|
Posted by NetMax on March 10, 2005, 7:24 pm
Please log in for more thread options
>
> NetMax wrote:
>> > Hi folks,
>> >
>> > Here's a 'speriment I'd like to try. Since it's so obvious,
> though, I
>> > bet it has occurred to some of you to try. So I'll describe it,
> and
>> > wait for you to tell me the answer, for I am lazy. haha.
>>
>> I won't try it either, and I also don't know what will happen, but
> it's
>> not too much work to just type, so here goes my ideas.
>>
>> > My hypothesis is that where a hunk o' coral is placed in a tank
> with
>> > CO2 injection and a pH controller, and where the pH is set to
> somewhere
>> > in the low sixes, the following will happen:
>> > 1.) pH will be maintained at that value to which the monitor is
> set.
>>
>> Assuming infinite supply (CO2 tank and not DIY) then yes.
>
> Yep. I guess "CO2 injection" can mean DIY to some people, so I should
> have been more precise. I assume here a goodly-sized CO2 tank. I
> canna' give you moor than tha', cap'n.
>
>
>> > 2.) KH will go up, up, up as coral dissolves
>>
>> Actually the rate of dissolution (is that a word?) will increase as
> the
>> water becomes more acidic.
>
> Aha, but the water here will not become more acidic! It will track a
> set pH, as per the pH controller setpoint. And it will not become more
> alkaline, either, since the co2 tank is large and can counter any such
> influence.
>
>>
>> > 3.) GH will go up, up, up as coral dissolves
>>
>> Ditto here, yes.
>
> As an aside, you don't happen to know a typical Ca/Mg ratio in coral,
> do you?
>
>> > 4.) As a result of constant pH and rising KH, [CO2] will go up,
> up,
>> > up.
>>
>> Here is where you have the potential for discrepancy. I think it
> will
>> take a lot more CO2 to maintain a high CO2 saturation level, because
> at
>> higher kH/pH, the CO2 will want to equalize to a much lower level
> faster
>> (see comment on infinite CO2 above).
>
> Put simply, what you're saying seems to be that the greater the
> difference in actual dissolved CO2 and equilibrium CO2 (commonly said
> to be 2-3ppm) then the more dissolved CO2 "wants" to escape to the
> atmosphere. To wit: a glass of seltzer at 1 atmosphere pressure will
> outgas, with respect to CO2, until the CO2 is equilibrated (at the same
> time it may well be in-gassing with respect to other gases! Ha!)
>
>> > There will, of course, be some sort of endpoint. I'm not sure what
> it
>> > is. The core practical question is whether the above setup will
> end up
>> > dissolving lethal (to fish) amounts of CO2 in the water. I suspect
> it
>> > can.
>>
>> I think the endpoint will be a function of the coral's surface area
> and
>> rate of decay as a ratio of the total water, so with a CO2 tank, you
>> might visibly see your coral shrinking (or at least it will break up
> and
>> leave you with a lot of ground particles slowly turning to smaller
> bits).
>> Eventually, chemically, that endpoint should move to tax your
> system's
>> ability to maintain that level of acidity. It will probably be a
>> significant amount of carbonic acid.
>
> My CO2 reactor can dissolve a *lot* of CO2. So it sounds like there'd
> be dead fishies. Needless to say, there will be no piscine test pilots
> in my experiment.
>
>>
>> > WITHOUT CO2 injection, I suspect what would happen is just a
> longterm
>> > increase in GH and KH, but CO2 will stay constant at atmospheric
>> > equilibrium.
>>
>> Nope, I think the CO2 level would decrease.
>
> Are you saying that given a high enough KH it is possible to keep less
> CO2 in the water than would be supplied by equilibration with the
> atmosphere? To me it only seems possible if the KH can change the
> equilibration point w.r.t. CO2, because there's always going to be the
> constant such-and-such partial pressure of CO2 in the air. Hrm. I
> shall have to think more about this in order to see if that is
> possible. It may well be, but the answer will have to wait for my chem
> textbook. :)
>
>
>> > Thoughts?
>> >
>> > --Trapper
>>
>> Like I said, just semi-educated guesses from me.
>> --
>> www.NetMax.tk
>
> I'm going away for a couple days soon. I've a mind to take my CO2
> contraption out of my plant tank, and run this 'spearmint in a 5-gal
> bucket. I suspect a couple days' worth of running will be enough at
> least to show the beginning of the trend.
>
> --Trapper
re: Ca/Mg mix of calcium: good question.
re: non-injected CO2 equilibrium to atmosphere: it is not 1:1 and the
ratio is affected by the pH and kH values.
--
www.NetMax.tk
| 
Yahoo! 
Google 
Windows Live 
del.icio.us 
digg 
Netscape 
XML Sitemap
> NetMax wrote: