Drop Checker Reference Solution - The Planted Tank Forum
 
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post #1 of 14 (permalink) Old 12-18-2008, 06:15 PM Thread Starter
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Drop Checker Reference Solution

I saw a drop checker that comes with two solutions: the indicator solution that changes with the CO2 level and a color reference solution that does not change. I have see here that the test solution is dKH 4 with some pH test stuff added to it. Does anyone know how to make the color reference solution?
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post #2 of 14 (permalink) Old 12-18-2008, 06:43 PM
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Making that reference solution is a lot more complicated than the 4 dKH solution. It has to be a buffer solution that remains at 6.6 pH even with slight contamination by tank water, CO2, indicator solution, etc. You can make the solution, but I don't know how.

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post #3 of 14 (permalink) Old 12-18-2008, 06:46 PM
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Maybe it's just water and green food coloring.

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post #4 of 14 (permalink) Old 12-18-2008, 08:17 PM
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Right, that's for the indicator. The OP is asking about the color reference solution used in those double checkers. It stands to reason that it wouldn't have pH indicator in it, considering it's expected to remain that same green color regardless of CO2 level in the water. Unless, as Hoppy suggests, it's got some magic buffering to keep it right at 6.6. A green dye seems more, well, reasonable for that purpose; I wasn't being facetious.

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post #5 of 14 (permalink) Old 12-18-2008, 08:30 PM
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I asked the vendor about this, and was told it is a buffer solution, with pH indicator in it. I added an extra drop of pH indicator to mine to get a more intense color.

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post #6 of 14 (permalink) Old 12-18-2008, 08:37 PM
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Alright then.

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post #7 of 14 (permalink) Old 12-19-2008, 03:21 AM Thread Starter
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Hoppy: Thanks for the input but I just want to make we have our nomelclature straight.

Indicator solution: Changes color with CO2 level. I am pretty sure I saw on here that it is simple 4 dKH (distaled water and Baking Soda) with pH test solution added.

Reference solution: Does not change color with CO2. I am seeking the recipe ofr the reference solution. Maybe the unit just keep it sealed off from exposure to the tank water. Anyway, I still need to know how to make it. So this is pH 6.6 buffer with pH inidcator? I guess I should ask, is the reference solution exposed to the tank water or sealed off? I can not really tell from the photos of the double drop checker.
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post #8 of 14 (permalink) Old 12-19-2008, 04:36 AM
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You can mix Seachem's acid buffer and alkaline buffer together with DI water to make the 6.6 pH buffer.

Here is a starting point. According to Seachem's literature, you can mix 1 part of acid buffer with 1.3 parts of alkaline buffer to make a buffer solution having a pH of 6.5.

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post #9 of 14 (permalink) Old 12-19-2008, 04:55 AM
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My double bulb drop checker has the reference solution open so there is just an air bubble separating it from the tank water, but from the illustration for that unit, it appears as if it is supposed to have a little plastic cap on that chamber. It is a solution which includes a buffer and some pH indicator reagent (bromothymol blue), but Cal Aqua says it has other things in it too. That is all I know about it, other than that it is intended to be a solution always at pH 6.6, and with the same concentration of pH indicator as in the 4 dKH chamber.

As LeftC said, you can make a 6.6 pH buffer solution with Seachem acid buffer and alkaline buffer, but I never did figure out the ratio of the two buffers to get that pH, nor how much of each was needed in what quantity of what quality of water. It isn't expensive to buy it from CalAqua, and the Seachem buffers cost $ too in any case.

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post #10 of 14 (permalink) Old 12-19-2008, 06:31 AM Thread Starter
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Ok cool. It happens that I have the Seachem buffers. I can also make some 6.6 using phospahte style buffers. I'll probably end up buying the official solutions anyway just to see if there is a difference. I would be nice to know if the reference is supposed to be sealed or not.
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post #11 of 14 (permalink) Old 12-19-2008, 02:50 PM
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Quote:
Originally Posted by rhodesengr View Post
Ok cool. It happens that I have the Seachem buffers. I can also make some 6.6 using phospahte style buffers. I'll probably end up buying the official solutions anyway just to see if there is a difference. It would be nice to know if the reference is supposed to be sealed or not.
You could use the CalAqua forum to ask. I don't know why that hasn't occurred to me before.

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post #12 of 14 (permalink) Old 12-19-2008, 03:12 PM Thread Starter
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did not know there was one. I'll do that fer sure.
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post #13 of 14 (permalink) Old 08-31-2009, 11:33 PM
 
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Seachem acid and alkaline buffers

Quote:
Originally Posted by Left C View Post
You can mix Seachem's acid buffer and alkaline buffer together with DI water to make the 6.6 pH buffer.

Here is a starting point. According to Seachem's literature, you can mix 1 part of acid buffer with 1.3 parts of alkaline buffer to make a buffer solution having a pH of 6.5.
I know this is last years thread but...
I'm in the middle of a thread on the seachem sunken garden forum about these "buffers". The thrust of my argument is that they can't work at acidic pH because the "alkaline buffer" is a bicarbonate and the "acid buffer" is an undisclosed acid. The so called "buffer" is an open equation, that is CO2 is a gas and is readily lost. I have tried using these products to target pH6.5 in my planted tank but the pH stabilises at ~8.2 within 24 hours, presumably as CO2 is lost, leaving the alkali (bicarbonates).
I tested their stated ratios of 1.3:1 to target pH 6.5 on 40l R/O water. pH greater than 7.6, KH 110ppm.
Any other user experiences with this product?
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post #14 of 14 (permalink) Old 09-01-2009, 02:22 AM
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Quote:
Originally Posted by Cardinals View Post
I know this is last years thread but...
I'm in the middle of a thread on the seachem sunken garden forum about these "buffers". The thrust of my argument is that they can't work at acidic pH because the "alkaline buffer" is a bicarbonate and the "acid buffer" is an undisclosed acid. The so called "buffer" is an open equation, that is CO2 is a gas and is readily lost. I have tried using these products to target pH6.5 in my planted tank but the pH stabilises at ~8.2 within 24 hours, presumably as CO2 is lost, leaving the alkali (bicarbonates).
I tested their stated ratios of 1.3:1 to target pH 6.5 on 40l R/O water. pH greater than 7.6, KH 110ppm.
Any other user experiences with this product?
Years ago I worked with both buffers. I found that their acid buffer was stronger than was mentioned. It actually required much less than suggested to reach a certain pH. The pH would indeed go much lower and approach a pH of 5. I can't remember all the details now because it was at least 10 years ago.

I read your thread. One possible problem could be your R/O water. Its membrane could be bad. You should use distilled or deionized water for your tests.

You state that your aquarium stabilizes at a pH of 8.2. What is your phosphate level? This could have a bearing.

Do you have any carbonate/bicarbonate substrates, rocks, decorations, phosphates, etc. in your aquarium?

You should only have DI water and Seachem's buffers in your test container. You don't want to have anything that could possibility give you skewed results. It would be a good idea to test your DI water's properties before you added anything to it.

The Seachem Tech Support group gave you very good responses. The Acidity/Alkalinity concept in chemistry is a very complex subject and a bit hard to grasp.

As Forest Gump said, "That's all I got to say about that." I can't think of anything else to mention.

I wish you good luck with your tests.

Hopefully, some of the chemists will chime in.

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