Static and dynamic light scattering and surface tension
measurements were used to study the effects of various
pentanol isomers on sodium dodecyl sulfate (SDS) micelles in 0.5 M
NaCl. The addition of any of the
pentanol isomers increased both the average hydrodynamic radius,
〈R
h〉, and the average radius of
gyration,
〈R
g〉; however, the magnitude of the effect
depended on both temperature and pentanol isomer. By
comparing
the ratio of these two measures of micellar size, it was found that the
addition of pentanol promotes an
elongation of the rodlike micelles. The effects of the pentanol
isomers on the critical micellar concentration
also were determined. Once more the various isomers did not all
behave identically. Last, the effect of
temperature on micellar size in the presence of the various isomers was
determined. In all cases an increase
in temperature resulted in a decrease in mean micellar size; once more
the overall effect depended on the
isomer in solution.
An experiment for introductory chemistry in which oxygenates are extracted from gasoline and analyzed by gas chromatography is described. The extraction of oxygenates from gasoline with water prior to analysis by gas chromatography allows for their easy identification and quantification since only the oxygenates dissolve in water. Both qualitative and quantitative versions of the experiment are described. Calculations which can be used to determine the weight percent of methanol, ethanol, or methyl tert-butyl ether (MTBE) in gasoline samples are given. The use of this experiment in discussing good laboratory technique, separation of mixtures, chromatography, the use of calibration curves, and error analysis is presented. The value of this experiment because of its current interest, its potential for allowing students to see the utility outside the classroom of what they are learning, and its connection to the political and social issues involved in addition of oxygenates to gasoline is also discussed.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.