7. Report
7.1 Report the calculated VGC to the nearest .002 unit.
7.2 If the viscosity at 100°C was used for the calculation, state this in the report.
8. Precision and Bias
8.1 The calculation of viscosity-gravity constant from kinematic viscosity at 40°C and density at 15°C is exact. Precision limits are not assigned to this calculation.
8.2 The precision of the calculated VGC is dependent only on the precision of the original determinations of viscosity and density. Those precision statements are found in their respective test methods. The precision can be calculated as follows:
8.2.1 For viscosity measured at 40°C,
where:
rY = precision of the VGC,
rG = precision of the gravity from D287,
rV = precision of the viscosity from D445,
V = measured viscosity, and
Y = VGC.
8.2.2 For viscosity measured at 100°C,
8.3 The VGC calculated from the viscosity at 100°C can differ slightly from that calculated from the viscosity at 40°C. A statistical evaluation of VGC data derived from equivalent viscosities at both 100°F and 210°F suggests that in the range from about 0.80 to 0.95 VGC, the expected average difference will be approximately 0.003 units. Whenever possible, it is preferable to determine the VGC using Eq 1.
8.4 Bias - The procedure in Test Method D2501 for calculation of viscosity-gravity constant has no bias because the value of viscosity-gravity constant can be defined only in terms of a test method.
8.5 The term viscosity-gravity constant is also used in Test Method D2140, for determining carbon-type composition of insulating oils of petroleum origin. The equations used are different from those in this test method; the bias between the two test methods is unknown.
9. Keywords
9.1 aromatic; density; kinematic viscosity; paraffinic