# Gas Solubility in water - constants, and calculations

• Solt
In summary: Hg (from Pbp-Pwv)β=exp(A1 + A2*(T/100) + A3*ln(T/100))ln(β)=exp(A1 + A2*(T/100) + A3*ln(T/100) + A4*(T/100) + S*(B1 + B2*(T/100) + B3*(T/100)^2)ln(β)=exp(A1 + A2*(T/100) + A3*ln(T/100) + A4*(T/100) + S*(B1 +
Solt
I can measure O2, Co2, TGP, and temperature, Want to calculate the rest gases, so N2, and Ar in my water.
There for i bulit up an axcel table. So i get to the point to calculate Bunsen contans on different Temperature.
I have this calculation:

ln(β)=exp(A1 + A2*(T/100) + A3*ln(T/100) + A4*(T/100) + S*(B1 + B2*(T/100) + B3*(T/100)^2

where β is in units of mL/L, and A# and B# are empirically derived least square fit constants, different for specifics gases.

Somehow, i wanted to find A1, A2, A3 and B1, B2, B3 constants for different Gases, but i dont finde.
I need for O2, CO2 , N2, Ar the constants.

Can somebody help where to finde, or how to get it ?

https://www.engineeringtoolbox.com/gases-solubility-water-d_1148.html

I think this will help. Be aware of STP (standard temperature and pressure) and the fact that Earth's atmosphere has different partial pressures for each atom/diatomic molecule. Which makes your job more difficult, IMO.

Note that temperature changes, higher for example, cause different results: gas A may have increased solubility at the higher temperature, gas B may have decreased solubility.

Last edited:
There's a fat PDF here. Doesn't have all your coefficients but are you sure you need them all ? What's the application and what accuracy do you think you can achieve ?

Hi thanks for helping me!

So engineeringtoolbox.com i found before, but these are curves, and i cannot bild in a excel table. but Thanks Jim Mcnamara

Dear BvU

no im not so sure, but than how, i mean easily i can just measure:
O2 - Saturation %, or mg/L optica sensor
CO2 - Sensor, mg/L (i need it in saturation %)
TGP - Total gas Presseure in %

Some how i need to know N2 Saturation %. And i have a PSA, what's make the oxygenation in our Fischfarm.
What i know PSA makes 94% pure O2 (the rest 6% i dont know, but Throught our LHO (low head Oxigeniation ) system its get to our water.
If the N2 saturation goes over100, i have a problem, and if N2 saturation gets over 103% fish stop to eat, and die.
I need to be sure, that's never happened, so i need to measure what's going on.

So i thought, i know Temperature,
I know P(barometric)
i know salinity
And Saturation % of TGP, CO2, O2, let's calcculate the rest if its possible.
if you have easier solution i will be happy : )

Now i so far
I calculate for all the gases Busen Solubility coefficient, for temperauter, and salinity

Than i can calculate partial pressure of gases
Except Argon i found Dissolved gas concentration constant
than i can calculate, partial gas pressure in gas form
what i can use for saturation (for all what i can measure, i can calculate
Than back from total gas pressure, and the partial gas pressure, i can calculate the rest gas pressure
and from that with temperature i can calculate saturatioon %, and also mg/L for N2

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Can't follow you now. The table you post has all the gases you mention, so you can calculate all the saturation pressures. For non-equilibrium you will have to rely on the actual measurements. You could estimate the ones you can't measure by scaling down their saturation in proportion to that of a suitable measured gas.

you mean this?

%sat.N2 = [%sat.Total gas – (20,946*%sat.O2)/100]*100/79,054
Knowing that in Total gas you have: 20,946%O2 and 78,09%N2. The reste is composed of: Argon (0.93%) and CO2 (0.03%).

i have a feeling its not really works, while i have different gas componenets in PSA.

jim mcnamara said:
https://www.engineeringtoolbox.com/gases-solubility-water-d_1148.html

I think this will help. Be aware of STP (standard temperature and pressure) and the fact that Earth's atmosphere has different partial pressures for each atom/diatomic molecule. Which makes your job more difficult, IMO.

