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KH reference methods, the drop checker and the pH probe adaptations

Discussion in 'CO2 Enrichment' started by Tom Barr, Dec 4, 2006.

  1. Tom Barr

    Tom Barr Founder
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    I have some sheets but it'll be Feb before I get to it really.
    Too many other projects going that are more important time wise.

    Regards,
    Tom Barr
     
  2. VaughnH

    VaughnH Lifetime Charter Member
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    Here is another idea! It is a CO2 "thermometer", a device that is an analogue of a digital thermometer. I haven't, of course, tried to make one of these yet, but only because I am busy with other things, and because I haven't yet figured out how to weld or glue a membrane to a piece of plastic without damaging the membrane. Who wants to make a prototype of this?

    [​IMG]
     
  3. Tom Barr

    Tom Barr Founder
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    Yes, this is the same thing I suggested to Greg Morin much like their ammonia alert thingy.

    Having a ref color scale next to it is ideal though, too many folks have trouble determining the color differences.

    Regards,
    Tom Barr
     
  4. VaughnH

    VaughnH Lifetime Charter Member
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    That would be great if they chose to produce something like this. But, without the technology to weld or glue the membrane to the plastic, achieving a perfect seal around each ref. KH well, it isn't a DIY project.
     
  5. Professor Myers

    Professor Myers Guru Class Expert

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    I'd be happy to take a shot at it as soon as it slows down a bit here. 3 Blizzards in 3 weeks and another on the way WTH ??? :eek: Shoveling snow is not nearly as much fun as I remember it to be. :confused: Should'a held out in PA for a few more weeks...:eek:

    I need as much feedback as possible on diffuser materials just as soon as folks try them out, as I really don't care to own an assortment of it. Happy Holidays ! Prof M
     
  6. Professor Myers

    Professor Myers Guru Class Expert

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    Which material are you working with Tom ? Grtz, Prof M
     
  7. defdac

    defdac Lifetime Members
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    Why not slap a webcam with a reference white/gray/exposure-point on it and you have a "Continous DIY Colorimeter Drop Checker (tm)".
     
  8. Bill

    Bill Lifetime Charter Member
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    Hi Tom,


    Earlier in this thread you said to dry baking soda like this.

    >>>Cooked/baked bakign soda: 400F for 45 min.
    Use about 2x what you think you need.
     
  9. Tom Barr

    Tom Barr Founder
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    Do you think it's time dependent?
    I do.

    I think it does raise a good point.

    So, rather than such high heat, maybe 100C or less, the air dryers work well to remove H20.

    And guess what's used in the air dryers? CaCl2, which is readily available.
    My advice is based off of what several reef folks have gone through at RC.

    I know there's issues with such methods, but for the hobbyists, I try and balance the trade offs with some things that they can do.

    You could place the Bakign soda in a sealed jar with a nice batch of CaCl2 and baking in thin layers in seperate trays. This will help remove the water from the baking soda, without decompsing it.

    CaCl2 is commonly used in air dryers for Chemistry.
    Might take awhile though.It's tough to rectify either situation to a very accurate degree for the hobbyists.

    I think maybe lower heat would work fairly well if you spread the baking soda out in a thin layer and just heat to about 80-90C.



    Regards,
    Tom Barr
     
  10. Mr G

    Mr G Junior Poster

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    Tom,

    Any thoughts on how baking at the higher temperature would affect the accuracy of the drop checker when trying to indicate a CO2 level of 30ppm.

    I made a 40dKH ref solution up having heated to 200c and mixed 90ml of this with 10ml of DI water to produce a 4dKH reference solution. I did a quick check with a Nutrafin KH testkit and it certainly given the inaccurcies of such test kits, the results did seem to be around 4dKH.

    When I get time I'll probably try mixing up a new batch of 40dKH solution, having baked the bicarb of soda at a lower temp (80c - 90c) and make up a 4dKH solution from this. Then I can compare 2 drop checkers in the same tank to see if there is an obvious difference in the colour reaction.

    Al
     
  11. intermediate_noob

    intermediate_noob Junior Poster

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    I asked this question in another thread of a similar topic, but wanted to ask again. Has anyone actually created one of these yet that we could see? I have the concept of what the DO probe does and how it looks but has anyone actually made the conversion for a pH probe?
     
  12. Tom Barr

    Tom Barr Founder
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    CI-6726 CO2 Ion Selective Probe - PASCO scientific

    IonSelectiveElectrodes

    Add this to a pH probe filled with a reference KH solution:
    Membrane for DO Sensor

    I'm trying to see about using a another method to measure CO2 from samples(namely the IR method, very accurate, but the sample needs removed from the tank) and using membranes(similar to the above and like the Dissolved O2 meter probes, they "look" the same as a DO probe with a membrane, you are not going gain or gleen or see anything different here).

