Volume 2, Issue 1, 01 January 1932
Index of content:
2(1932); http://dx.doi.org/10.1063/1.1745024View Description Hide Description
Simple formulas are developed for the impedance of short lengths of Lecher system terminated by resistances. This impedance is most simply expressible as a multiple of the surge impedance. The variation of impedance with system length is traced and certain simple relationships are found. It is shown that any system of loads across a Lecher system is equivalent to a certain length of system terminated by a certain resistance. The formulas account for Takagishi's double hump phenomenon and this phenomenon is applied to finding the bridge shortening of an actual bridge. A method of calculating resistance from a resonance curve is derived.
2(1932); http://dx.doi.org/10.1063/1.1745023View Description Hide Description
Measurements are reported on the color sensitivities of various photoelectric tubes having cathodes made of alkali metals. A composite surface of R‐Ag‐RO‐Ag of any alkali metal R shows a higher sensitivity over a wider range of wave‐lengths than R‐RO‐Ag and has two peaks, one between 330 and 370 mμ, and one at about 500 mμ for potassium and 550 mμ for rubidium and between 700 and 800 mμ for caesium. If a gas filled lamp at 2700°K is used as a light source, photoelectric currents from vacuum photo‐tubes are obtained sometimes as large as 29μa per lumen for potassium, and 10–15μa per lumen for rubidium, and 40–50μa per lumen for caesium. It is also reported that the potassium cell in combination with a proper filter would constitute a means for an ideal photometer.
ELECTROKINETIC POTENTIALS. XI. THE EFFECT OF SODIUM SOAPS ON THE ELECTRIC MOMENT OF THE DOUBLE LAYER AT AN AQUEOUS‐CELLULOSE INTERFACE2(1932); http://dx.doi.org/10.1063/1.1745025View Description Hide Description
1.Electrokinetic studies of aqueous solutions of sodium formate, sodium acetate, sodium propionate, sodium butyrate, sodium caprylate, sodium oleate and sodium oxalate have been conducted at a cellulose interface with the streaming potential technique.
2. It is suggested that in interest of clearness and accuracy the attempt to express electrokinetic data in terms of ``potentials'' be abandoned and that the electric moment of the double layer, which does not require a knowledge of the magnitude of the dielectric constant, be substituted for ζ.
3. It is indicated that after the fourth carbon atom has been added the electric moment of the double layer is essentially a constant.
4. It is noted that there is no correspondence between the ionization constant of the fatty acid from which the soap is derived and its effect on the electrokinetic conditions at the interface. This indicates that hydrolysis and the resulting OH ion plays a minor role.
5. It is pointed out that the electric moment of the double layer in the case of the longer chained soaps is almost independent of the concentration whereas that of the short chained soaps are much more sensitive to increased concentration.
6. The maximum electric moment is found at about 2×10−4 normal. This is true also for a number of salts.
2(1932); http://dx.doi.org/10.1063/1.1745026View Description Hide Description
The magnetic susceptibilities of eight series of alloys: tin‐thallium, antimony‐thallium, thallium‐cadmium, zinc‐cadmium, lead‐antimony, tin‐antimony, cadmium‐antimony and zinc‐antimony have been investigated by Gouy's method. In three series,—antimony‐cadmium, antimony‐zinc and tin‐antimony an intermetallic compound is indicated by an abrupt change in the slope of the susceptibility concentration curve. The compounds thus indicated are SnSb, CdSb, and ZnSb with some evidence for the compound Sn2Tl. There is nearly a linear relation between the susceptibility and the concentration of one of the constituents where the constituents form simple heterogeneous mixtures—a result best illustrated in the zinc‐antimony series of alloys.
2(1932); http://dx.doi.org/10.1063/1.1745027View Description Hide Description
The output voltage ep of a thermionic tube operated over a suitable restricted range of grid voltages eg may be represented by the parabola ep =b 0+b 1 eg +b 2 eg 2. By adding to this in opposite phase the output of another tube, operated on the straight line portion of its curve, we may balance out entirely the term b 1 eg , so that the characteristic of the combination of tubes is ec =b 0+b 2 eg 2. The system will then operate as a frequency doubler, for the output is proportional to eg 2 alone. In the experimental set‐up described, with a 201A tube, an output of 0.175 volts of frequency 2f is obtained from an input of 1.0 volts of frequency f. It is found that when the characteristic of the system is plotted, the curve is never a symmetrical parabola ec =b 0+b 2 eg 2 over a very wide range of grid voltages. This is because the coefficient of the cube term in the equation of the tube characteristic is not negligibly small, and the equation must be written ec =b 0+b 2 eg 2+b 3 eg 3. It is shown how the coefficient b 3 may be determined by measuring the dissymmetry of the curve.
2(1932); http://dx.doi.org/10.1063/1.1745028View Description Hide Description
An apparatus is described for the class‐room demonstration of electron diffraction photographs obtained from thin metallic films and using the range 2000 to 15000 volts. It is very simple to build and reasonably stable. The method of operation is explained.
2(1932); http://dx.doi.org/10.1063/1.1745029View Description Hide Description
An experimental comparison has been made of three methods of measuring the unpolarized resistivity of glass and fused quartz over a temperature range from 20 to 500°C. At high temperatures all three methods are in quantitative agreement and give a straight line when the logarithm of the resistivity is plotted against the reciprocal of the absolute temperature. At lower temperatures, however, the a.c. curve deviates from this straight line, indicating an additional component of loss which does not exist on d.c. This additional loss may be due to the orientation of polar molecules, though no definite proof can be given. The results obtained by the other two methods, both with direct current, are in close agreement over the whole temperature range, and give without doubt the true unpolarized resistivity.