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The possibility of higher oxides of lanthanum
(USC Thesis Other)
The possibility of higher oxides of lanthanum
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Content
THE POSSIBILITY OF
HIGHER OXIDES OF LANTHANUM
A T h e s is
P r e s e n t e d t o
t h e F a c u l t y o f t h e D e p a rtm e n t o f C h e m is try
U n i v e r s i t y o f S o u th e rn C a l i f o r n i a
I n P a r t i a l F u l f i l l m e n t
o f t h e R e q u ire m e n ts f o r th e D egree
M a s te r o f S c ie n c e
by-
F ra n k J u l i u s S t e i n e b r e y , J r
Ju n e 1939
UMI Number: EP41510
All rights reserved
INFORMATION TO ALL USERS
The quality of this reproduction is dependent upon the quality of the copy submitted.
In the unlikely event that the author did not send a complete manuscript
and there are missing pages, these will be noted. Also, if material had to be removed,
a note will indicate the deletion.
I MI'
' O lsB ertaSon:' Psfafehfcsg
UMI EP41510
Published by ProQuest LLC (2014). Copyright in the Dissertation held by the Author.
Microform Edition © ProQuest LLC.
All rights reserved. This work is protected against
unauthorized copying under Title 17, United States Code
ProQuest LLC.
789 East Eisenhower Parkway
P.O. Box 1346
Ann Arbor, MI-48106 -1346
This thesis, written by
Frank J u liu s S tein eb rey, J r.
under the direction of h:i s . Faculty Committee,
and a p p r o v e d by all its m em bers, has been
presented to and accepted by the Council on
Graduate Study and Research in partial fulfill
m ent of the requ irem en ts fo r the d eg ree of
Master o f Science
Dean
Secretary
D ate Jun.e.__1.9.39.
Faculty C om m ittee
Chairman
TABLE OF CONTENTS
CHAPTER PAGE
I . INTRODUCTION................................ . ...................................... . 1
I I . THEORETICAL POSSIBILITY OF A HIGHER OXIDE. . . . 10
I I I . MATERIALS AND EQUIPMENT. .............................. . 15
IV . EXPERIMENTAL W O H EC ............................................................. 21
V. DISCUSSION AND CONCLUSIONS ...................................... 40
BIBLIOGRAPHY . . ........................................................................................ 44
LIST OF TABLES
TABLE PAGE
I . Summary o f D a ta fro m t h e E lm q u is t T h e s i s . . . . 5
I I . Summary o f E lm q u is t T h e s is D a ta , c o n t ................. 6
I I I . D a ta fro m J a n t s c h a n d W ie s e n b e rg e r R e p o rt . . . 8
IV IA . P r o p e r t i e s o f Some o f th e E le m e n ts ........................ 11
IV B. E l e c t r o n C o n f i g u r a t io n o f th e E le m e n ts .............. 11a
V. C o m p ariso n o f P la tin u m -R h o d iu m T herm ocouple
w i t h t h e B en d in g T e m p e ra tu re o f S e g a r Cones . 19
V I. I g n i t i o n o f Im pure L anthanum O xide i n a
P la tin u m V e s s e l o v e r a Gas F la m e .......................................... 22
V I I . I g n i t i o n o f P u re L a203 o v e r a Gas Flam e . . . . 24
V I I I . D a ta on E x p e rim e n t 3 . . . ............................................. 27
IX. D a ta on E x p e rim e n t 3 , c o n t ............................................. 29
X. D a ta on E x p e rim e n t 3 , c o n t ............................................. 29
X I. R e s u l t s O b ta in e d by H e a tin g Im pure L anthanum
Oxide i n a P l a ti n u m C r u c i b l e . ............................... 31
X I I . I g n i t i o n o f Im pure L anthanum Oxide i n C oors
P o r c e l a i n C r u c i b l e s b y Means o f a n A ssa y
F u r n a c e .................................................................................... 37
X I I I . I g n i t i o n o f Im pure L anthanum O xide i n C o o rs
P o r c e l a i n C r u c i b l e s ........................................................ 38
CHAPTER I
INTRODUCTION
The q u e s t i o n o f t h e p o s s i b i l i t y o f t h e f o r m a t io n o f a
h i g h e r o x id e o f la n th a n u m h a s b e e n a m a t t e r o f s p e c u l a t i o n
f o r many y e a r s . D e s p ite a c o n s i d e r a b l e am ount o f w ork done
on th e p ro b le m , no d e f i n i t e c o n c l u s i o n s have seem ed t o t a l l y
j u s t i f i e d . I n t h i s t h e s i s i t i s a t t e m p t e d t o show some o f
t h e f a c t o r s t h a t m ig h t have o b s c u re d t h e s o l u t i o n o f t h e
p ro b le m i n th e p a s t a s w e l l a s t o o b t a i n a d d i t i o n a l d a t a on
th e b e h a v i o r o f la n th a n u m o x id e a t h ig h t e m p e r a t u r e s .
As e a r l y a s 1861 a g a i n o f w e ig h t on p ro lo n g u e d
i g n i t i o n o f la n th a n u m o x id e w as n o t i c e d b y H erm ann.-1 - He
r e p o r t e d a n i n c r e a s e o f 0 .2 4 $ . I n 1869 Z s e h ie c h e 2 f a i l e d
t o v e r i f y th e w ork o f Herm ann a n d d e c id e d t h a t t h e p r e v i o u s
w ork was i n e r r o r . The i g n i t i o n t e m p e r a t u r e s a r e n o t known.
I n t h e b o o k I n o r g a n i c an d T h e o r e t i c a l C h e m is tr y b y
E . S . H e d g es^ t h e s t a te m e n t a p p e a r s t h a t la n th a n u m a n d
praseodym ium b o th have q u a d r i v a l e n t o x i d e s . He a d d s t h a t
h y d ro g e n p e r o x id e a d d ed t o a n a l k a l i n e s o l u t i o n o f la n th a n u m
g i v e s a compound o f th e fo rm u la L a(O H )3* 00E. No c o n f i r m a t i o n
■hi. H erm ann, J . P r . Chem. , 8 2 :3 8 5 , 1 8 6 1 .
%I. Z s c h ie s e h e , J . P r . Chem. . 1 0 7 :6 5 , 186 9 .
^ E r n e s t S . H e d g e s, C h a p te r s i n M odern I n o r g a n i c and
T h e o r e t i c a l C h e m is tr y . L ondon: E dw ard A rn o ld C o ., 1 9 3 3 .
p p . 7 8 -9 .
o f t h e f i r s t s t a te m e n t c o u ld be f o u n d . M e lik o f f a n d P i s s a r -
jow sky4 r e p o r t a p e r o x id e f o r m a t io n upon t h e a d d i t i o n o f
p o ta s s iu m h y d ro x id e a n d h y d ro g e n p e r o x id e t o a s o l u t i o n o f
la n th a n u m n i t r a t e . T hey a s s i g n e d i t th e f o r m u la LagOs*xHgO
o r (OH) gLafO O H ) an d s t a t e t h a t i t i s a t r u e h y d r a t e d p e r
o x i d e . On t r e a t m e n t o f th e g e l a t i n o u s p r e c i p i t a t e w i t h
d i l u t e s u l f u r i c a c i d o r c a r b o n i c a c i d , h y d ro g e n p e r o x id e i s
r e l e a s e d .
L anth anum p e r s u l f i d e LagS4 c a n be fo rm e d b y h e a t i n g
la n th a n u m s u l f a t e i n a s t r e a m o f h y d ro g e n s u l f i d e g a s a t a
te m p e r a tu r e o f 580 - 6000. Klemm, M e i s e l, a n d Vogel*-* c la im
t h a t t h e d i s u l f i d e s o f la n th a n u m an d c e riu m p ro v e t o be o f
a p o l y s u l f i d e n a t u r e .
I n 1927 t h e b e h a v i o r o f r a r e e a r t h o x id e s a t h ig h
t e m p e r a t u r e s w as s t u d i e d b y S a r v e r a n d B r in to n .® I t was
fo u n d t h a t a l l o f t h e o x id e s s t u d i e d showed a te n d e n c y t o
d e c r e a s e w ith h e a t i n g to a minimum w e ig h t and t h e n g r a d u a l l y
i n c r e a s e on s u b s e q u e n t i g n i t i o n s . On sa m p le s i g n i t e d a s
o f t e n a s 30 tim e s f o r a n e l a p s e d tim e o f 50 h o u r s , g a in s o f
0 .1 t o 0 .2 m i l l i g r a m s p e r i g n i t i o n w ere o b s e r v e d . I n a n
4 rP . M e lik o f f and L . P i s s a r j e w s k y , Z. A n o rg . Chem. .
2 1 :7 0 , 1 899.
Klemm, K. M e i s e l, an d H. TJ. V o g e l, Z. A n o rg .
A llg e m . Chem. . 1 9 0 :1 2 3 -1 4 4 , 193 0 .
6L . A. S a r v e r an d P . H. M .-P . B r i n t o n , J . Am. Chem.
S o c . , 4 9 :9 4 3 , 1 9 2 7 .
a tt e m p t t o v e r i f y th e p o s s i b i l i t y o f h i g h e r o x id e f o r m a t i o n ,
t h e i n v e s t i g a t o r s h e a t e d a s m a ll p o r c e l a i n b o a t o f g a d o lin iu m
o x id e and a " t a r e ” b o a t f o r 13 h o u r s a t 700° i n a c u r r e n t o f
h y d ro g e n i n a n e l e c t r i c c o m b u s tio n h u r n a c e . I t l o s t 0 .7 $
o f i t s w e ig h t w h ic h i t d i d n o t r e g a i n u p o n h e a t i n g f o r n in e
h o u r s i n a s tr e a m o f o x y g e n . A g a in o f 0 .3 $ r e s u l t e d upon
h e a t i n g t e n h o u rs a t 900° w i t h a M eker b u r n e r , a n d a n a d d i
t i o n a l i n c r e a s e o f 0..1% w as fo u n d b y h e a t i n g i n t h e e l e c t r i c
m u f f le f u r n a c e i n a s tr e a m o f d r y a i r f o r n in e h o u r s . Ten
h o u r s o f a d d e d i g n i t i o n h a d no e f f e c t , b u t , when th e sam ple
was a g a i n h e a t e d b y m eans o f th e M eker b u r n e r , i t g a in e d
0.1% a f t e r f o u r h o u r s . No a p p r e c i a b l e c o n ta m in a tio n o f t h e
sam ple w i t h s u l f u r fro m t h e i l l u m i n a t i n g g a s c o u ld be d e t e c
t e d . No d e f i n i t e c o n c l u s i o n w as d raw n .
P a g e l a n d B r i n t o n 7 i n 1929 c o u ld n o t o b t a i n an i n c r e a s e
o f w e ig h t g r e a t e r t h a n 0 .0 3 - 0 .0 6 $ on 0 . 5 - 1 . 4 gram sa m p le s o f
la n th a n u m , neodym ium , sam ariu m , g a d o lin iu m , a n d y t t e r b i u m b y
h e a t i n g t o t e m p e r a t u r e s a s h i g h a s 950° u n d e r p r e s s u r e s up
t o 405 p o u n d s o f p u re o x y g e n . I t w as c o n c lu d e d t h a t no
h i g h e r o x id e s c o u ld be fo rm ed u n d e r t h e s e c o n d i t i o n s .
A p p a r e n tly th e m o st e x t e n s i v e s tu d y o f th e f o r m a tio n
o f h i g h e r o x id e s o f la n th a n u m was made b y R u th E . E lm q u is t
d u r in g a s t u d y o f th e q u a n t i t a t i v e d e t e r m i n a t i o n o f la n th a n u m
7H. A rm in P a g e l a n d P . H. M *-P. B r i n t o n , I . Am. Chem.
S o c . . 5 1 :4 2 , 1 9 2 9 .
