# co2 drop check how to



## Wistrick (Mar 13, 2007)

Ok so I have the ADA knock off drop checker, and I have ordered a bottle of Bill's KH 4 standard KH solution. But I am still not sure how to use the thing.

Instructions say to add couple drop of ph regent and then fill half way with tank water. Huh? seem to me all this does is create a ph tester?????

What I am thinking is I need to fill it half way with KH 4 solution and a couple drops of regent. Then according to the ph/co2 chart if its blue (7.0) ph then I am ok. 

Is my line of thinking correct

Dan


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## Muirner (Jan 9, 2007)

From what i understand after reading most of that 25 page drop checker thread, and most of hoppys posts is, you need to fill it with the KH solution, and distilled/RO/DI water (anyone of the 3), the equileberium (sp) that is reached by the air trapped in between the tank water and the bulb will give you the CO2 reading. Different KH solutions will give different PPM readings, but with KH 4, the bulb will turn green when there is 30ppm of CO2. 

(correct me if i'm wrong)


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## ed seeley (Dec 1, 2006)

Don't dilute the 4dKH solution with more Distilled water - it won't be 4dKH then!

Just add the 4dKH solution to the drop checker, add the indicator solution and then turn it over and submerge so the solution can't mix with the tank water. As Muirner said, the CO2 in the water will come out of solution into the air space in the drop checker and will then dissolve into the solution in the drop checker so that the level of CO2 in all three are the same. When this is 30ppm that will turn a 4dKH solution green. The fact that the CO2 has to get out of solution into the air space then back into solution in the drop checker solution means there is a time lag in the colour change.


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## Muirner (Jan 9, 2007)

OHHHHHHHHH i get it, so no distilled water then?


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## eklikewhoa (Jul 24, 2006)

NO!

Just add Bill's 4kdh water into the drop checker(about halfway) then add some of the ph reagent and that gives you a known Kh of 4deg. and the color changes from the reagent gives you an estimated ph so that tells you what co2 you have.


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## Wistrick (Mar 13, 2007)

The instructions that come with it say to add tank water then the regent, but all that does is make it a fancy ph tester. Using the KH4 and some regent give you a co2 drop checker. I get it now!!!!


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## tefsom85 (Jan 27, 2007)

One thing that Hoppy's thread also calls out is that it didnot seem to matter too much the exact number of drops of Ph reagent that is added. Seems that he was adding 2 to 6 drops, depending on whatever makes the color most readable. Can anyone explain to me why this is? If I remember my chemistry from many moons ago, when we were trying to detect a threshold via titration, the amount of reagent required determined the threshold.


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## hoppycalif (Apr 7, 2005)

The reason you can add more or less reagent than the test kit says to use is that the reagent is only slightly alkaline (as I recall from sodium hydroxide). As long as the quantity of reagent is small compared to the sample size it seems not to have any effect. I checked it at three different pH's and got the same color with 2 or 3 times the kit instruction dosage of reagent. Since the amount of water sample in an ADA type glass drop checker is smaller than that used in the API test kit test tube you can't add as much reagent as I used in the test tube. I just watch the color, and when it is intense enough to easily check the color, but not so much as to be opaque, I use that amount.


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