KN03 - Greenhouse grade?

[MWJ]

Before I knew about Lambentveteran I purchased some KN03 from Seed Ranch. When I got it the bag showed a label that said:

*********

Greenhouse Grade (KN03)

 

Potassium (K) 38.04%

Nitrogen (N) 13.5%

Soluble Potash (K20) 46.20%

Nitrate-nitrogen (N-No3) 13.5%

Net Weight 2 LBS

**********

Is this what I need for BP. This is the first time I used this company because of the price.

[Carbon796]

Yes, that will be perfectly fine. Using a good charcoal is what will be the difference between serviceable BP and good BP

[MWJ]

Very cool! Thanks. I don't know what all of that stuff means yet, but I will with a little bit more studying.

[LambentPyro]

I think that's what's read on the bags of KNO3 I have.

[shouldnoteatindat]

i have that same bag. i believe that it is telling you what is in the kno3

[Arthur]

That is the way that plant growers label pot nitrate. It could be 95% or better as it doesn't matter for horticulture! It will be fine for pyro too.

[BrainDamage]

your ready to go make BP

[MWJ]

Thanks Everyone! There's a lot to learn and it sounds like it never ends. That's what I like about this stuff.

[hindsight]

If Greenhouse Grade Haifa is 13.5-0-46.2 , what is it's percent purity? How does it compare with technical (tech) grade KNO3 from the chemical suppliers? Understand what Arthur is saying, but would like to know relative quality, anyway.

[MWJ]

When I bought it, it said it was 98.8%

[hindsight]

Thanks MWJ. Haifa technical grade, as listed on their site, is 99.7%. As Arthur and Carbon796 implied, GG is of sufficient purity for good BP, so I just PM'd Hunter for a bag.

[MWJ]

I just bought some from Dylan, $2.00 LB + Shipping.

[hindsight]

Hunter is willing to sell me 50lb bags of Champion greenhouse grade which is 13.75-0-46. I've googled but cannot find out what purity that would be.

Any help here?

 

(The manufacturer supplies it for growing medical marijuana- maybe it will make my rockets get higher).

[Mumbles]

You'll never be able to figure out the exact purity from the NPK numbers, since they're not really derived from any sort of purity information. Anything over 90 or 95% pure will have basically the same numbers. Your best bet is to look at the manufacturer's website to see if they give any information. Greenhouse Grade (GG) or hydroponic grade will probably be about as pure as you can get from fertilizer.

 

It's not like you can use KNO3 for colors anyway, so the purity largely doesn't matter past a certain level. Just people being neurotic or trying to find something else to blame besides their techniques for sub-par BP.

 

Champion has always been quite good. It's now owned by a company called SQM, so you may have more luck finding information from them.

[hindsight]

Thanks, Mumbles. I've been unable to find anything, like I said, by searching the internet. And neurosis is part and parcel of pyrotechnica. But if you say Champion GG is good, Hunter has made another sale.

[Paravani]

You'll never be able to figure out the exact purity from the NPK numbers, since they're not really derived from any sort of purity information. Anything over 90 or 95% pure will have basically the same numbers. Your best bet is to look at the manufacturer's website to see if they give any information.

 

Well, maybe not the "exact" purity, but you can make an excellent guess:

 

(Pyros with a strong chemistry background, forgive the elementary lesson that follows.)

 

KNO3 is a molecule with one atom of potassium, one atom of nitrogen, and three atoms of oxygen. Each type of atom has a weight, which can be found by looking at the periodic table of the elements:

 

 

Roughly speaking, the weight of each element is approximately twice its number in the periodic table (except Hydrogen, which is 1) -- so the weight of each atom in KNO3 is:

 

K = 38

N = 14

O = 16

 

We have three Oxygen, so the total weight of the molecule is 38 + 14 + 3(16) = 100.

 

Cool! The KNO3 molecule just happens to weigh 100. Hey, that makes it easy to figure out percentages, doesn't it?

 

What percentage of that molecule is Nitrogen(N)? 14/100 = 14.0%

 

What percentage of the molecule is Potassium(K)? 38/100 = 38.0%

 

The three numbers on a bag of fertilizer are N-P-K -- Nitrogen, Phosphorus, and Potassium. If the KNO3 is 100% pure, then these numbers should be 14 - 0 - 38.

