1. Characterization factors
Universal Oil Products (UOP): UOP ort Watson characterization factor (Kw)
Kw <10 for highly aromatic materials
Kw almost 15 for highly paraffinic compounds
FOR crude oil
10.5 (for highly naphthenic crude) < Kw < 12.9 (paraffinic base crude)
US Bureau of Mines Correlation Index (CI) : (CI) Is useful in evaluating individual fractions from crude oils.
CI=0 (straight chain paraffins)
CI=100 (benzene)
Low CI  high on paraffinic hydrocarbons
High CI high in naphthenes and aromatics 1

2. Crudes suitable for asphalt manufacture
O It is not possible to predict with 100% accuracy whether or not a particular crude will produce specification asphalts without actually separating the asphalts from the crude and running the test.
O There are, however, certain characteristics of crude oils that indicate if they are possible sources of asphalt.
 If the crude oil contains a residue (750 F or 399 C) mean average boiling point having a Watson characterization factor (Kw) of less than 11.8 and the gravity is below 35 oAPI, it is usually suitable for asphalt manufacture.
 If , however The difference between the characterization factors for the 750 F and 550 F fraction is greater than 0.15, the residue may contain too much wax to meet most asphalt specifications. 2

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5. Estimates of the shape of the TBP curve above 790 F( 421 C) can be obtained by plotting the distillation temperature versus % distilled on probability graph paper and extrapolating to 1100 F (593 C) 5

6. O The gravity mid-percent curve is plotted on the same chart with TBP curve.
O The gravity should be plotted on the average volume percent of the fraction, as the gravity is the average of the gravities from the first to the last drops in the fraction. 6

7. Crude oil classification
Usually, crude oils are classified as paraffin base, naphthene base, asphalt base, or mixed base. THE U.S. Bureay of mines has developed a system which classifies the crude according to two key fractions obtained in distillation:
No. 1 from 482 to 527 F ( 250 to 275 C) at atmospheric pressure.
No.2 from 527 to 572 F (275 to 300 C) at 40 mmHg pressure.
The gravity of these two fractions is used to classify crude oils into types as shown below 7

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