Dissolving oxygen

[chilled_fluorine]

I need a way to dissolve as much oxygen as I can in a saltwater solution. I was thinking of something with a tray full of saltwater on top with a tube leading to the vessel that needs the oxygen solution. The thing is, no electricity or pumps are allowed. The oxygen has to be from the air. No peroxide or bleach stuff.

[louis wu]

Any water that is direct contact with atmosphere will contain dissolved oxygen at ~8ppm. The exact amount will vary with atmospheric pressure and the temperature.

 

To obtain higher levels of dissolved oxygen: the oxygen content of the local environment can be raised, or compressed air can be used to pressurise a sealed vessel to a higher pressure than atmospheric. Indeed pure oxygen can be used to pressurise a sealed vessel (use of high oxygen gases requires special consideration to the vessel and piping materials, and pressure vessels themselves are the subject of safety legislation.

[CaptainPanic]

I need a way to dissolve as much oxygen as I can in a saltwater solution. I was thinking of something with a tray full of saltwater on top with a tube leading to the vessel that needs the oxygen solution. The thing is, no electricity or pumps are allowed. The oxygen has to be from the air. No peroxide or bleach stuff.

The amount of gas you can dissolve is roughly linear with the pressure of the gas above the liquid (if it reaches equilibrium).

 

Oxygen in air has a pressure of about 0.2 bar. So, with patience you will reach the maximum concentration in your salt solution - the max you can reach with air. Note that obviously CO2, nitrogen and some other gases dissolve too.

 

To get an even higher concentration, you need either a higher pressure of air, or a more pure source of oxygen.

 

You can increase the speed at which you achieve your equilibrium (that's the maximum concentration) by bubbling the air through the water.

[John Cuthber]

Cooling the water will also help.

[chilled_fluorine]

The amount of gas you can dissolve is roughly linear with the pressure of the gas above the liquid (if it reaches equilibrium).

 

Oxygen in air has a pressure of about 0.2 bar. So, with patience you will reach the maximum concentration in your salt solution - the max you can reach with air. Note that obviously CO2, nitrogen and some other gases dissolve too.

 

To get an even higher concentration, you need either a higher pressure of air, or a more pure source of oxygen.

 

You can increase the speed at which you achieve your equilibrium (that's the maximum concentration) by bubbling the air through the water.

Remember, no pumps or electricity. The oxygen dissolved is being depleted very quickly. I probably should have asked how I would go about dissolving O as quickly as I could. Time is the issue... as it is so often.

[Enthalpy]

Pour hydrogen peroxide in your saltwater solution, that will go faster. Use some way to decompose it. Estimate the amount and concentration to obtain a bit more than said 8ppm.

http://www.engineeringtoolbox.com/ has tables of solubility somewhere.

Edited September 6, 2012 by Enthalpy

[chilled_fluorine]

Cooling the water will also help.

Where I live, the day temperature is almost always in excess of 35c in the summer. Cooling without electricity isn't much of an option, although I guess I could come up with a few ways to do it. Any other thoughts John?I want to expose as much surface area of water as I can, and oxygenate the solution relatively quickly. It's the design of the container I want to discuss. Also, does anyone know if mercury can dissolve air? Doesn't seem to likely, but mercury would be much more ideal for my application.

 

Pour hydrogen peroxide in your saltwater solution, that will go faster. Use some way to decompose it. Estimate the amount and concentration to obtain a bit more than said 8ppm.

http://www.engineeringtoolbox.com/ has tables of solubility somewhere.

 

:facepalms: Seriously? I specifically said NO PEROXIDE. Nice link btw.

[John Cuthber]

Doing anything quickly without adding power is a challenge.

[CaptainPanic]

Remember, no pumps or electricity. The oxygen dissolved is being depleted very quickly. I probably should have asked how I would go about dissolving O as quickly as I could. Time is the issue... as it is so often.

That bold part is something you might want to explain, so that we can give you a better answer.

 

See, as I said, if you just leave some water standing in the open air, it will reach equilibrium. It might take some time, but it'll get there.

