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Davies equation

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85: 77: 350: 293: 214:. For 1:1 electrolytes the difference between measured values and those calculated with this equation is about 2% of the value for 0.1 M solutions. The calculations become less precise for electrolytes that dissociate into ions with higher charges. Further discrepancies will arise if there is association between the ions, with the formation of 210:, goes to zero as the ionic strength goes to zero, so the equation reduces to the Debye–Hückel equation at low concentration. However, as concentration increases, the second term becomes increasingly important, so the Davies equation can be used for solutions too concentrated to allow the use of the 198: 35:
solutions at relatively high concentrations at 25 °C. The equation, originally published in 1938, was refined by fitting to experimental data. The final form of the equation gives the mean
95: 391: 334: 425: 384: 415: 410: 430: 420: 327: 435: 377: 211: 24: 320: 193:{\displaystyle -\log f_{\pm }=0.5z_{1}z_{2}\left({\frac {\sqrt {I}}{1+{\sqrt {I}}}}-0.30I\right).} 28: 8: 365: 308: 247: 84: 76: 300: 252: 349: 361: 357: 304: 67: 404: 80:
Semi-log plot of activity coefficients calculated using the Davies equation
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Plot of activity coefficients calculated using the Davies equation
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of an electrolyte that dissociates into ions having charges
98: 192: 402: 385: 328: 392: 378: 335: 321: 16:Empirical extension of Debye–Hückel theory 83: 75: 276:. London: Butterworths. pp. 37–53. 403: 271: 344: 287: 13: 14: 447: 348: 291: 27:which can be used to calculate 265: 1: 258: 23:is an empirical extension of 364:. You can help Knowledge by 307:. You can help Knowledge by 7: 241: 10: 452: 343: 286: 426:Electrochemical equations 416:Chemical thermodynamics 411:Thermodynamic equations 431:Electrochemistry stubs 360:-related article is a 303:-related article is a 272:Davies, C. W. (1962). 194: 89: 81: 421:Equilibrium chemistry 212:Debye–Hückel equation 195: 87: 79: 39:activity coefficient 29:activity coefficients 436:Thermodynamics stubs 96: 248:Osmotic coefficient 25:Debye–Hückel theory 190: 90: 82: 373: 372: 316: 315: 203:The second term, 171: 168: 155: 66:as a function of 443: 394: 387: 380: 352: 345: 337: 330: 323: 301:electrochemistry 295: 288: 278: 277: 269: 253:Pitzer equations 237: 236: 235: 227: 226: 209: 199: 197: 196: 191: 186: 182: 172: 170: 169: 164: 151: 150: 143: 142: 133: 132: 117: 116: 72: 65: 56: 47: 451: 450: 446: 445: 444: 442: 441: 440: 401: 400: 399: 398: 342: 341: 284: 282: 281: 274:Ion Association 270: 266: 261: 244: 234: 231: 230: 229: 225: 223: 222: 221: 219: 204: 163: 156: 149: 148: 144: 138: 134: 128: 124: 112: 108: 97: 94: 93: 70: 64: 58: 55: 49: 46: 40: 21:Davies equation 17: 12: 11: 5: 449: 439: 438: 433: 428: 423: 418: 413: 397: 396: 389: 382: 374: 371: 370: 358:thermodynamics 353: 340: 339: 332: 325: 317: 314: 313: 296: 280: 279: 263: 262: 260: 257: 256: 255: 250: 243: 240: 232: 224: 201: 200: 189: 185: 181: 178: 175: 167: 162: 159: 154: 147: 141: 137: 131: 127: 123: 120: 115: 111: 107: 104: 101: 68:ionic strength 62: 53: 44: 15: 9: 6: 4: 3: 2: 448: 437: 434: 432: 429: 427: 424: 422: 419: 417: 414: 412: 409: 408: 406: 395: 390: 388: 383: 381: 376: 375: 369: 367: 363: 359: 354: 351: 347: 346: 338: 333: 331: 326: 324: 319: 318: 312: 310: 306: 302: 297: 294: 290: 289: 285: 275: 268: 264: 254: 251: 249: 246: 245: 239: 217: 213: 208: 187: 183: 179: 176: 173: 165: 160: 157: 152: 145: 139: 135: 129: 125: 121: 118: 113: 109: 105: 102: 99: 92: 91: 86: 78: 74: 69: 61: 52: 43: 38: 34: 30: 26: 22: 366:expanding it 355: 309:expanding it 298: 283: 273: 267: 206: 202: 59: 50: 41: 20: 18: 33:electrolyte 405:Categories 259:References 218:, such as 216:ion pairs 174:− 114:± 106:⁡ 100:− 242:See also 356:This 299:This 205:0.30 37:molal 362:stub 305:stub 177:0.30 57:and 19:The 122:0.5 103:log 31:of 407:: 238:. 228:SO 220:Mg 73:: 393:e 386:t 379:v 368:. 336:e 329:t 322:v 311:. 233:4 207:I 188:. 184:) 180:I 166:I 161:+ 158:1 153:I 146:( 140:2 136:z 130:1 126:z 119:= 110:f 71:I 63:2 60:z 54:1 51:z 45:± 42:f

Index

Debye–Hückel theory
activity coefficients
electrolyte
molal
ionic strength


Debye–Hückel equation
ion pairs
Osmotic coefficient
Pitzer equations
Stub icon
electrochemistry
stub
expanding it
v
t
e
Stub icon
thermodynamics
stub
expanding it
v
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Categories
Thermodynamic equations
Chemical thermodynamics
Equilibrium chemistry
Electrochemical equations

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