The silent editor of these “Rediscovery” arti - Evans, “The 50 years following Mosander,” cles —Gerard R. Dobson, 1990 Kuebler 16. However, Soddy did mention elsewhere 55 –65; (b) E. Baumgartner, “Welsbach,” Awardee, who has been invaluable for count - that Crookes was the first to conceive of the 113 –128. less corrections and suggestions over the past idea that all atoms of an element might not 15 years —has in his possession, and on dis - 6. Delfontaine’s collaborator was Jacques- be identical in all respects: F. Soddy, J. Chem. play in his home, one of the large crystalliza - Louis Soret (1827 –1890) of Geneva, Soc. , Trans, 1919 , 115 , 1 –26. tion dishes that Charles James used in his rare Switzerland, who is also known for his earth studies. determination of the composition of ozone (ref 5a).

WINTER 2015 /THE HEXAGON 77