Help Section

The equations used for the computations are described here. You can choose between the different applications:

 A. Addition of a gas in a water containing flask 
B. Gas dilution 
C. Equilibrium of a gas of known concentration 
D. Preparation of a standard solution 

A. Addition of a gas in a water containing flask 

The number of moles injected is given by

with

p1 =
 pressure in first flask, obtained from injected gas concentration
V1 =
 injected volume
R =
 gas constant (0.082057 atm*l*mol-1*K-1)
T =
 temperature (K)

 

exact value is given for the following cases:

injected volume is used in ml units.

gas concentration unit
ppmv
atm
micrg/ml
nM
n

where c is the injected gas concentration.

 

To calculate repartition between gas phase and solution, see the repartition section.

 
 

B. Gas dilution 

 

The number of moles injected is given by

with

p1 =
 pressure in first flask, obtained from injected gas concentration
V1 =
 injected volume
R =
 gas constant (0.082057 atm*l*mol-1*K-1)
T =
 temperature (K)

 

exact value is given for the following cases:

injected volume is used in ml units.

gas concentration unit
ppmv
atm
micrg/ml
nM
n

where c is the injected gas concentration.

If gas is injected from pure solution, the pressure of the gas in the pure solution flask is given by the partial pressure of the compound (P,atm). The amount of moles injected is then given by .

 
 

C. Equilibrium of a gas of known concentration 

Here the amount of moles is given by the following equations:

 

injected volume is used in ml units.

gas concentration unit
ppmv
atm
micrg/ml
nM
n

where c is the initial or final gas concentration.

 
 

Initial concentration:

For initial concentration values, equilibrium has to be reached after addition of the gas. The repartition between the two phases is given by the Henry constant:

when divided by RT, the constant is unitless, giving the ration of moles in gas phase and in solution:

so that we can compute the number of moles transferred in the solution:

we obtain then

and

.

 
 

Final concentration:

If the given concentration is the final concentration, the number of moles in solution is given by:

and the initial number of moles in solution is given by:

.
 

D. Preparation of a standard solution 

Here the number of moles in solution is given by

units micrg/l micrg/ml

nM
n

So that we can find the number of moles in the gas phase:

The volume of gas to be injected is then given by following equations:

c units ppmv atm micrg/ml nM
Vgas (l)