 

Before I knew about Lambentveteran I purchased some KN03 from Seed Ranch. When I got it the bag showed a label that said:

*********

Greenhouse Grade (KN03)

 

Potassium (K) 38.04%

Nitrogen (N) 13.5%

 

From the above numbers, we can calculate that the percentage of "pure" KNO3 is roughly

 

13.5%(actual N) divided by 14.0%(theoretical N) = 96.4% "pure" KNO3

 

However, they added some extra Potassium to the mix, so your KNO3 is only slightly deficient in Nitrogen. When you get really good at figuring out the combustion reactions in your formulas, you will be able to adjust your reactants to compensate for deficiencies and excesses. In the meantime, I wouldn't worry much about it. 96.4% is close enough.

 

-- Paravani

Edited July 11, 2014 by Paravani

[WSM]

Hi Paravani,

 

Thanks. I have a fair background in chemistry, but don't mind someone else spelling it out for those who don't (plus you saved me from doing it ). edit: Well Done!

 

Yup! That's how it's done folks.

 

WSM

Edited July 11, 2014 by WSM

[Mumbles]

That's actually not how it's done, but maybe they're switching to something that actually makes sense now like Paravani described. NPK is nitrogen-phosphorus-potassium, but it's not measured on a strict percentage by weight. Nitrogen is. Phosphorus and Potassium are measured by equivalents of P2O5 and K2O.

 

So 1 molecule of KNO3 will have 39g of potassium per 101.1g of KNO3, which is 38.57% by weight. This means that 100g of KNO3 has 38.57g of potassium, which is .989 moles. .989 moles of potassium corrosponds to .495moles of K2O. .495 equivalents of K2O weighs 46.58g.

 

Thus the NPK rating of KNO3 is 13.4-0-46.6 Which you can see basically match the pure grades here: http://www.haifa-group.com/products/plant_nutrition/multi_k_potassium_nitrate_fertilizer/

[Arthur]

In the days when BP was the army's gun propellant they didn't have great grading systems for the nitrate BUT they did coppice their own timber for the charcoal component.

[hindsight]

Pavarani, In your example are you assuming that all 13.5% of the Nitrogen is coming from the Nitrate of KNO3? What if there is another source of Nitrogen? Would not the percent purity be less than the 96.4% in your example?

I cannot call myself a chemist, but unless I am confused (which is common), something does not seem right about the example.

[Paravani]

Pavarani, In your example are you assuming that all 13.5% of the Nitrogen is coming from the Nitrate of KNO3? What if there is another source of Nitrogen? Would not the percent purity be less than the 96.4% in your example?

I cannot call myself a chemist, but unless I am confused (which is common), something does not seem right about the example.

 

Yup, that's why it's a "rough" estimate. (Notice how I CYA'd there?)

 

;-D

 

-- Paravani

[Paravani]

That's actually not how it's done, but maybe they're switching to something that actually makes sense now like Paravani described. NPK is nitrogen-phosphorus-potassium, but it's not measured on a strict percentage by weight. Nitrogen is. Phosphorus and Potassium are measured by equivalents of P2O5 and K2O.

 

So 1 mole of KNO3 will have 39g of potassium per 101.1g of KNO3, which is 38.57% by weight. This means that 100g of KNO3 has 38.57g of potassium, which is .989 moles. .989 moles of potassium corresponds to .495moles of K2O. .495 equivalents of K2O weighs 46.58g.

 

Thus the NPK rating of KNO3 is 13.4-0-46.6 Which you can see basically match the pure grades here: http://www.haifa-group.com/products/plant_nutrition/multi_k_potassium_nitrate_fertilizer/

 

Your calculation is more precise and less "back of the envelope" than mine... So for the benefit of the chemistry-deficient noobs, I'll re-post with more detail (and a clearer Periodic Table):

 

KNO3 is a molecule with one atom of potassium, one atom of nitrogen, and three atoms of oxygen. Each type of atom has a weight, which is shown below its symbol on the periodic table of the elements:

 

 

As you can see in the table above, each element's weight is approximately 2 times its number (which is its number of protons), because each proton is matched by a neutron, generally speaking. However, some elements are inconsistent in the number of neutrons per atom, with a few atoms out of every batch having more or less than the norm. The weight shown on the Periodic Table represents the average weight of a bunch of atoms, including these inconsistent "isotopes".

