The specific inductive capacity of a dielectric varies with the time and
temperature. That of glass rises 2.5 per cent. between 12° C. (53.6° F.)
and 83° C. (181.4° F.). If a condenser is discharged disruptively, it
retains a small residual charge which it can part with later. If a
metallic connection is made between the plates, the discharge is not
instantaneous. Vibration shaking and jarring facilitate the complete
discharge. All this shows that the charge is a phase of the dielectric
itself, and indicates a strained state into which it is brought.
The following table gives the specific inductive capacity of various
substances:
Specific Inductive Capacity.
Substance Specific
Inductive Authority
Capacity.
Vacuum, air at about 0.001 millimeters pressure 0.94 about Ayrton
Vacuum, air at about 5 millimeters 0.9985 Ayrton
0.99941 Boltzmann
Hydrogen at about 760 millimeters pressure 0.9997 Boltzmann
0.9998 Ayrton
Air at about 760 millimeters pressure 1.0 Taken as the
standard
Carbon Dioxide at about 760 millimeters pressure 1.000356 Boltzmann
1.0008 Ayrton
Olefiant Gas at about 760 millimeters pressure 1.000722 Boltzmann
Sulphur Dioxide at about 760 millimeters pressure 1.0037 Ayrton
Paraffin Wax, Clear 1.92 Schiller
1.96 Wüllner
1.977 Gibson and Barclay
2.32 Boltzmann
Paraffin Wax, Milky 2.47 Schiller
India Rubber, Pure 2.34 Schiller
India Rubber, Vulcanized 2.94 Schiller
Resin 2.55 Boltzmann
Ebonite 2.56 Wüllner
2.76 Schiller
3.15 Boltzmann
Sulphur 2.88 to 3.21 Wüllner
3.84 Boltzmann
Shellac 2.95 to 3.73 Wüllner
Gutta percha 4.2
Mica 5
Flint Glass, Very light 6.57 J. Hopkinson
Flint Glass, Light 6.85 J. Hopkinson
Flint Glass, Dense 7.4 J. Hopkinson
Flint Glass, Double extra dense 10.1 J. Hopkinson