the thermodynamic properties of neodymium hydroxide in acid, neutral, and alkaline solutions at ...

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THE THERMODYNAMIC PROPERTIES OF NEODYMIUM HYDROXIDE IN
ACID, NEUTRAL, AND ALKALINE SOLUTIONS AT 25°C.: AN
INTERPRETATION OF THE IONIC SPECIES PRESENT IN
AQUEOUS SOLUTIONS OF NEODYMIUM SALTS
DISSERTATION
Presented in Partial Fulfillment of the Requirements
for the Degree Doctor of Philosophy in the
Graduate School of The Ohio State
University
By
RUSSELL STUART TOBIAS, B. Sc.
4\ «V St i't
The Ohio State University
1956
Approved by:
Adviser
Department! of Chemistry
AC KNOWLEDGEMENT
The author wishes to express his sincere appreciation
to Professor A. B. Garrett for his encouragement and counsel
during the course of this investigation. I also wish to
thank him for his interest in my welfare while I have been
a student at The Ohio State University. I also wish to
thank The Ohio State University for the assistant ship
granted to me and the Visking Corporation, the General
Electric Corporation, E. I. du Pont de Nemours and Company,
and the Allied Chemical and Dye Company for financial
assistance during the course of my studies.
Finally, I would like to acknowledge the assistance
of Mr. G. W. Leddicotte, of the Oak Ridge National Labora­
tory, who performed the activation analyses described in
this work.
TABLE OF CONTENTS
Subject Page
INTRODUCTION ............................................. 1
HISTORICAL REVIEW ........................................ 3
The Basicity of the Rare Earth Oxides ............ 3
The System Neodymium Oxide-Water ................. 4
The Hydrolysis of Neodymium Solutions .......... 9
The Analyses of Solutions of Neodymium........... 11
EXPERIMENTAL . .. 18
General Procedure ................................... 18
Preparation of the Reagents ....................... 18
Neodymium Oxide ................................. 18
Hydrochloric Acid Solutions ................... 20
Sodium Hydroxide Solutions ........... . 20
Perchloric Acid Solutions ........... 21
Neodymium and Praseodymium Perchlorate Buffers 22
Sodium Chloride Solutions ..................... 22
Sodium Perchlorate Solutions ................. 22
Distilled Water ............................ 23
Hydrolysis Studies .................................. 23
Experimental Method ............................ 23
Electrochemical Cells ..................... 25
Electrical Circuits ................. 34
Details of the Experimental Procedure ....... 37
Analysis of the Free Acid Concentration of
the Rare Earth Buffers......... 41
iii
TABLE OF CONTENTS (Cont'd.)
Solubility Studies .................................... 42
Preparation of Samples ............ ............. 42
Equilibration ..................................... 43
Sedimentation ................................. 44
Transfer of the Solutions for Analysis.......... 44
Measurement of the Hydrogen Ion Concentration . 46
Spectrophotometric Analyses ..................... 47
Activation Analyses .............................. 55
Analysis of the Solid Phase in theE quilibria . 56
THE DATA .... a . . ..................................... 65
AN ANALYSIS OF THE DATA OBTAINED FROM THE DISSOLUTION
OF METALLIC HYDROXIDES IN DILUTE ACIDS AND FROM A
STUDY OF THE RESULTING EQUILIBRIA ..................... 104
AN ANALYSIS OF THE DATA OBTAINED FROM THE DISSOLUTION
OF METALLIC HYDROXIDES IN BASIC SOLUTION AND FROM
THE WATER SOLUBILITY .................................... 125
AN ANALYSIS OF THE EXPERIMENTAL DATA FOR NEODYMIUM
HYDROXIDE................................................. 129
Equilibria with Hydrochloric Acid.................... 129
Equilibria with Perchloric A c i d ............... 147
Equilibria with Water and with Sodium Hydroxide
Solutions ...................................... 148
Hydrolysis of the Tri-valent cations of Neodymium
and Praseodymium .............................. 154
CONCLUSIONS................................................. 166
iv
LIST OP TABLES
Table Page
1. A Comparison of the E.M.F. of the Glass and
Quinhydrone Electrodes in the Presence of 0.01
C Pr+3 ................................................... 32
2. A Comparison of the E.M.P. of the Glass and
Q,uinhydrone Electrodes in the Presence of 0.025 C
Nd+3 ..................................................... 33
3. Powder Photograph Data for the Water Equilibrated
Sample of Neodymium Oxide ............................ 61
4. Powder Photograph Data for the Anhydrous Oxide
of Neodymium........................................ 63
5. Hydrolysis of Neodymium Perchlorate, c » 24.45 mC,
Standardization of Electrodes ........................ 66
6. Hydrolysis of Neodymium Perchlorate, c = 24.45 mC,
Titration of Buffer Solution ......................... 67
7. Hydrolysis of Neodymium Perchlorate, c = 24.45 mC,
Calculation of Average Ligand Number ............... 68
8. Hydrolysis of Neodymium Perchlorate, c = 9.79 mC,
Standardization of Electrodes ................... 70
9. Hydrolysis of Neodymium Perchlorate, c » 9.79 mC,
Titration of Buffer Solution ........................ 71
10. Hydrolysis of Neodymium Perchlorate, c = 9.79 mC,
Calculation of Average Ligand Number ................ 72
11. Hydrolysis of Neodymium Perchlorate, c ** 4.895 mC,
Standardization of Electrodes ........................ 73
v
/
LIST OP TABLES (Cont'd.)
