ASTM D2779 Method for Estimation of Solubility of Gases in Petroleum Liquids
1. Scope
1.1 This test method covers the estimation of the equilibrium solubility of several common gases encountered in the aerospace industry in hydrocarbon liquids. These include petroleum fractions with densities in the range from 0.63 to 0.90 at 288 K (59°F). The solubilities can be estimated over the temperature range 228 K (-50°F) to 423 K (302°F).
1.2 This test method is based on the Clausius-Clapeyron equation, Henry's law, and the perfect gas law, with empirically assigned constants for the variation with density and for each gas.
1.3 The values stated in SI units are to be regarded as the standard. The values in parentheses are for information only.
1.4 This standard does not purport to address all of the safety concerns, if any, associated with its use. It is the responsibility of the user of this standard to establish appropriate safety and health practices and determine the applicability of regulatory limitations prior to use.
2. Referenced Documents
2.1 ASTM Standards:
D1298 Test Method for Density, Relative Density (Specific Gravity), or API Gravity of Crude Petroleum and Liquid Petroleum Products by the Hydrometer Method
3. Terminology
3.1 Definitions:
3.1.1 Ostwald coefficient - the solubility of a gas expressed as the volume of gas dissolved per volume of liquid when the gas and liquid are in equilibrium at the specified partial pressure of gas and at the specified temperature.
3.1.2 Bunsen coefficient - the solubility of a gas expressed as the volume, reduced to 273 K (32°F) and 101.3 kPa (1 atm), dissolved by 1 volume of liquid at the specified temperature and 101.3 kPa.
3.1.3 Henry's law - the principle that the ratio of partial pressure to mole fraction of gas in solution is a constant.
3.1.3.1 Discussion - In non-ideal systems the fugacity is used to replace the pressure, but the systems within the scope of this test method can be considered ideal within the limits of the accuracy statement.
3.2 Symbols:
d = density of the liquid at 288 K (59°F), kg/L,
T = specified temperature, K,
Lo = Ostwald coefficient at 273 K for a liquid of d = 0.85,
L = Ostwald coefficient at T for a liquid of d = 0.85,
Lc = Ostwald coefficient at T for a liquid of the specified density,
p = pressure of the gas, or mixed gases, MPa,
pv = vapor pressure of the liquid at the specified temperature, MPa,
p1, p2... pi = partial pressures of the gases in a mixture, MPa,
G = solubility, mg/kg,
B = Bunsen coefficient at the specified d, p, and T,
X = mole fraction of gas in equilibrium solution,
Lm, Bm = coefficients for mixture of gases,
M = molecular weight of the gas, g/mol,
Ml = molecular weight of the liquid, g/mol,
H = Henry's law constant, MPa, and
C = molarity, kg mol/m3.
