ASTM D4052 standard test method for density, relative density, and API gravity of liquids by digital density meter
13. Calculation
13.1 Calculating Density Analyzers - The recorded or printed value is the final result when a single determination is conducted (or taking the average of two determinations as the final result as identified in Section 12), expressed either as density in g/mL, kg/m3 or as relative density. Note that kg/m3 = 1000 x g/mL.
13.2 Noncalculating Density Analyzers - Using the observed T-value for the sample and the T-value for water and appropriate instrument constants determined in 10.4.3, calculate the density or relative density using Eq 6 and 7. Carry out all calculations to six significant figures and round the final results to four.
For density:
For relative density:
where:
Tw = observed period of oscillation for cell containing water,
Ts = observed period of oscillation for cell containing sample,
dw = density of water at test temperature,
K1 = instrument constant for density,
K2 = instrument constant for relative density, and
T = temperature of test, °C.
13.3 If it is necessary to convert a result obtained using the density meter to API Gravity, or a density or relative density at another temperature, Guide D1250 can be used only if the glass expansion factor has been excluded.
NOTE 5 - Some digital density analyzers are equipped to automatically calculate and report sample results in API gravity units (see Test Method D287 or D1298), based on the density or relative density results, or a combination thereof, determined by this test method and using the appropriate conversion equation derived from Guide D1250 (which excludes the glass expansion factor), for the specific sample type being analyzed.
14. Report
14.1 In reporting density, state the test temperature and the units (for example: density at 20°C = 0.8765 g/mL or 876.5 kg/m3).
14.2 In reporting relative density, state both the test temperature and the reference temperature, but no units (for example: relative density, 20/20°C = 0.xxxx).
14.3 Report the final result for density or relative density to four significant figures.
14.4 If reporting sample results in API gravity units (see Note 5), report the final results to the nearest 0.1° API.
14.5 In some cases, it may be necessary to report if results were based on a single determination or an average of two determinations, as well as if results were determined by manual injection or automated injection to meet specific requirements, such as data recipients wanting to know such information in order to understand how to interpret results relative to the published method precision values. In such cases, it is permissible to report this information along with the test results.