Chemical Forums
Chemistry Forums for Students => Physical Chemistry Forum => Topic started by: armand.favrot on April 27, 2018, 08:22:11 AM
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Hello,
I work on hypoxia (lack of oxygen) in fishes as part of an internship in applied mathematics and I have a big problem with partial pressure in liquids. I went to wikipedia and I find out that there were no such thing, only partial pressure in a mixture of gas above a liquid and concentration of disolved gas in a liquid (linked by Henry's law). Nevertheless, in many articles I work on, they talk about partial pressure in water and blood, which I don't understand.
Thanks for your help :)
Ps : forgive the mistakes I'm french!
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I have a big problem with partial pressure in liquids. I went to wikipedia and I find out that there were no such thing, only partial pressure in a mixture of gas above a liquid and concentration of disolved gas in a liquid (linked by Henry's law).
Correct.
Nevertheless, in many articles I work on, they talk about partial pressure in water and blood, which I don't understand.
Neither do I. Most likely it is part of a jargon used in the branch and not necessarily following the general meaning of the term. Nothing unusual in some applications, but confusing for newcomers.
This is tricky, as I can think of two slightly different meanings. One, is "same as the partial pressure of the gas above the liquid", second is "calculated assuming external pressure and solubilities of the gases" (that is, you treat all the dissolved gases together, calculate their total amount, calculate molar fraction of the oxygen, and then multiply it by the external pressure). These are not equivalent.
I would ask the supervisor.
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The thing is in this context with fishes, there is no external pressure since we're talking about gas exchange from water to blood, at the gill of the fish. And not exchange of oxygen between air and water.
I'm waiting for the supervisor :)
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Sure there is an external pressure - there always is. It can change with depth which makes things even more complicated in this case. I guess what you really mean is that there is no gas phase in which we can measure the pressure, but lack of gas and lack of pressures are two different things.
As I said earlier, this is ambiguous and you better consult someone working in the field.
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Yes that's what I meant. Thanks for the answers anyway :)