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High-Precision Coulometric Titrations of Acids Michael Charles Hadka Iowa State University

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High-Precision Coulometric Titrations of Acids Michael Charles Hadka Iowa State University Iowa State University Capstones, Theses and Retrospective Theses and Dissertations Dissertations 1980 High-precision coulometric titrations of acids Michael Charles Hadka Iowa State University Follow this and additional works at: https://lib.dr.iastate.edu/rtd Part of the Analytical Chemistry Commons Recommended Citation Hadka, Michael Charles, "High-precision coulometric titrations of acids " (1980). Retrospective Theses and Dissertations. 7375. https://lib.dr.iastate.edu/rtd/7375 This Dissertation is brought to you for free and open access by the Iowa State University Capstones, Theses and Dissertations at Iowa State University Digital Repository. It has been accepted for inclusion in Retrospective Theses and Dissertations by an authorized administrator of Iowa State University Digital Repository. For more information, please contact [email protected]. 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ZEEB ROAD, ANN ARBOR, Ml 48106 18 BEDFORD ROW, LONDON WCl R 4EJ, ENGLAND 8019633 HADKA, MICHAEL CHARLES HIGH-PRECISION COULOMETRIC TITRATIONS OF ACIDS Iowa State University PH.D. 1980 University Microfilms IntBrnâtiOPiâi 3% X. Z^b Road. Ann Arbor. MI 48106 18 Bedford Row. London WCLR 4EJ, England PLEASE NOTE: In all cases this material has been filmed in the best possible way from the available copy. Problems encountered with this document have been identified here with a check mark . 1. Glossy photographs 2. Colored illustrations 3. Photographs with dark background ^ '4. Illustrations are poor copy 5. °rint shows through as there is text on both sides of page 6. Indistinct, broken or small print on several pages __________ throughout 7. Tightly bound copy with print lost in spine S. Computer printout pages with indistinct print S. Page(s) lacking when material received, and not available from school or author 10. Page(s) seem to be missing in numbering only as text follows 11. Poor carbon copy 12. Not original copy, several pages with blurred type 13. Appendix pages are poor copy 14. Original copy with light type 15. Curling and wrinkled pages 16. Other UniversTv MtcrdTiims Intemarlonal 200 \ "====0. v; -S'Q5 •313: 761-1700 High-precision coulometric titrations of acids by Michael Charles Hadka A Dissertation Submitted to the Graduate Faculty in Partial Fulfillment of the Requirements for the Degree of DOCTOR OF PHILOSOPHY Department : Chemistry Major: Analytical Chemistry Approved : Signature was redacted for privacy. In Charge of Major Work Signature was redacted for privacy. For the Major Department Signature was redacted for privacy. For theii^Sad Œ^duate College Iowa State University Ames, Iowa 1980 il Page I. INTRODUCTION 1 A. Background of Coulometric Titrations 1 B. Current Status of the Faraday 3 G. Reexamination of the Value of the Faraday 9 D. Selection of Primary Chemicals and Solvents 14 II. APPARATUS AND PROCEDURE FOR HIGH-PRECISION COULOMETRIC TITRATION 17 A. Introduction 17 B. Apparatus and Measurement of the Various Physical Quantities 22 C. Measurement of Mass. Weighing Samples for Titration 37 D. Measurement of Temperature 39 E. Measurement of pH 4l F. Titration Cell 43 G. Reagents 55 H. Calculation of Results 57 III. LOCATION OF EQUIVALENCE-POINT 60 A. Introduction 60 B. Location of the Point of Inflection on a Titration Curve 6l C. Theoretical Treatment of the Equivalence- Point Region in the Titration of a Strong Acid with a Strong Base 64 D. Failure of the Koch, Poe and Diehl Method of Locating the Points of Inflection in the Titration of Perchloric Acid 90 ill IV. MIGRATION OF IONS THROUGH POROUS MEMBRANES 96 A. Introduction 96 B. Theory of Electrolytic Conduction of Current 102 C. Experimental Work. Apparatus 105 D. Experimental Work. Measurement of the Flow Rate through Membranes 107 E. Experimental Work. Migration of Ions Across a Membrane of Ultra Fine Fritted Glass, Potassium Chloride as Supporting Electrolyte 108 F. Experimental