V O L U M E 23, NO. 12, D E C E M B E R 1 9 5 1
1887
ferent crystallographic faces. The molecules or atoms of the object migrate t o different faces on t h e crystal tip, depending upoii t h e temperature t o which it is heated ( u p t o 1800" C.). Thus it is possible t o speculate on t h e nature of short-range interatomic forces. A motion picture film record of t h e fluorescent screen image of thermal migrations of various metals also proved t o be fascinating. Interpretation of these phenomena constitutes a real challenge. An w e n more recent development, the field ion microscope,
using protons, operated similarly was also desrrihed. Better resolution, on t h e order of 3 A,, shelving t h e atomic lattice spacings of t,he tungsten crystal point was illustrated by means of photographs. T h e point is, in this instrument, made positive so t h a t t h e adsorbed hydrogen atoms are liberated as protons w h c h owing t o scattering give rise t o a silhouette image of t h e object also adsorbed on t h e tungsten point. T h e high vacuum recjuirements a n d t h e necesPary thermal stability of t h e subject nxitter were outlined.
Electron Microscope Society of America F. A.
u m r
General Aniline & F i l m Corp., Easton, Pa.
THE ninth annual meeting of this society was held a t t h e Institute, Philadelphia, Pa., on S o v e m b e r 8, 9, aiid 10, 1951. T h e attendance of about 300 people set a n e x record which clearly defines t h e growth of this society. r
1 Franklin
The success of t h e meeting must be largely credited t o t h e program chairman, T. G. Rochow, American Cyananlid Co., Stamford, Conn., a n d t h e chairman of t h e committee on locai arrangements, D. D. Pendleton, Jr., Radio Corp. of .4merica, Camden, N. J. The meeting had been deliberately planned t o follow t h e Symposium on Electron Physics sponsored by t h e S a t i o n a l Bureau of Standards earlier during t h e same week. -4s a consequence, a new record for attendance by foreign electron microscupists was established, from t h e standpoint of 60th number of people a n d number of foreign countries represented. Five countries in t h e European area and Uruguay were represented; their personnel attended t h e meeting a n d Friday evening banquet as guests of t h e Electron Microscope Society of America. It developed t h a t t h e banquet was highlighted by these foreign electron microscopists, who gave brief but entertaining afterdinner talks. T h e incumbent president, Robley C. Williams, University of California, Berkeley, Calif., presided, and in t h e customary manner introduced t o t h e society t h e next year's president, R. D. Heidenreich, Bell Telephone Laboratories. hfurray Hill, N. J. The program of this meeting is abstracted below; only those papers of general interest t o t h e readers of A N ~ ~ r r r c . CHEarrs41~ TRY have been considered. T h e first session dealt largely with instrumentation. Empirical Treatment of the Influence of Morphology and Accelerating Voltage on Electron Diffraction Patterns. S. G. ELLIS, RCA Laborataries Division, Princeton, N. J. The first portion of this paper is described in the review of the Symposium on Electron Physics. The second portion was devoted to a discussion of the precision of electron diffraction with reference to the RCA E M U instrument. The correlation between diffraction ring sharpness and accuracy of measurement was outlined. Thin. well dispersed specimens permit accuracies of about 0.1%. Intermediate and Diffraction Lens for RCA Electron Microscope Type EMU. BENJAMINM. SIEOEL,Department of Engineering Physics, Cornell University, Ithaca, N. Y . The paper describes a useful technique for relating diffraction patterns with specific areas mithin the specimen. The usual modifications of removing lens pole pieces is eliminated. The ability to focus the image focal plane in the objective lens a t the object plane of the projector lens permits the formation of the specimen diffraction pattern. The removable aperture is a desirable feature because it conveniently permits a reduction in field size giving use to the diffraction pattern. Circuit diagrams for conjunctive n iring of projector with intermediate lens were explained.
This paper also described a technique for relating diffraction patierns with specific small areas within the specimen. Instrument modifirtitions such as removal of projector pole piece and insertion of a 120-micron condenser aperture are required. The distortion normally encountered can be minimized by placing a camera between the objective and projector lens, thereby eliminating the projector lens.
