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Old 03-04-2009, 08:25 PM   #1
Hoppy
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Default Calibrating Test Kits - for non-Chemists

I received a request to write something like this, so: (I hope someone will check this for accuracy.)

Calibrating Test Kits

Calibrating a test kit means using that kit to measure some water samples with known concentrations of the substance being tested for, and using those test results to verify that the test kit is accurate, or to train yourself to recognize the colors that correspond to the concentrations you want to test for. Hobby test kits are not laboratory quality tests. That means we donít need extreme accuracy in the standard test solutions we use for calibration. If we have a good quality gram scale, with +/-.01 gram accuracy, and good laboratory glass graduated cylinders to measure water volume, there are other articles that tell how to make very accurate standard solutions. The methods described here are for use with ordinary kitchen measuring equipment, measuring spoons and cups. And, the Fertilator calculator on APC was used to easily calculate how to mix these.

Nitrate Test Kits

First, buy a gallon of distilled water from your local grocery store. Use that to make the test standard solutions.

1. Add 1/4 teaspoon - a level measure, not a heaping measure - of KNO3 to 4 cups of distilled water (one quart). This gives you 4 cups of 800 ppm nitrate water.
2. Mix 1/4 cup of that 800 ppm water with 1 3/4 cups of distilled water. This gives you 2 cups of 100 ppm nitrate standard water.
3. Mix one cup of that 100 ppm water with one cup of distilled water. This gives you 2 cups of 50 ppm nitrate standard water.
4. Mix one cup of that 50 ppm water with one cup of distilled water. This gives you 2 cups of 25 ppm nitrate standard water.
5. Mix 1/2 cup of that 25 ppm water with 3/4 cup of distilled water. This gives you 1 1/4 cups of 10 ppm nitrate standard water.
6. Mix 1/4 cup of 25 ppm water with 1 cup of distilled water. This gives you 1 1/4 cups of 5 ppm nitrate standard water.
7. Use your test kit to measure the nitrate concentration in each of the 5,10,25, and 50 ppm nitrate standards. If you wish, add the 100 ppm standard to that set.
8. Compare the colors of those to the color card for your kit, and either verify the accuracy of the kit, or use those colors to train yourself to recognize the colors.

Your nitrate test kit is now calibrated. You can store the standard solutions in tightly sealed bottles for an indefinite period of time for future calibrations. Ideally, you calibrate the kit each time you use it.

Phosphate Test Kits

First, buy a gallon of distilled water from your local grocery store. Use that to make the test standard solutions.

1. Add 1/4 teaspoon - a level measure, not a heaping measure - of KH2PO4 to 4 cups of distilled water (one quart). This gives you 4 cups of 1000 ppm phosphate water.
2. Mix 1/4 cup of that 1000 ppm water with 2 1/4 cups of distilled water. This gives you 2 1/2 cups of 100 ppm phosphate standard water.
3. Mix one cup of that 100 ppm water with one cup of distilled water. This gives you 2 cups of 50 ppm phosphate standard water.
4. Mix one cup of that 50 ppm water with one cup of distilled water. This gives you 2 cups of 25 ppm phosphate standard water.
5. Mix 1/2 cup of that 25 ppm water with 3/4 cup of distilled water. This gives you 1 1/4 cups of 10 ppm phosphate standard water.
6. Mix 1/4 cup of 25 ppm water with 1 cup of distilled water. This gives you 1 1/4 cups of 5 ppm phosphate standard water.
7. Mix 1/4 cup of 5 ppm water with 1 cup of distilled water. This gives you 1 1/4 cups of 1 ppm phosphate standard water.
8. Use your test kit to measure the phosphate concentration in each of the 1,5,10, and 25 ppm phosphate standards. If you wish, add the 50 ppm standard to that set.
9. Compare the colors of those to the color card for your kit, and either verify the accuracy of the kit, or use those colors to train yourself to recognize the colors.

Your phosphate test kit is now calibrated. You can store the standard solutions in tightly sealed bottles for an indefinite period of time for future calibrations. Ideally, you calibrate the kit each time you use it.