If something is consuming the oxygen (microorganisms??), we have a different scenario.

 

Anyway, the quickest way to reach equilibrium is to make a larger surface area. If the water is in a glass, pour it into a soup bowl, and your water will reach (approach) equilibrium a lot faster. In industrial biotechnology they bubble water through the bioreactors. If you cannot do that, then just use a large surface area.

[John Cuthber]

There's something else you need to worry about.

As the solution gains oxygen it will lose water vapour. Eventually the salt solution will be saturated, after that the salt will start to crystallise out.

[chilled_fluorine]

Doing anything quickly without adding power is a challenge.

 

Making caesium hydroxide? LOL

 

There's something else you need to worry about.

As the solution gains oxygen it will lose water vapour. Eventually the salt solution will be saturated, after that the salt will start to crystallise out.

 

Replenishing the water is no problem. The solution is ideally around 50%.

 

That bold part is something you might want to explain, so that we can give you a better answer. Do you think I'm "trying to synthesize an illicit substance" ?

 

See, as I said, if you just leave some water standing in the open air, it will reach equilibrium. It might take some time, but it'll get there.

If something is consuming the oxygen (microorganisms??), we have a different scenario. Of course. Microorganisms just LOVE to live in mercury. LOL

 

Anyway, the quickest way to reach equilibrium is to make a larger surface area. If the water is in a glass, pour it into a soup bowl, and your water will reach (approach) equilibrium a lot faster. In industrial biotechnology they bubble water through the bioreactors. If you cannot do that, then just use a large surface area. Bubbling is not an option. Increasing surface area was my original thought. The problem is, there must be a low surface area, bulky central container. The idea is to have tubes leaving to a high surface area tray of salt water to oxygenate quickly. It doesn't need to reach equilibrium. Any ideas on the design? Maybe I should have posted this in the engineering section...

[elementcollector1]

Making caesium hydroxide? LOL

 

 

 

Replenishing the water is no problem. The solution is ideally around 50%.

 

 

 

"Making an illicit substance" Likely not. I've never seen a drug procedure where oxygen is required to dissolve in a salt solution; but we are curious as to what you intend with the dissolved oxygen.

"Bubbling" I would suggest (and this may seem too simple) that you take your salt solution and place it in a container, then fill the container somehow with pure oxygen. Shake rapidly to dissolve the oxygen (at least, I think that might work).

Er, mercury?

[CaptainPanic]

That bold part is something you might want to explain, so that we can give you a better answer.

Do you think I'm "trying to synthesize an illicit substance" ?

No, but I am clueless what you try to do, and without any further knowledge of the problem, I cannot help. You come here asking expert advice, but you don't explain the problem.

 

See, as I said, if you just leave some water standing in the open air, it will reach equilibrium. It might take some time, but it'll get there.

If something is consuming the oxygen (microorganisms??), we have a different scenario.

Of course. Microorganisms just LOVE to live in mercury. LOL

You said that the oxygen was being consumed (post #5). Solutions of salt in water usually do not consume oxygen. Microorganisms do.

 

Anyway, almost all practical experience with getting oxygen into water is from bio-tech, so whether you like it or not, you are gonna have to learn a thing or two about those reactors... Unless you want to tell us what you are actually doing , this is the best advice.

 

Anyway, the quickest way to reach equilibrium is to make a larger surface area. If the water is in a glass, pour it into a soup bowl, and your water will reach (approach) equilibrium a lot faster. In industrial biotechnology they bubble water through the bioreactors. If you cannot do that, then just use a large surface area.

Bubbling is not an option. Increasing surface area was my original thought. The problem is, there must be a low surface area, bulky central container. The idea is to have tubes leaving to a high surface area tray of salt water to oxygenate quickly. It doesn't need to reach equilibrium. Any ideas on the design? Maybe I should have posted this in the engineering section...

I'm guessing that also here you do not want any circulation system (no pumps?).

That salt solution is not going to move around from that high surface area to the bulky container by itself. And the oxygen will diffuse really slowly.

