CO2 revelations part 2#

[plantbrain]

Since the thread has gotten a bit large and convoluted, I'd suggest a follow up here.

Comments,

Dissolved versus undissolved bubbles.............this is where folks are getting boondoggled.
There is a two step process.

1.The initial few minutes/hour/s(typically 1 to 3 hours after the light/CO2 comes on) are mainly dissolving the CO2 into solution.

2.Once a high level builds up, then it becomes much more difficult for the CO2 mist to be dissolved. Chemically: it is more difficult to dissolve a substance against an increasingly larger concentrational gradient.

So in the AM when the lights first come on, the CO2 is poor and the gas rapidly dissolves entirely.

Say we get up to 30ppm dissolved in one hour.
Great, plants are bathed in a rich CO2 solution.
Still the same and works well as what was previously discussed for the last 40 years.

Now, what about the CO2 bubbles at 30ppm?

Are they so quick to dissolve at this level of CO2?

You are adding CO2 to a solution that is already heavily super saturated.
The O2 is at best only mildly super staurated.

After 1-2 hours, the micro bubbles will persist and float around the tank.
This is true for my venturi reactors as well.
That gas build up in the external reactor tubes as well as the internal venrturis are similar later in the day.Think about what that gas might be, I'd suggested it was O2 at one point, the flame test was not conclusive(it put the flame out, suggesting CO2, not O2).

I could see the external reactors perhaps building up O2 later in the day, but what about the internal venturi reactors?

No way, there's nothing to degas O2 in there! This rules out the O2 theory. No other gases are super saturated, thus unable to increase and degas of solution, only O2 and CO2, and CO2 is much higher than O2 relative to ambient in all cases, so this makes sense chemically regarding concentration.

So this means, and I know I'm right(rare), that the CO2 dissolving is greatly reduced later at a stable given CO2 dosing rate in the day after you build up to a certain level. What level? I'd guess about 30ppm.

After you get this into the tank( 30ppm dissolved CO2), then this CO2 micro bubble theory starts to work. You still have 30ppm in the tank, but now you have added pulse of pure CO2 mist on top of that for the plants.

It is not one _or_ the other, they are synergistic, one complement and builds on the other.
My mistake in the past was assuming that the gas in the tube was O2, it's not, it's CO2 excess that's much more difficult to dissolve.

Thinking about the internal venturi reactors has shown that it cannot be O2(why would it degas there just like in the external sealed tubes)?

I tried this without any plants(thus no O2 build up), I had gas build up later in the day, thus reduction in CO2 dissolving at higher ppm levels.
............so there.
I finally figure out why that dang little venturi diffuser worked so good, only took me 12 years ! haha

By using comparative diffusers, reactors etc, I was able to muddle through this.
One by itself would not have answered this question.

30ppm bathes the entire plant, the mist of relatively pure CO2 bathes part of the plant.
Together both drive photosynthesis at a rapid rate that I've observed.

Regards,
Tom Barr

www.BarrReport.com This month's very in depth K+ review article completed.

[BlueRam]

Thanks Tom for putting a summary together.

Good work!

[plantbrain]

Well, hopefully is will show that both difussers and reactors are both good methods and that the mist can help later in the day after reaching 30ppm.

The method work with, not an either or type of thing with dissolved CO2 in water.

But I think there is fairly clear evidence now that CO2 does not dissolve nearly as easily after it builds up good.

The rate of dissolution at 3.7ppm vs 30ppm is different.
That would explain the bubble presisting and still being CO2.

Thus the mist can help even if you have 30ppm in the water, which is what I suggested originally.

The venturi loop I add to my internals and now can be used on any external reactor also helps reactors perform better and the current using the Disc also helps better.

In all cases, there is a better understanding and improvement as well as another completely ignored delivery method.

So no matter what side/method you use, this knowledge will help and improve the understanding using CO2, which, given it's importance, is extremely important.

It also adds yet another layer to improve growth and CO2 dosing.

Regards,
Tom Barr

[StUk_In_AfRiKa]

Originally Posted by plantbrain

My mistake in the past was assuming that the gas in the tube was O2, it's not, it's CO2 excess that's much more difficult to dissolve.

Thinking about the internal venturi reactors has shown that it cannot be O2(why would it degas there just like in the external sealed tubes)?