Other Test Kits

To follow, maybe
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Last edited by Hoppy; 03-05-2009 at 01:45 AM.. Reason: Correct errors
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Old 03-04-2009, 10:17 PM   #2
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IMO this needs to be a sticky. I would check but I am procrastinating doing homework.
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Old 03-04-2009, 10:47 PM   #3
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[quote=plakat;800312]IMO this needs to be a sticky.


I second the motion
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Old 03-04-2009, 11:18 PM   #4
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Sticky, sticky, sticky - 5 stars from me! Excellent work, Hoppy. Now that you've made this so simple, I'm going to have to find something else to do with my digital scale!
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Old 03-04-2009, 11:30 PM   #5
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It's sort of EI for test kit calibration.


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Tom Barr
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Old 03-04-2009, 11:32 PM   #6
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Quote:
Originally Posted by plantbrain View Post
It's sort of EI for test kit calibration.


Regards,
Tom Barr
I was planning to call it the Julia Child calibration plan.
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Old 03-05-2009, 12:00 PM   #7
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IMO this needs to be a sticky. I would check but I am procrastinating doing homework.
I agree, great write up Hoppy. Thanks

Stickified.
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Old 03-04-2009, 11:43 PM   #8
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Nice work. Check the phosphate, it says to add KNO3 not kh2po4 or other compound
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Old 03-05-2009, 01:43 AM   #9
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Nice work. Check the phosphate, it says to add KNO3 not kh2po4 or other compound
Thank you! I corrected it.
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Old 03-05-2009, 01:16 AM   #10
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Thanks Hoppy...
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Old 03-05-2009, 04:15 AM   #11
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Yesterday I made some 4 dKH water, using 14 dKH water made from an ampule of lab standard water. When I used my KH test kit to measure the KH of that water, it said 3 dKH. So, that raised a lot of doubts in my mind about the KH test kits. Calibrating that kit is a much harder job. But, it finally occurred to me that I should be able to take advantage of a property of sodium bicarbonate to do that. The property is the solubility of NaHCO3 in water, which varies with temperature. I converted the graph of that solubility to read in solubility of carbonate instead of sodium bicarbonate, getting this graph:


The technique will be to start with distilled water, add a lot of baking soda to that, let it sit quietly on the kitchen counter (where else?) for an hour or so, with only very gentle stirring, to saturate the water with baking soda. It won't matter that my baking soda will contain some water in the crystal structure, since that water just joins the distilled water. Then I use a syringe to get a sample of that water, 1 ml, as closely as I can get, and quickly add it to enough distilled water to end up with 20 dKH water, by calculation. Then dilute that to get my standard solutions. Will this work? I know the saturated solution will be losing CO2 to the atmosphere, but if I do this rapidly I should still have saturated solution being added to the distilled water. Am I missing something?

If this will work, it is another way to make 4 dKH drop checker water.
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Old 03-05-2009, 11:51 PM   #12
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Default Calibrating KH test kit

KH Test Kit
This method, compliments of Cardinal's Keeper (http://www.plantedtank.net/forums/di...-solution.html)
(Note: You will need a whole gallon of distilled water to do this.)
1. Start with 6 cups of distilled water in a clean measuring container
2. Add 1/8 teaspoon Sodium Bicarbonate (baking soda, freshly opened) to the 6 cups of water and mix
3. Pour out 3 cups of this mix and discard
4. Add back 3 cups of distilled water and mix
5. Pour out 3 cups of this mix and discard
6. Add back 3 cups of distilled water and mix
7. Pour out 1 cup of this mix and discard
8. Add back 1 cup of distilled water and mix
7. Water comes out to a 4 dKH solution
8. To make a 2 dKH solution, mix one cup of the 4 dKH solution with one cup of distilled water.
9. To make a 1 dKH solution, mix one cup of the 2 dKH solution with one cup of distilled water.
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Last edited by Hoppy; 06-02-2012 at 05:22 AM.. Reason: A new method for making a standard KH solution
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Old 06-20-2012, 05:27 PM   #13
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Default Newbie issue: Non-standard issue of drop-cheker

