ASTM D2780 Test Method for Solubility of Fixed Gases in Liquids
10. Calculation
10.1 Calculate the volume of gas dissolved in the sample at the specified temperature and pressure of test in the following manner:
Vost = VB x (PB/PO) x [(To + 273.2)/(TB + 273.2)]
where:
Vost = volume of extracted gas at temperature and pressure of test, mL,
VB = volume of gas in gas buret, mL,
PB = pressure of gas in gas buret, Pa (or torr),
PO = test pressure, Pa (or torr),
TB = temperature of gas in gas buret,° C, and
To = test temperature,° C.
10.2 Calculate the volume of the liquid sample at the test temperature as follows:
VL = weight liquid/dT
where:
VL = volume liquid at the test temperature, mL, and
dT = density of liquid at the test temperature, g/mL.
10.3 Calculate the gas solubility, Vc as follows, reporting the result as the Ostwald coefficient:
Vc = Vost/VL
10.3.1 If the gas dissolved in the sample contains more than one component or if the gas contains an appreciable fraction of vapors from the liquid sample, connect the calculation of the Ostwald coefficient given in 10.3 by multiplying the calculated coefficient by the mol fraction of the desired component in the extracted gas. Thus:
Vc1 = Vc x N1, Vc2 = Vc x N2,• • •Vci = Vc x Ni
where:
Vc1• • •Vci = Ostwald coefficients of components 1 through i, and
N1• • • Ni = mole fraction of components 1 through i.
10.4 Alternatively, the gas solubility may be calculated as a Bunsen coefficient, B. In order to do this it is necessary to determine the volume of extracted gas at STP.
VSTP = VB x (PB/760) x [273.2/(TB + 273.2)]
where:
VSTP = volume of extracted gas at STP, mL,
VB = volume of gas in gas buret, mL,
PB = pressure of gas in gas buret, torr, and
TB = temperature of gas in gas buret, °C.
10.5 Calculate the volume of the liquid sample at 288.7 K (15.5°C) (60°F) as follows:
V15.5 = weight liquid/d15.5
where:
V = volume of liquid at 288.7 K (15.5°C) (60°F), and
d15.5 = density and liquid at 288.7 K (15.5°C) (60°F).
10.6 Calculate the Bunsen coefficient, B, as follows:
B = VSTP/V15.5
10.6.1 If the gas dissolved in the sample contains more than one component or if the gas contains an appreciable fraction of vapors from the liquid sample, the calculation of the Bunsen coefficient given in 10.6 must be corrected by multiplying the calculated coefficient by the mole fraction of the desired component in the extracted gas. Thus:
B1 = B x N1, B2 = B x N2,• • •Bi = B x Ni
where:
B1• • •Bi = corrected Bunsen coefficients of components 1 through i, and
N1• • •Ni = mole fractions of components 1 through i.
