A small neodymium magnet moves with constant velocity through a coil, and the voltage induced is recorded with a computer interface. The observed voltage is compared to that predicted by simple calculations of magnetic flux using spherical polar coordinates. The close agreement between predicted and observed values combined with the experience gained in modeling the magnetic dipole field make this a very good experiment for the undergraduate student.
Sulfur has been purified by a dynamic pyrolysis procedure that takes into account the unique viscosity-temperature relationship of the liquid. An apparatus is described that incorporates gas-bubbling and rocking to overcome diffusion-limited kinetics. For the first time, a mechanism is proposed for the pyrolytic purification of sulfur based upon Carsul formation and the H2S <-+ H2SX equilibrium. Infrared methods are delineated for qualitative analysis and quantitative estimates of anion contaminants, including the omnipresent hydrocarbon impurities. Our purified sulfur has a total carbon, oxygen, and hydrogen impurity level of <10 /xg/g.
X-ray diffraction radial distribution studies of glassy GexS1−x alloys, with x=0.33 and 0.42, have been performed. The interatomic distances in the x=0.33 sample, 2.2 and 3.55 Å, are consistent with those in the covalently bonded crystalline GeS2. The distances in the x=0.42 sample, 2.3 and 3.65 Å, are also consistent with covalent bonding, and show no relationship to those found in crystalline GeS. No evidence of a previously proposed octahedral coordination of Ge can be found. A tentative explanation for the existence of two separated glass-forming regions in this system is put forth.
Liquid sulfur was studied by Brillouin scattering from the melting point up to 200°C. Polarized spectra show no evidence of the λ transition. The velocity of sound extracted from the Brillouin spectra agrees with previous ultrasonic measurements. The width of the central line in the depolarized spectra exhibits a maximum near the λ transition temperature; this is in qualitative agreement with the known maximum in viscosity.
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