Work. Migration of Ions Across a Membrane of Unfired Vycor, Potassium Chloride as the Supporting Electrolyte 111 G. Experimental Work. Hydroxide Ion Migration Across Fritted-Glass Membranes. Effect of Flow Rates, pH, and Current Intensity on Migration ll6 H. Experimental Work. Effect of the Concentration of the Supporting Electrolyte, Potassium Chloride, on the Migration of Hydroxide Ions Across Fritted-Glass Membranes 124 I. Experimental Work. Migration of Hydroxide Ions and Hydrogen Phthalate Anions in Sodium Perchlorate Supporting Electrolyte 131 V. TITRATION OF POTASSIUM HYDROGEN PHTHALATE 137 A. Potassium Hydrogen Phthalate as a Primary Standard 137 B. The Atomic Weight Tables. The Atomic Weights of Carbon, Hydrogen, Oxygen and Potassium. The Molecular Weights of Potassium Hydrogen Phthalate and Benzoic Acid 149 C. Experimental Work 152 D. Results and Discussion 157 iv COULOMETRIC TITRATION OF BENZOIC ACID IN WATER AND IN WATER-ALCOHOL MIXTURES I6l A. Introduction l6l B. Physical and Chemical Properties 162 C. Purification 162 D. Benzoic Acid as a Primary Standard 163 E. Experimental Work 174 F. Results and Discussion 184 PURIFICATION AND TITRATION OF FUROIC ACID 190 A. Introduction 190 B. Experimental Work 191 C. Results and Discussion 195 PURIFICATION AND TITRATION OF ADIPIC ACID 199 A. Introduction 199 B. Experimental Work 200 C. Results and Discussion 202 SUMMARY 204 BIBLIOGRAPHY 218 ACKNOWLEDGEMENTS 226 APPENDIX: ATOMIC WEIGHTS OF THE ELEMENTS 228 A. Location of Successive Reports by the Commission on Atomic Weights of the International Union of Pure and Applied Chemistry 228 1 I. INTRODUCTION A. Background of Coulometric Titrations Coulometry is the analytical technique by which the amount of a material is determined by measuring the quantity of electricity required to generate at an electrode an amount of a second chemical just necessary to react completely and stoichemically with the material being determined. Faraday's Laws of electrolysis relate a quantity of electricity passed to the amount of a chemical changed at an electrode. The relationship is given by the equation G = ^ It Mol' Wt. (1) F n ^ in which G is the weight of the chemical undergoing a change at the electrode, in grams; P is a proportionality constant called the faraday, the current value (19,46) of which is 96,486. 57 1972 NES coulombs per gram-equivalent-weight ; I is the current, in amperes; t is the time, in seconds; Mol. Wt./n is the equivalent weight of the chemical under­ going the change at the electrode, that is, the molecular weight divided by the number of electrons involved in the reaction. All of the factors in equation (1) can be measured with a high degree of accuracy and precision. 2 1, The electron as the ultimate chemical standard The electron has been chosen as the ultimate standard in chemistry. There is only one kind of electron and it is the only really pure chemical known. The electron can be delivered to or removed from a liquid in any convenient quantity and this quantity can be measured with great accuracy and precision. The electron can be delivered or removed from a liquid at any desired potential over a range of some five volts and thus a variety of electrochemistry can be performed. One faraday of electricity contains one Avogadro's number of electrons, that is, one mole of electrons. Thus, one faraday is equivalent in chemical action to one liter of a one normal solution of an oxidizing agent, or of a reducing agent. The faraday is a surprisingly large amount of electricity; put into other units 96,486.57 coulombs is 26.80183 ampere-hours (per gram-equivalent- weight ). 2. History of coulometrlc titrations The history of coulometrlc titrations begins with the work of Szebelledy and Somogyi (80) prior to the second World War. Since then, coulometry has been applied to the determi­ nation of a variety of materials and improvements in the accuracy and precision have accompanied the development. Really high-precision coulometrlc titrations were first made in 1959 by Taylor and Smith (84). Later, Marinenko and 3 Taylor (62,62,6^,65) used coulometry to assay primary standard materials.
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