NEWS empirical. More recently, however, the approach has been based on quantitative measurement of equilibria involved in complex formation. I m p o r t a n t factors which must be considered a r e basicity of t h e ligand, n a t u r e of t h e donor atoms, number of rings formed, resonance, and steric hindrance. All of these affect stability of chelates. Structure of t h e ligand is systematically altered b y substitution t o determine t h e effect of substituent groups on each of these factors. I n this way, states Welcher, a single p r o p e r t y of a reagent m a y be determined, and all
possible factors affecting the property studied. This approach has resulted in a n u m ber of new and useful reagents, says Welcher. And, he adds, t h e prospect of future progress is bright. V o l t a m m e t r y at Solid Electrodes. Solid electrodes a r e "here t o stay," said R a l p h Adams, University of K a n sas. T h e y a r e competitive in m a n y cases with t h e chemical dropping mercury electrode. Adams reviewed mass t r a n s p o r t conditions a n d their effect on current p o tential curves. Such a study is im-
the most advanced idea in stirring PALO
See the flow lines occurring on the circumference of the mixing vessel.
IMPELATOR*
For all chemical and industrial laboratory stirring purposes. The Palo Impelator in s t i r r i n g combines centrifugal force, suction, shearing action and counter current whirl. The u p w a r d and downward turbulence is created by the angled conical tubes mounted on the disc. This action creates rapid and efficient mixing — ensures . j . maximum dispersion with minimum particle size.
IMPELATOR*
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p o r t a n t in choosing t h e best solid electrode technique for a particular job. Mass t r a n s p o r t a t quiet eleotrodes causes m a n y complications if slow polarographic methods are used, since n a t u r a l convection interferes with diffusion. Adams suggested t h a t rapid voltage sweep techniques, such as oscillographic polarography, b e used a t quiet electrodes. H e listed t h e r o t a t e d wire electrode as t h e most p r a c tical solid electrode system. Polarograms a t such electrodes are interpreted in t e r m s of hydrodynamic factors. Adams considers current scanning polarography a n d chronopotentiometry (voltammetry a t controlled currents) as promising methods for solid electrode work. H e also discussed anodic oxidation of amines, phenols, and m e r c a p t a n s in terms of practical analytical procedure. Adams described a mercury halide film electrode recently developed a t the University of Kansas. T h e electrode acts as a n inert surface for oxidation of m a n y organic compounds. With this electrode, for example, amines and phenols can be oxidized either b y chronopotentiometry or more conventional voltage scan polarography. One major advantage of t h e mercury halide film electrode is t h a t t h e surface m a y be renewed after each run b y cathodic stripping. Coulometry a t Controlled P o t e n tial. Coulometry a t controlled potential—a technique for measuring t h e electricity consumed while a single oxidation or reduction process takes place b y electrolysis a t controlled potential— was outlined b y Louis Meites, Polytechnic I n s t i t u t e of Brooklyn. H e r e -
* >>=S ^
Stainless steel, disc diameter 21/4" with 6 conical tubes. Mounted with removable stainless steel hexagon nut on 1/4" stainless steel rod, 10" long $19.50 233-E Same as 233-D except r/io" stainless steel rod, 16" long $21.50 233-F Impelator only same as above, movable. Can be locked with knurled adjustable nut a t any place on rod. To fit 1A" rod $18.00 233-G Same as 233-F to fit % 0 " rod $18.50 Information on details for your special requirements available on request. fPrices quoted on request for larger sizes for semi-industrial and manufacturing purposes — Food processing, oil refining, paint manufacturing, etc.
233-D
Let Impelator
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ANALYTICAL CHEMISTRY
Nobel prize winner A. J. P. Martin, of London, gave a progress report on gas-liquid chromatography
