NEWS by Karl H. Roberts of Mallinckrodt. He and coworkers found that certain naturally occurring opium alkaloids may be assayed by titration with perchloric acid in glacial acetic acid solutions with malachite green as the indicator. The end point color change is more distinct and accurate than with crystal violet and may be observed visually or spectrophotometrically. Use of paper chromatography for quantitative analysis was described by H. J. Pazdera, Pfizer. Elution of the desired compounds from the paper and subsequent determination of the compound by convenient methods have been used to control production of pure pharmaceutical products. Choice of solvent systems, paper, inoculation techniques, method of elution, and analysis must all be considered. Teaching Organic Analysis
An efficient analyst is one who can do the best job in the shortest time. Since there is no one method best for all analyses, to be efficient, the analyst must know what each type of analysis, chemical or instrumental, can do. In learning organic analysis, therefore, the student must be taught to coordinate both
chemical and physical methods and techniques. These general comments, made by S. Siggia, General Aniline and Film, introduced the symposium on teaching organic analysis, sponsored jointly by the Divisions of Analytical Chemistry and Chemical Education. Continuing along somewhat similar lines, E. W. Balis, General Electric, said that in teaching organic analysis, the situation to be encountered by the analysts upon graduation should be kept in mind. He noted, for example, that adequate equipment and instrumentation alone are not sufficient. The analyst must have adequate factual and theoretical knowledge. Time limits place restrictions on the extent of instruction that can be given in undergraduate and graduate courses, N. D. Cheronis, Brooklyn College, stated. After the fundamentals are taught, the decision has to be made as to the extent of chemical and instrumentation instruction to be given in school and that which is to be left for "in training." In instrumental analysis, it is desirable to teach how specific differences in structure relate to various properties
under study, L. B. Rogers, Massachusetts Institute of Technology, said. In Great Britain, according to W. A. Waters, University of Oxford, organic analysis does not form a separate course in undergraduate school. Only limited instruction is given in this area. Reliance is placed on graduate schools and industry to develop the necessary experimental proficiency. Reliance is also placed on technicians to do the analyses, with the scientists interpreting and evaluating results.
XVth International Congress IUPAC Analysts develop micromethods for analysis of petroleum I N the course of geological prospecting a considerable number of small samples of oil are obtained from surface seepages extraction of core samples, and oilstained surface rocks or sands. The
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analyst charged with making a s com plete a n analysis a s possible on such small samples will find work reported a t t h e X V t h Congress of Pure a n d Applied Chemistry in Lisbon in September of interest. T h e paper was one of a number, spon sored b y t h e section of Analytical Chem istry, devoted t o new a n d modified mieromethods. Other scientists gave details of basically new analytical methods which attracted wide interest. Among these were phosphorimetry a n d absorption in flame photometry as newanalytical tools. I n other work, a new a n d comparatively simple method developed for determining the magnetic susceptibility of compounds will prob ably greatly enhance t h e value of this property, which in t h e past h a s been restricted in use as a result of difficulty of obtaining it. Mieromethods in petroleum analysis are of considerable importance. Often only a few milliliters of a sample a r e available a n d from these, correlation of seepages with known reservoirs or commercial possibilities of crude oil from geological prospecting m u s t be a t least tentatively established. Archie R. Javes, who with colleagues a t t h e British Petroleum Research Station, had earlier worked o u t methods of dis tillation of these small samples, h a s now developed a scheme of analysis in which a number of fractions and res idues are obtained b y this distillation method a n d means perfected for ob taining inspection d a t a on them. T h e scheme (Figure 1) h a s been found practicable with miniature sam-
SAMPLE S p . gravit Fractional Disti lla't ι
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1 I D I S T I L L A T E T O 149tJC . S p . gravit y A n i l i n e point Aromatic content Bromine Sullur
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1 D I. S T IgLrLaAvTiE Sp t y 119 - 2 3 2 ° C . Ani line point Aromatic content
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149°C.
