Now with ONE instrument ; 4 > a-.»*- ' „ « - - . t L Ji •»· * »

« *rk. - ; t - f t

< *·» ι · > > - ** ~ ί » , ; t . -> %

• Measu re C 1 4 and H 3 ac t i v i t y to 10~ 1 2 Cur ies • M e a s u r e e lec t r i ca l p rope r t i e s : d e t e c t

1 0 - 1 7 a m p s ; 2 0 m ic rovo l t s ;

• and make a variety of other precise measurements Besides being the most accurate, convenient and inexpensive instrument for determining C1* and H3, the CARY Model 31 may be used to perform a variety of other tasks in the laboratory.

FOR EXAMPLE, The 31 may be used as:

• A sensitive detector for beta and gamma radiation. May often serve as a substitute for geiger or proportional counters.

• A spectrometer for measuring alpha energy in the presence of substantial beta and gamma emissions.

• A monitor for gamma background, surface alpha contamination, or air contamination.

• A DC amplifier for semi-conductor studies, pH measurement (detects changes to .0005 p H ) , insulation leakage measurements, determination of grid currents on vacuum tubes and many other measurements of electrical properties.

So, if you are considering instrumentation to perform these tasks, investigate the CABY Model 31. Its versatility, reliability, speed and compactness will save time, money and bench space.

FOR COMPLETE INFORMATION PHONE OR WRITE FOR DATA FILE Al l -69

A P P L I E D P H Y S I C S C O R P O R A T I O N · "24 SOUTH PECK ROAD . MONROVIA,CALIFORNIA Circle No. 20 on Readers' Service Card

INSTRUMENTATION

again in the form of an electrical read­out integrator, in order to obtain power gain. This class of amplifier does not faithfully reproduce the input signal. For sine wave input, a sine wave out­put is obtained with a 90° phase shift. A square wave input results in a tri­angular wave output. As the device is an integrator, the amplitude of the output is universely proportional to the input signal frequency. A flat fre­quency response from 0.1 cycle per second to about 2 cycles per hour can be achieved by using a capacitor of about 320 mf. in series with the input.

For a sine wave input of 0.01 cycle per second, a power gain of 27 db. can be achieved. At present such ampli­fiers have an upper frequency limit of 0.5 cycle per second.

A special design permits the use of Solions as pressure or flow measuring devices. In this case, there are two electrodes forming the anode and cathode in their individual compart­ments. The two compartments are interconnected with a tiny orifice into the side of which an auxiliary cathode is connected through a microammeter. Within the small orifice iodine is re­duced to iodide at the cathode and io­dine is rapidly depleted, and the indi­cated current drops to a negligible value of about 10 μΑ. This background current is largely due to diffusion of iodine into the orifice. If the anode compartment contains a flexible dia­phragm, a slight flexure of the latter will force iodine into the orifice and an increase of current will result. For a detector operating in linear fashion, the current output is given by the equation, I = FNdv/dt X 10~3 where F is the faraday, N the normality of the reducible substance on the anode side, and dv/dt is the flow rate in cm.Vsec. For an iodine concentration of 0.1A?\ a flow rate as low as 10~5

cm.Vsec. yields currents of about 100 μα., or about 10 times the background value. Linear outputs have been ob­tained over a range of four orders of magnitude in flow rate.

Electrochemical Phenomena Have Inf ini te Possibilities

This brief article does not begin to exhaust what is known about Solions, nor what the authors know about their possibilities. There is little that the electrochemist would learn from all this but it should startle him into a realiza­tion of the infinite possibilities of well known electrochemical phenomena. It is well known that soluble iodides are readily oxidized photochemically and typical Solions should therefore exhibit photovoltaic effects. It is one of thou-

7 8 A · ANALYTICAL CHEMISTRY

Cary