I tried this without any plants(thus no O2 build up), I had gas build up later in the day, thus reduction in CO2 dissolving at higher ppm levels.

I've been following the discussion and I grasp everything, except that. I don't have a degree in this subject so bare with me Even if there are no plants in the tank, the DO would still be around 7 or 8 ppm at sea level. Since the bubbles are pure CO2, other gases would want to dissolve into the bubble. When the CO2 concentration is low the CO2 dissolves quickly and other gasses that take longer to dissolve don't get a chance to move into the bubble. But as the CO2 concentration increases and the CO2 bubbles remain in the water longer, other gasses would have time to dissolve into the bubble. So wouldn't this still mean that the "stubborn" air in the reactor is a combination of CO2 and non-CO2 gasses?

[Hypancistrus]

So this means, and I know I'm right(rare), that the CO2 dissolving is greatly reduced later at a styable given CO2 dosing rate in the day after you build up to a certain level. What level? I'd guess about 30ppm.

My reactor1000 always filled up to the top with water when I initially turned CO2 on, then after a few hours would develop gas in the top. I've always wondered why. This must be it.

Today after I disconnected my CO2 from the reactor and hooked it up to the diffuser disc, I didn't disconnect my reactor. I just plugged up the top where the CO2 used to go in. No more gas build up in the reactor!

So what I am seeing here does follow what you are saying.

StUk_In_AfRiKa, because the reactor is a sealed unit. Water is being forced through it at pressure. You also don't get air pockets building up inside the cannister filter, UV unit, etc., due to O2 degassing. The reactor has the CO2 being directly injected into it. Tom is saying that after the water reaches a saturation point, the CO2 that is being injected into the reactor stops dissolving and forms a gas pocket. When using a diffuser disc, rather than form a gas pocket the tiny bubbles get blown around the tank and onto plant leaves.

[timr]

So all i might need to do is turn my reactor upside down and move my spray bar to the bottom of the tank? This may not get the co2 extremely small, but i know the spray bar does a good job of chopping up air that gets caught in the canister.

[StUk_In_AfRiKa]

Originally Posted by Hypancistrus

StUk_In_AfRiKa, because the reactor is a sealed unit. Water is being forced through it at pressure. You also don't get air pockets building up inside the cannister filter, UV unit, etc., due to O2 degassing. The reactor has the CO2 being directly injected into it. Tom is saying that after the water reaches a saturation point, the CO2 that is being injected into the reactor stops dissolving and forms a gas pocket. When using a diffuser disc, rather than form a gas pocket the tiny bubbles get blown around the tank and onto plant leaves.

I've only seen pictures of reactors, but when the CO2 concentration is high in the water then the CO2 bubbles remain at the top of the reactor for a while right? So with all that churning wouldn't other gasses (even small amounts) still dissolve out of solution into the CO2 pocket? I know that if no CO2 was being injected then the O2 wouldn't degass, but if the CO2 creates that big bubble there then gasses would want to equalize and dissolve into the bubble. And if the air pocket in there is CO2 along with other gasses, then it would also contribute to the "stubborness" of it to dissolve (because the CO2 is less oncentrated in the bubble) right?

And I'm sorry if I'm confusing anyone with all this :P

[anonapersona]

Originally Posted by Hypancistrus

Tom is saying that after the water reaches a saturation point, the CO2 that is being injected into the reactor stops dissolving and forms a gas pocket. When using a diffuser disc, rather than form a gas pocket the tiny bubbles get blown around the tank and onto plant leaves.

So, why wouldn't you just turn down the gas a bit? OK, gas is cheap, yes, but after the water reaches saturation point, you can either let gas build up in the reactor, or blow it around the tank as tiny bubbles. Either way ought to be the same... the water remains at saturation.

If the glass is full and you keep pouring water into it, do you really care if it pours over the top into a sponge or down the drain? The glass isn't going to be any more full either way. True the sponge (gas bubble in the reactor) may keep the excess there for later, while the other way just makes the glass wet and in a way oversaturated.

I think the more important point is that it is actually hard to keep the tank at more than 30 ppm.

Seems to me to be overkill, no matter what.

Anona, back from a second trip from Houston to New Orleans, this time through TWO hurricane wrecked areas, and reeling from the damages seen.

