This lab experiment illustrates the use of thermogravimetric analysis (TGA) to perform proximate analysis on a series of coal samples of different rank. Peat and coke are also examined. A total of four exercises are described. These are dry exercises as students interpret previously recorded scans. The weight percent moisture, volatile matter, fixed carbon, and ash content are determined for each sample and comparisons are made. Proximate analysis is performed on a coal sample from a local electric utility. From the weight percent sulfur found in the coal (determined by a separate procedure—the Eschka method) and the ash content, students calculate the quantity of sulfur dioxide emissions and ash produced annually by a large coal-fired electric power plant.

We analyzed the structure of open-circular and supercoiled dimeric DNA catenanes generated by site-specific recombination in vitro. Electron microscopy of open-circular catenanes shows that the number of duplex crossings in a plane is a linear function of the number of catenane interlinks (Ca/2), and that the length of the catenane axis is constant, independent of Ca. These relationships are similar to those observed with supercoiled DNA. Statistical analyses reveal, however, that the conformations of the individual rings of the catenanes are similar to those of unlinked circles. The distribution of distances between randomly chosen points on separate rings depends strongly on Ca and is consistent with a sharp decrease in the center-of-mass separation between rings with increasing Ca. Singly linked supercoiled catenanes are seen by microscopy to be linked predominantly through terminal loops in the respective superhelices. The observations suggest that chain entropy is a major factor determining the conformation of DNA catenanes.

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In this experiment, wrought aluminum alloys, fashioned into 3 in. × 1 in. coupons, were anodized and subsequently colored. To achieve the most attractive colors the 1100 Al alloy was selected over other wrought Al alloys. To further ensure attractive colors, an eight-step pretreatment protocol was followed. Sulfuric acid was used as the electrolyte solution in the anodizing bath, and a five-step post-treatment protocol was followed prior to coloring the anodized Al coupon. Inorganic pigments (yielding gold and Prussian blue) and electrolytic coloring (yielding burgundy red) were utilized to achieve the colored Al alloys. Using oxalic acid in place of sulfuric acid as the electrolyte solution in the anodizing bath and anodizing other wrought Al alloys, namely, the 2024, 3003, 5052, 6063, and 7075 wrought Al alloys, was also explored. This experiment was performed during two successive 3 h laboratory periods in a second-semester general chemistry course designed for undergraduate engineering students.