Creator:Michael Spiro
Date Created:
Place Created:
Keywords:transefernce numbers
Context:table of contents from chemistry book chapter
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Chapter • ▼
transference numbers
Michael Spiro
I
2
3
Introduction and Basic Theory 206
Conductance 207
Ionic or Electric Transport Number 208 Ion-Constituent Transference Number 209 Ion-Constituent Conductance and Mobility 213
Variation with Physical Factors 213
Variation with Concentration 213
Variation with Solvent, Temperature, and Pressure 217
Applications 220
Fundamental Information 220 Structural Investigations 221 Separations and Other Applications 222
Measurement of Transference Numbers 222
Comparison of Methods 222 Hittorf Method 223 Introduction and theory 223 Experimental 227 Analysis 227 Electrodes 228 Disturbing effects 229 Cell design 230 Quantity of electricity 234 Direct Moving Boundary Method 235 Introduction and theory 235 Experimental 239 Observation of the boundary 239 Indicator and initial indicator concentration 245 Electrodes 247
Cell design and filling techniques 248 Current and time 256 Reliability of the results 258
4
206 TRANSFERENCE NUMBERS
The Differential moving boundary method 258 Indirect Moving Boundary Method 259 Introduction and theory 259 Experimental 260 General conditions 260 External analysis 261 Internal conductometric analysis 262 Internal refractometric analysis 263 Analytical Boundary Method 264 Introduction and theory 264 Experimental 267 Quantity of electricity 267 The mechanical plane 267 Electrodes 267
Analysis, indicator, and cell design for two-salt systems 267 Tracer, analysis, and cell design for tagged systems 268 E.m.f. Method Using Cells with Transference 270 Introduction and theory 270 Experimental 274 Electrodes 274 Cell design 275 Electrical measurements 276 E.m.f. Method Using Cells in Force Fields 277 Introduction and theory 277 Experimental 278
5 Appendix 280
Accurate Transference Numbers of Some Electrolytes in Water at 25°C 280
Selected Transference Data in Several Solvents and at Various Temperatures 284
Transference Number Bibliographies 287
I INTRODUCTION AND BASIC THEORY
The electrical conductance of an electrolyte solution is a measure of the extent to which all the ions present in the solution move in the direction of an applied electric field and so carry the resulting electric current. The relative extent to which a given type of ion i participates in this process, and thus the proportion of the current it carries, is expressed by its ionic or electric transport number tt. Unfortunately, in the majority of cases (whenever, in fact, there are complex ions present) we simply cannot measure f,. What