CONDUCTIVITY OF ELECTROLYTES.
a collision with a molecule of the opposite kind n times in a second, then the average velocity will be half that which the force can communicate to the molecule in the nth part of a second.
According to the theory of Clausius, it is only a small proportion, say 1/p, of the molecules, which, at any given instant, are dissociated from molecules of the other kind, so as to be free to move under the action of the electromotive force, so that we must suppose each of the free molecules to continue free for a time pT; but since the proportion of free molecules to combined ones is quite unknown, the only definite result we can obtain from Kohlrausch's data is a certain very small time T, such that if the electromotive force acted on the molecules of the component during the time T, it would impress on them a velocity twice their actual average velocity.
Since the time T is very small, it is more convenient to speak of the molecule being brought to rest n times in a second, and to cal- culate n.
On the Ratio of the Charge of a Globe to that of a Circle of the same
The true value of this ratio is 1.570796....
Cavendish has given several different values as the results of his experiments.
In the account of his experiments, which represents his most matured conclusions, he states this ratio as 1·57 (Art. 237).
All the other values, however, either as stated by Cavendish or as deducible from his experiments, are lower than this.
In Art. 281 the charge of the globe of 12.1 inches diameter being 1, that of a circle 18.5 inches diameter is given as 992. The ratio of the charge of a globe to that of a circle of equal diameter as deduced from this is 1-542.
In Art. 445 the charge of the globe is compared with that of a pasteboard circle of 19.4 inches diameter. Cavendish gives the actual observations but does not deduce any numerical result from them, which shows that he did not attach much weight to them. As they seem to be the earliest measurements of the kind, I have endeavoured to in- terpret the observations by assuming that the positive and negative separations were equal when the observations are qualified in the same words by Cavendish.
I thus find 14.2 or 14.3 for the charge of the globe, and 15-2 for that of the circle, and from these we deduce for the ratio of the charge of a globe to that of a circle of equal diameter 1.5054.
In Art. 456 the ratio as deduced by Cavendish from the observations on the globe and the tin circle of 18.5 inches diameter is 1.56.
From the numerical data given in the same article, the ratio would be 1.554.
Cavendish evidently thought the result given here of some value, for he quotes it in the foot-note to Art. 473.
Another set of observations is recorded in Art. 478, from which we deduce the ratio 1.561.
It appears by a comparison of Arts. 506 and 581 that Cavendish, at the date of the latter article (which is doubtful), supposed the ratio to be 15. See foot-note to Art. 581.)
At Art. 648 the ratio is stated as 1.54.
At Art. 654 measures are given from which we deduce 1.542 and 1.37.
The numbers in Art. 682 are the same as those in Art. 281.
The references are to the Articles.
A, coated plate of glass so called, "First got" 589, 592; Nairne's 593, 314
A, Double 333, 451, 455, 461, 478, 483, 487, 489, 491, 508, 509, 533, note 35 Absorption, electric 523, note 15 Accuracy of measurements 261 Adjustment of charges of coated plates 316
Epinus (Franz Ulrich Theodor. b. 1724, d. 1802) 1, 134, 340, 549 Epinus' experiment 134, 340, 549 Air between plates not charged 344, 345, 511, 516; communication of electricity to 118-125, 208, note 9; electric properties of 99; electrified 117, 256; molecular constitution of 97 and notes 6 and 18; electric phe- nomena illustrated by means of 206; plate of 134, 340, 457, 517, 560 Alder 590
Basket salt 628 Battery of Florence flasks 521; of 49 jars 411, 432, 581; Nairne's 585, 616 Beccaria, Giacomo Battista (1716-1781) 136
Beech 590, 609
Bees'-wax 336, 371, 376 Bird's instrument, 459 Blighted straw 564
Brass plate of trial plate 297 Brass plates 511, 516
Breaking of electricity through plates
Calc. S. S. A. 626, 694 and note 34 Calibration of tubes 382, 383, 632-635 Calipers 459
Canal 40, 68, 69; bent 48, 49, 84-95 and note 3
Canton, John, F.R.S. (1718--1772) 117,
Cement 303, 484, 497
Centre of suspension 388 Chain 425, 428, 431
Chain machine 433, 605, 613
Charge defined 237; does not depend on material 68; of similar bodies as diameters 71; of thin plate inde- pendent of thickness 73; of conden- sers not affected by other bodies 317, 443, 555; of coated plates greater than by theory, 332; 'intended' 316; 'computed' 311, 326, 377, 458; 'real' 313, 377; with strong electrification 356, 357, 451, 539; with weak 358, 463, 539; with negative 463; effect of temperature, 366; measurements of,
