Cool! New drop checker. Ummm, now what? - The Planted Tank Forum
 
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post #1 of 13 (permalink) Old 03-08-2008, 01:20 AM Thread Starter
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Cool! New drop checker. Ummm, now what?

I bought a drop checker from eBay and it came with no instructions. So far no response from the seller.

Can anyone tell from this picture how I should use it? I've never had one before. From the 'net I know I should put some RO water in the checker with some of the pictured solution, but I don't know in what proportions. Also, I don't know what resulting colors correspond to what CO2 levels.



Any guidance would be greatly appreciated.

Regards,

Will
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post #2 of 13 (permalink) Old 03-08-2008, 01:21 AM
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First you need 4dkh for it. Then put 4dkh in it and stick in your tank.
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post #3 of 13 (permalink) Old 03-08-2008, 01:23 AM
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post #4 of 13 (permalink) Old 03-08-2008, 01:25 AM
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You need to get or make some 4 degree KH water (distilled + sodium bicarb) to fill the ball. Then you add a bunch of the bromthymol blue reagent that is in the bottle (or from most pH test kits). Place it about 3" below water level and give it a few hours to equilibrate. A pH of 6.6 will be green and have 30ppm.

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post #5 of 13 (permalink) Old 03-08-2008, 01:32 AM
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Do not add RO water to your drop checker. Do what the preceding posters said to do. If you add RO water the color changes won't tell you anything useful about your tank. Gotta be 4 dKH. (Or at least a known KH standard with no other buffers.)
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post #6 of 13 (permalink) Old 03-08-2008, 01:41 AM Thread Starter
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Who needs directions??

Awesome! Thanks everyone! Who need directions when you've got plantedtank.net.

Will
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post #7 of 13 (permalink) Old 03-08-2008, 01:50 AM
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Don't forget to check out the search feature. Since you're new around here, I have a feeling that a lot of the old discussion threads would be really useful to you. This place has an amazing archive of knowledge.
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post #8 of 13 (permalink) Old 03-08-2008, 10:26 AM Thread Starter
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Calculations

I wanted to verify VaughnH's calculations, but surprisingly I find that they differ by a factor of 2 (his recipe for a 4dHK solution, according to my calculations, should make an 8dKH solution). To make matters worse, when I test the standard I mixed according to VaughnH's recipe (using 2 different API test kits, BTW), they both return 7dKH (much closer to my calculated number than Tom's). This is scaring the hell out of me because there is no way VaughnH can be wrong!

Please help me find the error in my calculation:

1dKH is defined as 10.71mg of carbonate ion (CO3--) in 1 liter of water.

From the periodic table of elements, I calculated the mass of CO3-- in 1 gram of baking soda (sodium bicarbonate, or NaHCO3) to be:

.714g CO3-- (in 1g sodium bicarbonate, NaHCO3)

Using Tom's recipe, 6 grams of NaHCO3 dissolved in 1 liter of water will yield 4.28g of CO3--:

(6g NaHCO3 / 1L) * (0.714g CO3-- / 1g NaHCO3) = 4.28g CO3--/L

Since there 1dKH = 10.71mg CO3--/L, or 0.0107g CO3--/L, that yields a a dKH value of:

4.28g CO3--/L
---------------- = 400dKH, not the 200dKH reported by VaughnH
0.0107g CO3--/L

We differ at this point by a factor of 2!!

Continuing with Tom's recipe, he takes 10ml of his standard, which, assuming it's a 200dKH solution, contains 2mg CO3-- and adds that to 500ml of water, yielding a 4dKH sample:

200dKH (200mg CO3--/L or .200mg CO3--/ml) yields 2mg CO3--:

10ml X .200mg CO3--/ml = 2mg CO3--

That's in 500ml of water to yield:

(2mg CO3 / 500ml) * (1000ml / 1L) = 4mg CO3--/L or 4dKH

But when using my obtained 400dKH value for the first solution, the result of the second solution is 8dKH which more closely matches the API test results of the standard I mixed!

If my calculated result had simply missed the mark and the API test kits had shown something close to 4dKH, I'd think I just messed up the math, but since the test results are showing much closer to 8dKH, I went back and checked (then rechecked) the calculations and I can't find a mistake.

I'm hoping someone can find a bug here so that the sky won't start falling because I know VaughnH can't be wrong!!

Will

Last edited by willbldrco; 03-12-2008 at 06:40 AM. Reason: Corrected name of referenced author
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post #9 of 13 (permalink) Old 03-08-2008, 11:27 PM
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I made my carbonate solution using billionzz's instructions: https://www.plantedtank.net/forums/ge...ndard-how.html

My digital scales only measure to 1 decimal place and my final solution ended up being 4.26 dKH using my LaMotte Alkalinity test kit.

It was close enough for me and I used it.

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post #10 of 13 (permalink) Old 03-08-2008, 11:41 PM
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Also, don't just add "a bunch of brothymol blue". Only add 3-4 drops, enough to turn the 4dKh solution a deep, royal blue.
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post #11 of 13 (permalink) Old 03-10-2008, 10:11 PM
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Quote:
Originally Posted by willbldrco View Post
Please help me find the error in my calculation:

1dKH is defined as 10.71mg of carbonate ion (CO3--) in 1 liter of water.
Where'd you get 10.71? I thought it was 17.8575? Maybe I'm thinking of something else?
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post #12 of 13 (permalink) Old 03-11-2008, 09:00 AM Thread Starter
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Quote:
Originally Posted by Ransom View Post
Where'd you get 10.71? I thought it was 17.8575? Maybe I'm thinking of something else?
If I'm not mistaken, 17.8575 is the number of mg of CaCO3 to add if you want to raise one liter of water by 1dKH. But that's mg of CaCO3. Baking soda is Sodium Bicarbonate (NaHCO3). Since we're just interested in just how much carbonate (CO3--) equates to 1dKH in 1 liter of water, you have to subtract off the mass of calcium if you want to use the 17.8575 number: Ca++ (7.143 mg/liter), which, when subtracted, leaves (7.8575-7.143)= 10.7145mg/liter CO3--

I found this value of 1dKH on various web postings. Here are a couple:

https://www.plantedtank.net/forums/wa...tml#post227872
http://www.thekrib.com/Plants/CO2/ha...arryfrank.html

I'm going bonkers trying to find the source of mismatch between my result and VaughnH's!

Will

Last edited by willbldrco; 03-12-2008 at 06:41 AM. Reason: Corrected name of referenced author
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post #13 of 13 (permalink) Old 03-11-2008, 09:59 PM
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Originally Posted by Mishmosh View Post
You need to get or make some 4 degree KH water (distilled + sodium bicarb) to fill the ball. Then you add a bunch of the bromthymol blue reagent that is in the bottle (or from most pH test kits). Place it about 3" below water level and give it a few hours to equilibrate. A pH of 6.6 will be green and have 30ppm.

Question - you said to put it 3" below the water level. A while back someone told me to put it almost at the bottom of the tank. (about 5" about the surface) -I'm confused??? Which is it?
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