# CO2 drop checker



## sasexe (May 22, 2011)

Hi all,

I have read so many posts on this and they always ended with science fiction . I would like somebody just to answer two simple questions:

1. Is the little chamber on the CO2 drop checker filled with aquarium water or has to be filled with a special liquid?

2. How long does the mix of liquid and test drops last. When it should be replaced/refilled?

Thanks 
sasexe


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## Newt (Apr 1, 2004)

It is much more accurate to use dKH4 solution rather than tank water.
You only need to replace the solution when it fades. 1 to 2 months is typical.

Good price for drop checker kits at www.fish-street.com

You can get dKH solution on eBay


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## sasexe (May 22, 2011)

Thanks Newt. The problem is that the manual from the set I bought says to use tank water. I have read posts where other people say they have different sets with the same instruction.


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## virgo888 (Jun 25, 2009)

use 4dkh solution works the best and 3-4 drops of pH test for color.


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## Newt (Apr 1, 2004)

You can use tank water BUT if you dose EI it will not be accurate due to high PO4 interfering with the pH drops.

I get my 4 dKH solution from this guy on eBay:
http://cgi.ebay.com/4-dKH-Reference...920?pt=LH_DefaultDomain_0&hash=item35b1ddd8f8


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## rod (Aug 10, 2005)

What is the dKH solution that you refered to? I bought a dropchecker 4 years ago but have never gotten a good reading, maybe that's why.


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## Newt (Apr 1, 2004)

Its distilled water with additives (I forget exactly what) to make it precisley 4 dKH. It is lab tested for accuracy. You then use the CO2 chart and the pH chart to determine CO2 levels. You read the KH line at the 4 value and take the color of your drop checker solution and match the color to the appropriate pH and use that value on the alternate axis on the CO2 chart.

Let me know if you need me to post the CO2 chart.:fish2:


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## poly-sperm-ahhh (Jan 28, 2011)

Sorry for the noob question but how does these drop checkers work?


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## virgo888 (Jun 25, 2009)

Newt said:


> Its distilled water with additives (I forget exactly what) to make it precisley 4 dKH. It is lab tested for accuracy. You then use the CO2 chart and the pH chart to determine CO2 levels. You read the KH line at the 4 value and take the color of your drop checker solution and match the color to the appropriate pH and use that value on the alternate axis on the CO2 chart.
> 
> Let me know if you need me to post the CO2 chart.:fish2:


it's distilled wated and baking soda.


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## Newt (Apr 1, 2004)

That's one method, virgo888 but this is what I was thinking of>>>

"KH standards

Here is the information needed to make a KH standard. When I started using the drop checker method for measuring CO2 there was a lot of confusion as to the proper way to make a KH standard. After a lot of searching and asking questions I found the correct way to make a good KH standard.

I have made the KH standards with the following.

- baking soda (sodium bicarbonate) 
- sodium carbonate anhydrous 
- a lab certified Alkalinity Standard Solution as NA2CO3 in 10mL Ampules 
How accurate you want the standard is up to you. I think the sodium bicarbonate and the sodium carbonate standards are very accurate if they are made right. 

If you want a more accurate standard than that you could use the alkalinity standard solution. The reason for the increase in accuracy is because all that needs to be done is the dilution part, the weighing process is removed, which eliminates any errors from moisture in the sample or an inaccurate scale.

To make a KH standard using baking soda you would need the following.

distilled water 
baking soda (new and unopened would be best) 
.01 gram scale (a calibration weight) 
500 ml graduated cylinder 
50 ml graduated cylinder 




1. Measure 3000 ml of distilled water using the 500 ml graduated cylinder and put it in a clean container. The container could be an empty 1 gallon distilled water bottle. (I found it easier to use 3000 ml, instead of the often suggested 5000 ml because you can make your standard with 1 gallon of distilled water instead of having to have a larger container or multiple containers)

To read the precise water level in the graduated cylinder.

-Place the cylinder on a flat surface.
-Make sure your eye is on a level plane with the of the meniscus. 
-The meniscus is the half-moon curve formed at the surface of liquid.
-Water should be read from the bottom of the meniscus

2. Weigh 3.60 grams of baking soda, add it to the 3000 ml of distilled water and mix well, this will make a 40 dKH / KH standard.