4
O
i n 1 9 3 0 . She p r e s e n t s d a t a w h ic h a p p e a r t o show t h e p r e
se n c e o f th e tw o h i g h e r o x id e s L a£05 an d LagO? on t h e b a s i s
o f a s e r i e s o f d e t e r m i n a t i o n s made i n an e l e c t r i c m u f f le
f u r n a c e . She was u n a b le to v e r i f y t h e r e s u l t s when a n y o t h e r
m ethod o f h e a t i n g was u s e d . Some o f t h e o t h e r d e t e r m i n a t i o n s
d i d show c o n s i d e r a b l e w e ig h t i n c r e a s e s , h o w e v e r, b u t th e
w e ig h t d e c r e a s e d a g a i n on s u b s e q u e n t i g n i t i o n s . D u rin g t h e
s u g n i f i c a n t e x p e r im e n ts no m eans o f t e m p e r a t u r e m easurem ent
was a v a i l a b l e . A sum m ary o f h e r w ork i s shown i n T a b le s I
an d H . P l a tin u m v e s s e l s w ere u s e d t h r o u g h o u t. The v a r i o u s
d e v i c e s u s e d f o r o b t a i n i n g th e r e q u i r e d t e m p e r a t u r e s w ere
T i r r i l l b u r n e r s , M eker b u r n e r s , b l a s t la m p s, a n e l e c t r i c
m u f f le f u r n a c e , a n d an e l e c t r i c c o m b u s tio n f u r n a c e w i t h a
s i l i c a t u b e . Where t e m p e r a t u r e s a r e r e c o r d e d i n t h e r e p o r t
t h e y w ere m e a su re d b y m eans o f a C ro m el-A lu m el th e r m o c o u p le .
A t one p o i n t she s u s p e c t e d t h a t t h e p la t i n u m c o n t a i n e r was
c h a n g in g w e i g h t, b u t on h e a t i n g a p la t i n u m b o a t f o r 15 h o u r s
a t 1200°C . i n t h e e l e c t r i c c o m b u s tio n f u r n a c e no ch an g e w as
i n d i c a t e d . H er t h e s i s i n d i c a t e s t h a t a lt h o u g h P a g e l a n d
B r i n t o n (1 9 2 9 )9 had e q u ip m e n t a v a i l a b l e f o r w ork a t 405
8R u th E . E lm q u i s t , "The Q u a n t i t a t i v e D e te r m in a tio n o f
L anth anum a n d Some P r o p e r t i e s o f I t s Com pounds," ( u n p u b lis h e d
D o c t o r ’ s d i s s e r t a t i o n , U n i v e r s i t y o f M in n e s o ta , 1 9 3 0 ).
See a l s o I . M. K o l t h o f f an d R. E lm q u i s t , J . Am. Chem.
S o c . . 5 3 :1 2 2 5 , 1 9 3 1 .
9L o c. c i t .
TABLE I
SUMMARY OF DATA FROM THE ELMQUIST THESIS
P e r c e n t
S t a r t i n g m a t e r i a l _________ H e a tin g m ethod T em perature Sample in c r e a s e Time ( h r s .)
a i r d r i e d Lag0 x 3 g a s "burners
------
.3097 g . 0 .3 9 32
» » r it tt it
------
.3524 0 .7 4 32
La (OH) 5 e l e c t r i c m u ffle w h ite h e a t .1651 1 0 .4 8 107
it it it tt it
.1648 1 0 .2 5 ■107
it f! It it it
.1655 1 0 .8 2 36
it It ft it tt
.2585 6 .9 9 36
H n i t r i c a c i d t r e a t .
If tt it n tt
7 .4 6 63
o f p r e v . sam ple
Lar>0x3
It If tt it
.1631 1 0 .6 1 36
M n i t r i c a c id t r e a t .
If tt tt tt tt
1 2 .1 4 63
o f p r e v . sam ple
La(N 03)3
It If it tt
.1576 19.73" 23
La (OH) 3
It tt tt tt
.1651 18.4 9 23
La(N03)3
If tt
1000-1090
.2509 5 .6 5 31
n sam ple r e h e a t e d
If tt it it it
0 .4 3 7
La(NOg)3
ft If It T t
.4075 8 .5 9 31
” sam ple r e h e a t e d
It tt It tt tt
0 .6 3 7
TABLE I I
SUMMARY OF ELMQUIST THESIS DATA
P l a ti n u m "boats and a n e l e c t r i c c o m b u s tio n f u r n a c e w ere u s e d .
S t a r t i n g M a t e r i a l T e m p e ra tu re N o te s _____________________________
7 0 0 -1 1 0 0 ° Ho c h a n g e s n o t e d i n s e v e r a l
r u n s
1100 I n s t r e a m o f oxygen I t g a in e d
1%, b u t l o s t a g a i n on
f u r t h e r i g n i t i o n
7 0 0 -1 1 5 0 No c h a n g e s
" No c h a n g e s i n s tr e a m o f oxyg en
7 0 0-120 0 No c h a n g e s i n a i r
tt A g a i n o f 0.9% i n oxygen was
l o s t on s u b s e q u e n t i g n i
t i o n
An a tt e m p t was made t o se e i f th e f o r m a t io n o f a
h i g h e r o x id e c o u ld b e c a t a l y z e d b y th e u s e o f c e riu m a s an
i m p u r i t y an d a l s o u s i n g c h l o r o p l a t i n i c a c i d . The c e riu m
r e s u l t e d i n a 0.63% i n c r e a s e b u t t h e p la t i n u m h a d no e f f e c t .
From t h i s i t i s a p p a r e n t t h a t p l a t i n u m v e s s e l s can be u s e d
w i t h o u t i n f l u e n c i n g th e f i n a l r e s u l t s b y c a t a l y t i c a c t i o n .
I n a f u r t h e r e x p e r im e n t, h e a t i n g a t 8 5 0 ° u n d e r t h r e e
a tm o s p h e re s p r e s s u r e o f o x y g en gave a n i n c r e a s e o f o n ly
0.53% .
(The t h e o r e t i c a l w e ig h t i n c r e a s e c o r r e s p o n d in g t o a
change t o L a205 i s 9.81% a n d f o r La^Oy i t i s 19.6 3% .)
L a20xg
»»
La(NOg) 3
tt
La (QH) 2
po u n d s o f o x ygen and 9 5 0 ° , t h e w o rk on la n th a n u m w as done a t
300 po unds a n d 5 0 0 ° . An i n c r e a s e o f o n ly 0 .0 2 $ o c c u r r e d i n
t h r e e h o u r s o f tim e .
J a n t s c h an d W ie s e n b e rg e r i n 1 9 3 2 -^ c o n c lu d e d t h a t
” th e e x i s t e n c e o f s u c h o x i d e s i s v e r y d u b i o u s . ” T hey f u r t h e r
o b s e r v e t h a t th e K o l t h o f f a n d E lm q u is t w o rk c a n n o t be r e
c o n c i l e d w i t h p r e v i o u s e x p e r i m e n t a l w o rk . I n a s e r i e s o f
21 d e t e r m i n a t i o n s m in o r i n c r e a s e s a n d d e c r e a s e s w ere n o te d
b u t no c h a n g e s e v e n a p p r o a c h in g th o s e o b t a i n e d b y E u th
E lm q u is t c o u ld be p ro d u c e d . T hey t h e r e f o r e c o n c lu d e d t h a t
th e w e ig h t o f la n th a n u m o x id e w as e s s e n t i a l l y c o n s t a n t an d
no h i g h e r o x id e was p r o b a b l e . A c o m p le te summary o f t h e
w ork i s shown i n T a b le I I I .
A r e c e n t s t u d y o f t h e w e ig h t v a r i a t i o n o f la n th a n u m
o x id e w as made b y B o r g e r d i n g H . He c o n c lu d e s t h a t t h e e f f e c t s
n o t i c e d b y E . E lm q u is t do n o t ta k e p la c e u n d e r o r d i n a r y
l a b o r a t o r y c o n d i t i o n s . He s t a t e s t h a t th e i g n i t i o n o f l a n
thanum o x a l a t e t o th e o x id e i s n o t a m ethod o f h i g h r e l i a
b i l i t y o r a c c u r a c y . He c la im s t h a t t h e u se o f a p u re n i t r o
gen a tm o s p h e re h a s no d e f i n i t e e f f e c t . I n h i s o p i n io n t h e
c a u se o f g a s a d s o r p t i o n on t h e s u r f a c t o f th e o x id e a p p e a r s
t o him t o be th e m o st l o g i c a l e x p l a n a t i o n .
1°G . J a n t s c h an d E . W ie s e n b e r g e r , M o n a t. f . Chem. .
6 0 : 1 - 7 , 1 9 3 2 .
1 1
A. J . B o r g e r d in g , ( u n p u b lis h e d M a s t e r ’ s t h e s i s ,
U n i v e r s i t y o f S o u th e r n C a l i f o r n i a , 1 9 3 4 ) .
8
TABLE I I I
DATA FROM JAUTSCH AND WIESENBERGER REPORT
Time Temp. M a t e r i a l H e a te d W eigh t o f Change i n change
H o n rs °C . o f v e s s e l i n LapO^ ( g .) w t . ( g .) i n w t.
28 1200 1 .0 1 7 0 0 .0 0 2 3 0 .2 3
IB
tt
1 .2 8 9 9 .0017 .1 3
qJL tt
0 .3 8 7 6 .0 0 0 0
o
o
•
12
tt
0 .5 0 8 2 .0 0 0 8 .1 5
10 1100 0 .5 4 0 9 .0 0 0 2 .0 4
10
tt
0 .4 8 6 5 .0 0 0 3 .0 6
10 1000 P l a t inum d r y 02 0 .5 6 8 2 .0 0 1 3 .2 3
10 1100
tt tt
0 .4 7 0 0 .0 0 0 3 .0 6
10 1000 P o r c e l a i n
it
0 .4 6 9 3 .0 0 0 2 .0 4
12
tt tt it
0 .4 4 3 1 .0 0 0 1 .0 2
10 1200 P la tin u m
tt
0 .3 6 9 5 - .0 0 1 5 - .4 1
18 1300
tt tt
0 .5 1 4 4 - .0 0 3 5 - .6 8
9ir
tt tt
d r y a i r 0 .4 3 3 4 - .0 0 0 2 - .0 5
91
ti tt tt
0 .3 2 2 5 - .00 0 1 - .0 3
9fc
1200
tt tt
0 .3 8 0 2 - .0 0 0 2 - .0 5
9 i
tt tt tt
0 .3 0 0 4 - .0 0 0 1 - .0 3
9*
1100
tt tt
0 .3 3 3 5 .0000 .0 0
20 1300
tt tt
0 .3 2 7 7 - .0 0 1 2 - .3 7
21
tt tt
M o is t
a i r
0 .3 4 3 0 - .0 0 1 8 - .5 2
22 1100
it
d r y Og 0 .3 7 1 3 .0 0 0 4
to
r-i
•
22
tt
Aluminum
tt
0 .3 6 2 9 .0000
o
o
•
o x id e
A s t u d y b y N ic h o ls a n d S t a n f o r d i n 193612 was made o f
h e a t c h a n g e s in d u c e d b y e x p o s in g r a r e e a r t h o x id e s t o a
s tr e a m o f h y d ro g e n w h ile a t e l e v a t e d t e m p e r a t u r e s . A bnorm al
e f f e c t s w ere o b t a i n e d f o r CeOg, anc3- ^ ^ 2 * '^lie te m p e r a
t u r e i n c r e a s e s w ere due to r e d u c t i o n o f t h e h i g h e r o x i d e s .
The h e a t i n g c u r v e s w ere a b o u t n o rm a l f o r LagOg, Gdg03 , a n d
NdgOg. T e m p e ra tu re s up t o 990° w ere u s e d .
The s e n s i t i v i t y o f t h i s m ethod o f d e te r m in in g t h e
p r e s e n c e o f a h i g h e r o x id e m ust n e c e s s a r i l y b e r a t h e r low
s i n c e i t i s d i f f i c u l t t o m easu re h i g h t e m p e r a t u r e s a c c u r a t e l y .
H ow ever, th e p raseo d y m iu m o x id e gave a n 8 0 ° r i s e on c o n v e r
s i o n so t h a t a h i g h e r o x id e s h o u ld have b e e n d e t e c t e d i f a n y
a p p r e c i a b l e am ount h a d b e e n fo rm e d .
M ost o f t h e w ork o f r e c e n t i n v e s t i g a t o r s seem s t o
f a v o r t h e t h e o r y t h a t t h e w e ig h t v a r i a t i o n s a r e due t o g a s
a d s o r p t i o n on t h e s u r f a c e o f th e o x i d e . The o n ly e v id e n c e
f o r h i g h e r o x id e f o r m a t io n i s t h a t o f R u th E lm q u i s t . Thus
i t a p p e a r s t h a t no d e f i n i t e c o n c l u s i o n s have b e e n r e a c h e d
up t o th e p r e s e n t t im e .
IP .