Note that temperature changes, higher for example, cause different results: gas A may have increased solubility at the higher temperature, gas B may have decreased solubility.
Yes i found these curves, but these curves i want to build in my calculator-thanks

So thanks for helping me, i show you what i mean
in the excel the first two tabel is important, the first is a calculator for the future
The second is the background

I made this, from M.B. Timmons /J.M.Ebeling Recirculating Aquaculture Book i found the calculations, and also the constants.

Where
Mf -(some times he use Xi ) mole fraction
Ki - Ratio of the molacular weight to volume
mg/mL
A1
A2
A3
A4 (he dosent use at all)
Ji -Dissolved gas concetration constant in liquid
And B - for salinity he odesnt use and calcualte at all - that's what i want to build in

From that i can calculate the Busen coesfficient at different Temperature Tis in K, (so absolut)
β=exp(A1 + A2*(T/100) + A3*ln(T/100)

Pil=(Cmeas/β)*Ji
Where
Pil - Partial Pressure of gas in liquid
Cmeas - measured concentration level in mg/L

Knowing
Pbp - Barometric pressure
Pbp==10^(2.880814-(h/19748.2))
h - is above sea level
and
Pwv - water vapor pressure
Pwv=4.7603*(EXP(0.0645*T))
A0 = 4.7603, if Temperature used in °C

With thoose i can calculate
Pg - Partial Gas Pressure in gas form
Pg=Mf(Pbp-Pwv)

From that i can calculate from different gases all the saturation % what i measure in mg/L
Sat%=(Pil/Pg)*100

So frist step i have all my measurements what i need and i can calculate from measurements what i need to

Ptg sat% - Total gas Pressure - measured as saturation
Pil O2 - calculated from measured mg/L
Pil CO2 - calculated from measured mg/L
Pwv - Calculated from temperature
knowing that
Ptg=PilO2+PilN2+PilCO2+Pwv

Pil N2= Ptg-(PilO2+PilCO2+Pwv)
Pg N2 i can calculate
and
NO2 sat% =(PilN2/Pg N2)*100
so i have it.

My problem is there, Argon is missing from the calculation, ewhats also 0.93%, so would be nice to have
i dont finde A1, A2, A3 for Argon..or if i find, in the same table for known A1, A2, A3 is totally different (O2, CO2, N2) from Timmons given datas.

i want to bulid in the salinity, but somehow also totally different numbers and constants are given if i finde.

Thanks to take your time if you read it up to here.

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• TGP.xlsx
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BvU said:
Can't follow you now. The table you post has all the gases you mention, so you can calculate all the saturation pressures. For non-equilibrium you will have to rely on the actual measurements. You could estimate the ones you can't measure by scaling down their saturation in proportion to that of a suitable measured gas.
Sorry, now i made the excel, and the calculations vlearer i hope
Down

## 1. What is the definition of gas solubility in water?

Gas solubility in water refers to the ability of a gas to dissolve in water. It is measured by the concentration of the gas in the water, usually expressed in units of moles per liter.

## 2. What are some common factors that affect gas solubility in water?

The solubility of a gas in water is influenced by several factors, including temperature, pressure, and the chemical properties of the gas and water molecules. In general, gases are more soluble in cold water and at higher pressures.

## 3. What are some common constants used in gas solubility calculations?

The most commonly used constants in gas solubility calculations are the Henry's Law constant, which relates the concentration of a gas in a liquid to the partial pressure of the gas above the liquid, and the solubility product constant, which describes the equilibrium between a gas and a liquid at a specific temperature and pressure.

## 4. How can I calculate the solubility of a gas in water?

The solubility of a gas in water can be calculated using various mathematical equations, such as the Henry's Law equation or the ideal gas law. These calculations require knowledge of the gas and water properties, as well as the temperature and pressure conditions.

## 5. What are some practical applications of understanding gas solubility in water?

Understanding gas solubility in water is important in various fields, such as environmental science, industrial processes, and medical research. It can help predict the behavior of gases in water systems and inform decisions on water treatment and purification methods. It is also crucial in understanding the effects of air pollution on water quality and the role of dissolved gases in aquatic ecosystems.

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