Quote:
Originally Posted by Hoppy View Post
KH Test Kit
This method, compliments of Cardinal's Keeper (http://www.plantedtank.net/forums/di...-solution.html)
(Note: You will need a whole gallon of distilled water to do this.)
1. Start with 6 cups of distilled water in a clean measuring container
<.... selection deleted for brevity...>
8. To make a 2 dKH solution, mix one cup of the 4 dKH solution with one cup of distilled water.
9. To make a 1 dKH solution, mix one cup of the 2 dKH solution with one cup of distilled water.
Hi all of you, and Hoppy in particular. I am a newbie and want to do CO2 injection in an 80G planted aquarium. I don't want my plants to be completely slow-growing and low-tech, and I don't want them to be growing too vigorously either, as with 30ppm of CO2. [Yeah, I'm that Great Moderation guy! ] So, I'm thinking I'll go for moderation, say about 15ppm of CO2, moderate lighting. I have two questions:

(1) Does this approach seem reasonable, or am I forgetting/ignoring something important?
(2) Now the more "techy" question. MOst standard drop-checkers, set up with 4dKH, turn green at 30ppm. This works fine for those who want to keep their tanks at 30ppm CO2, but it wouldn't work well for me. I need an indicator that'll tell me (say go from blue to green) at 15ppm instead of 30ppm. So, looking at Hoppy's above post, I thought, why don't I make a 2dKH solution to put in the drop checker? The charts [ http://freshwateraquariumplants.com/...xidechart.html ] seem to say that 2dKH will get to pH=6.6 at about 15 ppm instead of 30ppm, so this should work for me, right? All I do is put 2dKH standard solution and a few drops of the indicator into the drop-checker, and voila! I calibrate CO2 to keep the solution green without going blue or yellow, just like everybody else does, but I'm keeping it at 15ppm, not 30ppm, right? What am I missing?

Thanks for your help in advance!

-aadro
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Old 07-02-2012, 07:25 PM   #14
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Quote:
Originally Posted by aadro View Post
Hi all of you, and Hoppy in particular. I am a newbie and want to do CO2 injection in an 80G planted aquarium. I don't want my plants to be completely slow-growing and low-tech, and I don't want them to be growing too vigorously either, as with 30ppm of CO2. [Yeah, I'm that Great Moderation guy! ] So, I'm thinking I'll go for moderation, say about 15ppm of CO2, moderate lighting. I have two questions:

(1) Does this approach seem reasonable, or am I forgetting/ignoring something important?
(2) Now the more "techy" question. MOst standard drop-checkers, set up with 4dKH, turn green at 30ppm. This works fine for those who want to keep their tanks at 30ppm CO2, but it wouldn't work well for me. I need an indicator that'll tell me (say go from blue to green) at 15ppm instead of 30ppm. So, looking at Hoppy's above post, I thought, why don't I make a 2dKH solution to put in the drop checker? The charts [ http://freshwateraquariumplants.com/...xidechart.html ] seem to say that 2dKH will get to pH=6.6 at about 15 ppm instead of 30ppm, so this should work for me, right? All I do is put 2dKH standard solution and a few drops of the indicator into the drop-checker, and voila! I calibrate CO2 to keep the solution green without going blue or yellow, just like everybody else does, but I'm keeping it at 15ppm, not 30ppm, right? What am I missing?

Thanks for your help in advance!

-aadro
That would work fine, but keep in mind that a drop checker with 4 dKH fluid will be "green" not at 30 ppm, but at something between about 20 and 40 ppm. There is a lot of built in uncertainty with this method, based on the limits of our eyes in seeing green as a specific color, and on the inaccuracy in measuring pH.

I experimented a lot with using a drop checker where yellow was the indication of the right amount of CO2. This was primarily for DIY CO2, where the battle is about getting enough CO2, not about avoiding too much CO2. I ended up using 1.7 dKH fluid. It worked pretty well for me when I was using it, but making 1.7 dKH fluid is hard to do without starting with a good, known KH solution. http://www.plantedtank.net/forums/sh...d.php?t=129720
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Old 07-02-2012, 08:19 PM   #15
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Default Newbie question on non-standard drop-checker use

Thanks Hoppy! That's useful. So, in that case, I'll be even "safer" using my method, so that if I use 2dKH instead of 4dKH, if the solution goes yellow, I'm less likely to overdose with CO2, although I realize from your comment that I am also likely to under-dose! May eventually need a more accurate meter of some sort!

Any ideas from anybody?
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