NEWS
table model centrifuges to meet your analytical needs From the most complete line of table model centrifuges . . . four Clay-Adams models de signed for industrial and chemical laboratories . . . all are shock-mounted precision instruments engineered and manufactured to assure years of superior performance.
c-ADAMS ANALYTICAL: For micro and semimicro separations . . . accommodates six tubes (5 or 3 ml.) . . . also adaptable for 2 and 0.5 ml. tubes . . . angle-head effi ciency . . . compact, portable, requires minimum table space . . . provides fixed 3,400 RPM speed.
a-ADAMS SAFEGUARD CENTRIFUGE-ANGLE AND STANDARD HEADS: A multi-purpose, basic instrument for labs with heavy work loads . . . accommodates any one of four standard or four angle heads . . . useful for all com mon separations and special analytic pro cedures . . . holds tubes of 15 ml. or less and up to 50 ml. . . . dial rheostat control pro vides variable RPM and R C F range.
d-ADAMS MICRO-CHEMISTRY: F o r m i c r o - a n alytic separations of organic and inorganic precipitates . . . eight-place angle head ac commodates 1, 0.5, and 0.25 ml. glass or plastic tubes . . . provides high fixed speed (13,500 R P M - 1 5 , 5 0 0 RCF) . . . high R C F assures separation of particles of similar specific gravities . . . complete, automatic stop in 60 seconds.
b-ADAMS SAFETY HEAD: For all commonly performed precipitate separations . . . adaptable for micro and semi-micro anal yses . . . six-tube capacity (15 ml. or less) . . . angle head provides fast, efficient centrifugation . . . variable R P M and R C F . . . compact, light and portable.
Available from your dealer
Clay-Adams New York 1 0 , Ν. Υ.
Circle No. 24 on Readers' Service Card
THIS VERSATILE
P-K LABORATORY BLENDER PRE-BLENDS, DISPERSES LIQUIDS, GRANULATES . . . IN JUST MINUTES If you have any liquid-solids or solidsolid blending requirements, consider the P-K Liquid-Solids Blender. It's a fast, efficient and extremely versatile laboratory tool. With it, you'll find most blending operations can be accom plished in 2 to 5 minutes, achieving a uniformity not attainable with other types of mixing equipment. 3 Different Blending Actions
Gentle Precision Blending. Unique "Twin-Shell" tumbling action will not cause attrition of even the most delicate crystals. Intensive Mixing of Hard-to-Blend Dry Solids. Exclusive "rabbit ear" dispersion blades on rapidly revolving bar break up agglomerates. Liquid Solids Blending. Disperses and
blends, uniformly, liquids of any viscos ity with dry solids. (Blends from %% liquids by weight to whatever percent age solids can absorb and still remain a solid.) Liquid is introduced into hol low shaft of revolving bar by gravity or pump. Then, flung outward from dis persion discs into the tumbling mass of dry materials. P-K Liquid Solids Laboratory Blend ers are available in 8- and 16-qt. capaci ties, in transparent lucite or stainless steel. For complete technical informa tion and prices, write to P-K's Chemical and Process Equipment Division, 1011 Hanson St., East Stroudsburg, Penna.
Patterson
Circle No. 75 on Readers' Service Card 56 A
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ANALYTICAL CHEMISTRY
Kelley
Dr. Robinson proposed a physical model of a photon as an attempt to help explain the structure of light. "Conclusive" evidence exists that light is both a wave and a particle. His model depicts the photon with a posi tive and negative charge rotating about its center of mass. This produces ro tational and translational energy. A combination of these energy forms can produce wave-like and particulate properties. With this model, many of the conflicting properties of light can be explained, according to Dr. Robin son, without violating any of the mathematical relationships which have boon shown to exist. NMR. Dr. James N. Shoolery of Varian Associates reviewed the devel opment of nuclear magnetic resonance and development of instruments sophis ticated enough to have the desired high performance when operated by nonspecialists in instrumentation. These demands on the instrument are great because the homogeneity and stability of the magnetic field must be better than one part in 100 million over the volume of the sample and only one nucleus out of every 10,000 iu a several milligram sample partici pates in the absorption process. One property of NMR spectroscopy not well appreciated by most analytical chemists is the integrated intensity of the individual absorption peaks, Dr. Shoolery said. The ability to measure the integrated intensity accurately by electronic integration of the spectrum enables a chemist to obtain very ac curate quantitative information with out the need to make allowances for variations in the strength of absorption from one sample to another. Because chemical shift increases linearly with applied magnetic field strength and because sensitivity in creases more rapidly, efforts have been focused on ways to obtain higher mag netic field strengths without sacrificing the field homogeneity. Research in struments are now available, Dr. Shoolery said, which operate at fields above 23,000 gauss. They have special application to problems where the amount of sample is small and where interpretation of the spectrum is com plicated by many overlapping multi plets. Recently, a technique known as "spin-decoupling" has become widelyused to simplify interpretation of spectra and to make more certain identification and measurement of the spin coupling and chemical shift parameters. This technique involves simultaneously irradiating a sample with two different radio-frequency mag-