E . L . N ic h o ls a n d C. L . S t a n f o r d , J . O p t i c a l S o c . Am.
2 6 :9 1 - 9 8 , 1 9 3 6 . “ —
CHAPTER I I
THE THEORETICAL POSSIBILITY OF A HIGHER OXIDE
From a t h e o r e t i c a l s t a n d p o i n t t h e r e c an he h i g h e r
o x id e f o r m a t io n e i t h e r b y a n a c t u a l v a le n c e change o f t h e
la n th a n u m o r b y th e f o r m a t io n o f a p e r o x i d e . I n o r d e r t o
d e te r m in e w h e th e r a v a le n c e chang e i s p o s s i b l e , i t i s n e c e s
s a r y t o c o n s i d e r th e o r b i t a l e l e c t r o n a rra n g e m e n t o f th e
r a r e e a r t h e le m e n t s .
The r a r e e a r t h s i n g e n e r a l o c cu p y a r a t h e r u n iq u e
p o s i t i o n i n t h e p e r i o d i c p la c e m e n t o f th e e le m e n t s . T a b le
IV show s t h e o r b i t a l e l e c t r o n d i s t r i b u t i o n i n t h e v a r i o u s
e n e r g y l e v e l s o f t h e r a r e e a r t h e le m e n t s . S e v e r a l commoner
e le m e n ts have b e e n i n c l u d e d f o r c o m p a ris o n . I t w i l l be s e e n
t h a t w i t h t h e e x c e p t i o n o f l u t e c i u m t h e N4 l e v e l i s incom
p l e t e . D ata w h ic h i n d i c a t e s t h e s u c c e s s i v e f i l l i n g o f t h e
U4 l e v e l a s one c o n s i d e r s th e r a r e e a r t h s e le m e n ts i n o r d e r
o f i n c r e a s i n g a to m ic num ber h a s b e e n o b t a i n e d b y a s t u d y o f
t h e a to m ic vo lum es o f th e e le m e n t s . I n t r a v e l i n g down a
colum n i n t h e p e r i o d i c s y s te m th e a to m ic vo lu m es i n c r e a s e ,
b u t i n th e c a s e o f th e r a r e e a r t h e le m e n ts th e a to m ic v o lum es
d e c r e a s e w ith a n i n c r e a s e i n t h e i r a,tom ic num ber. T h is e f f e c t
i s so m e tim es c a l l e d t h e ’’l a n t h a n i d e c o n t r a c t i o n ” .
U nder t h e p r o p e r c o n d i t i o n s , c h a n g e s a re known t o
o c c u r t o t h e N4 l e v e l s o f c e riu m , p raseo d y m iu m , neodym ium .
11
TABLE IV A
PROPERTIES OF SOME OF THE ELEMENTS
M a g n e tic s u s c e p t .
E le m e n t A t. No. V a le n c e o f o x i d e . x l 0 “ 6 C o lo r
S candium 21 3 d . * 0 .0 1 8 c o l o r l e s s
I r o n 26 2 ,3
P-
2 0 .6 p a l e g r e e n
C opper 29 1 ,2
P-
3 .8 b lu e
Y ttr iu m 39 3
P .
0 .5 3 c o l o r l e s s
B ariu m 56 2 d . 0 .1 3 c o l o r l e s s
L anthanum 57 3 d . 0 .4 0 c o l o r l e s s
C erium 58 3 ,4
P*
0 .3 9 o ra n g e
P raseo dym ium 59 3 ,4
P*
1 5 .6 p a l e g r e e n
Neodymium 60 3 ,4
P.
30.: 3 r e d - v i o l e t
I l l i n i u m 61 3?
------ ------
Sam arium 62 2 ,3
P .
6 .0 2 t o p a z y e llo w
E uro pium 63 2 ,3
P*
3 0 .0 ? p a le r o s e
G a d o lin iu m 64 3
P«
1 3 0 .1 c o l o r l e s s
T erb iu m 65 3 ,4
P*
2 0 0 .0 ? r o s e
D y sp ro siu m 66 3
P-
2 2 9 .0 g r e e n
Holmium 67 3
P-
2 4 3 .0 r o s e
E rb iu m 68 3
P*
1 8 9 .1 d a r k r o s e
T h u liu m 69 3
------
b l u e - g r e e n
Y tte r b iu m 70 2 , 3
P»
3 8 .0 c o l o r l e s s
L u te c iu m 71 3 c o l o r l e s s
* d . = d ia m a g n e tic ; p . * p a r a m a g n e tic .
1 1a
T a b le IV B
E l e c t r o n C o n f i g u r a t i o n o f E le m e n ts I*5
E le m e n t E l e c t r o n s i n t h e O r b i t s
K
S i
S2
5 l
m2 m3
N1 n 2
H
O
f t
to
f t
° 2 ° 3
P
S candium 2 2 6 2 6 I 2
I r o n 2 2 6 2 6 6 2
C opper
2 2 6 2 6 10 1
Y ttr iu m
2 2 6 2 6 10 2 6 1 - 2
B arium
2 2 6 2 6 10 2 )6 10 - 2 6
m m
:2
L anthanum 2 2 6 2 6 10 2 6 10 - 2 6 1 2
C erium 2 2 6 2 6 10 2 6 10 1 2 B 1 2
P r a s eodymium 2 2 6 2 6 10 2 6 10
2 2 6 1
2
Neodymium 2 2 6 2 6 10 2 6 10 3 2 6 1 2
I l l i n i u m
2 2 6 2 6 10 2 6 10 4 2 6 1 2
Sam arium
2 2 6 2 6 10 2 6 10 5 2 6 1 2
E uropium
2 2 6 2 6 10 2 6 10 6 2 6 1 2
G a d o lin iu m
2 2 6 2 6 10 2 6 10 7 2 6 1 2
T erbium
2 2 6 2 6 10 2 6 10
8 2 6 1 2
D y sp ro siu m
2 2 6 2
6 10 2 6 10 9 2 6 1 2
Holmium
2 2 6 2 6 10 2 6 10
10 2 6 1 2
E rbium
2 2 6 2 6 10 2 6 10 11 2 6 1 2
T h u liu m
2 2 6 2 6 10 2 6 10 12 2 6 1 2
Y tte r b iu m
2 2 6 2
6 10 2 6 10
13 2 6 1 2
L u te c iu m
2 2 6 2 6 10 2 6 10 14 2 6 1 2
13 C o ndensed fro m " I n t r o d u c t i o n t o M odern P h y s i c s 1 1 b y
P . K* H ic h tm y e r , M cG raw -H ill Book Co* , New Y ork , 1 9 3 4 .
1-2
sam ariu m , e u ro p iu m , te r b i u m , an d y t t e r b i u m . O x id es o f t h e
f o r m u la s CeOg, P rO g, P r g O ^ , N d ^ ^ , a n d T b ^ ? a r e known.
C erium fo rm s q u a d r i v a l e n t com pounds a n d e u ro p iu m fo rm s d i
v a l e n t com pounds. L an thanum c o n t a i n s no e l e c t r o n s i n t h e
N4 e n e r g y l e v e l a n d so m u st be c o n s i d e r e d more s t a b l e t h a n
a n y o f th e o t h e r r a r e e a r t h e l e m e n t s . One w ould n o t e x p e c t
t o f i n d v a l e n c i e s o t h e r t h a n t h r e e f o r t h i s e le m e n t. T h is
c o n c l u s i o n i s s t r o n g l y s u p p o r te d by th e f a c t t h a t la n th a n u m
i s n e i t h e r c o lo r e d n o r p a ra m a g n e tic w h e re a s th e o t h e r r a r e
e a r t h e le m e n ts a r e a l l e x c e p t i o n a l l y p a r a m a g n e tic , a n d w ith
th e e x c e p t i o n o f g a d o lin iu m , y t t e r b i u m , an d l u t e c i u m a r e
c o l o r e d . C o lo r m ust be r e c o g n i z e d a s a n im p o r ta n t i n d i c a t i o n
o f th e p r e s e n c e o f in c o m p le te s u b - v a l e n c y e l e c t r o n o r b i t s
a n d o f p o s s i b l e m u l t i - v a l e n c y . C o n v e r s e ly , th e a b s e n c e o f
c o l o r i n d i c a t e s t h a t t h e e le m e n t p r o b a b l y h a s o n ly one v a l e n c y
s t a t e . I t i s b e l i e v e d t h a t th e su b d u ed n a t u r e o f t h e c o l o r s
o f t h e r a r e e a r t h s i s due t o t h e s c r e e n i n g e f f e c t o f t h e
0 o r b i t e l e c t r o n s b e tw e e n th e i n n e r N o r b i t and th e P v a le n c e
e l e c t r o n s . T h is s c r e e n i n g e f f e c t w o u ld a l s o e x p l a i n why
v a r i a b l e v a le n c e i s n o t more common i n t h e r a r e e a r t h g r o u p .
I n e le m e n ts su ch a s c o p p e r , i r o n , chrom ium , e t c . th e u n s t a b l e
e l e c t r o n s a r e n o t s c r e e n e d , so t h a t t h e f u l l e f f e c t o f t h e s e
e l e c t r o n s on th e v a le n c e i s f o u n d .
A c c o rd in g t o a t h e o r y d e v e lo p e d b y F e rm i1^ no atom
h a v in g an a to m ic num ber l e s s t h a n 55 s h o u ld be a b le t o hav e
14E . F e rm i, N a t u r e , 1 2 1 :5 0 2 , 1 9 2 8 .
13
s t a b l e o r b i t a l e l e c t r o n s w i t h a z im u th a l quantum num b ers o f
f o u r . L anthanu m h a s a n a to m ic num ber o f 57 an d c o u ld p o s
s i b l y a d d a n e l e c t r o n t o t h i s l e v e l . How ever t h e o n ly
e l e c t r o n f r e e t o s h i f t i n la n th a n u m i s th e s i n g l e O3 e l e c
t r o n . I f i t s h i f t e d la n th a n u m w ould have a v a le n c e o f tw o .
A p p a r e n t l y t h e p o s s i b i l i t y o f a tw o v a l e n c y h a s b e e n c o n
f i r m e d , a s M eggers a n d W h e e le r15 r e p o r t th e e x i s t e n c e o f
l i n e s i n th e a r c sp ecru m o f la n th a n u m o x id e a s c r i b e d to a
d ia to m ic m o le c u le o f la n th a n u m w i t h o x yg en (fo rm u la L a O ). No
m y seem s open f o r t h e f o r m a t io n o f a h i g h e r v a le n c y t h a n
t h r e e f o r la n th a n u m a lt h o u g h a lo w e r v a le n c e i s p r o v id e d f o r
b y th e t h e o r y .
The f o r m a t io n o f a p e r o x id e o f la n th a n u m d o e s n o t
a p p e a r v e r y p r o b a b l e . A lth o u g h b a riu m , t h e e le m e n t j u s t
b e lo w la n th a n u m i n a to m ic n u m b er, d o e s fo rm a p e r o x i d e , i t
i s r a t h e r u n l i k e l y t h a t a t r i v a l e n t e le m e n t w o u ld fo rm o n e .
H ow ever, i n c a s e one w ere fo rm e d , i t m ig h t p ro v e t o be o f
an i l l u s i v e n a t u r e s in c e b a riu m p e r o x id e i s n o t fo rm e d a t
t e m p e r a t u r e s much b e lo w 500°C . a n d decom poses a g a i n a t
t e m p e r a t u r e s ago ve 8 0 0 ° . (The e x a c t t e m p e r a t u r e s o f fo rm a
t i o n a n d d e c o m p o s itio n d e p e n d on t h e p r e s s u r e . ) The l a n
th an u m p e r o x i d e , a ssu m in g one c o u ld be fo rm e d , m ig h t be
fo rm ed o n ly i n a v e r y n a rro w te m p e r a tu r e r a n g e . As was
15
Wm. F . M eggers and Jo h n A. W h e e le r, B u r . S ta n d a r d s
£ • R e s e a r c h . 6 :2 3 9 - 2 7 5 , 1 9 3 1 .
14
p o i n t e d o u t i n t h e i n t r o d u c t i o n , la n th a n u m w i l l fo rm a p o l y
s u l f i d e and a t r u e h y d r a t e d p e r o x i d e . I t w o u ld be e x p e c te d
t h a t t h e p e r o x id e w o u ld decom pose e a s i l y on h e a t i n g , s i n c e
i t i s fo rm ed i n w a t e r s o l u t i o n b y th e a d d i t i o n o f h y d ro g e n
p e r o x id e to a n a l k a l i n e s o l u t i o n o f la n th a n u m a n d i t i s d e
com posed e v e n b y a n a c i d a s weak a s c a rb o n ic a c i d . I t w ould
a p p e a r t h e n t h a t i t i s im p ro b a b le t h a t a h i g h e r o x id e can
be fo rm ed and t h a t th e w e ig h t i n c o n s i s t e n c i e s a r e more l i k e
l y to be due t o g a s a b s o r p t i o n o r some o t h e r e f f e c t o f t h a t
n a t u r e . T h is e x p l a n a t i o n h a s b e e n o f f e r e d b y s e v e r a l o t h e r
i n v e s t i g a t o r s .
CHAPTER I I I
MATERIALS AND EQUIPMENT
Two sa m p le s o f la n th a n u m w ere p r o v i d e d b y D o c to r P a u l
H. M .-P . B r i n t o n . The one w h ic h w i l l be d e s i g n a t e d a s p u re
la n th a n u m o x id e i n t h i s t h e s i s was a sa m p le o f h i g h e s t
p u r i t y s e s q u i o x i d e w h ic h h ad b e e n u s e d p r e v i o u s l y i n s e v e r a l
r e s e a r c h p ro b le m s . I t was u s e d w i t h o u t f u r t h e r t r e a t m e n t .
The se c o n d sam ple w h ic h w i l l b e i d e n t i f i e d b y th e t i t l e o f
im pure la n th a n u m o x id e was o b t a i n e d i n t h e fo rm o f t h e o x a
l a t e a n d c o n t a i n e d c e riu m p raseo d y m iu m , a n d neodymium a s
i m p u r i t i e s . The sam ple w as t r e a t e d a s o u t l i n e d b e lo w b e f o r e
u s e .
The im pure o x a l a t e was p l a c e d i n a t h r e e in c h p o r c e
l a i n e v a p o r a t i n g d is h a n d w as i g n i t e d a t t h e maximum te m p e r a
t u r e o f a F i s h e r b u r n e r . T w e n ty - th r e e gram s o f b ro w n is h
c o l o r e d o x id e w as o b t a i n e d . The o x id e was t h e n d i s s o l v e d
i n 33 m l. o f c o n c e n t r a t e d h y d r o c h l o r i c a c i d a n d d i l u t e d u n t i l
one m i l l i l i t e r c o n ta in e d a b o u t 53n m i l l i g r a m s o f la n th a n u m
o x i d e . The s o l u t i o n was a l i g h t g r e e n i n c o l o r . The a b s o r p
t i o n s p e c t r a i n d i c a t e d th e p r e s e n c e o f some neodym ium a n d
p raseo d y m iu m . T h is s t o c k s o l u t i o n o f la n th a n u m c h l o r i d e w as
c o n v e r t e d t o t h e o x id e b y t h e m ethod b elo w a s i t was n e e d e d .
S in c e p raseo d y m iu m a n d neodymium a r e p r e s e n t i t i s p o s s i b l e
t h a t th e sam ple c o n t a i n s c e riu m . A c c o rd in g t o P a g e l and
16
B r i n t o n (1 9 2 3 )16 c e riu m c a t a l y z e s t h e f o r m a t i o n o f a h i g h e r
o x id e o f p raseo d y m iu m w h ile la n th a n u m a n d neodymium h a v e a
s u p p r e s s i n g e f f e c t . The t r a c e s o f i m p u r i t i e s w ould be e x
p e c t e d t o ch an g e t h e r a t e o f h i g h e r o x id e f o r m a t i o n b u t n o t
t o p r e v e n t i t . The im pure sam ple was t h e r e f o r e u s e d t o
d e v e lo p te c h n iq u e a n d t o d e te r m in e th e a p p ro x im a te c h a n g e s
t o be e x p e c te d , w h ile t h e p u re sam ple o f t h e o x id e w as r e
s e r v e d f o r t h e c o n f i r m a t i o n o f o b s e r v a t i o n s made on t h e
im pure o x id e w here n e c e s s a r y .
To p r e p a r e t h e im pure o x i d e , t h r e e v o lu m e s o f t h e
la n th a n u m c h l o r i d e s o l u t i o n w ere h e a t e d a lm o s t to b o i l i n g ,
a n d one volum e o f p u r e , c o l d , s a t u r a t e d o x a l i c a c i d s o l u t i o n
w as a d d e d s l o w l y w i t h c o n s t a n t s t i r r i n g . The h e a t i n g a n d
s t i r r i n g w e re c o n ti n u e d f o r one h o u r and t h e n t h e s o l u t i o n
w as s e t a s i d e o v e r n i g h t . Whatman § 40 f i l t e r p a p e r was u s e d .
The p r e c i p i t a t e o f la n th a n u m o x a l a t e w as w ashed w i t h a one
t o t e n d i l u t i o n o f s a t u r a t e d o x a l i c a c i d u n t i l a d ro p o f th e
was l i q u i d gave no c l o u d i n e s s w i t h a d ro p o f s i l v e r n i t r a t e
s o l u t i o n s t r o n g l y a c i d i f i e d w i t h n i t r i c a c i d . The p r e c i p i
t a t e was n e x t c a r e f u l l y i g n i t e d t o th e o x id e and f i n a l l y
h e a t e d a t a t e m p e r a t u r e 800 t o 900° t o c o n s t a n t w e ig h t, a s
S a r v e r a n d B r i n t o n 17 h a d p r e v i o u s l y fo u n d t h a t t h e o x id e
• ^ P a g e l a n d B r i n t o n , 1 . Am. Chem. S o c . . 4 5 :1 4 6 0 - 5 , 1 9 2 5 .
1 7 L o c . c i t .
17
was p e r f e c t l y c o n s t a n t i n w e ig h t a t t h i s te m p e r a tu r e a l t h o u g h
b e in g 0.15% to o h e a v y on a b a s i s o f t h e a c t u a l la n th a n u m
c o n te n t a s fo u n d b y a c a r e f u l a n a l y s i s .
S e v e r a l m eth o d s o f o b t a i n i n g a h ig h t e m p e r a tu r e w ere
u s e d . D e s p ite t h e d a n g e r o f s u l f u r c o n ta m i n a ti o n a s p o i n t e d
o u t b y S a r v e r an d Brinton-*-^ a g as flam e was u s e d d u r i n g th e
f i r s t i g n i t i o n s s in c e i t w as hoped t h a t b y u se o f a h e a t
r e f l e c t o r a n d s e c o n d a ry a i r w i t h th e b u r n e r a s u f f i c i e n t l y
h ig h te m p e r a t u r e w ould be a t t a i n e d t o p r e v e n t t h e f o r m a t io n
o f la n th a n u m s u l f a t e . (L a g (804)3 ^-s c o m p l e t e l y decom posed
a t a t e m p e r a t u r e o f 1 1 5 0 ° .) A lso th e C a l i f o r n i a n a t u r a l
g a s i s r a t h e r low i n s u l f u r . I n s t e a d o f t h e sa m p le s g a i n i n g
w e ig h t a s t h e y w ould due to s u l f u r c o n ta m i n a ti o n t h e y l o s t
d u r in g a l l o f t h e g a s i g n i t i o n s i n p l a t i n u m . T u b u la r e l e c
t r i c c o m b u s tio n f u r n a c e s w ere t r i e d b u t due t o p r e v i o u s u se
t h e maximum t e m p e r a t u r e s o f t h e s e w e re a b o u t 1000°G . A
s i l l i m a n i t e tu b e was u s e d . I n l a t e r d e t e r m i n a t i o n s m u f f le
ty p e a s s a y f u r n a c e s w ere u s e d . T hey a r e c a p a b le o f p r o d u c in g
t e m p e r a t u r e s up t o 1500°C . u n d e r f a v o r a b l e c o n d i t i o n s . An
" A l f r a x ” c e ra m ic r i n g h a s b e e n t r i e d a s a h e a t r e f l e c t o r on
some o f th e w o rk . T e m p e ra tu re s above 1 100 ° c a n be o b t a i n e d
w i t h a new ty p e D 'ish er b u r n e r and t h i s c e ra m ic r i n g , u s i n g
s e c o n d a r y a i r .
The o x id e w as h e a t e d i n c r u c i b l e s o f p l a t i n u m , p o r c e l a i n ,
a n d A l f r a x . C oors p o r c e l a i n b o a t s w ere e n t i r e l y s a t i s f a c t o r y
1 7 L o c . c i t .
18
a t t e m p e r a t u r e s up t o a t l e a s t 1050° C e n t i g r a d e .
The b a la n c e u s e d w as a C h r i s t i a n B e c k e r C h a in o m a tic
r e a d i n g t o o n e - t e n t h o f a m i l l i g r a m . The w e i g h ts a n d a
s e c t i o n o f th e c h a in w ere c a l i b r a t e d . R e s u l t s a r e r e p r o
d u c ib l e t o a t e n t h o f a m i l l i g r a m . A s e m i- m ic r o b a la n c e
s e n s i t i v e t o 0 .0 2 m i l l i g r a m s was t r i e d b u t p ro v e d t o . b e
u n s a t i s f a c t o r y due to m o is tu r e a b s o r p t i o n d u r i n g t h e w e ig h
in g o p e r a t i o n .
T e m p e ra tu re m e a su re m e n ts w e re f i r s t made b y m eans o f
a p l a t i n u m a n d p la tin u m - r h o d iu m (8 7 $ -1 3 $ ) th e r m o c o u p le . The
e l e c t r o m o t i v e f o r c e p ro d u c e d w as r e a d b y m eans o f a L e e d s
a n d N o r th ru p S tu d e n t P o t e n t i o m e t e r a n d a s s o c i a t e d e q u ip m e n t.
To be s u r e t h a t t h e i n s t r u m e n t w as w o rk in g p r o p e r l y , i t w as
c h e c k e d a g a i n s t S e g a r p y r o m e t r ic c o n e s a s shovm. i n T a b le V.
The e . m . f . - t e m p e r a t u r e d a t a fro m t h e 2 1 s t e d i t i o n o f th e
"H andbook o f C h e m is try a n d P h y s i c s " w e re t h e n u s e d . The
i n s t r u m e n t w as u n a b le t o s t a n d t h e h ig h t e m p e r a t u r e u s e d i n
some o f t h e w ork a n d t h e g u a rd tu b e f i n a l l y c r a c k e d . L a t e r
a H ichrom e an d A lum el th e rm o c o u p le w as made f o r c o n t r o l o f
lo w e r t e m p e r a t u r e s d u r i n g a t t e m p t s t o o b t a i n a c o n s t a n t
w e ig h t o x i d e . A T r i p l e t t m e te r h a v in g a f u l l s c a l e d e f l e c
t i o n o f 33 m i l l i v o l t s w as u s e d .
Two o t h e r t e m p e r a t u r e m easu rem en t d e v i c e s w ere u s e d ,
b o t h o f w h ic h w ere d e s ig n e d and b u i l t s p e c i a l l y f o r t h i s
w o rk . The f i r s t w as a s i m p l i f i e d ty p e o f o p t i c a l p y ro m e te r
19
TABLE V
COMPARISON OP PLATINUM-RHODIBM THERMOCOUPLE
WITH THE BENDING TEMPERATURE OF SEGAR CONES
C a l c u l a t e d
S e g a r No. T e m p e ra tu re P o t e n t i o m e t e r Room Temp. Temp.
012* 875° 0 .0 0 9 1 7 v o l t 22° C. 903°
07 1010 0 .0 1 0 6 8 24 1017
04 1070 0 .0 1 1 6 0 24 1085
8 1290 0 .0 1 2 2 0 25 1130*
10 1330 0 .0 1 2 2 0 26 1130*
*The p y ro m e te r w as u n r e l i a b l e above 1100° 0 . R e a d in g s
up t o 1 4 .4 5 m i l l i v o l t s c o r r e s p o n d i n g t o a t e m p e r a tu r e o f
1 2 8 5 ° hav e b e e n o b t a i n e d . The c a u se o f e r r a t i c a c t i o n i s
n o t known.
I t m ust be n o te d t h a t th e e x a c t t e m p e r a tu r e a t t h e
b e n d in g p o i n t o f t h e c o n e s i s a f u n c t i o n o f th e r a t e o f
h e a t i n g a s w e l l a s t h e a c t u a l t e m p e r a t u r e i n t h e f u r n a c e .
B ecau se o f t h e r a t h e r f a s t h e a t i n g r a t e o f t h e f u r n a c e t h a t
w as u s e d , th e th e rm o c o u p le was r e a d when th e t i p o f t h e cone
h a d b e n t a b o u t 20 d e g r e e s i n s t e a d o f when th e t i p to u c h e d t h e
b a s e a s i s more c u s to m a ry . The c o n e s w ere s e t i n s a n d i n a
c e ra m ic d i s h . B ecau se o f t h e p r e s e n c e o f l e a d i n t h e 012-J
c o n e , c a r e was u s e d i n i t s p la c e m e n t.
20
w o rk in g on t h e u s u a l p r i n c i p l e o f th e f i l a m e n t o f a s t a n d a r d
lam p beco m in g i n v i s i b l e when a t th e same c o l o r te m p e r a t u r e
a s t h e im age o f t h e f u r n a c e f o c u s e d a t t h e same p o i n t . The
a p p a r a t u s was s a t i s f a c t o r y b u t was r a t h e r c lu m sy to u s e .
Time d id n o t p e r m i t r e f i n i n g t h e a p p a r a t u s t o t h e d e s i r e d
p o i n t . As a r e s u l t i t was u s e d o n ly once t o m a i n t a i n a
te m p e r a t u r e o f 8 0 0 -9 0 0 ° f o r p r o d u c in g a c o n s t a n t w e ig h t
o x i d e . C a l i b r a t i o n was c h e c k e d a g a i n s t S e g a r c o n e s . The
se c o n d was o f u n iq u e d e s i g n f o r h ig h t e m p e r a tu r e m e a su re m e n t,
b e in g a m o d if ie d form o f r a d i a t i o n p y r o m e te r . I t gav e
p r a c t i c a l l y no r e a d i n g up t o a te m p e r a t u r e o f 8 0 0 ° , b u t
fro m t h a t p o i n t on up t o t h e maximum t e m p e r a t u r e f o r w h ich
a b s o r p t i o n s c r e e n s w ere a v a i l a b l e i t i n d i c a t e d t e m p e r a t u r e
c h a n g e s t o a h i g h d e g r e e o f a c c u r a c y . The r e s u l t s w ere
q u i t e s a t i s f a c t o r y . C a l i b r a t i o n w as c h e c k e d a s b e f o r e
a g a i n s t S e g a r c o n e s .
The u se o f b o i l e d s u l p h u r i c a c i d a s a d e s i c c a n t i n
p la c e o f c a lc iu m c h l o r i d e d i d n o t make a n o t i c e a b l e d i f f e r e n c e
i n t h e r e s u l t s . A f t e r d i s c a r d i n g t h e s u l p h u r i c a c i d , one
d e s i c c a t o r w as c h a rg e d w i t h d e h y d r i t e an d a s c a r i t e t o d e t e r
m ine i f t h e sa m p le s w ere b e in g c o n ta m in a te d b y c a r b o n d i o x i d e .
CHAPTER T V -
EXPERIMENTAL WORK
E x p e rim e n t 1 . Im pure la n th a n u m o x id e was h e a t e d i n
a p l a t i n u m c r u c i b l e w it h o u t t h e c o v e r u n t i l i t was c e r t a i n
t h a t t h e o x a l a t e fro m w h ic h i t w as fo rm ed w as c o m p le te ly de
com posed a s i n d i c a t e d b y t h e a t t a i n m e n t o f c o n s t a n t w e i g h t.
A F i s h e r b u r n e r p r o v i d e d w i t h a n a i r i n l e t c o n n e c te d t o t h e
c o m p re sse d a i r l i n e w as u s e d . The p l a t i n u m c r u c i b l e was
s u p p o r t e d on a s i l i c a t r i a n g l e to a v o id c o n ta m i n a ti o n . A
p e r f o r a t e d c l a y c r u c i b l e w as i n v e r t e d o v e r t h e c r u c i b l e t o
a c t a s a h e a t c o n c e n t r a t o r . The sam ple o f la n th a n u m o x id e
was c o n s i d e r e d t o w e ig h 0 .3 0 5 8 gram s on a b a s i s o f t h e c o n
s t a n t w e ig h t o b t a i n e d a f t e r t h e f o u r t h h e a t i n g shown b e lo w .
I t i s b e l i e v e d t h a t th e te m p e r a t u r e w as a b o u t 900°C . The
t e m p e r a t u r e u s e d w as n o t t h e maximum p o s s i b l e w i t h t h i s
e q u ip m e n t. The p l a t i n u m c r u c i b l e a p p a r e n t l y l o s t 0 . 4 m i l l i
gram s d u r i n g t h e i g n i t i o n o f a p p r o x i m a t e ly e i g h t h o u r s .
See T ab le V I.
22;
TABLE VI
IGNITION OF IMPURE LANTHANUM OXIDE IN A
PLATINUM VESSEL OVER A GAS FLAME
The te m p e r a t u r e w as i n t h e n e ig h b o r h o o d o f 900°C .
Time o f h e a t i n g W eig h t o f C ru o . a n d Sam ple . N o te s
i h o u r
i
s
A
e
A
s
A
s
A
3
A
3
1
S'
10 m in.
40 m in .
50 m in .
B E .9032 gram s
2 2 .8 9 8 7
2 2 .8 8 9 4
2 2 .8 8 9 0
2 2 .8 8 9 1
2 2 .8 8 9 0
2 2 .8 8 9 1
2 2 .8 8 8 5
22.8886
2 2 .8 8 8 5
2 2 .8 8 9 0
22.8886
U n co v ered
ft
L id on f o r a l l
f o l l o w i n g
C o n s ta n t w e ig h t
E x p o sed t o a i r
b e f o r e h e a t i n g
E x p e rim e n t 2 . L an th an u m o x id e o f th e h i g h e s t p u r i t y
w as h e a t e d i n a p l a t i n u m c r u c i b l e i n th e same m anner a s i n
t h e p r e c e d i n g i g n i t i o n s . H ow ever, a h i g h e r te m p e r a t u r e was
o b t a i n e d b y r e s t i n g a c ro m e l gauze on t h e b u r n e r so t h a t th e
g a s s t r e a m was b r o k e n up m ore a n d a g r e a t e r am ount o f a i r
a n d g a s c o u ld be a d m i t te d t o t h e b u r n e r . A dded s u p p o r t w as
n e e d e d a s t h e u s u a l i r o n r i n g s u s e d i n t h e l a b o r a t o r y b e g a n
t o b e n d . The sam p le w e ig h e d 0 .5 8 4 3 g ra m s. The o x id e w as
c o n s i d e r e d t o be a t c o n s t a n t w e ig h t when t h e c r u c i b l e an d
c o n t e n t s w e ig h ed 2 3 .1 6 7 0 i'. The w e ig h t, s l o w l y d ro p p e d t o
2 3 .1 6 4 8 gram s b y th e a p p l i c a t i o n o f t h e h i g h e s t h e a t o b t a i n
a b l e . The t e m p e r a t u r e was b e l i e v e d t o a p p ro a c h 1000°C .
S c a le d ro p p e d on t h e l i d o f th e c r u c i b l e a t one p o i n t , b u t
th e l i d w as c a r e f u l l y c le a n e d so t h a t th e d e t e r m i n a t i o n s
c o u ld be c o n t i n u e d . S in c e t h i s c o n tin u e d l o s s i n w e ig h t was
c o n t r a r y t o w h at was e x p e c t e d , t h e d e t e r m i n a t i o n s w ere s t o p
p e d an d a n a tt e m p t was made t o f i n d t h e c a u s e . U n f o r t u n a t e l y
t h e c r u c i b l e w as n o t w e ig h e d a f t e r th e sam ple w as rem o v ed .
I t i s now b e l i e v e d t h a t th e change was c a u s e d m a in ly b y l o s s
i n w e ig h t o f th e p l a t i n u m . See T a b le V I I .
TABLE V II
IGNITION OE PURE LA20 3 OVER A GAS ELAME
A p l a t i n u m c r u c i b l e w as u s e d ; t e m p e r a t u r e b e l i e v e d t o
be a b o u t 1000°C .
Time o f h e a t i n g W eight o f c r u c i b l e an d c o n t e n t s
I n i t i a l 2 5 .2 7 2 5 gram s
i h o u r 2 3 .1 6 7 3
x
s
ft
2 3 .1 6 6 8
2 3 .1 6 7 1
35 m in
h o u r
' ”
2 3 .1 6 7 0
2 3 .1 6 6 9
2 3 .1 6 6 7
2 3 .1 6 6 7
2 » 2 3 .1 6 6 6
2 3 .1 6 6 4
2 3 .1 6 6 1
2 3 .1 6 5 9
50 m in
3 h o u r s
2 3 .1 6 5 9
2 3 .1 6 5 6
4 rt
2 3 .1 6 4 9 ( v e r y h ig h te m p .)
2 3 .1 6 4 8
2 3 .1 6 5 4 ( s c a l e d ro p p e d on l i d )
( s c a l e rem oved)
i i tt
-•-2
2 3 .1 6 5 0
2 3 .1 6 4 5
2 3 .1 6 4 7
2 3 .1 6 4 3
2 3 .1 6 4 2
25
E x p e rim e n t 5 . S in c e S a r v e r an d B r i n t o n 18 p o i n t o u t
th e d a n g e r o f s u l f u r c o n ta m i n a ti o n fro m t h e g a s fla m e i n
work, on th e r a r e e a r t h o x i d e s , a n d Benner^-9 n o t e s t h a t a
p l a t i n u m c r u c i b l e i n a h i g h s u l f u r c o n t e n t g a s flam e a t
8 0 0 ° w i l l l o s e a s much a s one m i l l i g r a m p e r h o u r (15 gram
c r u c i b l e ) , i t w as d e c i d e d t o change t h e m eth od o f h e a t i n g .
T h is s e r i e s o f i g n i t i o n s was made i n a C o o rs p o r c e l a i n b o a t
p l a c e d i n a t u b u l a r r e s i s t a n c e f u r n a c e . To d e te r m in e t h e
t e m p e r a tu r e a p la tin u m - r h o d iu m th e rm o c o u p le w as u s e d i n
c o n j u n c t i o n w i t h a L e e d s a n d N o rth ru p s t u d e n t p o t e n t i o m e t e r
an d a u x i l i a r y e q u ip m e n t. The room t e m p e r a t u r e c o r r e c t i o n s
f o r t h e c o ld j u n c t i o n w ere made b y a d d in g t h e m i l l i v o l t
v a lu e c o r r e s p o n d in g to th e room t e m p e r a tu r e t o th e r e a d i n g s
o b t a i n e d fro m t h e p o t e n t i o m e t e r . T a b le s i n t h e "H andbook
o f C h e m is try and P h y s i c s " w ere u s e d t o c o n v e r t m i l l i v o l t s t o
d e g r e e s c e n t i g r a d e . S in c e th e b o a t o c c u p ie d a c o n s i d e r a b l e
sp a c e i n t h e f u r n a c e a n d i t c o u ld n o t be p l a c e d a c c u r a t e l y
i n t h e same p l a c e e a c h t i m e , i t was n e c e s s a r y t o d e te r m in e
t h e te m p e r a t u r e g r a d i e n t i n t h e c e n t e r s e c t i o n o f t h e com
b u s t i o n t u b e . W ith th e th e rm o c o u p le w ith d ra w n tw o i n c h e s ,
th e t e m p e r a tu r e d ro p was o n ly 2 0 ° , b u t fro m t h i s p o i n t o u t
t h e te m p e r a t u r e d r o p p e d v e r y r a p i d l y . The f i r s t f u r n a c e
18Lo o. c i t .
1 9R. C. B e n n e r, I n d . a n d E n g . C hem ., 4 : 4 3 , 1 9 1 2 .
t e s t e d was u n s a t i s f a c t o r y . The se c o n d w as b e t t e r , b u t i t s
maximum t e m p e r a tu r e w as o n ly 9 8 0 ° . W ith a l l r e s i s t a n c e r e
moved th e t e m p e r a t u r e o f t h i s f u r n a c e re m a in e d c o n s t a n t
w i t h i n p l u s o r m in u s f i v e d e g r e e s .
To d e te r m in e t h e change i n w e ig h t o f t h e la n th a n u m
o x id e w i t h g r e a t e r a c c u r a c y , th e b o a t s u s e d w e re h e a t e d em p ty
f o r a p p r o x i m a t e ly t h e same l e n g t h o f tim e a s w ere th e sa m p le s
o f o x i d e . To be d o u b ly s u r e t h a t a l l o f t h e change was due
t o v a r i a t i o n i n th e w e ig h t o f th e o x id e a n d n o t t h e p o r c e
l a i n b o a t , t h e b o a t u s e d i n one o f t h e i g n i t i o n s was c a r e
f u l l y c le a n e d a n d r e - w e ig h e d . The d a t a show t h a t th e b o a t s
w ere n o t a f f e c t e d i n th e l e a s t by e i t h e r t h e h ig h te m p e r a
t u r e o r t h e p r e s e n c e o f th e o x i d e . See T a b le V I I I f o r t h i s
d a t a .
27
TABLE V I I I
DATA ON EXPERIMENT 3
Em pty C o o rs p o r c e l a i n b o a t s w ere w e ig h e d a f t e r h e a t i n g
a t a t e m p e r a t u r e o f 980°C . S u l f u r i c a c i d w as u s e d i n t h e
d e s i c c a t o r .
_______________________________ B o a t #1__________________________________
Time o f h e a t i n g W eight
one h o u r
h a l f «
one "
6 .6 2 7 3 gram s
6 .6 2 7 4 «
6 .6 2 7 3 "
A sam ple o f t h e o x id e was n e x t h e a t e d i n th e b o a t
f o r 22 h o u r s . The b o a t w as t h e n c a r e f u l l y c le a n e d a n d r e
w e ig h e d . 6 .6 2 7 3 gram s
B o a t f z
Time o f h e a t i n g We i g h t
t h r e e h o u r s
one "
20ir
7 .3 6 2 9 gram s
7 .3 6 2 7 "
7 .3 6 2 8 "
N ex t s a m p le s o f b o th t h e im pure a n d th e p u re o x id e
w ere p l a c e d i n t h e b o a t s . I n th e c a s e o f t h e f i r s t sam ple
o f th e im pure o x id e i t was n o t i c e d t h a t c o n s t a n t w e ig h t had
n o t b e e n o b t a i n e d . The d a t a t h e r e f o r e w i l l n o t be show n.
A s e c o n d sam ple w as p r e p a r e d a n d gave t h e r e s u l t s shown i n
T a b le IX .
A sam p le o f t h e h i g h e s t p u r i t y o x id e w as n e x t h e a t e d
a n d t h e d a t a shown i n T a b le X w ere o b t a i n e d .
The a p p a r e n t i n c r e a s e o f 0 . 2 m i l l i g r a m s i s e q u i v a l e n t
t o a n i n c r e a s e o f 0 .0 2 fo a n d i s to o s m a ll t o have a n y s i g n i
f i c a n c e s i n c e t h e w e ig h in g e r r o r s o f t e n am ount t o t h i s much
u n l e s s a m ore s e n s i t i v e b a la n c e i s u s e d . I t a p p e a r s t h e n
t h a t no h i g h e r o x id e i s fo rm e d u n d e r t h e s e c o n d i t i o n s , a
t e m p e r a t u r e o f 980° a n d a p p r o x i m a t e ly 20 h o u r s o f h e a t i n g .
29
TABLE IX
DATA ON EXPERIMENT 3
0 .4 8 7 0 gram s o f • im pure la n th a n u m o x id e w ere h e a t e d i n
a C o o rs p o r c e l a i n b o a t a t 9 8 0 ° . S u l f u r i c a c i d was u s e d i n
th e d e s i c c a t o r .
Time o f h e a t i n g We i g h t
16 h o u r s 7 .8 0 3 3 g ram s
2& " 7*8036 «
19 " 7 .8 0 3 3 «
TABLE X
DATA ON EXPERIMENT 3
1 .0 0 1 6 gram s o f th e h i g h e s t p u r i t y la n th a n u m o x id e
w ere h e a t e d i n a C o o rs p o r c e l a i n b o a t a t 9 8 0 ° . S u l f u r i c
a c i d was u s e d a s a d e s i c c a n t .
Time o f h e a t i n g ___________ We i g h t
h o u r 7 .6 2 8 8 gram s
a ti
s
7 .6 2 9 0
X ri
s
7 .6 2 8 8
X ! »
s
7 .6 2 9 0
20 " 7 .6 2 9 2
30
E x p e rim e n t 4 . T h is d e t e r m i n a t i o n was made u s i n g a
p l a t i n u m c r u c i b l e i n th e m u f f le o f a n a s s a y f u r n a c e . I t
w as b e l i e v e d t h a t t h e m u f f le w o u ld p r o t e c t th e p l a t i n u m
c r u c i b l e fro m t h e f u r n a c e g a s e s a n d re d u c e t h i s s o u r c e o f
e r r o r i n t h e m easu rem en t o f t h e w e ig h t change o f t h e l a n t h a
num o x i d e . The o x a l a t e was decom posed o v e r an o r d i n a r y
b u r n e r , b u t th e im pure o x id e o b t a i n e d was h e a t e d t o c o n s t a n t
w e ig h t i n t h e m u f f le so t h a t t h e p la tin u m - r h o d iu m th e rm o c o u p le
c o u ld be u s e d f o r t e m p e r a t u r e c o n t r o l . The sam ple was i g
n i t e d a t a te m p e r a t u r e o f a b o u t 8 0 0 ° - 9 0 0 ° , s i n c e S a r v e r a n d
B r i n t o n 20 fo u n d t h a t la n th a n u m o x id e m o st c l o s e l y a p p r o a c h e s
i t s t h e o r e t i c a l w e ig h t a t t h i s t e m p e r a t u r e . The sam ple
a p p a r e n t l y l o s t so much w e ig h t d u r i n g t h e f i r s t h i g h te m p e r a
t u r e i g n i t i o n t h a t t h e e x p e r im e n t w as s to p p e d a n d th e c r u c i
b le w as c l e a n e d a n d r e w e ig h e d . M ost o f th e l o s s p r o v e d t o
be due t o d e t e r i o r a t i o n o f t h e p l a t i n u m . The th e rm o c o u p le
i n d i c a t e d a t e m p e r a t u r e b e tw e e n 1100 a n d 1 2 0 0 ° C ., b u t i t i s
s u s p e c t e d t h a t th e t e m p e r a tu r e w as h i g h e r , a s i n p r e v i o u s
w o rk t h e th e rm o c o u p le p r o v e d u n r e l i a b l e above 1 1 0 0 ° . The
o x id e o b t a i n e d was d i s s o l v e d i n h y d r o c h l o r i c a c i d , a n d i t
vras n o t i c e d t h a t c h l o r i n e g a s w as l i b e r a t e d . T h is i s a
p o s s i b l e i n d i c a t i o n o f a h i g h e r o x i d e , b u t i t i s p r o b a b le
t h a t i t w as c a u s e d b y i m p u r i t i e s s u c h a s praseo d y m iu m a n d
c e r iu m i n th e o r i g i n a l s a m p le . See T a b le X I f o r d a t a .
20Loc. c i t .
TABLE XI
RESULTS OBTAINED BY HEATING
IMPURE LANTHANUM OXIDE IN A PLATINUM CRUCIBLE
W eig h t o f sam p le w as 0 .9 2 0 8 gram s o f im pure o x id e
Time o f h e a t i n g T e m p e ra tu re W eight
l | r h o u r s
1 h o u r
3 h r s . , 20 m in .
1 h o u r
750° C.
660-700
1100
1160
L o ss i n w e ig h t
L o ss i n w e ig h t o f th e p l a t i n u m
2 3 .4 4 3 6 gram s
2 3 .4 4 3 7 "
2 3 .4 3 2 1 "
0 .0 1 1 6 g ra m s , 1.26%
0 .0 1 0 0 ”
N e t a p p a r e n t l o s s i n 0 .0 0 1 6 g ra m s , 0.17%
32
E x p e rim e n t 5 . B e ca u se o f tlie t r o u b l e e n c o u n te r e d
w i t h p l a t i n u m i n a l l e x p e r i m e n t s , i t w as d e c i d e d t o t r y
o t h e r t y p e s o f c r u c i b l e s . I n t h i s e x p e r im e n t Cham pion
S i l l i m a n i t e c r u c i b l e s w ere t r i e d . The new se m im ic ro b a la n c e
w as u s e d i n a n a t t e m p t t o i n c r e a s e t h e a c c u r a c y o f t h e w o rk
s i n c e i t c o u ld w e ig h d i f f e r e n c e s o f 0 .0 2 m i l l i g r a m s . How
e v e r , i t w as fo u n d t h a t t h e " c h a in o r a a tic " w as b e t t e r , a s t h e
la n th a n u m o x id e g a in e d a p p r o x i m a t e ly 0 .0 5 m i l l i g r a m s d u r i n g
a s i n g l e e x c u r s i o n o f th e p o i n t e r . An em p ty c r u c i b l e w as
u s e d a s a t a r e to e q u a l i z e w e ig h t c h a n g e s due to t h e l a r g e
a r e a o f p o r c e l a i n e x p o s e d t o t h e a i r , b u t t h e r e s u l t s w ere
n o t a n y b e t t e r . The im pure la n th a n u m o x a l a t e was a g a i n
i g n i t e d t o t h e c o n s t a n t w e ig h t o x i d e . The m u f f le f u r n a c e
w as u s e d and th e rm o c o u p le r e a d i n g s up to 1 4 .4 5 m i l l i v o l t s
e q u i v a l e n t t o a t e m p e r a t u r e o f 12 8 5 °C . w ere o b t a i n e d . The
t e m p e r a t u r e wqs so h ig h t h a t t h e im pure o x id e p a r t i a l l y
f u s e d i n t o th e p o r c e l a i n , an d t h e p o r c e l a i n c r u c i b l e s t u c k
t o t h e m u f f l e . I t c a n be c o n c lu d e d t h a t p o r c e l a i n c a n n o t
be u s e d s a f e l y w i t h o u t c a r e f u l t e m p e r a t u r e c o n t r o l a t t h e s e
h ig h t e m p e r a t u r e s . The th e rm o c o u p le a v a i l a b l e w as n o t
s a t i s f a c t o r y f o r t h i s c o n t r o l w o rk a n d S e g a r c o n e s c o u ld
n o t be u s e d b e c a u s e o f t h e l a r g e num ber t h a t w o u ld be r e
q u i r e d an d t h e d i f f i c u l t y o f i n t r o d u c i n g th em i n t o t h e f u r
n a c e w h ile i t i s h o t . The n u m e r ic a l r e s u l t s a r e o f no
i n t e r e s t and so t h e y hav e n o t b e e n i n c l u d e d .
33
E x p e rim e n t 6 . I n l o o k in g f o r a s u i t a b l e m a t e r i a l
w i t h w h ic h to h o l d t h e o x i d e , i t was fo u n d t h a t a c c o r d i n g
t o W inze r 2-^ c r u c i b l e s o f alum inum o x id e a r e s t a b l e i n a l l
g a s e s e x c e p t i n g f l u o r i n e a t 18 00°C . and t h e y r e s i s t m o lte n
f l u x e s b e t t e r t h a n a n y o t h e r ty p e o f o x id e c r u c i b l e . An
O p
a d v e r t i s e m e n t f o r " A l f r a x " w as i n v e s t i g a t e d and a c r u c i b l e
o b t a i n e d . On h e a t i n g t h e em p ty c r u c i b l e t h e f o l l o w i n g d a t a
on c o n s t a n c y o f w e ig h t was o b t a i n e d .
H e a te d one h o u r a t a b o u t 900°C . 9 .9 2 5 0 gram s
" t o c o n s t a n t w e ig h t a t 900° 9 .9 2 3 8 "
" a t 1 3 5 0 ° f o r t h r e e h o u r s 9 .9 1 8 3 "
(The c r u c i b l e s t u c k t o a r e f r a c t o r y p l a t e i n
th e m u f f l e . The p l a t e w as rem oved i n s u b s e
q u e n t w ork)
H e a te d a t 900° f o r one h o u r 9 .9 1 8 2 gram s
" a t 1 3 0 0 ° f o r s i x h o u r s 9 .9 2 5 6 "
(The f u r n a c e w as u s e d b y someone e l s e f o r a
l e a d a s s a y . The l e a d o r f l u x a p p a r e n t l y p e r
m e a te d t h e w h o le m u f fle an d a new m u f f le h a d
t o be i n s t a l l e d . )
H e a te d a t 80 0° f o r one h o u r 9 .9 2 5 0 gram s
" a t 1 1 0 0 ° f o r one h o u r (g a s fla m e ) 9 .9 2 5 4 gram s
21R o b e rt W in z e r, Chem. A b s t r a c t s . 2 6 I5 1 8 7 1 , 1 9 3 2 .
