Society for Analytical Chemistry

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V O L U M E 28, NO. 5, M A Y 1 9 5 6 General Session on Analytical Research Application of Vapor-Phase Chromatography to the Analysis of Liquid Petroleum Fractions. D. H. DESTYAND B. H. F. WHYMAN, British Petroleum Co., Ltd., Sunbury-on-Thames, Middlesex, England. In this day of atomic reactors, electronic brains, and other advanced technology, we seldom hear of scientists turning in their more complicated tools for simpler ones. However, a new technique for analyzing gases and liquids, called “vapor-phase chromatography,” may prove t o be the exception. Though no one intends junking his multithousanddollar equipment for doing such things, analytical chemists are looking toward vapor-phase chromatography as a rapid inexpensive method for determining the composition of natural gas, gasolines, and other products-even of smog. The paper presents an example of what vapor-phase chromatography will do. The authors report successful separation and analysis of hitherto unidentified trace impurities present in nearly pure materials such as octane number reference fuels. Quantitative Analysis of Organic Disulfides. R. L. HUBBARD,

m7.E. HAINES,AND J. S. BALL,Petroleum and Oil-Shale Experiment Station, U. S. Bureau of Mines, Laramie, Wyo. A new, fast, and simple method for determining disulfides in petroleum products was developed. Disulfide determinations are important in product control, particularly in “sweetening” processes. The new method was tested, together with three older methods, for its reactivity toward disulfides of various structures. It was found t o be superior to older methods when applied to disulfides in the gasoline boiling range. Determination of Fuel Oil Stability to Optical Density Measurements. W. H. ARMSTRONG, D. MILSOM,H. P. HEBERT,AND A. R. RESCORL.4, Cities Service Research and Development Co., New York, N. Y. For the past number of years a considerable amount of research has been conducted to develop a satisfactory method for measuring the storage stability of distillate fuel oils. Several methods employ filter pad discoloration, filterability, and actual insoluble determinations by gravimetric procedures. A method for determining the insoluble content of an oxidized fuel oil by use of absorbance consists of measurements employing a I-cm. light path and 500 mp on oxidized oil samples before and after filtration through a fine sintered-glass filter (4.5-5 microns). Correlations have been established for determining the insoluble content with an accuracy equivalent to the gravimetric procedure from the difference in absorbance on the filtered and unfiltered samples. The correlation established between absorbance and insoluble content has been developed, using oils from varying types of crudes and oxidized over a range of temperatures. Additional correlations permit the establishment of predicted storage time at ambient storage.

Rapid, Precise Micro Vapor Pressure Method. A. Y . MOTTLAU, Products Research Division, Esso Research and Engineering Co., Linden, N. J. To manufacture motor gasolines of high quality, the refiner must build into them many important characteristics. Of these characteristics, vapor pressure is one of the most critical from the consumer’s standpoint. There is a desirable vapor pressure for each season of the year, for each geographical location. If the vapor pressure is too high for the air temperature, the customer’s car may vaporlock. If the vapor pressure is too low for the air temperature, the car will be difficult to start and warm up. Vapor pressure is also an important property of many other fuels. The precise adjustment of fuel vapor pressure will be made much easier by a newly developed device for measuring it. The new vaporpressure method has five times the accuracy of the old method, greater speed, and an improved sample handling procedure. This means improved performance for the consumer’s equipment and a savings in money to the refiner. Another big advantage of the new vapor-pressure measuring apparatus is the small amount of sample required to make a measurement. Only 1 cc., now used about 0.034 ounce, is needed. The apparatus requires over 130 times this amount. This will be a great help t o the researcher who oftentimes would like to measure the vapor pressure of very small samples obtained from laboratory scale counterparts of the huge refinery stills and cracking units. Combustion and EDTA Titrimetric Determination of Total Sulfur in Petroleum Products. 0. N. HINSVARK AND F. J. O’HARA,The Girdler Co., Louisville, Ky. An improved method, applicable to control procedures, for the determination of sulfur in petroleum samples permits determination