An Objective Aperture Alignment Device. hI.mK E. GETTSER, Sloan-Kettering Institute for Cancer Research, S e w York, N . T. The value of this technique is based upon the ability to see on the final viewing screen the motion of the objective aperture caused by motion of the stage control knobs. The friction ring between the pole piece sections makes contact with a dummy specimen holder, 30 that stage movement causes movement of the aperture under the iriction ring. After alignment, the regular specimen holder replacer the dummy probe. Reliability of Internal Standards for Calibrating Electron Microscopes. JOHN H. L. TTATSOX, Edsel B. Ford Institute for Medical Research, Henry Ford Hospital, Detroit, Mich.. AND WILLI.\ML. GRCBE,Research Laboratories Division, General Motors COIp . , Detroit 2, Mich. The limitations of using Dow Latex 550 G spheres were outlined. Bacterial growth a t the expense of the latex under nonsterile storage conditions is important. Collodion grating replicas, calibrated before use by means of spectroscopic methods, appear to be the best internal magnification calibration standards. The calculated grating dimensions are checked to about +2%. Calibration of the grating replicas directly on the electron microscope specimen screen, to be subsequently used for specimen support, minimizes possible errors due to manipulation of the grating replica. Experimental Improvements in the Performance of an Electron HILLIER,RCri Laboratories Division. PrinceMicroscope. JAMES ton. N.J. Several new instrument modifications were outlined. The use of a small (5-micron) centerable condenser aperture reduces thermal loading of the specimen and decreases the exposure time to several seconds a t high magnification. The use of a double objective pole piece permits useful instrument magnification up to about 50,000 diameters and reduces the effects of stray magnetic fields and lack of coincident voltage and magnetic alignment. Vibration in the specimen can be virtually eliminated by tightening a screw through the stage against the specimen holder. Examination of the final image through a low power stereoscopic microscope permits more precise focus and detection of image defects. Critical Studies on the Contrast at the Resolving Limit of the Electron Microscope. JAMES HILLIER. RCA Laboratories Division, Princeton, N. J.
T h c resolution of structure a t the lower limits (below 25 .I.) I t was pointed out that photographic emulsions normally used in electron micrography are much too sensitive to the electron 'to permit minute variations in electron beam intensity distribution in the image. Theoretically the photographic grains should be much less sensitive to the electron, so that intensity variations in the image comparable Electron Diffraction from Small Areas of Electron Microscope Specimens Using an RCA Electron Microscope. J. D. BOADWAY, in magnitude to the just perceptible density variations (about 1%) Hhawinigan Chemirale, Ltd., Shawinigan Falls, Quebec, Canada. on the photographic plate would be recorded. rrre;;tly depends upon the contrast in the image.
1888
ANALYTICAL CHEMISTRY
Some Attempts to Produce Structureless Films, Replicas, and Shadows. s. G. ELLIS A R D J ~ M EHILLIER, S RCA Laboratories Diviaion, Princeton, N. J. The limitations imposed by substrate grain on resolution of struct u r e smaller than 50 9. is serious enough to cause extended investigations leading to films with less structure. This paper described an evaporat,ed film of graphite, prepared by passing current through a bar of graphite in high T-acuum. which showed less structure than the usual csollodion films. Sensitometry of Photographic Materials Exposed to Electrons. .\..I.. QCHOEN AND J . F. H . ~ M I ~ T O Research N, Laboratories, Eastman
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X d r k Co., Rochester. K. I’. The wide variety of density and contrast in electron microscope images makes it desirable to he able to choose the proper photographic emulsion for sperifir electron microscope specimens. Contrast conditions in normal specimens were simulated by preparing a shadow-cast metallic step wedge. Electron micrographs of this wrdge were recorded on sex-era1 different emulsions. The D-log E m r v e plots may t,hen he used to prescribe the pl’oper photographic emulsion, depending oii the spechien. Electron Microscope Pictures in Color. GEORGEIT. CUCHH w, Utah State Agricultural College, Logan, Utah, AND JOHNCHIDESTER, Dugway Proving Ground, Tooele, Utah. The Bensley technique for producing colors by the judicious development of controlled exposures of black and white emulsions has been applied to electron micrographs, in preparing both positive transparencies and paper prints. The dark-room techniques were described. In general. somewhat greater contrast is gained by the ronversion to color process, but no real increase in resolution ia gained. Some choire of color is possible, although in general light areas on the positive electron micrograph give rise to dark blue or gieen areas in the color print.
The second semion riiicrowopy.
W:LS
devoted t o applications of elect roii
1~111cir:i-
The ver;iatility of mthoclic etching in revealing grain boundaries and the various alloy components in ateels was illustrated by electron micrographs. The characteristic structures of martensite, bainite, and other eutectoids appear to be extremely well defined by replication of cathodically etched specimens. New and implored techniques in this etching proress were outlined. Empiiical Survey of Inorganic Compounds Useful as Stains. A . G. RICHARDS, Universit,y of Minnesota, At. Paul, Minn. The technique of metal staining of biological tissue has never met with profound success. This paper described an extensive survey in which a very large number of inorganic compounds wew applied. Two per cent solutions were used: insect cwticles which are highly electron-transparent were used as test specimens. Favorable staining (specimen contrast) was observed with iridium tetrachloride, zirconyl nitrate, thorium nitrate, mercuric chloride, and others. Preparation of Uniformly Dispersed Specimens of Particulate Matter for Examination with the Electron Microscope. T . D. GREEN,J. B. B.\TEMAB,R . E. H.4RTM.LN, c. A. SENSENEY, AND G. E. HEW,Chemical Corps, Biological Laboratories, Camp Detrick, Frederi
