Fluorescence depolarization measurements are used to determine the size of
asphaltene molecules and of model compounds for comparison. Mean molecular
weights of 750 amu have been found for petroleum asphaltenes, A strong corr
elation is established between the size of fused rings in asphaltene molecu
les and the overall size of these molecules, showing that asphaltenes have
one or perhaps two fused ring systems per molecule. Coal asphaltene molecul
es are found to be much smaller than petroleum asphaltenes.