The role of NO 2 and O 2 in the combustion of soot was investigated by analysing the soot combustion characteristic and the DRIFT spectra of surface oxygen complexes (SOCs) as soot oxidation intermediates. It is found that in NO 2 /O 2 -soot, like in the CRT system, the oxidation of soot is initiated by the NO 2 -soot reaction to create SOCs as intermediates. O 2 reacts with SOCs, eventually yielding CO and/or CO 2 . This mechanism results in a higher oxidation rate when NO 2 -soot reaction occurs in the presence of O 2 . The potential of using Printex-U, a flame soot, in exploratory diesel soot combustion studies is discussed. It is concluded that in general this is the case except for the fact that real soot can contain adsorbed hydrocarbons that will increase the reactivity of the soot in the absence of NO 2 .

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Students learned the principles and practice of photometry through project-based learning. They addressed the challenge of measuring the unknown concentration of a colored substance using a photometer they were required to design, build, and test. Then, they used that instrument to carry out the experiment and fulfill the challenge. A photometer was designed and built by students consisting of a green laser pointer as the light source and a lux meter as the detector and readout. Using this photometer students have determined the concentration of the unknown sample of KMnO 4 solutions. The concentration of this sample solution was calculated to be (4.62 ± 0.06) × 10 −4 M; this value agrees within 6% of the expected value from the measurement using the commercial spectrophotometer which was calculated to be (4.96 ± 0.005) × 10 −4 M. The experiments fit well into an analytical chemistry course and take a standard (1 h) lab period. This project has facilitated improved student understanding of the photometry concepts and increased the creative problem-solving. In general, the students' response to this laboratory was positive.

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