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ANALYTICAL
CHEMISTRY
AVAILABLE INSTRUMENTATION
9
Reasons Why
KERN LK-30
Micro-electrophoresis Apparatus The K e r n LK 3 0 a l o n e features all nine of these outstanding advantages.1 / / / / / /
Accurate Rapid Easy to operate Portable Compactly constructed Versatile
The only electrophoresis appara tus for quantitative analysis ot MICRO quantities (0.1 cc. oi serum). The only apparatus that makes possible a complete analysis within lYx hours from start to finish. The only instrument that gives a picture of distribution of refractive index over the entire horizontal cross-section of the cell. The LK 30 uses interferometry*. *Ref. — L. Θ. Longsworth, Anal. Chem., p. 344. Feb. 1951.
G e f the full défaits the Kern LK 30 by for complete literature
abouf writing today!
KERN COMPANY 5 Beekman St., New York 38, Ν. Υ.
current of 950 ma., at an applied anode potential of only 6 volts. The average slope of this curve corresponds to a current amplification of about 90 to 1. If an attempt is made to exceed a cer tain output, the retarding field at the cathode disappears and the output sat urates at a limit set by temperaturelimited emission of the cathode. The dynamic response of the Plasmatron is encouragingly high. The gain as a function of frequency is con stant and equal to the steady or d.c. value of gain up to 2 or 3 kilocycles. At 10 kc. it is still 8 3 % of maximum and appears to drop off rapidly above that value, to attain about 50% at 20 kc. This behavior is characteristic of all gas tubes and is determined by the rate of diffusion of the changed particles to the electrode surfaces. The time constant of plasma decay varies directly as the gas pressure, directly as the square root of the mass of the gas atoms, and as the square of the geometric di mensions of the plasma region. Experimental forms of the tube have been used for direct speaker drive in audio amplifiers, in motor control cir cuits, in pulsing circuits, and in other electronic applications. I t promises much in applications requiring low fre quency, low impedance performance whose continuous variation of relatively large currents is required. The an alyst may expect to see the Plasmatrôn employed in many devices for control or measurement. No extensive data are as yet available concerning life or reproducibility, but from the experience gained on older types, usually operating under much higher voltages, the prospects seem very favorable for dependable service. Patents on Electron
Tubes
Some years ago we had the opportunity to examine a comprehensive collection of patents dealing with electron tubes. It was astonishing to note the advanced thinking and skilled experimentation which these depositions revealed. Very little of this information has ever appeared in the more formal scientific literature, and perhaps no more than 5% of these devices have ever reached commercial production. In the scientific sense, this is unfortunate, though understandable. At the time, we gained the impression that (Continued on page 3β A)
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