The Microscope - Volume 70, First Quarter 2023
On the cover:
The McCrone Dispersion Staining Color Chart provides the colors observed with dispersion staining and either type of stop: annular stop or central stop. The colors shown are a continuous series throughout the entire range of the matching wavelength (λ0). See The Calibration of Dispersion Staining Colors, page 3. (Courtesy of McCrone Research Institute)
Gary J. Laughlin
The Microscope 70:1, p ii, 2023
Excerpt: Amazing but true, many criminalists regard forensic microscopy and the light microscope as the single most important instrument in their laboratories for the examination of physical trace evidence. They emphasize proper training as the key to success. McCrone Research Institute began by teaching chemical microscopy courses with the polarized light microscope to chemists and forensic scientists first at Cornell University, then Armour Research Foundation (ARF), Illinois Institute of Technology (IIT), University of Illinois at Chicago (UIC), and in its classrooms and laboratories still located on the South Side of Chicago since 1960. But it hasn’t been an easy path.
The Microscope 70:1, pp 3 – 21, 2023
Abstract: Dispersion staining (DS) is an effective and versatile technique for measuring the refractive index (RI) of non-opaque materials by polarized light microscopy (PLM) and has been widely applied in the analysis of asbestos minerals. DS converts the RI difference between an object and its surrounding liquid medium with known RI into an observable color, i.e., the DS color, in the visible spectrum, resulting from the corresponding matching wavelength λm between the RI of the object and its surrounding liquid. Based on the relationship between DS color and λm, λm can be quantitatively evaluated from the observed DS color. Once λm is known, the RI difference between the object and liquid can be calculated. From the liquid’s RI value, the RI value of the object is then measured. The accuracy of RI measurement is directly and primarily dependent on the accuracy of the DS color estimation. Therefore, it’s paramount to obtain an accurate estimation of DS color. In order to improve the accuracy of DS color estimation, it must be carefully calibrated against the specific polarized light microscope used and the specific eyes of the analyst performing the measurement. This paper presents a practical, step-by-step procedure for the calibration of DS color with necessary RI-λm conversion tables at different working temperatures.
Russ Crutcher and Heidie Crutcher
The Microscope 70:1, pp 23 – 34, 2023
Abstract: We often identify what we expect to see, what is familiar, or what we want to see based on limited information (1). For example, while reading we may skim a word based on the first and last letters; however, it may not be the actual word. The brain is very busy, and it often skips ahead when it comes to a conclusion based on a limited set of data. We may have to go back and view all the letters to identify the actual word. Looking at particles under the light microscope is similar. Working memory is limited at any given time and must be regularly updated while the many visible properties of a particle are examined. There are more than 40 optical properties that may be used to characterize a particle in a fixed mounting medium. Information on how the particle was generated, where it came from, how it was transported, its composition, and other aspects of its history are often written in its optical properties. A list of the morphological properties is presented here with information on how to look for them. Without such a list it is easy to overlook important characteristics that may be critical in understanding how a particle relates to the analytical questions being asked.
Brian J. Ford
The Microscope 70:1, p 35 – 47, 2023
Excerpt: Social media are already subverting scientific truth, and our conventional view of the living cell is being replaced with mythical models that look more like blobs and jellybeans.
The other afternoon I was doing what we all do, peering intently down the microscope and marveling at the unique spectacles we see, when suddenly the world went away. You remember the real world we knew — a place with the solidity of science and the certainty of facts. If you weren’t sure, you would consult the acknowledged authority who would soon put you right. Or you would look it up. Not anymore. Suddenly that world disappeared. There are no facts any longer, and authorities exist not because the scholarly world acknowledges their wisdom, but because they assure you that’s what they are.
Afterimage | Microcrystal Test with Sodium Carbonate Reagent
The Microscope 70:1, p 48, 2023
Microcrystal test for lysergic acid diethylamide (LSD) using a 5% aqueous sodium carbonate reagent, rapidly brought to dryness on a hot plate set to 100° C; crossed polars. Although this test was unsuccessful for detecting the drug, Mr. Dunlop included this photomicrograph in his presentation, “Microchemical Analysis of Lysergic Acid Diethylamide (LSD),” at Inter/Micro 2023 in Chicago.
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