919 of all types of sulfur which might be present in a wide variety of sample materials ranging from low boiling naphthas t o high boiling coker gas oils. In general, the sample is aspirated into an oxyhydrogen flame of a Beckman atomizer burner and burned. As products of combustion are formed, they are swept by air into a hydrogen peroxide scrubber, where oxides of sulfur are converted t o sulfate. The sulfate formed in the scrubber is then measured by adding an excess of barium acetate and determining the excess barium by an EDTA titration. Samples covering a wide range of concentration from 100 to several thousand parts per million of sulfur have been successfully analyzed without danger of interference from halides or nitrogen in the sample. An error of f 1 6 p.p.m. is expected at the lower level with a slightly greater value at a higher level. By combining the combustion procedure and the highly selective titrimetric determination, a single reliable value can be obtained in about 45 minutes. Fluorescent X-Ray Spectral Analysis of Powdered Solids by Matrix Dilution. E. L. GUNN,Humble Oil and Refining Co., Baytown, Tex. Present-day petroleum technology requires the fastest and most precise analytical tools available for determining elements in varied substances encountered in the industry. The determination and control of elements are important because in some materials the presence of certain elements is highly detrimental, whereas in other materials elements occurring as specific compounds are very useful for enhancing the manufacture or final quality of a finished product. In recent years a number of rapid precise instrumental techniques have become available for inspection of the materials of petroleum refining. The x-ray fluorescent spectrograph is in the forefront of new instruments for elemental analysis of such materials. Basically, the x-ray fluorescence spectrograph consists of a highpower x-ray tube, the beam of which causes the elements in a specimen to emit their own characteristic x-rays or to fluoresce, a diffracting device to separate the x-rays into their respective unique wave lengths, and a device to detect and measure each wave length. The measurement of an element is independent of the manner of chemical combination with other elements but not of their mutual presence in the substance. The elements influence each other in such a way that the intensity of x-rays emitted by a given element is not a direct measure of its concentration. This paper describes a technique for lessening or eliminating this effect so that a number of elements coexisting in a powdered solid can be measured with reasonable accuracy. Determination of Calcium or Zinc Additives in Lubricating Oils and Concentrates by an EDTA Titration Method. P. B. GERHARDT AND E. R. HARTXANN, Products Research Division, Esso Research and Engineering Co., Linden, N. J. In many chemical and petroleum processes it is important to know when a particular unit operation is completed or when to proceed to the next operational phase. The stepwise following of a process to establish the quality of an intermediate or end product is commonly referred to as plant control. Although most chemical methods of analysis are time-consuming, they nevertheless can be used to control a batch process. How can these methods be used to control a continuous flow operation? As more manufacturing procedures are converted from batch t o continuous flow operations, this question assumes greater importance. The most satisfactory solution to the problem is t o develop rapid methods applicable to control of a continuous process. Chemists at the Esso Research and Engineering Co. have developed a rapid method for determining either calcium or zinc. This can be used to control additive manufacturing plants or the blending of lubricating oils. The procedure consists of a direct titration of the metal in an acetone solution of oil with an organic complexing agent. With this procedure it is possible to complete an analysis in about 20 minutes, as compared to 4 hours by conventional methods. The method has been used successfully t o control the manufacture of various additives and the blending of many lubricating oils with additives containing calcium or zinc.

Society for Analytical Chemistry meeting of Microchemistry Group, held January 27 in A London, the following papers were presented and discussed : T THE

Microchemical Methods in the Art Gallery and Museum. A. E. WERNER,Research Laboratory, British Museum.

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ANALYTICAL CHEMISTRY

Microanalytical techniques are indispensable in the scientific examination of paintings and other works of art, since the very nature of the objects permits the taking of only minute samples. I n the case of paintings, microchemical methods have been devised for the identification of pigments and media. Modern speciiic organic reagents for the detection of metals have been applied to the detection of pigments using Feigl’s spot test technique. This has certain advantages over the previously used microscopical precipitation reactions-for example, it can be carried out on individual layers of a paint sample mounted in a synthetic resin as a cross section. On occasion, spectrographical and spectrophotometrical methods are used to supplement microchemical methods. The technique of partition chromatography has recently been used for,the examination of paint media, both tempera (protein) and oleores:iious. For the latter a special reversed phase system has been devised in the Kational Gallery Laboratory. A scheme for the quantitative analysis of bronzes and other metallic museum object8 has been worked out using microdeposition supplemented by photometric methods using organic reagents. Finally, micro spot tests have been applied for specific purposes in museum work-e.g., the iodine-azide reagent for the identification of niello and a phosphate test for classifying early English porcelains. Ring-Oven Technique and Its Application in Archeology. H.

WEISZ,Department of Chemistry, University of Birmingham.

The ring-oven technique is a simple method for separating ions, or groups of ions, in a single drop. An apparatus called the ring oven is designed to wash soluble materials out from a spot on a filter paper and to concentrate them in a sharply bounded circular ring zone, where they can be detected. Some other pieces of equipment have been developed for this purpose. With the aid of this method an analytical szheme for 14 commoner ions has been worked out; 1 drop of about 1.5 pl. is sufficient for the analysis. The method has also been employed for ring colorimetric analysis. I n the examination of valuable museum specimens, microsamples must be taken, so that the minimum damage is done to the specimens. The available methods for the qualitative examination of such samples are laborious or require expensive apparatus. The ring oven is, however, particularly suited to this type of analysis. A description was given of the analysis of eight Egyptian bronzes of archeological interest.

A meeting of the Midlands Section was held February 7 in Birmingham, a t which the following papers were presented and discussed : Analytical Chemistry of Germanium. Wembley.

H. J. CLULEY,G.E.C.,

Methods of separation and determination of germanium were reviewed. Recent work, stimulated by the use of germanium as a semiconductor and the consequent search for new sources of the element, has mainly concerned the development of colorimetric methods; these methods have greatly facilitated the determination of germanium in coal, flue dust, minerah, etc. On the other hand, gravimetric and volumetric methods have received little attention in recent years and fen of the existing methods possess both accuracy and selectivity. Analytical Chemistry of Gallium. G. 17.C. hIILxER, il.E.R.E., Harwell. Important improvements have taken place in gravimetric and volumetric methods for the determination of milligram amounts of gallium. Similarly absorptiometric methods for the determination of microgram amounts of this constituent have been reported recently. These developments were considered in s m ~ detail, e together with improvements for the s-paration of gallium from other elements by aolvent extraction. Examples were given in alloy analvsis of volumetric procedures with EDTA 4 hich avoid the need for the preliminary separation of the gallium. T h e Physical hfethods Groups met February 14 in London

for a presentation of papers on polarography. Comparison of Three Highly Sensitive Polarographs. D. J. FERRET, G. W. C. MILNER,H. I. SHALGOSKY, A X D L. J. SLEE,U. K. Atomic Energy Establishment, Harwell. The new sensitive polarographs include the cathode ray polarograph, the square wave polarograph, and the Cambridge univector unit. Experiments have been carried out to obtain information on the relative merits of the three instruments, and details of the results

of these tests were described. The instruments have been tested for sensitivity for reversible and irreversible reductions at the dropping mercury electrode, resolution for elements with Eli* values very close together, effects of the reduction of a major constituent at more positive potentials on the determination of a minor constituent, and speed of application, reproducibility, and usefulness in analytical chemistry. Polarography of the Dithionite (Hydrosulfite) Anion and Some Related Oxy Acids of Sulfur. W. Furness, Brotherton & Co., Ltd., Leeds. In the polarography of anions three kinds of reactions at the dropping mercury electrode are distinguishable. First, if the anion is oxidized it yields an anodic wave. Secondly, a reducible anion yields a cathodic wave. Thirdly, in the presence of certain anions, the mercury of the dropping electrode may itself be oxidized and then an anodic wave results. In the analysis of commercial dithionites and their decomposition products, at least six of the oxy acids of sulfur are encountered. Polarography provides a useful method for the determination of dithionite in such mixtures. The principal wave is anodic and the electrode reaction is of the first kind. Mathematical examination of the polarogram suggest,s the electrochemical reaction S Z O + ~ ~ ~ 2SOz,, 2 e - , and gives a value for its standard potential from which the free energy of sulfur dioxide in aqueous solution can be calculated. In certain supporting electrolytes polarograms of the dithionite ion show a small cathodic wave. In slightly acidic solution one of the principal decomposition products of dithionite, though not formerly recognized as such, is the trithionate ion. At the dropping mercury electrode this ion undergoes a reaction of the second kind and the cathodic wave is useful for analytical purposes. The polarography of the thiosulfate ion, a well known decomposition product of dithionite, provides an example of a reaction of the third kind.

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Polarographic Determination of Uranium in Ores. H. 1. SHALU. K. Atomic Energy Establishment, Royal Arsenal, Woolwich, S.E. 18. GOSKY,

The method developed at the Chemical Research Laboratory, D.S.I.R., for the polarographic determination of uranium in an acid tartrate medium has been examined. Under the conditions used to achieve maximum sensitivity, the method gives low results. This is shown to be due to the effect of heating uranium in concentrated sulfuric acid solution. Satisfactory results are obtained when perchloric acid is used in place of sulfuric acid for the destruction of organic matter. The factors which affect sensitivity were discussed and the sensitivity of the final method was shown to be similar t o that of other polarographic methods. At a meeting of the hlidlands Section on March 6, C. J. Van Xeuwenburg, Delft, Holland, spoke on “Modern Qualitative Analysis and Industrial Practice.” After a short historical survey, the essential features of modern qualitative analysis were given: microscopic reactions and spot tests as identification reactions superimposed on traditional separations. and the trend towards microtechniques. The desirability of adhering t o separations and the importance of trace analysis for bioohemical and metallurgical practice were discussed, then the possibility of an analysis in situ, without destroying the structure of the sample, and the growing importance of the less common elements. Finally, the competition which must be expected from chromatography and spectrography, and the use of inorganic reagents for groups in organic molecules, came up for discussion. The following officers have been elected for 1956: Microchemistry Section. Chairman, G. F. Hodsman; vice chairman, D . F. Phillips; secretary, D. R.Wilson, Sir John Cass College, Jewry St., Aldgate, London E. C. 3; treasurer, G. Ingram. Midlands Section. Chairman, J. R. Leech; vice chairman, R . Belcher; secretary, G . W.Cherry, 48 George Frederick Road, Sutton Coldfield, Warxicke; treasurer, E’. C. J. Poulton. North of England Section. Chairman, J. R. Kalmsley; vice chairman, .4.N. Leather; secretary-treasurer, A. C. Wiggins, J. Lyons & Co., Ltd., 5 Laurel Road, Liverpool 7 . Scottish Section. Chairman, F. J. Elliott; vice chairman, Magnus Pyke; secretary-treasurer, J. A. Eggleston, Boots Pure D r u g Co., Ltd., Airdrie Works, Airdrie, Lanarkshire.