You get these added advantages with S&S Analytical Filter Papers
New Clues in Silver Bromide Mystery Kodak researchers rum the camera on photography —to learn what happens when silver is exposed to light, t h e basis of photography. Using a 10,000-volt-percentimeter electric field at a single silver bromide grain, Kodak gets this picture of "arrested development" (left). It shows how wandering electrons gathered on t h e positive side (lower left), and triggered formation during development of black threads of metallic silver. T h e six-sided white area shows original shape of the crystal. Arrowhead (right) was formed w h e n a crystal was developed to metallic silver filaments.
0 3 Pegs Double Bond Ozone may replace bromine as the analytical tool for determining olefinic imsaturation. That's the opinion of A. Maggiolo, director of organic re search and development at the Welsbach Foundation, Philadelphia. H e , S. Knesbach, and A. Tumolo have devel oped an analytical technique which measures imsaturation in mono- as well as polyunsaturates, whether the double bond is conjugated or not. In 1951, Boer and Kooyman dis covered that a constant stream of ozone is an excellent titrimetric reagent for the double bond. But the procedure they developed was too elaborate and time consuming, Maggiolo says; five hours were required for one determina tion. The older method involves using dyes which react with ozone giving a color change to show the endpoint. T h e new method eliminates the elaborate equipment that Boer and
Kooyman used. Maggiolo uses readily available commercial apparatus—a gasliquid reactor and an ozone meter. First, a weighed sample of olefin is cooled to —10° C. in a dry ice-alcohol bath. The researchers find that at this temperature they get a sharp end point of ozone absorption—at higher tempera tures, t h e products of ozonolysis, carbonyl compounds, react with the ozone. Then, ozone is passed into the reaction vessel, and the contents are stirred at about 1200 to 1500 r.p.m. At the end point, a sharp deflection of the meter's indicating needle shows the marked increase in unabsorbed ozone. The researchers express results as imsaturation equivalents—number of grams of material containing one double bond. They prefer this term to "ozone number," which they say has no chemi cal significance. One advantage of this method over bromination: The pres ence of tertiary hydrogens does not cause high varying results.
Ozone DeterminesUnsaturationQuantitatively
• Lower Ash Content than any filter paper we have tested—less than 0.007% for quantitative grades. m Higher Alpha Cellulose Con tent than any filter paper we have tested—97-98% for quantitative and qualitative grades, Φ No Price Premium* Your company purchasing agent pays no more for the finest. For the chemist who can specify his brand of filter papers, S & S Analyti cal Filter Papers offer outstanding advantages. These advantages are possible because of the skill, care and quality control methods used by S & S from selection of raws through to the finished product. Every Lot Pre-tested A substantial test portion of each batch of S & S Analytical Filter Papers is used for quality control determinations in our laboratories. This helps assure that you receive fil ter papers uniform physically and chemically—lot after lot, month after month, year after year. Specify S & S Analytical Filter Papers for extra advantages to you in your work at no extra cost. Get the "mar gin of safety** in your analyses that comes with using what many chem ists believe to be the finest analytical filter paper in the world. FREE S A M P L E R Contains assortment of quantitative and qualitative grades. Also, S & S Filtra tion Chart, Quick Reference Catalog, table of compara tive filter paper grades.
£fr ?^J5'Dimethyl'
: Crotonic odd ;. ~ Sorbic a c i d ^ * uM e t h y l oleote * N u m b e r o f grams of material containing one double b o n d .
Carl Schleicher & Schuell Co. Keene. New Hampshire
OCT.
2 0.
·
1958
Dept, C-58
C8EN
41
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RESEARCH
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