 

But as long as I have no clue what you're going to do, or what chemical reaction you want to achieve, I have no way to determine whether the system is diffusion limited or whether you're fine.

[pippo]

Any water that is direct contact with atmosphere will contain dissolved oxygen at ~8ppm. The exact amount will vary with atmospheric pressure and the temperature.

 

 

I dont believe thats true. 8ppm is quite high, actually, especially in natural bodies of water. I can site at least one example- my actual experience, and a sad one: My pond which was stocked with fish had only about 2 ppm after heavy rains. They all died.

 

Your 8ppm is way off.

[John Cuthber]

According to this

http://www.engineeringtoolbox.com/oxygen-solubility-water-d_841.html

8ppm (m/m) looks about right for pure oxygen

Water saturated with air will contain about a fifth of that.

[pippo]

John,

 

That statement from louis is still not accurate. Read it again........It says "any" water. My pond situation proves it wrong. Politicians can make statement like that and get away with it. Not scientists.

[CaptainPanic]

The Henry Constant of oxygen in water at 20 degrees Celsius is 4.06*10^9 Pa.

 

Since P = H*x (where P is partial pressure of oxygen in Pa, x is the mole fraction in water), we calculate that:

 

x = P/H = 0.2*101325 / 4.06*10^9 = 5 * 10^-6, or 5 ppm (mol).

 

The Henry coefficient of oxygen in water is a very strong function of temperature. At zero Celsius, it is 2.58*10^9 Pa, and at 100 Celsius, it is 7.10*10^9 Pa. In other words, the concentration of oxygen in water varies by about a factor 3 between 0 and 100 degrees Celsius.

 

I'm afraid I cannot link to these numbers, because they're printed on paper. But it is a decent engineering source, and the values correspond to other sources mentioned here in this discussion by John Cuthber and louis wu, although both failed to specify at what temperature.

 

That statement from louis is still not accurate. Read it again........It says "any" water. My pond situation proves it wrong.

To pippo and louis wu: It would help if you state what kind of ppm you talk about. Weight/weight, mol/mol or volume/volume are three quite different things. If you do not specify it, you cannot argue which is right. John Cuthber does it the correct way. He stated it is weight/weight. His 8 ppm (w/w) is about the same as my 5 ppm (mol/mol). Also, it would help if you all specified what temperature you are talking about.

 

Finally pippo, your pond had fish in it. Fish breathe oxygen, so the concentration would never reach equilibrium. I doubt that louis wu was talking about a pond. Any water is just water, without living things in it.

[John Cuthber]

John,

 

That statement from louis is still not accurate. Read it again........It says "any" water. My pond situation proves it wrong. Politicians can make statement like that and get away with it. Not scientists.

 

Pippo,

For a start, before you go on about what science can and cannot do, you need to specify your units

"ppm" is meaningless without a qualification

What I said was that water would typically dissolve about 8ppm w/w in pure oxygen at 1 atm. (and, BTW, Captain- it's fairly clear from the value I cited what temperature I was referring to)

 

In air you would get about a fifth of that.

"About 2ppm" (units unspecified) is about a a fifth of 8ppm (w/w)

So - at least as far as anyone can tell (given that you have not said what units you are using) what I said agrees with what you measured.

 

What did you think you were arguing about?

[pippo]

John,

 

All I said was when you say "any water", that includes water in lakes, water in ponds, water in oceans, water in a swimming pool. I was not the one that made the statement. Louis did. Thats all, My situation was a pond, yes, it has "any" water. It also happens to have fish (had). It also has algae. It also has frogs. It also has nitrates, phosphate, etc etc etc. I take you as a scientist, based on your competent and respectable posts here, no doubt about it. Not to mention the gracious replies you have given me in the past that were v helpful.

 

Any water is any water. There is no natural body of water that is pure DI- right? Loius was the one who stated "any" water.