see Tables; of battery 412; divided 288
Charging jar 223, 225
Circuit, divided 397, 417
Coated plates 300, 314, 441; theory of,
74, 160, 169; lists of, see Tables Coatings, electricity does not reside in
Communication 100, 219; of charge to battery 414, 618
Comparison of charges 236
Compound plate 379-381, 560, 677— 679
Compression (or pressure) 179; distin-
guished from condensation 200 Computed charge 311, 312 Condensation distinguished from com- pression 200
Conduction by hot glass 369
Conductivity 469, 491; of straws 565 Conductor defined 98
Cone, attraction on particle at vertex 7 Conical point, escape of electricity from
Contact 306; impossible 196 note; of
brass and glass 541, 558
Copper wire, resistance of 636-646 Cork balls 116, 117, 441, 451 Counterpoise 295
Crown glass 301, 330, 378, 411, 430, 585, 595
Cylinder 54, 148-151; charge of 281, 285-287 and note 12; two 152 and note 13; glass coated 382, 454, 479; large tin 358, 539 and note 25
D, coated plate 483, 487 Deal 590, 609
Deficient fluid 67, note DEFINITIONS:
Canal 40 Charge 237
Communication 100 Compression 199 Computed charge 311 Condensation 200 Conductor 98
Deficient fluid 67, note
Distance of spreading 328 Electrification 102, 201 Immoveable fluid 12
Inches of electricity, circular 458, 648; globular 654; square 648, 654 Incompressible fluid 69 Insulation 100 Non-conductors 98 Observed charge 325 Overcharge 6, 201 Real charge 313 Redundant fluid 13 Saturated body 6 Undercharge 6
Degrees of electrification 329, 356; of electrometer 560, note
Dephlegmated wax 371, 375, 518 Discharge, divided 397, 417, 576, 597, 613 Distance to which electricity spreads 309, 323, 328
Dividing machine 341, 459, 517, 591 Divisions of trial plate 297 Double plates 333
Earth connexion 258, 271
Electric organ of torpedo 396, note 29 Electricity an elastic fluid 195; diffused through bodies not electrified 216; inches of 647, 648
Electrification, degree of 102, 201 and note 7
Electrodes, large 258, 271 Electrometer:
Cavendish's discharging 402, 405, 427, 430, 434
gauge (paper cylinders) 224, 248, 295, 495, 511, 524, 542, 559; new wood 525, 563
Divisions of 560, note
Henly's 559, 568, 570, 571, 580; on rod 569
Lane's 263, 329, 559, 569, 570, 571,
580, 589, 603, 604
Paper cylinders 486 Pith ball 581
Straw 249, 404, 559, 570, 571, 581; with variable weights 387; corks 441, 451, 566
Testing 244, 296, 358, 359 English plate glass 301, 496 Equivalent thickness of compound plates 379
Error, greater with coated plates than with simple conductors 299; probable of estimation of capacity 250, 261; in Exp. I. 234; due to unequal charg- ing 250
Excess of redundant fluid in coated plates 560 and note 30
Experiment I. 218, 233, 291, 512, 562 and note 19
II. 235, 292, 561 III. 265, 467
IV. 269, 293, 471, 480, 481 and note 20
V. 273, 447, 448, 452, 454, 472, 473, 474, 475, 681 and note 21
VI. 279, 453, 476, 477, 683 VIL. 281, 448, 478, 682 and note 13
VIII. 288, 542 and note 23
Floor, effect of 335
Florence flask 521; battery 521
Fluid, electric 195, 216, note 1; real 91; incompressible 69, 94, 236, 273, 276, 278, 294, 348 and note 3
Force near an electrified surface 154; inversely as square of distance 232, 512, 513, 562 and note 17
Fore and back room 469 Frame placed below circles 274 Frames 221
Franklin, Benjamin, F.R.S. (1706- 1790) 350 note, 363
Fringe of dirt on coated plates 308, 326, 538
Garden, copper wire stretched round 643
Gauge electrometer 224, 248
General conclusion 291 Gilt straws 249, 394, 567
Glass, different electric qualities of 301, 322
Glass house 378
Glauber's salt 626, 694
Globe, charge of compared with that of circle 237, 282, 445, 455, 456, 654, 681, 687, note 35
Globe, electrified 20-27, 280; capacity of 281, 282; compared with double plate 333, 334
Globe, meaning the world 214
Globe of electrical machine 248, 495,
Globe within hemispheres 218, 512, 562, note 19
Globes, coated 523, 542, 559, 563 Gradual spreading of electricity 302 Guide for the eye 249, 525, 571 Gum lac 371, 374, 376 Gymnotus 437, 601
Hamilton, Dr, Prof. of Philosophy, Dublin (Priestley, p. 429) 126
Heat, effect on charge of glass, &c. 366, 368, 548, 549, 556, 680, note 26 Heat produced by current 212 Height and size of room 335 Hemispheres 219
Henly (William, F.R.S., d. 1779); linen draper in London; his electrometer 559, 568, 569, 580
Hissing noise before spark 213
Hot glass a conductor 369, note 26; compared with cold 366, 368 Hunter (John, F.R.S., b. 1728, d. 1793) 436, 601, 614
Hygrometer corks 459; Smeaton's 468; common 468 Hypothesis 3, 202
Immoveable fluid 12, 351
Inches of electricity 458, 648, 654 Incompressible fluid 40, 236, 273, 276, 278, 294, 348 and note 3
Increase of charge of globe due to in-
duction 339, 652 and note 24
« PreviousContinue » |