REPORT FOR ANALYTICAL CHEMISTS
ods required up to two days. The original spectrographic procedure was based upon cast metal samples and standards, graphite counter electrodes, and a high-inductance spark discharge. Spectrographic production analysis developed rap idly with the unprecedented expan sion of the industry during World War II. In the peak year 1943, 13 million determinations were made. In current practice, samples are often delivered to the laboratory by pneumatic tube. Rapid analysis is carried out with direct-reading photoelectric instruments. During the past decade, control analysis has become standard practice throughout the metallurgical in dustry. The result is higher pro duction rates, closer control of physical properties, and elimination of off-composition metal. Such instrumentation has widened the scope of metallurgical analysis. Alcoa's analytical staff, for example, includes physicists, physical chemists, pharmacists, or ganic chemists, and electronics en gineers as well as analytical chem ists. Such a team is well suited to develop new methods to attack old analytical problems. An example of the results of such teamwork is a reflectivity analyzer developed by Alcoa's analytical staff. The instrument was designed to replace visual tes~;s for quality of finish on aluminum automotive trim. A good finish gives a sharp, well-defined reflected image, while a poor finish gives a fuzzy, indis tinct image. The analyzer measures photo metrically the sharpness of a re flected image, using the sample as a mirror in a simple optical system. Collimated light beams from two parallel slits are reflected from the specimen. A lens converges the beams to form an image of the two slits. The final image is scanned for sharpness through a single slit by a photocell. If the image is fuzzy, scattered light will be observed be tween the lines. A plot of image brightness versus position of the scanning slit is thus a curve with two peaks—one for the image of each primary slit. The ratio of peak height to the depth of the valley between is a measure of
scattering, or image clarity. Sur face brightness does not affect the results.
FREE
Petroleum Industry
The pattern of progress in fuels and lubricants since World War I has been a steady rise in octane ratings for fuels and a growing number of additives for all petro leum products. Because of the im proving octane ratings for gasolines, compression ratios of automobile engines rose from about 4.4 : 1 in 1925 to 9 : 1 and more today. Gasoline compositions have changed toward reduced saturates and increased aromatic content. Tetraethyl lead was introduced as an antiknock compound in 1923. Since then, such fuel additives as antioxidants, anti-icing agents, metal deactivators, carburetor de tergents, upper cylinder lubricants, and corrosion inhibitors have ap peared. Dispersants, detergents, water repellants, color stabilizers, antifoam agents, and pour-point de pressants are among the additives now found in lubricants. Progress in fuel quality has been brought about by increasingly com plex refining processes. Prior to World War I, gasoline was pro duced by straight distillation. Fractions distilled from crude stocks were separated simply by boiling range. The properties of this straight-run gasoline varied widely. Thermal cracking processes came into use during World War I to meet the suddenly increased de mand for gasoline. These processes break up heavy hydrocarbons into smaller molecules usable in fuels. Thermal polymerization, a process to build up usable hydrocarbons from C4 and lighter gases, was also used. Catalytic polymerization ap peared in the middle thirties, fol lowed about 1940 by catalytic cracking processes. The catalysts used accelerate those reactions which yield the most desirable hy drocarbons. The resulting gaso lines generally are more stable than those produced by thermal reform ing, and they have higher antiknock values.
THE ^ ^ ^ F CHROMATOGRAPHER'S COMPANION The new F & M Columns and Accessories Catalog is filled with useful information and in cludes answers to many questions often asked by gas chromatography users. HOW TO SELECT A COLUMN— A condensed treatise on the subject; includes literature references and sug gests column materials for separating various classes of compounds. PRICES AND SPECIFICATIONS FOR: • Liquid phases • Adsorbents • Solid supports
• Packed columns and kits
SAMPLING ACCESSORIES FOR: • Liquids (a full line of syringes)
• Gases • Solids
COMPONENTS FOR THE LABORATORY:
• Temperature controllers & programmers
"Recorders • Integrators • Attenuator
For your copy of this useful catalog, write or call F & M Scientific Cor poration, Route 41 and Starr Road, Avondale, Pennsylvania, 215-COlony R.99B1
F&M Ρ & M SCIENTIFIC CORPORATION AVONDALE,
PENNSYLVANIA
Circle No. 136 on Readers' Service Card VOL. 3 5 , N O . 7 , JUNE 1 9 6 3
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