 

I know what ppm is, and usually means by the applied science community. it usually means ppm in w/v. Besides, I was not the one who first used the ppm term- louis chose to use that- I was only responding to his term in the most usual acceptable way- was never disputing that ppm should not be the unit of measure. Even had he used the term microgram/milliliter or even another would not have changes the issue at all, so lets not waste our time on this trivial point . To focus on that is irrelevant, basically.

 

Captain,

 

Like I said above- I did not state "any water", loius did. Im not sure whats the confusion. When one says any water, that is a strong point, and a specific point. Thats the only issue I had with the statement. You cant say any water. Any water includes my pond, your pond, John's pond, Obama's pond. My pond contained at a high about 4-5ppm,, and a dangerous low of about 2. Thats all folks.

Edited September 12, 2012 by pippo

[louis wu]

John,

 

All I said was when you say "any water", that includes water in lakes, water in ponds, water in oceans, water in a swimming pool. I was not the one that made the statement. Louis did. Thats all, My situation was a pond, yes, it has "any" water. It also happens to have fish (had). It also has algae. It also has frogs. It also has nitrates, phosphate, etc etc etc. I take you as a scientist, based on your competent and respectable posts here, no doubt about it. Not to mention the gracious replies you have given me in the past that were v helpful.

 

Any water is any water. There is no natural body of water that is pure DI- right? Loius was the one who stated "any" water.

 

I know what ppm is, and usually means by the applied science community. it usually means ppm in w/v. Besides, I was not the one who first used the ppm term- louis chose to use that- I was only responding to his term in the most usual acceptable way- was never disputing that ppm should not be the unit of measure. Even had he used the term microgram/milliliter or even another would not have changes the issue at all, so lets not waste our time on this trivial point . To focus on that is irrelevant, basically.

 

Captain,

 

Like I said above- I did not state "any water", loius did. Im not sure whats the confusion. When one says any water, that is a strong point, and a specific point. Thats the only issue I had with the statement. You cant say any water. Any water includes my pond, your pond, John's pond, Obama's pond. My pond contained at a high about 4-5ppm,, and a dangerous low of about 2. Thats all folks.

Well, the actual quote was 'water in direct contact with atmosphere', a condition that your pond fails to meet.

To be specific, the algae and other organisms form an organic chemical layer on top of the pond. So the oxygen in air must pass through a barrier layer before reaching the water. This slows down the rate at which oxygen can penetrate into the water to a level where the lifeforms consume oxygen faster than it can be replenished. As the organisms die and decompose, the oxygen levels fall further. Stagnant fresh water is particularly prone to decomposing algae removing the oxygen.

Algal blooms can act even on the open sea, by producing large amounts of toxins that kill any lifeforms present; resulting decomposition reduces oxygen levels over large dead areas.

wiki

lake scientist

In the case of a clean garden pond, of shallow depth, the fish will not consume oxygen faster than it can be replenished. Obviously there will be a concentration gradient in replenishment, so the fish will reduce the oxygen level slightly. In water without any organic film the reduction will be trivial.

 

Of more relevance to the actual opening post: I have designed and carried out many experiments in which exact dissolved oxygen levels had to be controlled and measured. The popular Orbisphere electrochemical sensors for measuring dissolved oxygen rely for their calibration on a beaker of water exposed to atmosphere. The dissolved oxygen at 25°C is 8.x ppm on a wt per Kg or litre basis, as I have verified all too often.

http://shop.hach-lange.com/shop/action_q/highlights/highlight_id/1454/lkz/II/spkz/en/TOKEN/vAtZzeQkkE8dqTzPdOCaHtzmbhs/M/t1Dyvw

Even large concentrations of dissolved ions do not affect oxygen solubility greatly. Full on seawater at 35000 ppm has only a fall in oxygen levels of 20%.

Here is data, John Cuthber posted the link earlier. This information is accurate, mg/l is equivalent to ppm as commonly used by workers in this field.

some oxygen solubility data

 

I concur with other posters that the is an information shortage on the set-up from the opening post. Is the system some kind of bio-reactor? What has Mercury to do with the project? What exactly is depleting the oxygen?

