THE VAPOR PRESSURE OF TITANIUM TETRACHLORIDE DISSERTATION Presented in Partial Fulfillment of the Requirements for the Degree Doctor of Philosophy in the Graduate School of The Ohio State University By HOMER CLYDE WEED, JR., B.S., M.S. ** «* The Ohio State University 1957 Approved by: // / 'Adviser Jepartment of Chemistry ACKNOWLEDGMENTS The author wishes to thank Dr. George E. MacWood for the helpful guidance and encouragement given by him throughout the course of the research. Professor P. M. Harris and Professor W. J. Taylor have generously lent equipment essential for the ex­ perimental workj the thanks of the author go to them also. The cell compartment used in the spectrophoto- metric measurements was constructed by Messrs. P. G. Laverack and Roy Morris of the Chemistry Department Instrument Shopj their cooperation and their sugges­ tions concerning the mechanical design are appreciated. The author is indebted to Mrs. Carl G. Kauffmann for her efforts in connection with the arrangement of the dissertation and fer her execution of a difficult typing assignment. Financial support for this research was provided by the Office of Naval Research under Contract No. NONR-495(06). This support is hereby acknowledged. -ii TABLE OF CONTENTS Page I. INTRODUCTION................................. 1 A. Statement of Problem................... 1 B. Survey of Relevant Investigations 2 II. EXPERIMENTAL................................ 9 A. Apparatus....... 10 Transfer Systems............. 10 System for Absolute Vapor Pressure Measurements........................... 13 System for Spectrophotometric Measurements......... 17 B. Operating Procedures.................. 20 Sample Transfer......................... 20 Absolute Vapor Pressure Measurements.. 20 Spectrophotometric Measurements 22 Calibration of Thermocouples..... 23 III. ANALYSIS OF DATA............................ 25 A. Reduction of Observations............. 25 Time.................................... 25 Temperature...................... 26 Pressure......................... 46 Absorbance, Wave Length and 7r ........ 55 B. Thermodynamic Functions.............. 84 Theory........... 84 Least Squares Analysis, Absolute Measurements.............. 87 Numerical Expressions for the Heat, Free Energy and Entropy of Vaporisation........................... 88 Numerical Expressions for the Heat, Free Energy and Entropy of Sublimation.................. 90 -iii- TABLE OF CONTENTS, eont. Pag£ C. Spectrophotometric Functions.......... 90 The ory............... 91 Calculation of A Q for the 50 mm Cell.. 92 The Cell Constants K*.................. 93 The Molar Absorbancy Index ajj....... 96 D. Tabulated Thermal Functions........... 99 Spectroscopic Values for the Gas...... 99 Tabular Differences from Vapor Pressure Results ............... 107 Thermal Functions of Condensed Phases............ 118 E. Estimation of Errors................... 119 Time..................................... 119 Temperature............................. 119 Pressure................................ 122 Absorbance, Wave Length, and t c ........ 123 Thermal Functions...................... 124- Molar Absorbancy Index................. 129 IV. RESULTS AND CONCLUSIONS..................... 131 A. Vapor Pressures.............. 131 B. Heats and Entropies of Vaporization... 133 C. Molar Absorbancy Index a^.............. 135 BIBLIOGRAPHY....................................... 136 AUTOBIOGRAPHY...................................... 139 -iv- LIST OF TABLES Table Number Page * . I. (R^./R0) v s . Temperature................... 2S II. Bridge Temperature Correction Factors.. 32 III. Self-Consistency Corrections............ 33 IV. EMF vs. Temperature for the Copper- Constantan Thermocouple Above 273.16°K................. 37 V. Calibration Data for the Copper- Constantan Thermocouple from 0°C to 30°C.................................... 39 VI. Corrections on Absolute Temperatures Above 273.16 K for the Copper-Constan- tan Thermocouple..........................4.0 VII. Calibration Data for the Copper- Constantan Thermocouple below 0°C....... 4.2 VIII. EMF vs. Temperature for the Chromel- Alumel Thermocouple................ 4-3 IX. Calibration Data for the Chromel- Alumel Thermocouple..................... 4-7 X. Correction do for Thermal Expansion of Scale............ 51 XI. Capillary Depression d. of the Mercury Meniscus in a Fyrex Tube,....... 53 XII. Correction for Thermal Expansion of Mercury............... 54 XIII. The Vapor Pressure of Liquid Titanium Tetrachloride: Absolute Manometric Data............................. 56 XIV, A 0 vs. T' for the l.mm Cell............ 60 XV. The Vapor Pressure of Liquid Titanium Tetrachloride: Data for the 1 Mm Cell. 6l LIST OF TABLES, cont. Table Humber Page. XVI, A 0 vs, T1 for the 5 mm Cell,,,.,....... 