Chemical inhomogeneities, measurements with

Modifications of the conventional spinning drop tensiometer were required for operating at temperatures up to 200°C. Measurements carried out with heavy oil samples required the use of D20 instead of H20 to maintain a sufficient density difference between oil and water. For accurate measurements, considerable care must be used to ensure that heavy oil drops do not lag behind the rotation of the capillary tube in the tensiometer. Also, repeatability of measurements conducted with chemically ill-defined substances may be hampered by the inhomogeneity of the oil drops. 

Basic aim of PMS04 was not to waste valuable sets of measurements acquired during the years by several authors in galactic PNe, whose resulting chemical abundances are however not easy to handle, because of the inhomogeneity of the analyses due to different atomic data and different procedures used by the various authors to interpret the data. We decided to go back to the original measurements and interpret all of them with an unique best assessed procedure. 

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