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V O L U M E 20, NO. 7, J U L Y 1 9 4 8 Vogel, Kolthoff, and Tomula, nor does it contain any experimental 01’ analytical data. In certain respects the method of the authors differs from that of Stengel. In the first place, instead of dissolving a sample in dilute hydrochloric acid, oxidizing with nitric acid, and treating the dry residue with dilute hydrochloric acid, the authors employ aqua regia and hydrofluoric acid iollowed by treatment with perchloric acid. which effects the complete solution of all carbidic residues. Secondly. in the case of Stengel’s procedure nickel interferes with the photometric reading for cobalt and must be separately determined. In the rase of the authors’ process the background color due to nickel. etc., is colorinietrically read before and after the development of the coloi due to the cobalt thiocyanate complex. In the third place, the method of the authors is far more rapid than that of Stengel. The entire procedure of the authors may be completed in the time required to take the Stengel solution to dryness on the steam bath at the outset of his procedure. Finally, the 24 different types of cobalt alloys shown in Table I1 of the authors’ paper is an indication of the wide adaptability of the method in the presence of a large variety of other alloying elements. W , F. M. of thcir c,lectron diffrxction patterns;. >IlSCELLANEOLS
Hospital, Detroit, RIich. The need for evaluating the size and structure of small particle aggregates was demonstrated. Too often too much emphasis is placed on the fundamental particle size, which may not be so significant as the aggregate data. 9critical discussion of the interpretation of the electron microscope image in terms of tlllipticity and distance from the supporting membrane wa,s prewnted. The accuracy of the technique and its relation to ruhhcr compounding were mentioned.
Electron Diffraction-An Instrument and Some Applications. .T. G. H ~ T T O SGeneral , Electric Co., Schenertady, S . T. The new G.E. electron diffraction instrument ’r\.as dt.scrit)ed from its functional and applica,bility viewpoints.
Statistical Analysis of Electron Microscope Particle Size Determinations. PAEL I,. COPELAND,Illinois Institute of Technology, Chicago, 111. This paper in part fills a strong need for a critical analysis of the accuracy of electron microscope particle size determinations. The practical results from a large number of measurementh were compared with a theoretical (statistical) calculation. The measurements made on a large number of imaged particles do not agree with the calculated values, probably because of an inadequate representation of the whole sample due t o the Iargt. number of very small particles.
Techniques of High Speed Microtomy. ERSESTF. F ’ L - m x q General Electric Co., Schenectady, K. T. The need for a technique in the preparation of sections sufficiently thin for examination in the electron mici,owopc~ha< been partially filled. dnimal tissue, fibers, plastirs, v t c.. h ~ v i ’been sectioned in thickness of 0.5 micron or l t w .
Properties of Evaporated Gold. P. G. WILKINSOS~ X D I.. 3 . BIRKS,Waval Research Laboratory, Washington, D. C. Evaporated gold blacks and thin films were exaniind in thts electron microscope in order to relate continuity with thickncw and electrical resistance. Gold films may be continuou:: or discontinuous, depending upon their thickness, as determined by electrical measurements. Gold blacks are discontinuous in nature. Results of Electron Microscope Studies on Bacteriophage F. AI~DERSON, Johnson Foundation, L-niversity Action. THOMAS of Pennsylvania, Philadelphia, Pa. The electron microscope !vas shown to be a useful tool in c>xamining viruses from the standpoint of their morphological identification, response to sonic vibrations, and the mechanism ~ i t h which they adsorb on the host bacteria cell followed by proliferation within the infected cell. The sonic treatment breaks up only the larger tadpole-shaped viruses; the fragments continut5 to survive. Certain phages must be activated with amino acids before they will absorb on the host cell. Seven phage5 011 *t min B of E . Coli were cited as examples. Electron Microscopy of the Tubercle Bacillus (BCG) by Metal Shadow Casting Technique. C. I. REED, S. R. ROSEXTHAI.. A N D B. P. REED,L-niversity of Illinois, 1-rbana, Ill. The advantages of metal-shadowing (chromium) the surfact. of bacteria were once again demonstrated. Surfacr (capsule‘i structure and also some internal deta,ils were made more recognizable by the increase in the contrast in the electron microscope image. The history (preparation) of the BCG vaccine and its relation to the morphology of the bacillus vere presented. Electron Metallography. ROBERT D. HEIDESREICH,Bell Telephone Laboratories, Inc., Murray Hill, S . J. The combination of electron microscopy and electron diffraction in the study of surfacr metal structure might appropriately he called “electron metnllography.” Electron reflection diffra.ction, although subject to many qualifications, is useful for identifying the surface films. Slip planes, grain size and structure, height of surface elevations, etc., may be studied by several replica techniques. Three types (plastic, silica, and oxide film) of replicas were described with emphasis on their resolving power. The oxide film type i3 probahly the only one that resolves better than 50 b. Electron Microscopical Study of Organic Pigments. F. A. Aniline & Film Corp., Easton, Pa. -4variety of organic pigments (dyes) have been analyzed for the sake of identification and evaluation of their microphysical
HAIfM, General
High Vacuum Metallizing. GEORGE €1. B.ksCRow, Ilistillation Products, Inc., Rochester, S . Y. -1 new 12-inch vacuuni coater (D.P.1.) wits d~ rluding its required high vacuum techniqu?.
-It the panel sesion on high speed microtomy. It. R. Allen of Custom Scientific Instruments, Inc., -%rlington, X. J., and K.F. Fullani of Hemsdale International, Inc., 350 Fifth Ave., Sen- I-ork. S . T., described their respective instruments and their new improvements. It is non- possible to evacuate the chamber in which the sections are cut, cool (frrezel the sample before sectioning, and adapt the disk to serve as an ultracentrifuge.
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Second Symposium on Analytical Chemistry -1ri angemelits are nom being made fui holding tlic Second .Iiinual Summer Srmposiuni on Analytical Chemistry sponsored by the Division of hnalyti’cal and l1icro Chemistry and ANALYTIC A L CIIEVISTRT, a t Wesleyan University, lliddletown, Conn., In June 19-19, The conference will run tvio full days and will include four technical sessions and a get-together on the evening of the first day. 11. G. Burford, Tesleyan Universitv, \Till be chairman in charge of arrangements.
Symposium on Nucleonics and Analytical Chemistry. Divirion of A4nalvtical and lIicro Chemistry, Xorthwestern University, Evanqton, Ill., 4ug. 13 and 14. Second Annual Summer Symposium on Analytical Chemistry. Weslevan I-niverqitl, \Iiddlrtown, Conn., June 1949.
Raman Spectra of Hydrocarbons-Correction In the article 011 . .Raman SpectIa of H>-drocarbons” [AYAI,. CHEX., 19, 700 (19-17)],on page 710 the second paragraph under “Disubstituted .kromatics” should read: “The 1,Cdisuhstitution is characterized by” . Page 711, the dates for reference ( 7 ) should tie 1939, 19-10, and 1946. Page 721, in apectruiii table S o . 162, the scattering coefficient value for the I\v 651 cm --I line should be 0.560. 31. R . FEXSKE
