V O L U M E 21, N 0 . ’ 4 , A P R I L 1 9 4 9 LITERATURE CITED
(1) Doub, Leona;d, and Vandenbelt, J M., J . Am. Chem. Soc., 69, 2714 (1947). (2) Vandenbelt, J. hi.,and Doub, Leonard, private communication.
CHARLES J. KERN
Ferrous Metallurgy SIR: I n the February issue there was a bibliography connected with the article on “Ferrous Metallurgy” [Beeghly, H. F., ASAL. CHEM.,21, 241 (1949)l which contained a number of excellent references to the colorimetric determination of molybdenum. I should like to offer as an addition to this list an article by George M. Poole, chief chemist of the Ingersoll Steel and Disc Division of the Borg-Warner Corporation, New Castle, Ind. [Iron Age, 148, No. 15, 62, 164-5 (1941)]. This is an excellent article and well worth including. L. A STARRETT 167 Webster Park Ave. Columbus 2, Ohio
Optical Society of America HE Optical Society of America held its winter meeting a t Tthe Hotel Statler, Kew York, 1;. Y., March 10 to 12, 1949. The program included a Symposium on Luminescence and contributed papers on vision, general optics, color, infrared, ultraviolet microscopy, and spectroscopy. The papers of particular interest to analytical chemists are abstracted here.
An Automatic, Continuous Tristimulus Integrator. H. R. DAVIDSOS AND L. W. IMM, Central Research Laboratory, General Aniline & Film Corp., and Librascope, Inc., Easton, Pa. An automatic tristimulus integrator has been developed for use with the General Electric recording spectrophotometer. Selsyn transmitters mounted on the spectrophotometer relay the wave length and reflectance to the computer where integration is carried out by means of mechanical analog techniques developed during the war. The integrations are performed continuously while the curve is being drawn a t either fast or slow speed. Tristimulus values for any curve may, therefore, be obtained by the spectrophotometer operator with no additional expenditure of time other than that required to record the values and return the counters to zero. The precision of the prototype computer is about ~ 0 . 0 0 0 5&-hen the tristimulus values are so normalized that Y=l.OOOO for a sample whose reflectance is 100%. The combination of spectrophotometer and integrator is a t least as sensitive and usually more sensitive than the eye for the detection and evaluation of small color differences. The absolute accuracy of the tristimulus values obtained is approximately +0.001. Examples were given to indicate that this high speed computer, which will be available commercially, makes practical the application of numerical methods to the solution of color problems. Tristimulus Computation in the Dyestuff and Textile Field. I. H. GODLOVE, General Aniline & Film Corp., Easton, Pa. The tristimulus integrator described by Davidson and Imm has been found, because of its high precision and saving of time, t o yield many results of interest t o the textile dyeing field not conveniently obtained previously. It permits statistical analyses7 for example, obtaining a measure of “unlevelness” (nonuniformity) of dyeings. The average differences between the trichromatic coefficients x and y for A.M. and P.M. repeats on six red wool dyeings were 0.0004. This includes the over-all errors due to the spectrophotometer itself, the positioning of samples, and the integrator. Other work indicates that the precision is adequate for small-difference colorimetry. Work has been done on liquid and film filters to yield analyses for night lighting as well as daylight, “change of shade in artificial light” being of much interest to dyers. Results contrasting additive mixing on a “union” (cotton and wool) dyeing and the subtractive mixture of dye solutions, were shown; also studies on “dyer’s brightness,”
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which is related to saturation. The computer has also been used to follow the striking changes of color due to aggregation of dye molecules in solution; this and other dye phenomena were illustrated. Performance of a New Double Beam Infrared Spectrophotometer. JOHN U. WHITE ASD M.4x D. LISTON, The PerhnElmer Corp., Stamford, Conn. A new recording infrared spectrophotometer has been constructed and tested under a variety of operating conditions. Resolution has been observed approaching the theoretical limit for the rock salt prism used. Stability corresponds to 1.5 times the Johnson noise of the thermocouple used as detector, or to an to 0.5 X watt, r.m.s. equivalent noise input of 1.5 X depending on the speed of response. The variation of IO with wave length is small, and the scattered light is kept to less than 1% throughout the useful range. The instrument’s performance was illustrated with spectra measured under conditions showing its versatility in such variables as resolution, speed, and stability. A Rapid-Scanning Spectrometer for the Kear Infrared. B. W. S. SILVERMAN,Applied Physics Laboratory, i n e Zoiiris Eiopiiina ’u’riiveiaiGy,Baltimore, Md.
BPLLOCKAKD
A scanning spectrometer has been built for use in the lead sulfide region. Suitable spectra in emission as well as in absorption have been obtained a t scanning rates up to 120 spectra per second in the region 360 millimicrons to 3 mu. Scanning time per cycle is approximately 20% of the total cycle. Scanning is achieved by oscillating the Littrow mirror of the spectrometer, using a torque motor and direct link as the driving mechanism. This results in an approximate $ne wave oscillation with a maxiWith lithium fluoride optics. mum usable amplitude of 1.5 the region 1 to 3 microns can be covered in a single range. Preliminary results have also been obtained with a rocking grating as the dispersive element. Resolving power limitations are set by the time constant (approximately 30 microseconds) of the Pb-S cell and amplifier. A liquid air-cooled Pb-Te cell was tried in the instrument; however, the long time constant (1 to 2 milliseconds) required a decrease in scanning speed to a few cycles per second.
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Infrared Absorption Spectra of Ten Substituted Methanes. EARLEK. PLYLER AND W. S. BENEDICT, National Bureau of Standards, Washington, D. C. The infrared absorption spectra of CHCls, CHBra, CHI,, CH2C12, CH& CHBrC12, CHBrZCl, CBrC13, CBr2C12,and CClr have been measured in the region from 2 to 38 mu. Chloroform and bromoform were investigated in the vapor state and in the liquid state. A comparison of the spectra for the two different states reveals only small shifts in the wave lengths of the bands. The spectra of the other compounds were obtained in the liquid state or in solutions. Cell thicknesses from 0.05 to 2.0 mm. were used. The thick cells made it possible to observe many combination bands. The observed bands have all been interpreted as fundamentals, combination and overtone bands, and difference bands. In the compounds with similar structures, the relative intensities of the various bands show regularities. The fundamentals may be assigned to different symmetry types, on the basis of a normal coordinate treatment, using force constants similar to those reported by Decius.
A Color-Translating Ultraviolet hlicroscope. Polaroid Corp., Boston, Mass.
E. H. LAND,
The translating ultraviolet microscope is a highly specialized apparatus designed primarily to aid biophysicists in identifying cell structures. Not only is the resolution of the ultraviolet microscope approximately twice that of the visible light microscope, but the complex organic molecules in tissue cells exhibit their own specific absorption spectra in the ultraviolet. This new microscope utilizes this latter phenomenon to record the absorption data, thereby “fingerprinting” the specimen. This instrument is still in the development stage; probably the time factor (almost a minute) to record the absorption on photographic film will eventually be reduced considerably. At present several sources of ultraviolet are being used; the G. E. light pressure mercury arc (H-6) enjoys some favor because it provides a continuous and discontinuous spectrum. A Wadsworth (diffraction grating) type of monochromator is used t o isolate the desired wave lengths (over very narrow regions). Refracting components of quartz and fluorite have been added to the Schwarzschild mirror type of microscope objective so as t o