[plantbrain]

Hehe,

Unless you have seen the difference doing this method does to your plants and the pearling, you cannot really say too much about it not being overkill or not.

That same arguement can be posed for non CO2 vs CO2.........

Once you see the vigor and growth, I'm talking any of the plants species you might have issues with, the finikyest plants you can think of............, then you'll know and see that this is not the same as CO2 in a liquid..........30ppm is fine and will not help by adding more, but that is for a liquid medium........

No one ever said anything nor tested it with gas+the liquid at 30ppm.

Given folk's complacency and CO2 related issues, amping the CO2 is a good thing and does not require that much effort or cost to do so.

We do not have to add so much PO4 either............but many do............

You can slow plant growth down the simplest way, use less light.

I have made some graphs and have 3 more test to complete on this issue, then I'll present it in the BarrReport this month.
8 folks have reported the same results as myself in terms of tank response.

Regards,
Tom Barr

www.BarrReport.com

[Happy Camper]

Originally Posted by StUk_In_AfRiKa

And I'm sorry if I'm confusing anyone with all this :P

Hello Stuck in Africa, I've seen you round the G4Y forums, nice to see you here. Do you have pics of your tank to share? I'd love to see.

Kind Regards
Cameron

[jbaker6953]

Originally Posted by plantbrain

1.The initial few minutes/hour/s(typically 1 to 3 hours after the light/CO2 comes on) are mainly dissolving the CO2 into solution.

2.Once a high level builds up, then it becomes much more difficult for the CO2 mist to be dissolved. Chemically: it is more difficult to dissolve a substance against an increasingly larger concentrational gradient.

According to ""The Solubility of Carbon Dioxide in Water at Low Pressure", Journal of Physical and Chemical Reference Data, 20, 1201-1209, (1991), CO2 isn't saturated until you approach 622 ppm at 25C.

Originally Posted by plantbrain

Now, what about the CO2 bubbles at 30ppm?

Are they so quick to dissolve at this level of CO2?

They should, it's only about 4.8% of saturation.

Originally Posted by plantbrain

You are adding CO2 to a solution that is already heavily super saturated.
The O2 is at best only mildly super staurated.

The CO2 is nowhere near saturated. See above reference.

Originally Posted by plantbrain

After 1-2 hours, the micro bubbles will persist and float around the tank.
This is true for my venturi reactors as well.
That gas build up in the external reactor tubes as well as the internal venrturis are similar later in the day.Think about what that gas might be, I'd suggested it was O2 at one point, the flame test was not conclusive(it put the flame out, suggesting CO2, not O2).

The problem with using a flame test to determine the presence of O2 is that organic substances will not burn when the concentration of O2 is below around 16% at normal humidity levels. See "Burning of forest materials under late Paleozoic high atmospheric oxygen levels." So, you could have 15% O2 in the reactor tube and your flame test would lead you to conclude that it wasn't O2.

Originally Posted by plantbrain

So this means, and I know I'm right(rare), that the CO2 dissolving is greatly reduced later at a stable given CO2 dosing rate in the day after you build up to a certain level. What level? I'd guess about 30ppm.

Why not measure it instead of guessing? It will only take a second.

Originally Posted by plantbrain

It is not one _or_ the other, they are synergistic, one complement and builds on the other.
My mistake in the past was assuming that the gas in the tube was O2, it's not, it's CO2 excess that's much more difficult to dissolve.

This is speculation without testing and other data seems to contraindicate insoluble CO2.

Originally Posted by plantbrain

30ppm bathes the entire plant, the mist of relatively pure CO2 bathes part of the plant.
Together both drive photosynthesis at a rapid rate that I've observed.

It has been noted by Dave Huebert that photosynthesis in submerged macrophytes (aquatic plants) is saturated at 30ppm CO2. If that is the case, increasing availability of CO2 above and beyond saturation will have no effect. There are some experimental data that suggest increasing CO2 very much above saturation actually decreases O2 production ("Effects of CO2 concentration and light intensity on photosynthesis of a rootless submerged plant, Ceratophyllum demersum L... ", Adv Space Res. 2003;31(7):1743-9).

[unirdna]

Originally Posted by plantbrain

Dissolved versus undissolved bubbles.............this is where folks are getting boondoggled.
There is a two step process.

1.The initial few minutes/hour/s(typically 1 to 3 hours after the light/CO2 comes on) are mainly dissolving the CO2 into solution.

2.Once a high level builds up, then it becomes much more difficult for the CO2 mist to be dissolved. Chemically: it is more difficult to dissolve a substance against an increasingly larger concentrational gradient.

So in the AM when the lights first come on, the CO2 is poor and the gas rapidly dissolves entirely.

Say we get up to 30ppm dissolved in one hour.
Great, plants are bathed in a rich CO2 solution.
Still the same and works well as what was previously discussed for the last 40 years.

Now, what about the CO2 bubbles at 30ppm?

Are they so quick to dissolve at this level of CO2?

You are adding CO2 to a solution that is already heavily super saturated.
The O2 is at best only mildly super staurated.

I don't think I'm getting boondoggled at all. Your data simply is not convincing. This is because CO2 solubility and O2 solubility are apples and oranges. O2 reaches saturation at around 12ppm (parts per million). CO2 saturation is significantly higher - much much much higher.

Graph from the pages of Dr. James Baird, Professor, Chemical Physics - Brown University


At 25C, saturation of CO2 is .15g/100ml water. That is 1500ppm! Your claim that CO2 is "already heavily supersaturated, while O2 is mildly supersaturated" is incorrect. CO2 is not supersaturated. O2, on the other hand, is frequenly saturated, and this is why plants pearl. Supersaturation is also achieved by reducing temp or increasing pressure (thus, increasing the solubility of O2), and then returning to the original conditions. O2 will then bubble out of solution because the solubility is decreased. This is why bubbles form on the walls of tanks when they are first set up with tap water. Tap water is under pressure (higher O2 solubility). It's also the reason that we frequently see pearling after a water change. The addition of supersaturated (O2) water can saturate or supersaturate that tank water with O2; thus, any/all O2 given off by the plants will not dissolve - creating the pearling effect.

Your claim that CO2 is more saturated than O2 is also incorrect. Again, I draw your attention to the solubilty graph of CO2. 30ppm out of the 1500ppm means that the "magic number" - 30ppm - for CO2 levels in planted aqaria is less than 1% of CO2 saturation. To claim that CO2 starts to become harder to dissolve at .2% saturation seems unlikely. Furthermore, there are many anecdotal instances of pH crashes, fish kills, etc. that add further speculation to the "harder to dissolve" idea.

On the other hand, we know that most fish species need at least 5ppm O2 to survive. And, since water becomes saturated with O2 at about 12 ppm, we would know that it would take a maximum 7ppm increase in O2 (for any tank) to create conditions where O2 would be saturated. And you say that in the AM when the lights come on, the tiny bubbles are not present. Yet later on, once the plants been photosynthesizing for a while, these bubbles become present. hmmm.

Originally Posted by plantbrain

After 1-2 hours, the micro bubbles will persist and float around the tank.
This is true for my venturi reactors as well.
That gas build up in the external reactor tubes as well as the internal venrturis are similar later in the day.Think about what that gas might be, I'd suggested it was O2 at one point, the flame test was not conclusive(it put the flame out, suggesting CO2, not O2).

I could see the external reactors perhaps building up O2 later in the day, but what about the internal venturi reactors?

No way, there's nothing to degas O2 in there! This rules out the O2 theory. No other gases are super saturated, thus unable to increase and degas of solution, only O2 and CO2, and CO2 is much higher than O2 relative to ambient in all cases, so this makes sense chemically regarding concentration.

I'm starting to think you are putting too much stock in your "flame test" results. I question the methods in which your flame test was performed. You say that the gas put out the flame. You must have had a method in which you collected this gas, and then inserted a flame into an enclosed area with this gas. Is it possible that the flame quickly exhausted all the O2 and put itself out? Explain your methods.

As for your venturi reactors, what you have described is exactly what I would expect. First off, as we have seen, CO2 is NOT at supersaturation. The only gas that IS is O2. Thus the only gas eager to come out of solution would be O2.

I think your venturi only helps to do one thing - get rid of O2 buildup. The O2 in continually chopped up into smaller bubbles that do not have enough buoyancy to fight the current, and are thus forced out the bottome of your reactor and escape to the surface. That buildup of gas is NOT CO2.

