KNO3 dosing

[yajur]

I planned to increase my NO3 to 2ppm currently at 1ppm and my tank volume is 520gallon and i got KNO3 and how Stock Solution should i make ?

 

[Randy Holmes-Farley]

Do you have a scale to weigh the KNO3?

 

[yajur]

Do you have a scale to weigh the KNO3?

Yes randy having scale to measure it.

 

[Randy Holmes-Farley]

Potassium nitrate is about 61% nitrate by weight.

Dissolve 100 grams in 1 L of fresh water.

That stock solution will contain 61 grams (61,000 mg) of nitrate, or 61 mg/mL.

Your tank volume is 520 gallons or 1968 liters.

Consequently, adding 50 mL of stock solution to your tank will boost nitrate by 50 mL x 61 mg/mL / 1968 L = 1.55 ppm.

 

[marke]

Randy
I am sure you are correct, but how do we determine the % nitrate in potassium nitrate? I found the following online and would like to learn how to calculate this for other elements based on molecular wt. Thanks for the education!

Molecular weight calculation:
39.0983 + 14.0067 + 15.9994*3


Percent composition by element
Element Symbol Atomic Mass # of Atoms Mass Percent
Nitrogen N 14.0067 1 13.854%
Oxygen O 15.9994 3 47.474%
Potassium K 39.0983 1 38.672%

 

[Randy Holmes-Farley]

Sure. In this case, if you add the N and O%, you get the answer.

In general, you add up the weight of the elements in the ion of interest (in this case, N + 3 x O) and divide by the total molecular weight of the chemical (K + N + 3 x O). In some cases, you may also need to a count for water in the crystal, which in some cases might be as much as half of the weight of the solids (as in magnesium chloride hexahydrate or magnesium sulfate heptahydrate or calcium chloride dihydrate).

 

[marke]

Thanks Randy! I thought the element of interest in this case is just N? Why are we adding in the 3O2 into the percentage? Without the O its just about 14% nitrate? Thats also what is says on the bag I bought--14% Nitrogen?

PS: In this case it does not state the hydrate in the product? Can we assume anything? Found the same thing with the K chloride and K sulfate I recently purchased to betta test with. No dihydrate or any other mentioned? Any reason or conclusion?

 

[Randy Holmes-Farley]

Nitrate is NO3-, so you need to count all of the atoms in it if the unit of measure is ppm nitrate (and not ppm-N, which some people use and you would do your way, but almost no online reefers use that unit anymore).

There is no hydrate in KNO3.