Some inherent instrument capabilities/limitations can be described in terms of signal to noise ratio (S/N). Two three-hour experiments are described to give students appreciation of the importance of signal strength and noise level in instrument performance and how S/N can be increased by choice of conditions and data manipulation. (Author/JN)

Discusses methods of measuring organic vapors, various compounds, and particulates in laboratory atmospheres, reviewing criteria for safe levels. Does not discuss other ways that toxic materials enter the body as through skin or by ingestion. (Author/JN)

To assess the ability of current analytical methods to approach the single-atom detection level, theoretical and experimentally determined detection levels are presented for several chemical elements. A comparison of these methods shows that the most sensitive atomic spectrochemical technique currently available is based on emission from…

Laser enhanced ionization (LEI) occurs when a tunable dye laser is used to excite a specific atomic population in a flame. Explores the origin of LEI's high sensitivity and identifies possible avenues to higher sensitivity by describing instrument used and experimental procedures and discussing ion formation/detection. (Author/JN)

Major instrumental concerns in molecular solution fluorimetry have recently turned away from sensitivity enhancement to an orientation more directed toward selectivity. This trend simply recognizes that such methodology has historically been blank limited. Thus, the described uses of liquid chromatography, line narrowing, and time resolution…

Describes sensitive and specific methods used to monitor tetrachlorodibenzodioxins and tetrachlorodibenzofurans. The procedures are suitable for detecting and quantifying these substances at the parts-per-trillion levels in complex environmental and biological samples. (Author/JN)

Discusses two newer methods in mass spectrometry and shows how they can increase signal and signal-to-noise ratios, respectively. The first method, desorption ionization (DI), increases sensitivity while the second method, mass spectrometry/mass spectrometry (MS/MS), increases specificity. Together, the two methods offer improved analytical…

Discusses the nature and applications of mass-selective laser photoionization. The ionization can be done with a single intense laser pulse lasting a few billionths of a second with no molecular fragmentation. Applications focus on: (1) benzene clusters, excimers, and exciplexes; (2) metal clusters; and (3) triplet formation and decay. (Author/JN)

Taking a prototype chemical reaction (molecular hydrogen plus hydrogen atom), constructs an accurate semiempirical, generalized diatomics-in-molecules potential energy surface, calculates motions of these atoms on this surface using REACTS trajectory program, and presents results as moving picture on a microcomputer graphics system. Provides…

The temperature at which the onset of coordinated segmental motion begins is called the glass-rubber transition temperature (Tg). Natural rubber at room temperature is a good example of a material above its Tg. Describes an experiment examining the response of a typical polymer to temperature variations above and below Tg. (Author/JN)

Discusses general corrosion reactions (iron to rust), including corrosion of iron, sulfur dioxide, chlorides, immersed corrosion, and underground corrosion. Also discusses corrosion inhibition, including corrosion inhibitors (anodic, cathodic, mixed, organic); safe/dangerous inhibitors; and corrosion/inhibition in concrete/marble, showcases/boxes,…

Discusses the solid state chemistry of iron and steel in terms of the iron-iron carbide phase diagram. Suggests that this is an excellent way of introducing the phase diagram (equilibrium diagram) to undergraduate students while at the same time introducing the descriptive solid state chemistry of iron and steel. (Author/JN)

Indicates that academe must emphasize professional responsibility for chemical health and safety and engender a similar concern in students. Suggests this may be accomplished both by informing students and by helping them make reasoned decisions concerning their exposure to these hazards. (Author/JN)

Presents some aspects of concept learning theory (what concepts are and how to analyze them) and proposes ways to improve the teaching of concepts in introductory chemistry courses. Emphasizes the lecture format, although ideas presented are applicable to other teaching methods. (Author/JN)

Clarifies misunderstanding of Millikan's experiment measuring charge on electrons. Most books describing the experiment indicate ionization of air in the apparatus caused liberation of electrons, and that these electrons were picked up by oil droplets. However, in Millikan's discussion, it is stated clearly that ions were attached to oil droplets.…