 

So, we see from the table below that the average weight of each atom in KNO3 is:

 

K = 39.10

N = 14.01

O = 16.00

 

39.10 + 14.01 + 3(16.00) = 101.11

 

The total average weight of a molecule of KNO3 is therefore 101.11 grams/mole, or 101.1 when rounded to four significant figures, as Mumbles states.

 

(A "mole" is a specific number of atoms used in Chemistry to normalize measurements by weight. There is one "mole" of Oxygen atoms in 16.00 grams of Oxygen. We won't worry much about moles here because for all intents and purposes, you can simply add up the atomic weights of the molecules and choose whatever units you want -- grams or pounds, kilos or tons -- as long as you stick to the same units your reactions will be balanced.)

 

To calculate percentages of elements, divide the element's weight by the total weight of the molecule:

 

%Potassium(K) = 39.10/101.11 = 38.67%

 

% Nitrogen = 14.01/101.11 = 13.86%

 

% Oxygen = 3(16.00)/101.11 = 47.47%

 

 

Next, Mumbles' K2O calculation (without moles) --

 

K2O is two atoms of Potassium(K) and one atom of Oxygen. However, we don't have two atoms of potassium in KNO3 -- we only have one. So to find the percentage of K2O in KNO3, we need to multiply the KNO3 by two to find the percentage:

 

%K2O in 2(KNO3)

 

K2O weighs 2(39.10) + 16.00 = 78.20 + 16 = 94.20

 

2(KNO3) weighs 2(101.11) = 202.22

 

94.20/202.22 = 46.58% K2O

 

To figure out the percentage purity (a guesstimate, since the mfgr may have added a little bit of this, a little bit of that to try to even things out), just divide the number on the box or bag by the theoretical amount:

 

13.4 (N) / 13.86 (N) = 96.7% pure KNO3, based on the percentage of Nitrogen

 

How did I do, Mumbles? Close enough for gubmit work?

 

;-D

 

-- Paravani

Edited July 11, 2014 by Paravani

[layedbackkustomz]

Hey guys I use champion brand kno3 fert grade and it works very well. I also use local black willow for my charcoal and 90 percent sulfur fert grade. I use to use other sulfur but I cant tell a real difference in the performance. here is a vid of champion kno3 bp milled for 3 hours http://www.youtube.com/watch?v=uTA-RiKv9PM. its not the best video but you will see it does work. I use this powder for everything ex rice hulls to lift. -LBK-

[WSM]

That's actually not how it's done, but maybe they're switching to something that actually makes sense now like Paravani described. NPK is nitrogen-phosphorus-potassium, but it's not measured on a strict percentage by weight. Nitrogen is. Phosphorus and Potassium are measured by equivalents of P2O5 and K2O.

 

So 1 molecule of KNO3 will have 39g of potassium per 101.1g of KNO3, which is 38.57% by weight. This means that 100g of KNO3 has 38.57g of potassium, which is .989 moles. .989 moles of potassium corrosponds to .495moles of K2O. .495 equivalents of K2O weighs 46.58g.

 

Thus the NPK rating of KNO3 is 13.4-0-46.6 Which you can see basically match the pure grades here: http://www.haifa-group.com/products/plant_nutrition/multi_k_potassium_nitrate_fertilizer/

 

I may have misrepresented what I was thinking when I said that.

 

My thinking was how I appreciated that he referred to the periodic table and built molecular weights by adding the atomic weights, to show the weight in grams of a mole of that molecule (based on Avogadro's number; pardon misspelled words).

 

When balancing equations and formulas, once we know the mass ratios of the parts, we can apply those ratios to scale up or down to match the quantities of our starting materials or the mass quantity of the end product we desire.

 

Very useful. Thanks again.

 

WSM

[Mumbles]

The weight percent thing was perfectly correct, and is quite useful to know how to do. I was referring more to the use of K2O and P2O5 in NPK ratings instead of percent by mass of potassium itself. Weight percent to me would be much more useful and logical, but alas, I don't make the rules, just follow them. If you tried to find KNO3 with 13.4-0-38.7 NPK rating, you'd have trouble. It seems bags are starting to list both though.

 

I honestly didn't even notice that I was using slightly different masses for potassium nitrate and potassium itself until Paravani made a point of it. Working with chemistry all the time, these are just numbers I have at the top of my head. I was also really trying to avoid using the term mole, but I couldn't help it. My hands were unwilling to listen to my brain to type that one molecule of KNO3 weighs 101.1g for simplicity sake.