point
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RESIDUE ABOVE 232°C. S p . f;ravity ViscosiLy Asphaltc-nes
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1
RESIDUE
D I S T I L L A T E :S71 - 5ôO°C . Sp. gravity Wax
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Figure 1 ANALYTICAL
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NEWS
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pies of about 5-ml. total volume—as contrasted with some conventional assay methods using 5 liters. After the specific gravity of the crude oil is determined, the whole sample is frac tionally distilled to give a distillate up to and a residue about 145° C. Tests shown are made at this point and fur ther separations and analysis indicated by the scheme continued. Actual microanalytical procedures are specific in each case and based on ac cepted tests. An example is determi nation of aniline point, based on I P 2/53 (Method C). Equal volumes of aniline and sample are transferred by a capillary pipet of 0.002- to 0.05-ml. capacity to a small bulb blown in soda glass tubing 1 to 2 mm. in internal diameter. (Figure 2.) The pipet is emptied into the capillary bulb by placing bulb and pipet in the cup of a small hand centrifuge and centrifuging. The same pipet is used to transfer both
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34 A
SODA GLASS CAPILLARY
1 - 2 mm.I.D. SODA GLASS CAPILLARY
Figure 2
aniline and sample. .The top of the capillary is then drawn off and a sealed bulb attached by a rubber band to the aniline point thermometer. The ther mometer is inserted into a test tube filled with water to the immersion mark, and the tube is surrounded by a large tube which serves as an air bath. The aniline point is determined at this point by the accepted method. Results ob tained agree with the I P result within reproducibility limits of the latter method. According to Javes, the majority of tests normally carried out on petroleum products can be performed on very small samples with little loss of accuracy. In most of the micromethods developed at BP, results for all tests agree with those obtained by recognized procedures ANALYTICAL
CHEMISTRY
NEWS using larger samples within the pre cision limits of the recognized tests. The principal source of error in carry ing out small scale assay on petroleum samples is a result of difficulty in han dling volatile distillates and viscous residues without change in composition due to preferential evaporation or mechanical loss. It is therefore desir able to carry out an assay on a larger sample when such is available. How ever, with proper precautions and care,
results obtained on a 5-ml. sample agree sufficiently well with those from a 5-liter assay to give valuable evidence as to the type or origin of the oil in many cases. Phosphorimetry as N e w Analytical Method
Phosphorimetry is a new method of chemical analysis based on the nature and intensity of the phosphorescent light emitted by an appropriately ex-
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cited molecule. Most organic molecules containing multiple bonds can be made to phosphoresce under suitable conditions when excited by lights of appropriate frequency. Usually a compound must be in a rigid state in order for phosphorescence to be observed. This condition is obtained by dissolving the compound in a suitable solvent, which by cooling in a liquid nitrogen bath yields a transparent rigid glass. Each phosphorescence is unique in regard to its frequency, lifetime, vibrational pattern, and quantum yield. Such properties may serve for a qualitative identification. In work conducted by Russell J. Keirs and colleagues at ONR, Tallahassee, it has been established that the intensity of phosphorescence is a function of the concentration and can serve as a basis for quantitative measurement. The method has been applied to the determination of phosphorescent compounds and their mixtures. The resolution of mixtures is possible in three ways, according to Keirs: by selective excitation, spectroscopically, and phosphoroscopically on the basis of the phosphorescent lifetimes. In studies at ONR, resolution and determination of mixtures of benzaldehyde, benzophencne, and 4-nitrobiphenyl, of acetophenone and benzophenone, and of diphenylamine and triphenylamine have been carried out. N e w Method for Determination of Diamagnetic Susceptibility
Diamagnetic susceptibility is an additive constitutive property of matter. It is a characteristic coefficient of purity and structure. However, up to the present time, measuring apparatus utilized to determine the property consisted of huge magnets and microbalances, and, as a result of cost, space requirements, and operating power, was found only in specialized laboratories. Workers at the Physical Chemistry Laboratory of the University of Bordeaux have designed and tested apparatus for quickly determining magnetic susceptibility with comparatively simple equipment. As a result, it is expected that this property, which is actually known for 10,000 or more compounds, might be used as a valuable means of identification. A. Pacault described the new electronic equipment utilized in magnetic susceptibility studies and identification. The apparatus is based on the variation in frequency of an oscillating induction coil capacity circuit when a substance is introduced into the coil. Position finding of the frequency is effected with aid of a cathode tube on which is seen a series of arcs of a circle ANALYTICAL
CHEMISTRY
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Solemn opening of the XVth Congress was held in Portugal's impressive National Assembly
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