    Here's one designed to used in human's blood:

    mmadou.eng.uci.edu/Classes/Biomems_Winter2005/Classes/Biomems_4.ppt

    I'm not sure how much more detail you need here.

    The smaller the probe, the better and more sensitive it can be(less time-> distance for diffusion to occur).

    The ppt is more along the lines of what I'd like to design,

    Regards,
    Tom Barr
     
  13. Tom Barr

    Tom Barr Founder
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  14. intermediate_noob

    intermediate_noob Junior Poster

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    Thanks Tom, I was really just trying to see how somone modified a standard probe to do the job. I have a controller, but too much is going on in my water to really guage my CO2 from just the pH. I have been reading to see if anyone has adapted one of the standard probes so that a membrane container could be added easily and be refilled etc.

    I read that you did one with a an o-ring, and another container for the 4 Kh solution, but wanted some image to try to wrap my head around it more. Thank you for the links again, I have my weekend studying ready for me now.
     
  15. Tom Barr

    Tom Barr Founder
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    The links were given for a reason.

    Not a photo.

    The photo is less detailed. I used flat headed pH probe, glue a rubber outer tip to extend it a tad, then snapped a membrane over that that's filled with 4 KH ref solution.

    A question is why do you need a photo of that?

    The links show in more detail how you can make one and how to modify existing items you might have available.

    Regards,
    Tom Barr
     
  16. intermediate_noob

    intermediate_noob Junior Poster

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    Thank you for the clarification. Once again, I was looking for the materials I would need to extend the body of the probe to make an area for the reference solution and the membrane. I will make sure to review the links in greater detail prior to responding again.
     
  17. VaughnH

    VaughnH Lifetime Charter Member
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    It is pretty easy to work with hard plastic materials and a ml or more of liquid. But, when you start working with gas permeable membranes and very thin layers of liquid, the difficulties increase exponentially. So, it isn't going to be easy for most of us to modify our pH probes to be fast reacting CO2 probes. This has to be right near the limits for DIY projects, and possibly over the limits for most of us.

    If I had the money and the inclination to dig into this I think I would get a small probe and separate meter, sticking to a probe that I could buy ready made membrane caps for. Those links Tom gave us show that this can be done without a lot of difficulty.
     
  18. Tom Barr

    Tom Barr Founder
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    Sorry, I did not see the question as asked:

    Rubber tubing that fits slightly over the tip, the caps often used on pH probes they are shipped with can work, I wanted something a bit meatier, so I wedged a piece of rubber vinyl tubing over it. Note; this was for a flat tipped pH probe.
    Not the standard round bulb.

    You do not want to extend the body, you want very close distance between the probe tip and the membrane, thus the idea to use a micro probe.

    This will help improve response time by having less distance and less surface to volume ratio, as things get smaller, their S/V ratio goes down, thus they diffuse more rapidly/easily.

    This is one reason why algae are not limited and very sensitive to nutrient levels vs plants. They have a really good surface to volume ratio for uptake.

    Same deal here.

    Just take a look at the ppt link in particular and think about adding a little KH ref solution on a flat tip, much like the drop checker ideas. Flat tip pH probe would be ideal, vs a round more common pH probe(this will improve response time).


    Since you have a standard round tip, you do not need any thing to extend over those, just wrap the membrane around it and use a small rubber o ring, you can buy the membranes on line, and you can get an o ring at Home Depot or OSH.

    The standard pH probe tips have a round tip with 4 plastic protectors around them, so as long as the membrane does not get ripped, you can use those.
    Sand the edges of the plastic some, to smooth the edges.

    You can also snip the plastic edges off, and add a rigid mesh basket and wrap that with the mebrane KH solution. Not sure where you might find it, but as plumbing shop might have a small strainer that might work etc. Use plastic, not metal.

    Regards.
    Tom Barr
     
  19. Anti-Pjerrot

    Anti-Pjerrot Prolific Poster

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    I just want to take a step back to the NaHCO3 heating.

    The way you work around the drying part, is that you take out an amount, say 4 times the amount you want to use for your kH-standard plus 1 gram.

    You then leave it a room temp. for ~ a day, and weigh off 2 x 0,5 gram and note the exact amount. Then you dry the 2 x 0,5 @ 105°C (or above) for 6 hours, and place the baked NaHCO3 with a waterremoving chemical. When the NaHCO3 is cooled to room temperature, you weigh it again, and determine the LOD (Loss on drying).

    You now know exately how much of you NaHCO3 is water, and how much is NaHCO3.
    Now you can make your kH-solution when weighing off the NaHCO3 with the LOD in mind...
     
  20. Tom Barr

    Tom Barr Founder
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    You likely do not require sodium bicarbonate, sodium carbonate works fine and is better here.

    That's what is used for references for CO3-2
    It's what I use.


    Regards,
    Tom Barr
     
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