12. Hydrolysis of Neodymium Perchlorate, c = 4.895 mC,
Titration of Buffer Solution ...................... 74
13. Hydrolysis of Neodymium Perchlorate, c = 4.895 mC,
Calculation of Average Ligand Number ................ 75
14. Hydrolysis of Praseodymium Perchlorate, c = 25.00 mC,
Standardization of Electrodes .................. 78
15. Hydrolysis of Praseodymium Perchlorate, c = 25.00 mC,
Titration of Buffer Solution .......................... 79
16. Hydrolysis of Praseodymium Perchlorate, c = 25.00 mC,
Calculation of Average Ligand Number ................ 81
17. Hydrolysis of Praseodymium Perchlorate, c = 12.50 mC,
Standardization of Electrodes.............. 83
18. Hydrolysis of Praseodymium Perchlorate, c = 12.50 mC,
Titration of Buffer Solution ......................... 84
19. Hydrolysis of Praseodymium Perchlorate, c = 12.50 mC,
Calculation of Average Ligand Number ............. 85
20. Hydrolysis of Praseodymium Perchlorate, c =< 10.24 mC,
Standardization of Electrodes ........................ 86
21. Hydrolysis of Praseodymium Perchlorate, c = 10.24 mC,
Titration of Buffer Solution ........ 87
22. Hydrolysis of Praseodymium Perchlorate, c = 10.24 mC,
Calculation of Average Ligand Number ................ 88
23. Hydrolysis of Praseodymium Perchlorate, c «= 5.00 mC,
Standardization of Electrodes ........................ 90
vi
i
LIST OP TABLES (Cont'd.)
24. Hydrolysis of Praseodymium Perchlorate, c « 5.00 mC,
Titration of Buffer Solution ......................... 91
25. Hydrolysis of Praseodymium Perchlorate, c *> 5.00 mC,
Calculation of Average Ligand Number ............... 92
26. Solubility of Neodymium Hydroxide in Hydrochloric
Acid at 25°C............................................. 94
27. Data on the Equilibrium between Neodymium Hydroxide
and Hydrochloric Acid at 25°C......................... 96
28. Studies on the Completeness of the Reaction between
Hydrochloric Acid and Neodymium Oxide ........ 99
29. Data on the Equilibrium between Neodymium Hydroxide
and Perchloric Acid at 25°C'......................... 100
30. The Water Solubility of Neodymium Hydroxide at
25°C...................................................... 101
31. The Solubility of Neodymium Hydroxide in Sodium
Hydroxide Solutions at 25°C.............. 101
32. Data on the Equilibrium between Mercuric Oxide and
Nitric A c i d ............................................. 116
33. Data on the Equilibrium between Beryllium Hydroxide
and Hydrochloric Acid ................................. 119
34. Data on the Equilibrium between Thorium Hydroxide
and Perchloric A c i d ............................ 123
35. Summary of Data on Neodymium Hydroxide............. 171
vil
LIST OP FIGURES
Figure Page
1. Hydrolysis C e l l ........................................ 27
2. A Comparison of the Glass and Quinhydrone Elec­
trodes in a 0.01 C Pr+3 Solution .................... 35
3. A Comparison of the Glass and Q,uinhydrone Elec­
trodes in a 0.025 C Nd+^ Solution ................... 36
4. Apparatus for Transferring the Filtering Samples ,. 45
5. Standard Curve for Neodymium Analysis-10 cm Cells . 50
6. Standard Curve for Neodymium Analysis-1 cm Cells .. 51
7. Molar Extinction versus Wave Length-1 cm Cells .... 52
8. X-Ray Powder Patterns of Oxide Samples ............ 59
9. Determination of the Free Acid in the Neodymium
Buffers, c => 24.45 and 9.79 mC ................. 69
10. Determination of the Free Acid in the Neodymium
Buffers, c => 4.90 mC .................................. 76
11. Hydrolysis of Neodymium Perchlorate ................ 77
12. Determination of the Free Acid in the Praseodymium
Buffers, c = 25.0 and 12.5 m C ........... 82
13. Determination of the Free Acid in the Praseodymium
Buffers, c = 10.24 and 5.00 mC ................. 89
14. Hydrolysis of Praseodymium Perchlorate ............. 93
15. Solubility of Nd(0H)3 in Dilute Hydrochloric Acid . 95
16. as a Function of the Equilibrium Hydrogen Ion
Activity........................ 98
viii
LIST OP FIGURES (Cont'd.)
17. Solubility of Nd(OH)g in Sodium Hydroxide Solutions. 102
18. Solubility of NdCOHjg in Sodium Hydroxide and
Hydrochloric Acid Solutions ........................... 103
ix
INTRODUCTION
The purpose of this investigation was to obtain data
on the equilibria between crystalline neodymium hydroxide
and hydrogen ions and hydroxyl ions in aqueous solution
at 25°C. and to study the hydrolysis of the tri-valent
neodymium ion at 25°C.
Such data make possible (1) the determination of
the ionic species present in aqueous solutions as a function
of the hydrogen ion concentration, (2) a calculation of the
free energy of formation of the solid, crystalline neodymium
hydroxide, (3) the determination of the solubility product
of the hydroxide, (4) a quantitative determination of the
amphoteric properties of the hydroxide.
As a great deal of work has been done recently in
the solution chemistry of uranium, thorium, and the first
row transition elements, it is of interest to compare the
chemistry of the rare earths to that of these other elements
which also contain only partially filled inner electron
shells. At the present time, analogy with the rare earths
affords the only method of obtaining qualitative informa­
tion on actinum. Also the chemistry of the actinides with
high atomic numbers is quite similar to that of the lan­
thanides, as the plus 3 oxidation state becomes most stable
in these elements.^"
-*-G. T. Seaborg, Nucleonics. 5, 16 (1949).
1