Originally Posted by plantbrain

So this means, and I know I'm right(rare), that the CO2 dissolving is greatly reduced later at a stable given CO2 dosing rate in the day after you build up to a certain level. What level? I'd guess about 30ppm.

After you get this into the tank( 30ppm dissolved CO2), then this CO2 micro bubble theory starts to work. You still have 30ppm in the tank, but now you have added pulse of pure CO2 mist on top of that for the plants.

It is not one _or_ the other, they are synergistic, one complement and builds on the other.
My mistake in the past was assuming that the gas in the tube was O2, it's not, it's CO2 excess that's much more difficult to dissolve.

Thinking about the internal venturi reactors has shown that it cannot be O2(why would it degas there just like in the external sealed tubes)?

See about explanation for why the gas in the venturi is "dissolving".

You have confused cause and effect because of a few minor confusions -your flame test, and your misunderstanding of CO2 solubility.

Originally Posted by plantbrain

I tried this without any plants(thus no O2 build up), I had gas build up later in the day, thus reduction in CO2 dissolving at higher ppm levels.

This is the only piece of compelling data I see. Yet, again, I draw your attention to the vast solubility differences between CO2 and O2. It wouldn't take much "impurity" O2 (from your CO2 system - eg. small line leaks, tank impurities, diffusion into tubing, etc) to saturated the water, thus allowing small bubbles of O2 to circulate in the tank.


To conclude. I want to reiterate that I do NOT question whether or not this "blowing diffusion" method helps plants grow. I do not doubt that good circulation of CO2 around a tank it a good thing. I know I see better growth near my spray bar than on the other side of the tank. But all your claims about CO2 solubility are wrong, and you steadfast conclusions need to be reexamined.

Ted

[jbaker6953]

Originally Posted by unirdna

At 25C, saturation of CO2 is .15g/100ml water. That is 1500ppm!

For those that might be confused because the paper I linked to suggests 622ppm and Henry's Law suggests 1500ppm, there is an explanation. The 622ppm was a figure meaning, "622 molecules of CO2 and 999,378 molecules of water." When we use the figure in our aquariums, we are using mg/L. The 622 figure works out to 1519 mg/L.

I feel compelled to point out that I took this data from the wrong table in the report, and the actual value is 0.000609 mole fractions - that is closer 1,488 mg/L for CO2 saturation at 25C.

[jgc]

just to points.

1) if there is measurable increase in plant growth, something is happening. We may disagree why, but the first step is to duplicate the experiment. We have seen cold fusion claims here. But so far there appears to be people able to duplicate and we will get more comfimation tests over the next few weeks (either positive or negitive).

2) Lab and real world are two seperate places. Lab experiments for disolving c02 are probably using deionized water or distilled. We are using water with tons of impurities intentionally and unintentionally disolved in it, not to mention our water hits 02 saturation daily. How does the real world environment we grow stuff in change the lab results.
---
I have very little education in science. It was a hobby once upon a time. A hobby that managed to get me a fully scholarship back then, but was only persued via other hobbies since.

[jbaker6953]

Originally Posted by jgc

just to points.

1) if there is measurable increase in plant growth, something is happening. We may disagree why, but the first step is to duplicate the experiment. We have seen cold fusion claims here. But so far there appears to be people able to duplicate and we will get more comfimation tests over the next few weeks (either positive or negitive).

We do not yet have enough data to make a determination about whether the reports of successful duplication are the result of increased CO2 availability. Did the reporters have equal circulation prior to beginning the experiment? What was the growth rate prior, and what is it now? Is it measured, or just eyeballed?

Originally Posted by jgc

2) Lab and real world are two seperate places. Lab experiments for disolving c02 are probably using deionized water or distilled. We are using water with tons of impurities intentionally and unintentionally disolved in it, not to mention our water hits 02 saturation daily. How does the real world environment we grow stuff in change the lab results.

The lab and the real world are two different places, but luckily for us the laws of nature remain the same regardless of physical location. Water has the same density everywhere, and CO2 solubility is the same everywhere. The effect of dissolved solids even in hard freshwater (500 ppm) on the solubility of CO2 is negligible. Probably somewhere around 0.5% if I recall correctly.