The interpretation of Fizeau interferograms of optical flats is not straightforward because they are composed of more than two reflections. This results in a confusing fringe pattern. There are three main contributions to the interferogram given by the reflections from the reference surface, the front and the rear surface of the sample. We present a new to the best of our knowledge solution to the problem. We use phase shifting measurements of the wave fields, which are reflected by and transmitted through the sample. This eliminates the need for the suppression of reflections by immersion or other methods. As an illustration of this method, several examples will also be presented.

The hydrocarbon load of contaminated soils is usually mainly adsorbed to the soil organic matter. The laboratory determination of; the sorption equilibration of volatiles suffers from severe-drawbacks due to volatilization losses of the analytes and low recoveries if liquid extraction methods are applied.The presented headspace technique for the determination of partition coefficients produces reliable results, also under adsorptive as I well as under desorptive conditions. It was shown that the volatiles tested are subject to rather severe ad-/desorption hysteresis which strengthens the necessity to determine the desorptive K-oc in contaminated sites. Additionally significant data were obtained that demonstrated a very strong effect of the organic matters quality on the partition ratios of volatiles.