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Potassium Nitrate (KNO3) Purchased from Internet

ceg4048

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I've seen a couple of threads here and there about folks buying KNO3 from ebay and other internet sources and later getting BGA or other Nitrogen related deficiencies. It's now clear to me that some sellers may be sending out non-Potassium Nitrate products such as Calcium Nitrate or Magnesium Nitrate.

Although these are legitimate Nitrate containing salts, you should get what you are paying for. KNO3 is the best widely available Nitrate compound. The reason is simple - by weight and (atomic ratio), no other salt produces a high percentage of NO3 in the water column at very low toxicity. Ammonium Nitrate produces a higher NO3 concentration per teaspoon, and a higher Nitrogen content overall, but not without the toxicity issues.

The reasons for KNO3 superiority is obvious when you look at the weight ratio of NO3 in these products:
NO3 by itself weighs about 62 grams per mole.

Potassium Nitrate
(KNO3) weighs about 100 gram per mole, therefore NO3 is roughly 60% by weight of Nitrate.

Magnesium Nitrate
Ordinarily would have the formula Mg(NO3)2 but is typically sold in it's hydrated form Mg(NO3)2·6H2O (Magnesium Nitrate Hexahydrate 256 grams per mole) which lowers the percentage of Nitrate from 40% to about 24%. If someone sends you this product instead of KNO3 then you need to dose about 3X as much to get the same target Nitrate concentration that you would ordinarily get by dosing KNO3.

Calcium Nitrate
A similar story here. Ordinarily it has the formula Ca(NO3)2 but is typically sold in it's hydrated form Ca(NO3)2.4H2O (Calcium Nitrate Tetrahydrate 236 grams per mole) which lowers it's Nitrate content to about 53%.

Ammonium Nitrate
This is a completely different ballgame. Highly potent, use with care. This salt (NH4NO3) weighs a mere 80 grams per mole and is a Nitrogen superhero. Not only does it produce a whopping 74% Nitrate concentration, but the cation NH4 is also roughly composed of 78% Nitrogen. This is why most fertilizers, especially the terrestrial versions like Miracle Grow, derive at least some of their Nitrogen source via this salt.

Sodium Nitrate
While NaNO3 delivers a highly efficient 84% Nitrate concentration, Sodium, generally is very bad for plants and for most fish. So this salt should be avoided unless there are simply no other alternatives available at your location. It's efficiency at delivering NO3 however is good enough that depending on your lighting you might be able to use it effectively. It's also about 50% less soluble than Calcium Nitrate.

If you paid money for KNO3 then you need to ensure that it's what you got. I'll borrow the image from the EI tutorial. KNO3 is at the top of the image. You can see that it has a tendency to clump. Potassium Phosphate is shown in the middle of the image. You can see the difference in colour between the two salts. The Nitrate has a very slight yellow tinge in comparison. Also, most importantly, KNO3 has a funky, almost blue cheese odour to it, making it unmistakeable. Do not get fooled. If it does not have these characteristics then there is a strong probability that it is one of the other salts discussed above. This can easily explain why we have Nitrogen related difficulties.

EDIT: It should be noted that highly reputable sources of plant nutrients such as all of our sponsors, as well as garden centres such as Gardens Direct, have Quality Assurance measures in place to help ensure the integrity of their KNO3 and other dry powders. However, many anonymous internet trading sources do not. The mix ups may not even be intentional, as the vendor themselves may have been duped or they may not have systems in place to reduce the possibility of errors. Since almost all the various powders look very similar, i.e. all white powders, it is not surprising that mix ups can occur with identification, labelling , or shipping. Since we all know that Nitrate and Phosphate test kits are rubbish, then these are not reliable methods of determining which powder is which.

Top to bottom: KNO3, KH2PO4, Trace mix:
8394086363_b84709efd9_c.jpg


Cheers,
 
Last edited:

CeeJay

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Hi Clive

That may well explain a few things round here.
Thanks for taking the time out to post.

The last 1kg I bought off there seems to be the legitimate stuff. Been using it since February and no problems to report :D .
 

ghostsword

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It is a great post, and should be made a sticky, so that people know how to visually differentiate between the good stuff and the bad stuff.