22,lA l f r a x R e f r a c t o r y M a t e r i a l s , " Chem. and M e t. ,
p . 38A, D ec. 1 9 3 8 .
34
T ills c r u c i b l e i s a p p a r e n t l y u n s u i t e d f o r t h i s w o rk ,
a s t h e b i n d i n g m a t e r i a l u s e d i n th e c r u c i b l e i s v o l a t i l e a t
t h i s h ig h t e m p e r a t u r e .
35
E x p e rim e n t 7 . F o r t h i s l a s t e x p e r im e n t i t w as d e c id e d
t o t r y C o o rs p o r c e l a i n c r u c i b l e s . S in c e t h e r a d i a t i o n p y r o
m e te r w as now a v a i l a b l e , i t w as p o s s i b l e t o c o n t r o l t h e
t e m p e r a t u r e s u f f i c i e n t l y so t h a t t h e c r u c i b l e s w o u ld n o t be
f u s e d i n t o t h e m u f f le a s h a p p e n e d i n E x p e rim e n t 5 . A s t a r t
w as made u s i n g # 0 c r u c i b l e s , b u t i t w as im m e d ia te ly a p p a r e n t
t h a t t h e y c o u ld n o t be w e ig h e d a c c u r a t e l y due t o m o is tu r e
a b s o r p t i o n . S ix # 00 c r u c i b l e s w ere o b t a i n e d t o g e t h e r w i t h
two l a r g e - a i z e d w e ig h in g b o t t l e s . F iv e w e re f i l l e d w i t h
sa m p le s o f t h e im pure la n th a n u m o x id e a n d t h e s i x t h was l e f t
em pty b u t t r e a t e d i n t h e same m anner a s t h e r e s t a s a c h e c k
on th e w o rk . By w o rk in g r a p i d l y i t w as p o s s i b l e t o w e ig h
s a t i s f a c t o r i l y b y p l a c i n g t h e c r u c i b l e s one b y one i n th e
w e ig h in g b o t t l e s . S in c e s a m p le s l e f t i n a d e s i c c a t o r w ould
g a in m o is tu r e a f t e r s e v e r a l c r u c i b l e s h a d b e e n rem oved two
d e s i c c a t o r s w ere u s e d to re d u c e t h i s e r r o r . A f t e r t h e f i r s t
w e ig h in g i t was fo u n d t h a t t h e w e ig h in g b o t t l e s g a in e d 0 . 3
m i l l i g r a m s a f t e r re m o v in g fro m t h e d e s i c c a t o r a n d s e t t i n g
f o r a h a l f h o u r . By l e a v i n g th em o u t o f th e d e s i c c a t o r
v e r y l i t t l e change o c c u r r e d a n d no s e r i o u s am ount o f m o is tu r e
c o u ld be p i c k e d up i n t h e s h o r t tim e r e q u i r e d t o move a
c r u c i b l e fro m t h e d e s i c c a t o r t o a w e ig h in g b o t t l e . One o f
th e d e s i c c a t o r s c o n ta in e d a s c a r i t e an d d e h y d r i t e a n d t h e
o t h e r c o n t a i n e d c a lc iu m c h l o r i d e . H e a t i n g was done b y m eans
o f t h e a s s a y f u r n a c e a s i n t h e p r e v i o u s w o rk . H ow ever, d r y
36
a i r was s l c w l y p a s s e d i n t o t h e m u f f le d u r i n g m o st o f t h e
e x p e r im e n t to he s u re t h a t r e d u c i n g g a s s e s w ere n o t p r e s e n t .
The m o u th o f t h e m u f f le w as l e f t open a t a l l t im e s t o f u r t h e r
a i d i n m a i n t a i n i n g an o x i d i z i n g a tm o s p h e re i n t h e m u f f l e .
T a b le s X I I a n d X I I I c o n t a i n th e d a ta fro m t h e s e i g n i t i o n s .
T h e re a r e some p o i n t s a b o u t t h i s e x p e r im e n t t h a t
s h o u ld be p a r t i c u l a r l y n o t e d . The p o r c e l a i n w as t o t a l l y
unharm ed b y lo n g p e r i o d s o f i g n i t i o n u n t i l t h e t e m p e r a tu r e
w as r a i s e d t o 1100°C . a t w h ic h tim e th e g l a z e was s l i g h t l y
a t t a c k e d i n t h e c r u c i b l e s c o n t a i n i n g t h e o x i d e . The w r i t e r
b e l i e v e s t h a t no n o t i c e a b l e e r r o r w ould be c a u s e d b y t h i s i f
t h e sa m p le s w ere h e a t e d t o a maximum te m p e r a tu r e o f 1 0 5 0 ° C.
I t s h o u ld be p a r t i c u l a r l y o b s e r v e d t h a t th e sa m p le s a lw a y s
g a i n i n w e ig h t when a llo w e d t o c o o l slo w ly , a p p a r e n t l y b e c a u s e
o f c o m b in a tio n w i t h c a r b o n d io x id e fro m t h e a i r . T h is i n
c r e a s e i s o b s e r v e d e v e n i n c a s e s w here t h e s a m p le s w ere o n l y
a llo w e d t o c o o l to a b o u t 700° b e f o r e re m o v a l t o t h e d e s i c
c a t o r . Two h o u r s a t a t e m p e r a t u r e o f 350° r e s u l t e d i n i n
c r e a s e s o f 1 . 9 , 4 . 2 , 4 . 7 an d 3 .8 m i l l i g r a m s i n th e w e i g h ts
o f t h e c r u c i b l e s . I t w as t h e r e f o r e a p p a r e n t t h a t f o r a c
c u r a c y i n t h i s w ork t h e sa m p le s s h o u ld be rem oved im m e d ia te ly
fro m th e r e d h o t m u f f le a n d p l a c e d i n t h e d e s i c c a t o r a s w as
done i n t h e l a t e r p a r t o f t h i s e x p e r im e n t. The l a s t i g n i t i o n
w as done u n d e r c o n d i t i o n s b e l i e v e d to be a s n e a r l y l i k e t h o s e
o f R u th E lm q u is t a s p o s s i b l e a n d w i t h t h e e x c e p t i o n o f sam ple §1
37
TABLE X II
IGNITION OP IMPURE LANTHANUM OXIDE IN
COORS PORCELAIN CRUCIBLES BY MEANS OP AN ASSAY PURNACE
D e h y d r ite a n d a s c a r i t e u s e d i n d e s i c c a t o r . The te m p e
r a t u r e w as m e a s u re d b y m eans o f th e r a d i a t i o n p y r o m e te r . D ry
a i r was a d m i t t e d t o t h e m u f f le e x c e p t f o r $ 1 0 , 1 1 , an d 1 8 .
No. Time T e m p e ra tu re C o n d i ti o n s 3
......#1
Sam ple
. jt2
. #3
(W eight o f sam p le i n g ra m s) 0 .9 1 9 8 0 .6 1 0 6 0 .9 7 1 8
1 5 h r 8 4 0 -8 9 0 ° C . C o o le d slo w 5 0 .8 7 3 6 4 8 .8 1 0 2 4 9 .0 6 7 4
8 3 8 4 0 -8 8 0 ” f a s t e r 5 0 .2 7 8 8 4 8 .8 0 9 5 4 9 .0 6 6 1
3 3 8 4 0 -9 1 0 ” s lo w ly 5 0 .2 7 3 8 4 8 .8 1 0 1 4 9 .0 6 6 2
4 1 8 4 0 -8 9 0
tt it
5 0 .2 7 3 6 4 8 .8 0 9 4 4 9 .0 6 5 4
5 4 8 4 0 -8 9 0 lo n g c o o l 5 0 .2 7 3 5 4 8 .8 1 0 0 4 9 .0 6 6 4
6 8 350b ------
5 0 .2 7 5 4 4 8 .8 1 3 2 4 8 .9 7 5 1 °
7 SO m in . 800 -8 5 0 r a p i d c o o l 5 0 .2 7 4 3 4 8 .8 1 1 2 4 8 .9 6 8 5
8 8 8 70 -9 6 0 c o o le d t o
5 5 0 ° i n a i r
5 0 .2 7 3 8 4 8 .8 0 9 1 4 8 .9 6 5 7
9 3 880-9 7 0 c o o le d f a s t
fro m 8 8 0 °
5 0 .2 7 3 5 4 8 .8 0 8 4 4 8 .9 6 4 5
10
11
18
8
8
9 30 -9 7 0
1 0 10-10 60
1 0 1 0 -1 0 3 0
c o o le d f a s t
fro m 930°
5 0 .2 7 2 5
n o t
4 8 .8 0 6 9
w e ig h e d
4 8 .9 6 2 9
i
3
1 04 0 -1 1 1 0 c o o le d f a s t
fro m 1010°
5 0 .2 7 4 8 4 8 .8 0 5 9 4 8 .9 6 1 8
a By th e te r m ’’c o o le d s lo w ly ” i t w as m eant t h a t t h e w c r u c i b l e s
w ere a llo w e d t o re m a in i n t h e m u f f le u n t i l t h e m u f f le r e a c h e d
a t e m p e r a tu r e o f a b o u t 600°C . ’’C o o le d f a s t ” i n d i c a t e s t h a t i t
was rem oved fro m t h e m u f f le a lm o s t im m e d ia te ly .
^ N ic h ro m e -a lu m e l th e rm o c o u p le u s e d t o m easu re th e t e m p e r a t u r e .
CA sam ple w as rem oved a n d t e s t e d w i t h HC1 a s i n E x p . 4 . C h lo r in e
w as g iv e n o f f a n d s i n c e t h e te m p e r a t u r e w as s u p p o s e d ly to o low t o
fo rm a h i g h e r o x i d e , t h i s w ould i n d i c a t e t h a t th e c h l o r i n e i s r e
l e a s e d due t o i m p u r i t i e s i n t h e sa m p le . The sam p le r e m a in in g
w e ig h e d 0 .8 7 0 9 g ra m s.
38
TABLE X I I I
IGNITION OF IMPURE LANTHANUM OXIDE IN COORS PORCELAIN CRUCIBLES
A ssa y f u r n a c e a n d r a d i a t i o n p y r o m e te r w as u s e d . C a lc iu m
c h l o r i d e was u s e d a s a d e s i c c a n t . D ry a i r u s e d i n m u f f le e x c e p t
f o r #10 a n d 1 1 .
No. Time . T e m p e ra tu re C o n d i t i o n s a #4
Sam ple
#5 #6
(We i g h t o f sam ple i n gram s 0 .9 4 2 4 0 .9 3 4 7 em p ty
. 1 5 h r s . 8 4 0 -9 8 0 °C . C o o le d slo w 3 9 .5 3 9 7 3 9 .6 2 5 2 3 8 .3 9 9 7
2 3 840 -8 8 0 ” f a s t e r 39!.5388 3 9 .6 2 4 2 3 8 .3 9 9 7
3 3 8 4 0 -9 1 0 " s lo w ly 3 9 .5 3 9 5 3 9 .6 2 4 7 3 8 .3 9 9 7
4 1 840 -9 1 0
» t t»
3 9 .5 3 9 8 3 9 .6 2 4 7 3 8 .3 9 9 7
5 4 8 4 0 -8 9 0 lo n g c o o l 3 9 .5 3 9 6 3 9 .6 2 5 0 3 8 .3 9 9 7
6 2 350b
------
3 9 .5 4 3 8 3 9 .6 2 9 7
------
7 1 8 3 0 -8 7 5 c o o le d f a s t n o t w e ig h e d
8 ' 2 8 7 0 -9 6 0 * » s lo w ly 3 9 .5 3 7 6
t o 550 i n a i r
3 9 .6 2 2 8 3 8 .4 0 0 3
9 3 920-970 c o o le d f a s t
fro m 8 8 0 °
3 9 .5 3 6 7 3 9 .6 2 2 1 3 8 .3 9 9 7
10
11
12
2
2
930-970
1 0 1 0 -1 0 6 0
101 0 -1 0 3 0
c o o le d f a s t
fro m 930°
3 9 .5 3 5 6 3 9 .6 2 0 6
n o t w e ig h e d
3 8 .3 9 9 8
X
S
104 0 -1 1 1 0 c o o le d f a s t
fro m 1010°
3 9 .5 3 3 4 3 9 .6 1 7 6 3 8 .4 0 0 5
a By t h e te r m ” c o o le d s lo w ly ” i t was m ean t t h a t t h e c r u c i b l e s
w ere a llo w e d t o re m a in i n th e m u ff le u n t i l t h e m u f f le r e a c h e d a
t e m p e r a t u r e o f a b o u t 600°C . " C o o le d f a s t ” i n d i c a t e s t h a t i t
w as rem oved fro m t h e m u f f le a lm o s t im m e d ia te ly .
bN ic h ro m e -a lu m e l th e rm o c o u p le u s e d t o m easu re th e t e m p e r a t u r e .
39
t h e y a l l show ed d e c r e a s e s i n s t e a d o f i n c r e a s e s a s she c l a i m s .
H ow ever, she may have o b t a i n e d f a l s e r e a d i n g s due to c a rb o n
d i o x id e a b s o r p t i o n o r t o some o t h e r c a u s e a n d t h e w r i t e r ’ s
d a t a may c o n t a i n e r r o r s due t o r e d u c t i o n o f t h e i m p u r i t i e s
p r e s e n t i n th e la n th a n u m o x i d e . The sa m p le s seem t o a p p ro a c h
c o n s t a n t w e ig h t when h e a t e d i n th e n e ig h b o rh o o d o f 8 5 0 ° a n d
a r e r a p i d l y c o o le d . I t seem s p r o b a b le t h a t some o f t h e v a r i a
t i o n s a r e due t o a t t e m p t i n g t o h a n d le to o many s a m p le s a t
o n c e . The u se o f two s a m p le s a n d tw o d e s i c c a t o r s w o u ld have
b e e n m ore f o r t u n a t e . The u se o f d e h y d r i t e an d a s c a r i t e i n
p l a c e o f c a lc iu m c h l o r i d e p r o b a b l y h a d a s m a ll e f f e c t s i n c e
t h e d a t a f o r c r u c i b l e f o u r i n t h e c a lc iu m c h l o r i d e d e s i c c a t o r
i s m ore e r r a t i c t h a n t h a t f o r c r u c i b l e one i n t h e a s c a r i t e
a n d d e h y d r i t e d e s i c c a t o r .
CHAPTER V
DISCUSSION AND CONCLUSIONS
Much tim e was s p e n t i n t r y i n g t o f i n d a ty p e o f c r u
c i b l e t h a t was s u i t a b l e f o r t h e w o rk o f t h i s t h e s i s . Xt h a s
b e e n d e f i n i t e l y shown t h a t p l a t i n u m c r u c i b l e s l o s e i n w e ig h t
when h e a t e d t o h i g h t e m p e r a t u r e s . A f t e r e i g h t h o u r s o f i g
n i t i o n a t 90 0 °C . , a SB gram p l a t i n u m c r u c i b l e l o s t 0 . 4 m i l l i
g ra m s . A f t e r o n l y f o u r h o u r s o f i g n i t i o n a t 1S00°C . a n o t h e r
p l a t i n u m c r u c i b l e l o s t t e n m i l l i g r a m s . " A l f r a x ” c r u c i b l e s
p ro v e d to be u n s a t i s f a c t o r y b e c a u s e o f t h e p r e s e n c e o f a
p a r t i a l l y v o l a t i l e b i n d e r i n t h e c r u c i b l e . T h e i r m e l t i n g
p o i n t i s s u f f i c i e n t l y h ig h , how ever, so t h a t t h e y a r e s a t i s
f a c t o r y f o r m ak in g i g n i t i o n s i n w h ich th e f i n a l p r o d u c t i s
n o t to be w e ig h e d i n t h e " A lf r a x " c r u c i b l e . T h e i r r o u g h ,
p o r o u s s u r f a c e f u r t h e r l i m i t s t h e i r u s e . P o r c e l a i n c r u c i b l e s
a n d b o a t s w ere fo u n d t o be v e r y s a t i s f a c t o r y p r o v id e d t h a t
th e t e m p e r a t u r e was n o t a llo w e d t o e x c e e d 1050°G . A s t u d y o f
th e l i t e r a t u r e f a i l e d t o show a t y p e o f c r u c i b l e t o t a l l y
s a t i s f a c t o r y f o r t h i s w o rk . C r u c i b l e s o f p u re f u s e d a lu m in a
o r z ir c o n iu m o x id e c o u ld be made s p e c i a l l y f o r t h i s w o rk .
T h e i r m a n u fa c tu r e i s d e s c r i b e d b y R u ff a n d R i e b e t h . ^ How
e v e r , i t i s b e l i e v e d t h e c r u c i b l e s a r e n o t a v a i l a b l e a n d
e q u ip m e n t c a n n o t be o b t a i n e d f o r t h e i r m a n u f a c tu r e a t t h i s
t i m e . I t seem s p o s s i b l e t h a t t h e s l i g h t r e a c t i o n o f t h e
la n th a n u m o x id e w i t h t h e g l a z e o f a p o r c e l a i n c r u c i b l e w ould
2 3 0 R u ff a n d A. R i e b e t h , Z. A n o rg . A llg e m . Chem. ,
1 7 3 :3 7 3 - 9 4 , 1 9 2 8 .
41
n o t be a s e r i o u s s o u rc e o f e r r o r so t h a t f u t u r e w ork m ig h t
be t r i e d i n p o r c e l a i n a t h i g h e r t e m p e r a t u r e s .
I t may be p o s s i b l e to d e te r m in e t h e p r e s e n c e o f a
h i g h e r o x id e w i t h o u t kn o w in g th e w e ig h t o f th e c r u c i b l e .
T h is c o u ld be done b y a n a l y z i n g t h e sam ple o f la n th a n u m
o x id e b o th b e f o r e a n d a f t e r t r e a t m e n t u n d e r t h e c o n d i t i o n s
b e l i e v e d t o have b e e n u s e d b y E u th E lm q u is t when she r e p o r t
e d l y fo u n d a h i g h e r o x i d e .
I t was fo u n d t h a t b o t h th e p u re a n d im pure la n th a n u m
o x id e a r e c o n s t a n t i n w e ig h t a t l e a s t w i t h i n 0.02% e v e n a f t e r
i g n i t i o n a t 980°C . f o r 20 h o u r s i n a i r b y m eans o f a n e l e c
t r i c c o m b u s tio n tu b e f u r n a c e . I n w o rk done u s i n g a n a s s a y
f u r n a c e , t h e w e ig h t o f th e o x id e s h i f t e d e r r a t i c a l l y , a p p a
r e n t l y due t o a b s o r p t i o n o f m o is tu r e a n d c a r b o n d i o x i d e .
Some r e d u c t i o n b y f u r n a c e g a s s e s m ig h t h av e c o n t r i b u t e d t o
t h e w e ig h t c h a n g e s . I t s h o u ld be n o t e d , h o w e v e r, t h a t t h e s e
w ere o n ly s l i g h t c h a n g e s i n th e sam ple com pared to th e change
t o be e x p e c te d i f a h i g h e r o x id e had b e e n fo rm e d i n a n y c a s e .
I t t h e r e f o r e a p p e a r s t h a t no h i g h e r o x id e i s fo rm ed b e tw ee n
850 a n d 1050°C .
I n e x p l a n a t i o n o f t h e a p p a r e n t i n c o n s i s t e n c y o f h a v in g
e x c e e d i n g l y c o n s t a n t w e ig h t i n e x p e r im e n ts #3 a n d f l u c t u a t i o n s
i n e x p e r im e n t # 7 , i t m ig h t be p o i n t e d o u t t h a t , w h ile t h e
r e s u l t s o f e x p e r im e n t # 3 w ere c o n s i s t e n t among t h e m s e lv e s ,
t h e t r u e w e ig h t o f th e la n th a n u m o x id e p r e s e n t was p o s s i b l y
42
n e v e r fo u n d b e c a u s e o f t h e g r e a t d i f f i c u l t y i n re m o v in g a l l
w a t e r an d c a rb o n d i o x i d e . I t h a s b e e n p r e v i o u s l y n o t e d b y
S a r v e r an d B r i n to n ^ ^ t h a t t h e o x id e i s n o t r e d u c e d t o i t s
t r u e w e ig h t b y h e a t i n g i n a i r . I t i s p r o b a b le t h a t e x p e r i
m ent #3 i s m ore c o n s t a n t t h a n #7 b e c a u s e t h e c o n d i t i o n s o f
c o o l i n g c o u ld be c o n t r o l l e d m ore a c c u r a t e l y i n #3 so t h a t th e
same e r r o r s due t o c a r b o n d i o x id e a b s o r p t i o n and so f o r t h
w as o b t a i n e d i n e a c h w e i g h in g . The h u m id i t y w as much h i g h e r
d u r i n g e x p e r im e n t #7 a n d c o m b u s tio n g a s s e s p o s s i b l y may have
r e a c h e d t h e o x id e d e s p i t e p r e c a u t i o n s t a k e n .
I t i s b e l i e v e d t h a t i t w o u ld be p o s s i b l e t o d e s i g n a
s p e c i a l b a la n c e i n w h ic h c r u c i b l e s s u s p e n d e d on p l a t i n u m
w i r e s fro m th e beam o f t h e b a la n c e c o u ld be h e a t e d t o a
h ig h t e m p e r a t u r e b y m eans o f tw o i d e n t i c a l e l e c t r i c m u f f le
f u r n a c e s a n d th e s a m p le s o f la n th a n u m o x id e w e ig h e d a t a
h i g h t e m p e r a t u r e . By t h i s m eans i t w ou ld be p o s s i b l e to o b
t a i n t h e t r u e w e ig h t o f th e o x id e a t a h i g h t e m p e r a t u r e
in d e p e n d e n t o f a n y c h a n g e s t h a t m ig h t o c c u r d u r i n g c o o l i n g .
OK
A b a la n c e o f su c h n a t u r e h a s b e e n c o n s t r u c t e d i n J a p a n .
W hile no c o n f i r m a t i o n h a s e v e r b e e n o b t a i n e d f o r t h e
w o rk o f R u th E lm q u i s t , i t h a s n o t b e e n p ro v e d t h a t a h i g h e r
o x id e c an n o t e x i s t . H ow ever, i n v ie w o f th e o t h e r w o rk s on
£ 4 l o c . c i t .
2 5Chem. A b s t r a c t s . 2 3 :3 8 3 1 1 , 1 9 2 9 , c i t i n g J . S a c .
Chem. I n d .' ( J a p a n ) ', 52;"249 -55, 1 9 2 9 .
4 3
th e s u b j e c t , i t i s more l o g i c a l t o e x p l a i n t h e i r r e g u l a r i t i e s
i n w e ig h t o f t h e la n th a n u m o x id e a s b e in g due t o a b s o r p t i o n
o f g a s s e s . I t m ust be c o n s i d e r e d t h a t i n some c h e m ic a l
r e a c t i o n s a -very c r i t i c a l t h e r m a l c o n d i t i o n m u st be a t t a i n e d .
C o n s e q u e n tly , w h ile t h e a b s e n c e o f w e ig h t change d a t a a t
a n y g iv e n s e t o f c o n d i t i o n s dem ands t h e c o n c l u s i o n t h a t no
h i g h e r o x id e i s fo rm ed u n d e r th o s e p a r t i c u l a r c i r c u m s t a n c e s ,
i t m ust n o t be c o n c lu d e d t h a t a h i g h e r o x id e i s n o t p o s s i b l e
a t e i t h e r a h i g h e r o r a lo w e r t e m p e r a t u r e . A lso t h e e x a c t
t e m p e r a t u r e s u s e d b y m o st o f th e i n v e s t i g a t o r s a r e n o t a c
c u r a t e l y known. U n t i l a l l p o s s i b l e te m p e r a t u r e r a n g e s h a v e
b e e n a d e q u a t e l y c o v e r e d b y c o n t r o l l e d e x p e r im e n ts we can n o t
r e j e c t th e p o s s i b i l i t y o f t h e e x i s t e n c e o f a h i g h e r o x i d e .
BIBLIOGRAPHY
" A l f r a x R e f r a c t o r y M a t e r i a l s , ” Chem. and M e t ., p . 38A, D ec.
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C h e m is tr y . L ondon: E dw ard A rn o ld C o ., 1 9 3 2 . p p . 7 8 - 9 .
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R ic h tm y e r , F . K . , I n t r o d u c t i o n t o M odern P h y s i c s . New Y ork:
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The possibility of higher oxides of lanthanum
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