ASTM D3238 for Calculation of Carbon Distributiono and Structural Group Analysis
ASTM D3238 Standard Test Method for Calculation of Carbon Distribution and Structural Group Analysis of Petroleum Oils by the n-d-M Method
3. Summary of Test Method
3.1 The refractive index and density of the oil are determined at 20°C. The molecular weight is determined experimentally or estimated from measurements of viscosity at 37.8 and 98.89°C (100 and 210°F). These data are then used to calculate the carbon distribution (% CA, % CN, % CP) or the ring analysis (RA, R N) using the appropriate set of equations.
4. Significance and Use
4.1 The carbon distribution and ring content serve to express the gross composition of the heavier fractions of petroleum. These data can be used as an adjunct to the bulk properties in monitoring the manufacture of lubricating oil base stocks by distillation, solvent refining or hydrogenation, or both, and in comparing the composition of stocks from different crude sources. Furthermore, the data can often be correlated with critical product performance properties.
