KNO3 suitable?

[Kwokwok]

Hi all,

Took my first step in dry dosing and got me some KNO3 (potassium nitrate)

What came with the 500g of dry fert was a test anaylsis:

N: 13%
K: 38%
K2O: 46%
Cl: .17%

The fact that they have provided me an analysis makes me think that there COULD be a variation in KNO3 production

Being no chemist I thought better safe than sorry so asking if anyone know if this is typical KNO3 used for safe dry dosing?

Thanks heaps =)

 

[dw1305]

Hi all,
It is standard KNO3, if you buy "KNO3" that is what you will get. The differing grades "Fertiliser", "Laboratory", "Analytical" are only really relevant for lab work, even fertiliser grade (the lowest purity) will be over 95% KNO3 (just checked it is actually over 99% pure). The only way you get anything else is if the compounds had been re-packaged and wrongly labelled by the seller.

If you are concerned about purity and have access to distilled water (or other source of pure H2O) and an accurate balance, you can dissolve a known volume of your KNO3 in warm water, and them cool this, before dehydrating the salt. Details here: <http://www.nakka-rocketry.net/knpurify.html>.

The analysis means KNO3 contains 39% K, but only ~14% N. (the other 47% is the oxygen).
K = 39, N= 14 and O3 = (16 + 16 + 16) = the RMM 39+14+48 = 101, so 39/101 = ~39% etc.

The N content is quoted as "13%" as 14/101 is very slightly under 14%.
The K2O content is listed because traditionally potassium fertilisers are quoted as the "di-potassium oxide content" rather than as the percentage K.

In this case we have K2O = (39 + 39) + 16 = 94, but we need 2 x K, so this means we need to start with 2 x K (NO3), so that becomes 101 + 101 = 202, and therefore it is 94/202 = 46.5% K2O.

The 0.17% Cl is a measure of the chlorine impurity, it is irrelevant to us, but would mean that this is not an analytical grade of chemical.

The chlorine comes from the method of manufacture, combining ammonium nitrate and potassium chloride, to give:

NH4NO3 (aq) + KCl (aq) → NH4Cl (aq) + KNO3 (aq)

Hope that puts your mind at rest.

cheers Darrel

 

[ceg4048]

The fact that they have provided me an analysis makes me think that there COULD be a variation in KNO3 production

Yes, there is some variation but it's not a big deal. The variations are meaningless for our purposes. There are other uses for this product in which the user needs to know the level of impurity, but we don't care.

Being no chemist I thought better safe than sorry so asking if anyone know if this is typical KNO3 used for safe dry dosing?

Did you realize that you are doing more damage to your fish by adding food into the tank? Food decays or produces fecal and urinal waste which is more deadly to your fish than any KNO3 product could ever dream of being, so stop worrying about it. The benefits that KNO3 produces by feeding your plants is that the plants will produce more oxygen and will remove ammonia from the water, so on balance, there is nothing but goodness in KNO3, regardless of it's level of impurities. You will not be sorry as this product is very safe.

Cheers,

 

[Kwokwok]

thanks heaps to the both of you

The information provided was amazing! Thanks for the effort.. will have to read over it a few more times to fully understand (if ever..).. but at least I have a peace of mind =)