Without mains power I could generate oxygen using car batteries, though I would also be generating hydrogen. With some design work the hydrogen could be generated in a separate vessel, but I would still have to be monitored and stores or safely vented (to a flame trap?)

 

Even knowledgeable people cannot solve a problem without sufficient information.

[chilled_fluorine]

In the time I spent bickering with you guys, the first batch has completed itself, however slowly. Thanks for helping to pass the time.

 

No, but I am clueless what you try to do, and without any further knowledge of the problem, I cannot help. You come here asking expert advice, but you don't explain the problem.

The problem is exactly as I asked: How can I dissolve oxygen into water rapidly, and with no external source of power? If I feel it makes a difference, I will provide you with more information. But I don't. Why do you need more information to answer that simple question? Give me a valid reason and I will gladly elaborate.

You said that the oxygen was being consumed (post #5). Solutions of salt in water usually do not consume oxygen. Microorganisms do.

 

Anyway, almost all practical experience with getting oxygen into water is from bio-tech, so whether you like it or not, you are gonna have to learn a thing or two about those reactors... Unless you want to tell us what you are actually doing , this is the best advice.

I personally find biology to be stupid, except for bean plants, I love to tweak with bean plant genes... I also enjoy watching amoebas move... Strange, I know. Fine, you win. I want to make an oxide-hydroxide of a certain metal, so that I may dissolve this in a certain acid that the metal itself is not soluble in. Then I plan to use this certain salt for a certain purpose. (not synthesizing illicits) The oxide-hydroxide needs o and h2o to form. Care to provide an answer now? Or do you need to know my street address as well?

I'm guessing that also here you do not want any circulation system (no pumps?).

That salt solution is not going to move around from that high surface area to the bulky container by itself. And the oxygen will diffuse really slowly.

The oxygen should move through the solution in the tubes very quickly, no?

But as long as I have no clue what you're going to do, or what chemical reaction you want to achieve, I have no way to determine whether the system is diffusion limited or whether you're fine.

Edited September 14, 2012 by chilled_fluorine

[elementcollector1]

Chill, chilled. No one's out to get you.

Biology's not stupid, either. I'm not a biologist, but no one can say that any given branch of actual science is 'stupid' without me thinking of those dropout highschoolers who think math is useless. No offense.

Ooh, what metal? I'd like a chance to see oxyhydroxides.

I agree, electrolytic production seems a good choice here. I know, it uses outside power, but there's really not many ways to get out of that without chemical means like peroxide, chlorate, etc.

[CaptainPanic]

The problem is exactly as I asked: How can I dissolve oxygen into water rapidly, and with no external source of power?

Big surface area.

 

If I feel it makes a difference, I will provide you with more information. But I don't. Why do you need more information to answer that simple question? Give me a valid reason and I will gladly elaborate.

A chemical engineer can only improve and optimize a system when he knows the design criteria and boundary conditions.

 

I want to make an oxide-hydroxide of a certain metal, so that I may dissolve this in a certain acid that the metal itself is not soluble in. Then I plan to use this certain salt for a certain purpose. (not synthesizing illicits) The oxide-hydroxide needs o and h2o to form. Care to provide an answer now?

 

Are you sure this exists? Oxides are usually not stable in solution. They react to form hydroxides in water. So, I am in doubt whether step 1 will even work (making that oxide-hydroxide in a solution). The reaction is an acid/base equilibrium. If you look at the table of acid/base strength, then the reaction of hydroxide to oxide is even below the bottom one on that list, meaning the equilibrium is completely at the hydroxide.

 

Using oxygen will not create an oxide. You need to get two electrons from somewhere... it's a redox reaction. You probably need an oxidizing agent instead.

 

But assuming this will actually work with oxygen, in solution, I still completely fail to see why you cannot either bubble some oxygen through the mixture... or at least stir it. Your oxygen will get transported quicker if the liquid moves. That is achieved by pumping it around, or by stirring. And you need a large surface area to get enough oxygen into the liquid, which you normally do by bubbling.