63 XVII, The Vapor Pressure of Liquid Titanium Tetrachloride: Data for the 5 mm Cell.. 64. XVIII. Calculated Values of A for the 50 mm C e l l , . ..... 68 XIX. The Vapor Pressure of Solid and Liquid Titanium Tetrachloride: Data for the 50 mm Cell.. ........................ 69 XX. A 0 vs. T 1 for the 50 mm Cell.............. 74 XXI. Wave Length Calibration................. 76 XXII. The Molar Absorbancy Index aM for Titanium Tetrachloride Vapor from 980 to 200 mmu........................... 78 XXIII. Summary of Results for Absorption Constants................................ 95 XXIV. Comparison of Molar Absorbancy Index Values . 100 XXV. Calculated or Graphically Interpolated Corrections for Thermal Functions of Titanium Tetrachloride in the Ideal Gaseous State........................... 104 XXVI. Fundamental Vibration Frequencies and Degeneracies for Titanium Tetra­ chloride Gas.................. 106 XXVII. Thermal Functions for Titanium Tetra­ chloride in the Ideal Gaseous State.... 108 XXVIII. Calculation of ....................... Ill XXIX. Thermal Functions for Titanium Tetra­ chloride Solid and Liquid .....* 113 XXX. Tabular and Interpolated Values of Thermal Functions.......... 116 -vi- LIST-OF TABLES, cont. Table Humber Paae XXXI. Comparison of Thermal Functions at 200°K................................... 127 XXXII, Comparison of Experimental Vapor Pressures of Schaefer and Zeppernick with Calculated Vapor Pressures from This Investigation,.,.................... 132 -vii- LIST OF ILLUSTRATIONS Figure Number Pa^je 1. Vacuum System for Filling Optical Cells........................................ 12 2. Measuring System and Vacuum System for Absolute Manometry.............. 15 3. Cell Compartment for Absorbance Measurements with Beckman DU Spectrophotometer...................... 19 4. Absorption Coefficient of Titanium Tetrachloride vs Wave Length............... 102 -viiil- I. INTRODUCTION A.. Statement of the Problem In connection with an investigation of the thermo­ dynamic properties of titanium halides, particularly titanium chlorides, it became apparent that the vapor pressure of solid titanium tetrachloride had not been measured experimentally and that there were discrep­ ancies between the results of the previous investi- (12 3) gators * * who had measured values for liquid (1) Kimio Arii, Bulletin of the Institute for Physical Chemical Research (Tokyo), 714.-718 (i929). (2) Kimio Arii, Science Reports, Tohoku Imperial University, First Series, 22, 182-199 (1933). (3) Harold Schaefer and Friedrich Zeppernick, Zeitschrift fhr anorganische und allgemeine Chemie, 222, 274. (1953). titanium tetrachloride. The work of this dissertation was undertaken in order to check on these results and to extend the range of measurement far enough to obtain experimental vapor pressure values for solid titanium tetrachloride, so that related thermodynamic properties such as heat and entropy of vaporization and sublimation could be calculated. Spectrophotometric methods ap­ peared suitable for most of the temperature and pressure range to be explored; in connection with their use, the absorption spectrum of titanium tetrachloride vapor was determined over the visible and ultraviolet wave-length range since it was not known with precision at that time. B. Survey of Relevant Investigations (1 2 Although the results of Arii * ) were quite self consistent they could not be verified by Schaefer (4.) K. K. Kelley, Contributions to the Data of Theoretical Metallurgy, III. The Free Energies of Vaporization and Vapor Pressures of Inorganic Substances. Bureau of Mines Bulletin 3S3, Washington (1935), p. 106. (3) and Zeppernick, who found that their measured vapor pressures were consistently lower than those of Arii in the same temperature range and attributed this differ­ ence to the presence of residual inert gas in the measuring cell of Aril's apparatus. Aril's measurements O 0 covered the range from 4-08.16 K to 293.16 K: Schaefer and Zeppernick1s from 359.56°K to 312.76°K. The dis­ crepancy between the two sets of results and the lack of data below 293.16°K made it desirable to check both sets over at least a part of their temperature range and to obtain further information for temperatures below 293.16°K. (5) The experimental work of Latimer on the specific 3 (5 ) W* M s La timer, Journal of the American Qhest­ eal Society, 90-97 (1922). heat capacity of solid and liquid titanium tetrachloride and on the heat of fusion of the solid has been used by Skinner in calculating values of thermal functions (6 ) Gordon Skinner, Charles E. Beckett and H. L. Johnston, Titanium and Its Compounds. Herrick L. Johnston Enterprises, Columbus, Ohio (1954)> p. 108. for solid titanium tetrachloride from 50°K to the melting point and for