How do you dry an oil solid sample to get its dry weight without causing the oil to evaporate? Every dessication technique I've tried doesn't work....vaccuum suction or incubation in a dessicant atmosphere. It seems that the oil smothers the water droplets, preventing them from escaping. Any other old school chemistry suggestions?

Can you measure the water instead. A Karl-Fisher titration is the complicated but sensitive way or you can dilute a known mass of it it with a solvent like isooctane and distill the water (and isooctane) out. Ideally you do this in a Dean-Stark aparatus. If there's enogh water it forms a layer at the bottom. If not you are stuck with the K-F titration.

P4o10?