Quantometry in 1950 - Analytical Chemistry (ACS Publications)

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V O L U M E 22, NO. 12, D E C E M B E R 1 9 5 0 present potentialities for the increase of accuracy and sensitivity in spectrochemical analysis. No theoretical deductions have thus far been made. Analysis of the Excitation Characteristics of Spectra Emitted by Ferrous Alloys. J. CONVEYASD J. ITANSFIELD, JR.,J . c. FUHRIIEISTER, A X D D. L. FRY, Research Laboratories Division, General hIotors Corp. Methods were described for the semiquant,itative determination of bromine, chlorine, and sulfur in lead-carbon matrices using ordinary spectrographic equipment. One to 2 mg. of powdered sample diluted with an equal weight of pure zinc powder are pressed into the end of a pure silver pellet, which is sparked against a pure silver counter electrode. Analytical curves for the concentration range 1 to 670 have been used. Corrections for background are necessary. By properly blowing helium through the analytical gap during the exposure, background corrections are eliminated and detectability is enhanced. Spectra were shown for comparison. Analytical curves for the concentration range 1 to 10% have been used. Precision of *1570 is claimed. Minimum ddectability for qualitative analyses of 0.17’ is indicated. Reasons for the effects produced by helium are suggested. Excitation condit>ionswere given for two sources (one commercial) as used with two different spectrographs. Spectrochemical Analysis of Biological Leaf Material. J. T . ROZSA,Kational Spectrographic Laboratories, Inc., Cleveland, Ohio. The increasing utilization of chemical treatment prior to direct spectrographic techniques is again illustrated in analysis of biological leaf and fruit materials. Oontrolled dry ashing followed by fusion techniques ensures relative freedom from element loss, matrix effects, and similar considerations. It is then possible with a high intensity multiple discharge tandem gap spark source to obtain adequate sensitivity for the majority of the elements involved with the resultant increase in accuracy compared t o conventional direct current arc methods. Comparat,ive figures de-

1579 rived chemically for about 100 samples were given to verify this new method. Spectrochemical Determination of Major Constituents of Limestone. R. K. LEININGER, Division of Geology, Indiana Department of ConPervation.

A spectrochemical method for the determination of major constituents of limestone has been utilized by the Division of Geology, Indiana Department of Conservation. A 4-mg. samplc of 2 parts by weight SP-2 graphite and 1 part limestone is burned to completion in a graphite anode. An initial direct current of 10 amperes and an electrode gap of 2 mm. are not adjusted during a 100-second exposure. Intensity is controlled by a rotating sector. Spectra are recorded on ESA-1 film in a grating spectrograph with Wadsworth mount. Per cent transmittances of the following lines are determined: Ca 3005.8, 3361.9; RIg 2779.8, 3091.1, 3336.7; Si 2519.2, 2881.6, 2987.6; Fe, 2966.9, 3008.1, 3020.6; A1 2575.1, 3082.2; Ti 3372.8. Calculation is according to the mutual standard method described by Churchill, Rozsa, and others. Results are expressed as percentages of CaC03, MgC03, SiO2, Fe208, A1203, and TiO2. For a series of 19 routine samples the average deviation from the chemical values (which averaged, respectively, 76.3, 15.7, 6.17, 0.476, 0.797, and 0.0592) was, respectively, 1.29, 0.84, 0.67, 0.10, 0.11, and 0.010. Analog Computer for Spectrographic Analysis of High Alloys. J. JURMAIN ASD D. E. WILLIAMSON, Baird Associates, Inc. An operational description was given for an electrical analog computer to solve the problem of atomic dilution in the spectrographic analysis of high alloys. Its application was demonstrated for both photographic and direct reading methods of analysis. I t was further illustrated that when used as an adjunct to the direct-reading type instrument, the analysis of all types of alloys is reduced to a truly direct reading process with no intermediate computations involved. Quantometry in 1950. M. F. HASLER,Applied Research Laboratories, Glendale, Calif Direct-rcading analysis, a$ obtained with the Quantometer, has hurdled several basic obstacles during the past year. Instrumentally, there are several significant advances. Multipurpose instruments have been introduced and are in successful operation in a number of industries. These instruments allow the immediate analysiq of any one of up to three basic materialsfor example, aluminum alloys, zinc alloys, lead alloys, etc Several such instruments were described as to their basic requirements. Duplicate direct-reading recordings have been perfected using a ball point pen on the recorder and regular carbon paper. Such records eliminate the need for transferring figures from one record to another and allow very high speed objective analysis. More positive means of standardization have been developed, yhich were dewibed in detail (2). Methodwiw, the rigorous theory of calculations in a multicomponent system has been reduced to a simple, practical operation. This has been applied to an eltension of the method of stainless-steel analysis introduced in 1949 to cover all types of such steels ( 1 ) . I t has also bcen applied to tool-steel analysis and to copper-alloy analysis. These applications were discussed. (1) (2)

“Analysis of Stainless Steels Covering Wide Ranges of Composltion ARL Quantometer,” ARL release, Aug. 14, 1950. “Spectrochemical Calculation Suitable for Multicomponent System.” ARL release, Aug. 1, 1950.

Conference on X-Ray and Electron Diffraction The eighth annual Pittsburgh Conference on X-Ray and Electron Diffraction, held November 2 and 3, was highlighted this year by the attendance and contributions of three French scientists from the Sorbonne, Universitk de Paris. Andre Guinier described recent refinements in the design of rotating anode tubes, new to America, which make possible employment of crystal monochromatized radiation useful in the investigation of lattice imperfections. Yvette Cauchois presented a discussion, based on her many years of experience, on improvements in bent-crystal technique for concentrating x-ray beams. Professor Trillat gave a report of researches by electron diffraction on the cementation of steel. Abstracts of interest to analytical chemists are: