REPORT into a small volume for measure ment with a great gain in sensitivi ty. Because the formation constants of ο,ο'-dihydroxyazo compounds toward magnesium are always sev eral orders of m a g n i t u d e greater t h a n those toward calcium, the re verse of the E D T A type reagents, the solution to the tifrimetric m a g nesium problem could conceivably come from using an o,o'-dihydroxyazo compound as a s t a n d a r d solu tion. This brings u p the interesting question : have we missed reaction of the alkaline earths with such compounds because the criterion, a change in color on ad:ling the metal ion, was false? Obtaining an alkaline earth de rivative of an ο,ο'-dihydroxyazo compound in crystalline form for xr a y crystal structure study would appear straightforward enough but concerted a t t e m p t s on our p a r t to isolate the magnesium derivative of ο,ο'-dihydroxyazoben zene failed. We did obtain a crystalline product from a water-dioxane mixture but the elemental analysis was just suf ficiently off from the theoretical values expected for a one to one compound to cast doubt on the composition; preliminary x-ray work on the crystals indicated a disorder which was going to serious ly complicate the study, and t h e work was stopped without arriving at any conclusion as to the location of the magnesium atom relative to the azo group. Of one thing we can be sure. T h e work just reported is going out of date rapidly, and even the problems just mentioned may be pointless with the passage o:: only a few weeks. Life on the chemical front during the last half o'? the twentieth century is, to mix metaphors, the exciting business of riding an expo nential growth curve into its verti cal phase. Remembering t h a t the derivative of an expDnential func tion is also an exponential function, it seems t h a t the best thing we can do for our students is to instill in them the ability to cope with change. P e r h a p s t h a t is just w h a t most teachers are already doing— witness the almost hysterical push evident in the universities these days to get undergraduates into re search quickly. Oddly enough, graduate education still t a k e s three
PI
ewrote include both glass and reference in a single probe for the entire range 0 to 14 pH, from 0 to 80°C. All-glass construction has no rubber or plastic to contaminate the sample, and no crevices or pockets to trap solution for carry over from one sample to the next. In both standard and miniature sizes for as little as 1 ml and % ml of sample. Range, 0 to 14 pH with linear response even in highly acid solutions. Alkali ion response is insignificant below pH 12.5; it is low and — more important - stable in higher pH solutions. Shock-resistant construction derived from inherent strength of the glass and careful fabrication. Fast response, both in sensitivity of the glass and in symmetrical internal and external references-for rapid temperature equilibrium. High efficiency, with a millivolt/pH response close to the Nernst coefficient. Shown Actual Size S-30070-10 COMBINATION E L E C T R O D E - 0 to 14 pH, Miniature, Sargent/Jena. pH range, 0-14; temperature, 0-80°C; total length, 6 inches; stem diameter, 5 m m ; immersion depth, 10 to 78 m m ; cap length, % inch; cap diameter, 8 m m . Complete with 20-inch connecting cable and plugs directly fitting Sargent, Corning, Cole man and Beckman pH meters 38.00 S-30072-15 COMBINATION ELECTRODE - 0 to 14 pH, Sargent/Jena. pH range, 0-14; tem perature, 0-80°C; internal buffer, pH 7; total length, 8 inches; body diameter, 12 m m ; cap diameter, 4 1 / 6 4 inch; cap length, 1 inch. Complete with 30-inch connecting lead and plugs directly f i t t i n g Sargent, Corning, Cole man and Beckman pH meters 35.00
SARGENT E. H. SARGENT & CO. 4647 West Foster Avenue Chicago, Illinois 60630
SCIENTIFIC LABORATORY INSTRUMENTS
APPARATUS-CHEMICALS
Chicago · Anaheim, Calif. · Birmingham · Cincinnati · Cleveland Dallas · Denver · Detroit · Springfield, N.J. · Toronto, Canada Circle No. 218 on Readers' Service Card VOL. 39, NO. 3, MARCH 1967
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