Pauling’s valence-bond (VB) method for determining bond lengths is compared to ten recent literature experimental and theoretical results and is shown to give comparable results. His method only requires computation of the number of Kekulé (K) and Dewar structures (DS) of conjugated hydrocarbons. Both K and DS are obtained from the last two coefficients of the matching polynomial which is also used to obtain topological resonance energy (TRE). A molecular fragmentation method is given for determining DS of essentially disconnected polycyclic aromatic hydrocarbons (PAHs). Both Kekuléan alternant and nonalternant PAHs, including essentially disconnected and non-Kekuléan systems, have bond lengths that are easily determined by this method.

Although asphaltenes are always present in crude oils, they create problems only when they become insoluble in the remainder of the oil. A change in asphaltene solubility can occur because of changes in pressure, composition, or temperature. Whether asphaltene insolubility constitutes a problem, however, depends primarily on when and where in the oil production, transportation, and processing stream it occurs. Instability leading to deposition in a deepwater well is high on the list of potentially problematic situations. While insolubility is a necessary condition, it is not sufficient to predict the buildup of an asphaltene deposit in a production well. Flocculated asphaltenes may deposit or be carried out of the well in the flowing oil phase. To improve understanding and, hence, prediction of asphaltene deposition, several tests have been reported. A capillary deposition test in long stainless steel capillaries has been used to investigate the tendency of a wide variety of oils to create deposits. Observations, in addition to pressure increases during flow through a capillary, include changes in morphology of asphaltene flocs as they slowly separate from unstable oils, the amount of asphaltene produced as a function of time, and chemical analysis of deposits recovered from capillary tests. Other tests have used glass capillaries and a Taylor–Couette cell. As insight grows, the data produced are being used to develop simulators to predict the rate of growth of arterial asphaltene deposits under wellbore conditions.

For all Kekuléan perifusenes with 4, 5, and 6 benzenoid rings the partitions of π-electrons in each ring have been calculated. Trends in the partitions are discussed in connection with Clar's structures. Partition values are useful for discerning similarity/dissimilarity among benzenoids independently of visual overlapping of formulas and for comparing local features of benzenoids such as bay or cove regions.