3. Pour 450 ml of distilled water into the 500 ml graduated cylinder.

4. Pour 50 ml of the 40 dKH standard into the 50 ml graduated cylinder 

5. Pour the 50 ml of 40 dKH standard into the 500 ml graduated cylinder and mix well, this will give you 500 ml of a 4 dKH standard.

6. If you want a 5 dKH standard instead of a 4 dKH - change step 3 from 450 ml to 400 ml and you will end up with 450 ml of a 5 dKH standard.


A few additional items:

1. Don’t heat your baking soda to dry it out or it will change from sodium bicarbonate into sodium carbonate. You could then end up with a mixture of sodium bicarbonate and sodium carbonate, this would change the sample weight needed because it takes less sodium carbonate to make the KH standard than sodium bicarbonate.

2. You can use sodium carbonate anhydrous instead of baking soda. When I found out that heating baking soda turns it to sodium carbonate I thought this might be a good alternative to using baking soda. I bought Lab grade sodium carbonate that is 99.95% pure, thinking it might make a more accurate standard. While in theory it should, I really can’t say for sure that it does because when I follow the above instructions both the baking soda and sodium carbonate standards come out correct. 

3. Not all of the calculators on the web are correct for calculating how much baking soda or sodium carbonate to use. 

If you want to calculate your own weights here is the calculator to use.

'Reef Chemistry Calculator FV'

This calculator is correct, it was off when calculating sodium carbonate but Jose 
changed it in the last couple of weeks and now it’s right.

This calculator rounds everything up because it was made for calculating 
aquarium water not small samples. To get precise weights just add some zero’s to the sample size.
For example: if you wanted to know how much baking soda to add to 3 liters of water to get a standard that was 40 dkh the calculator would give you a weight of 3.6 grams to add. We want to be accurate to at least .01 grams so instead of putting in 3 liters of water you can put in 300 liters, the calculator will then give you a weight of 360 grams to add which you know would be 3.60 grams.

It has been said that there are a lot of assumptions built into these calculators but that’s not correct statement for this calculator when calculating how much sodium bicarbonate or sodium carbonate to use for KH. This calculator will give you the same answer you would get if you calculated long hand, except that it rounds up the numbers (the solution for that is in the above paragraph).

Although there is one assumption in this calculator when using sodium carbonate, it assumes that the sodium carbonate is 100%. You will need to calculate the difference between your sodium carbonate and 100%
For example:
I purchased lab grade sodium carbonate anhydrous and it is 99.95% pure. After I calculate how much to use I have then multiply the answer given by the calculator by .5% and add that to the weight given by the calculator.

4. I have made these KH standards several times with sodium bicarbonate and sodium carbonate. When I follow the instructions listed above the standards has always came out right. 

I have also made the KH standards using a lab certified Alkalinity Standard Solution as NA2CO3 in 10mL Ampules. As long as the accurate dilutions are done this should make the most accurate standard. This is what the EPA uses as an alkalinity standard when they are monitoring and assessing water quality.

************************************************** ********

I hope this helps when others when they are making their KH standards and that they won’t have to do all of the research I had to do just to get a good KH standard."


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## Left C (Jun 14, 2005)

I made my 4 dKH solution by following Newt's directions. It was really quite easy. Then I checked the accuracy of my finished product with a LaMotte Alkalinity Test Kit.



dutchy, on another forum, wrote a very simple method, but I haven't tried it:

Add 6 grams of bicarbonate of soda to one liter of distilled water. This gives you one liter of water with a KH of 200 dKH. Now take 10 ml of that water and mix with 490 ml of distilled water (a dilution of 1 in 50) and you get 500 ml of 4 dKH water. 

regards,
dutchy.


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## Blacksunshine (Aug 11, 2006)

Do not use tank water. its almost impossible to expect consistent or accurate results. As noted you will want to use a known PH mixture so that it is reliable. There are some members of the community that sell premade mixture. Generally using commonly available scales you would have to make a large amount of mixture. So its probably easiest to just get premade.


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