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The Microscope - Volume 56, First Quarter 2008

IN THIS ISSUE:

Editorial | Cheap, Fast, and Good

Gary J. Laughlin
The Microscope 56 (1), p ii
Excerpt: There is a saying that when it comes to service, you can have almost anything you want but you have to obey the Cheap/Fast/Good rule. In other words, you can’t have it cheap, fast, and good … all at the same time. Ordinarily, as it goes, if you want something done cheap, it won’t be fast and it won’t be good. If you want it done fast, it won’t be cheap and it won’t be good. And finally, if you want something done good (well?), it won’t be cheap and it won’t be fast. Microscopical analysis, especially with the Polarized Light Microscope (PLM), may be the only possible exception to this rule.  Full article (PDF)


Filter Preparation For Particle Analysis By Transmission Electron Microscopy

P. Few and J.R. Millette
The Microscope 56 (1), pp 3 – 11
Abstract: To prepare airborne or liquid-borne particles for analysis by transmission electron microscopy (TEM), filtration through filters of polycarbonate (PC) and mixed esters of cellulose (commonly known as mixed cellulose ester-MCE) is often used. Polycarbonate filters are prepared by carbon coating the filters and gently dissolving away the filter material, with an appropriate solvent, leaving the particles caught in a carbon film. Mixed cellulose ester filters are prepared by collapsing the filter, etching the top filter residue, carbon coating the filter and dissolving away the resid ual filter material. This paper describes the procedures in detail with illustrations of the key steps.  Full article (PDF)


Extinction Characteristics of Six Tremolites with Differing Morphologies

Matthew S. Sanchez, Richard J. Lee, and Drew Van Orden
The Microscope 56 (1), pp 13 – 27
Abstract: There has been considerable discussion in the literature related to the use of standard optical properties of commercial asbestos minerals for the classification of amphibole minerals found in raw materials as either asbestiform or as non-asbestos (1-4). The goal of this study was to ascertain if there is a relationship between particle morphology and extinction characteristics in monoclinic tremolite amphiboles. Six tremolitic amphiboles were chosen for this study: three are fibrous (five from natural sites (i.e., mining locales)) and one is the NIST SRM 1867a tremolite standard. The morphology of these tremolites ranged from blocky to asbestiform. A particle-by-particle analysis was performed to determine extinction characteristics and the number of EPA-defined asbestos characteristics. In general, zero or near-zero extinction angles correlate to the number of asbestiform characteristics. Exceptions to this occur when a non-fibrous tremolite has (100) parting as a result of twinning or when fibrous tremolites are elongated in the α-crystallographic direction, therefore preferentially lying on (010). However, when using extinction characteristics in conjunction with morphology, the differences between habit is discemable. The three fibrous tremolites have different fiber widths and, as such, exhibit different extinction characteristics. The smaller the diameter of the fibers, the greater number of particles exhibiting parallel extinction. The sample with the smallest widths (< 0.5 μm).  Full article (PDF)


Heated Asbestos: Analytical Challenges Posed by Heating Crocidolite and Other Fibrous Amphiboles

Myron R.C. Getman and James S. Webber
The Microscope 56 (1), pp 29 – 36
Abstract: Trained polarized light microscopists can easily identify any of the six regulated asbestiform minerals on the basis of their well-established optical properties. An experienced analyst can also recognize changes in these properties when heat-altered asbestos is present in the sample as received. Many analysts, however, may not be aware of how quickly crocidolite alters during ashing in muffle furnaces at routine ashing temperatures. We heated samples of South African crocidolite at various temperatures for measured intervals and then examined the samples using several microscopical techniques. Polarized light microscopy (PLM) observations revealed that crocidolite’s negative sign of elongation changed to positive in less than 90 min. at only 350° C. The intersection of parallel and perpendicular refractive indices (RIs), where the “change” occurred, was 1.717 at both 350° and 475° C. However, neither energy-dispersive X-ray spectroscopy (EDX) nor selected-area electron diffraction (SAED) coupled with transmission electron microscopy (TEM) revealed any differences between unheated and heated crocidolite. Microscopical Fourier-transformed infrared spectroscopy (FTIR-M) revealed subtle differences between the two, but the source of these differences was not determined.  Full article (PDF)


Tricks of the Trade | Inexpensive Tungsten Needle Holder

The Microscope 56 (1), pp 37 – 38
Abstract: Being an instructor at McCrone Research Institute, I am often exposed to people with wonderful ideas for techniques and tools they use to solve problems in their own laboratories. I often feel that I benefit from the courses to the same degree the students do. During a course in January 2007, I learned of an excellent idea for a tungsten needle holder: a mechanical pencil!  Full article (PDF)


100 Years Ago | Obituary: Henry Clifton Sorby, 1826-1908

The Microscope 56 (1), pp 39 – 40
Excerpt from p. 431 of the Journal of the Royal Microscopical Society (1908), with the kind permission of the Honorable Society.
Excerpt: Microscopical Science, as well as this Society, has suffered a serious loss by the death, on March 9, of Dr. Sorby. As President of the Society, in 1875-7, he contributed to our Journal two addresses of a very striking and suggestive character, while our own publications, as well as those of other scientific societies, contain many important communications from his pen, illustrating the enormous value of the Microscope as an instrument of scientific research.  Full article (PDF)


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