From direct observation of the CH3, CH3S, CHzS and S2 produced in the flash photolysis of CH3SSCH3 (-1950 A) it was concluded that the primary processes are : CH3SSCH3 +hv +CH3SSCH; CH3SS* + CH:, /I CH,SSCH*,+2CH,S CH2S+CH3SH CH3SS" +CH3 + Sz IM +CH,SS.

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The Moessbauer spectra at 4.2K for five ferrihydrites (one natural, four synthetic) have been determined. Two of the samples contained silicon (atomic ratio Si/Fe= 18%, 21%) and one contained aluminium (Al/Fe = 19%). The Moessbauer parameters were calculated from peak positions estimated by a fit of one set of six Lorentzian lines to each spectrum and by judging absorption maxima by eye. Hyperfine magnetic field (H) values were between 50.0 and 50.4 T for pure samples and between 48.3 and 49.2 T for samples containing silicon or aluminium. Variations as small as these, due to impurities, would not prevent ferrihydrite being distinguished from lepidocrocite (H= 46.0 � 0.5 T for pure, well-crystallized material) in Moessbauer spectra of soil samples at 4.2 K.

The ultrasonic absorption of dimethyl sulfoxide solutions of several alkali halides has been studied in the frequency range 1.5 to 52 MHz. An excess absorption, relaxing between 3 and 8 MHz, was observed. The relaxation was assigned to the final step in the stepwise formation of a contact ion pair, with the relaxation frequency controlled by the rate of movement of a solvent molecule rather than an ion. Data on the system water – dimethyl sulfoxide are also presented and the effect of water on the relaxation discussed.