 

The oxygen should move through the solution in the tubes very quickly, no?

Probably not. If the water is stagnant, all you have is diffusion. That is a pretty slow process.

Depending on your design, it might even be possible that differences in density prevent it from spreading at all... like when you drop some sugar into a glass of water. The sugar dissolves into the bottom bit, but does not really reach all the liquid unless you stir it.

 

But your strange behavior probably means that you are either doing something illegal, or you think you're about to make a major breakthrough which will make you rich, famous and get you a nobel prize, which you are afraid of losing. Whichever it is, I struggle to help and my motivation is going down rapidly. So, good luck! I'm not sure I am interested anymore.

[chilled_fluorine]

Big surface area.

 

 

A chemical engineer can only improve and optimize a system when he knows the design criteria and boundary conditions.

 

 

 

Are you sure this exists? Oxides are usually not stable in solution. They react to form hydroxides in water. So, I am in doubt whether step 1 will even work (making that oxide-hydroxide in a solution). The reaction is an acid/base equilibrium. If you look at the table of acid/base strength, then the reaction of hydroxide to oxide is even below the bottom one on that list, meaning the equilibrium is completely at the hydroxide.

 

Using oxygen will not create an oxide. You need to get two electrons from somewhere... it's a redox reaction. You probably need an oxidizing agent instead.

 

But assuming this will actually work with oxygen, in solution, I still completely fail to see why you cannot either bubble some oxygen through the mixture... or at least stir it. Your oxygen will get transported quicker if the liquid moves. That is achieved by pumping it around, or by stirring. And you need a large surface area to get enough oxygen into the liquid, which you normally do by bubbling.

 

 

Probably not. If the water is stagnant, all you have is diffusion. That is a pretty slow process.

Depending on your design, it might even be possible that differences in density prevent it from spreading at all... like when you drop some sugar into a glass of water. The sugar dissolves into the bottom bit, but does not really reach all the liquid unless you stir it.

 

But your strange behavior probably means that you are either doing something illegal, or you think you're about to make a major breakthrough which will make you rich, famous and get you a nobel prize, which you are afraid of losing. Whichever it is, I struggle to help and my motivation is going down rapidly. So, good luck! I'm not sure I am interested anymore.

Maybe I want you to mind your own business, mkay? If I was trying to make crystal meth or something, I would be with those nuts on sciencemadness. Nobel prize? No. I have personally seen oxide hydroxides in suspension, they tend not to be soluble for the trans. metals. Maybe I wanted to make a hydroxide that dehydrates to an oxide hydroxide in air. I really wish someone could provide a simple answer, not cluttered with criticisms or more questions than the poster has brain cells.

 

Chill, chilled. No one's out to get you.

Biology's not stupid, either. I'm not a biologist, but no one can say that any given branch of actual science is 'stupid' without me thinking of those dropout highschoolers who think math is useless. No offense.

Ooh, what metal? I'd like a chance to see oxyhydroxides.

I agree, electrolytic production seems a good choice here. I know, it uses outside power, but there's really not many ways to get out of that without chemical means like peroxide, chlorate, etc.

 

This is a proof of concept, it is not necessarily supposed to be the best way. It is my opinion that biology is stupid. I find it boring, and less productive than my other pursuits. I enjoy math, and I didn't drop out of high school. LOL, top of the class. If you enjoy biology, great, I'm not going to challenge that. Why do you want to see oxyhydroxides? Not much exciting about them... I would tell you what metal I'm using, but then you would play 20 questions with me; are you going to make meth with it? Where did you get such an exceptionally rare metal? Do you want to make a bomb? Etcetera, etcetera.

[mississippichem]

Chilled,

 

Did you really just mention that you had some exceptionally rare metal, then say you wouldn't tell us what it was?

 

I know how to make all sorts of illicit things (I don't make meth, but I damn sure could), so if you are not doing anything wrong, why not tell us what kind of chemistry you are up to.

 

Or else I'll assume you are cooking crank