# Chemistry behind API freshwater test kit



## nixx (Nov 10, 2010)

Any chemist here or anyone know the chemicals inside these test kits?
I am interested in how they detect these chemicals and the chemical reactions behind each test
I assume it would be cool to know since we use them so often


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## Darkblade48 (Jan 28, 2008)

Which one are you interested in?

The low pH test kit is bromothymol blue. I believe the high range pH test kit is meta-cresol purple. These are both simply dyes that change colour when protonated/deprotonated.

The ammonia test kit is based off of either Nessler chemistry (older) or the newer complexed salicylate chemistry. I can give a further explanation if you want.


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## nixx (Nov 10, 2010)

Ahh i see it. so i guess they use griess reaction for nitrite and either brown ring test, devarda, or diphenylamine test for nitrate then?


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## Darkblade48 (Jan 28, 2008)

nixx said:


> Ahh i see it. so i guess they use griess reaction for nitrite and either brown ring test, devarda, or diphenylamine test for nitrate then?


For the nitrite, it is likely the Griess, but I am unsure. For the nitrate, it is neither Devarda nor the Brown Ring. It may be the diphenylamine, but it depends as well. There were some older test kits that used powdered zinc as well, to reduce the nitrate to nitrite (I believe in these kits, the reagents were also interchangeable).


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## nixx (Nov 10, 2010)

Do you know what we can add into the tube to increase the reading for all the test? preferably things we can find at home


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## Darkblade48 (Jan 28, 2008)

nixx said:


> Do you know what we can add into the tube to increase the reading for all the test? preferably things we can find at home


What do you mean by "increase the reading" of the test? Increase sensitivity? Increase accuracy? Increase the range? Not too sure what you are asking for here.


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## nixx (Nov 10, 2010)

srry, I mean like what can I add (preferably stuff I can find at home) to increase the ppm reading for all the test and the pH as well


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## Darkblade48 (Jan 28, 2008)

nixx said:


> srry, I mean like what can I add (preferably stuff I can find at home) to increase the ppm reading for all the test and the pH as well


I am still not quite sure what you are asking. Are you trying to increase the upper limit of the test kit? Or are you trying to find a substance that will increase the readings artificially (i.e. to create a standard)?


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## nixx (Nov 10, 2010)

Lets say I am testing ammonia and I have a reading of 1ppm, what can I add into the tube to lower and increase the ppm reading. And same thing for other tests
I wanted to show my cousin that the reading changes when you put substance to contain more/less ammonia lets say.


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## Darkblade48 (Jan 28, 2008)

So you just want to make a range of standards?

You can easily make a range of ammonia standards with distilled water and household ammonia. 

For a nitrate standard, you can make one with potassium nitrate. 

For the nitrite standard, it will be difficult unless you have access to a lab.


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## nixx (Nov 10, 2010)

yep tats wat I was looking for. srry for the confusion w bad writing lol


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