I was battling with BGA for a while, couldn't get rid of it, wasn't all over the tank, but it was there. Bought some KNO3 from FluidSensor and the BGA went away in under a month. Started to use Fluidsensor's one as it came on a nice box, easy to reseal, the other was on a plastic bag.

Went yesterday to check the left over kno3 that I had purchased from ebay, and it is different from the one I bought from fluidsensor, very white, as the post below said it shouldn't be.

I threw it away now, don't know what it is.
 

xim

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Are these methods valid ?

Test Calcium Nitrate and Magnesium Nitrate with GH test kit.

Test Ammonium Nitrate with NH3/4 test kit.

Differentiate Potassium Nitrate from Sodium Nitrate by solubility in 25? water.
(KNO3 is 3.6 g/10 ml while NaNO3 is 9.21 g/10 ml)
 

ceg4048

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Hi,
Yes, the methods you suggest are theoretically valid, especially if you dissolve the samples in RO or distilled water, however, as I stated in my post, I don't trust any test kits and there is no way, I would go buy a test kit just to see what powder I had. That would be throwing good money after bad.

Since you don't know from the beginning which of the five powders you have, you would need several test kits. If you already have the test kits, and if you have easy access to Distilled/RO then it might be worth pursuing. I also don't own a scale accurate enough to determine solubility.

At the end of the day, in my opinion, none of these methods works better, or are cheaper than my nose and my eyes, because I've been using KNO3 for donkey's years, but they are definitely valid if you lack the confidence in your ability to distinguish.

Cheers,
 

CeeJay

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Hi all
ghostsword said:
I was battling with BGA for a while, couldn't get rid of it, wasn't all over the tank, but it was there. Bought some KNO3 from FluidSensor and the BGA went away in under a month.
What took you so long Luis. My BGA went in 4 days ;)

@xim
xim said:
Are these methods valid ?

Test Calcium Nitrate and Magnesium Nitrate with GH test kit.

Test Ammonium Nitrate with NH3/4 test kit.

Differentiate Potassium Nitrate from Sodium Nitrate by solubility in 25? water.
(KNO3 is 3.6 g/10 ml while NaNO3 is 9.21 g/10 ml)
You will find a large majority of us have binned our test kits and rely on the condition of our plants and livestock to tell us if something is wrong :D
 

flygja

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I was quite glad when I got home, opened up my container of KNO3 and saw that big lump in the corner :lol:
IMAG0036.jpg


It does have a whiff of blue cheese but only if I stick my nose quite close to it. Never noticed that before. Speaking of BGA, I saw a patch of BGA in my tank about 3 inches long and dosed a 1/4 teaspoon of KNO3. The very next day, it was reduced to about a half inch!

Thanks a lot ceg!
 

madlan

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I recently got some from eBay, it has clumped slightly but smells more like plastic than cheese!
Here it is on the right, next to some Mono potassium phosphate from the same supplier:



Is there any other method of testing? I have a nitrate test kit plus scales that measure to .00g
 
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Ebay UK have stopped people selling KNO3 because it's listed as a pyrotechnic so that should prevent a lot of the dodgy sellers out there. The stuff off our sponsors is pretty cheap all things considered for a tank like mine anyway so considering your source of no3 is act one scene one, get this wrong and everything else will fail is not worth saving a couple of quid for me.
I suppose if you already have a large amount of it it's worth testing it, If not it's maybe worth biting the bullet on it and binning it.
 

xim

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CeeJay said:
You will find a large majority of us have binned our test kits and rely on the condition of our plants and livestock to tell us if something is wrong :D

Hehe, been lurking here loooong enough to know about the trend here. :D

madlan said:
I recently got some from eBay, it has clumped slightly but smells more like plastic than cheese!
Here it is on the right, next to some Mono potassium phosphate from the same supplier:



Is there any other method of testing? I have a nitrate test kit plus scales that measure to .00g

Yep, I think. But it's probably better to buy new ones from a popular source (like one of the web's sponsers).
This way you will have others in the same boat to consult with. And the test is just telling what it is not,
not what it is. :crazy:

Here you go, using solubility in 20? water (preferably RO/DI or distilled).
Because KNO3 is far less soluble in cool water than other suspects.
http://en.wikipedia.org/wiki/Solubility_table

Let's say if you can dissolve 4 or 5 grams of it in 10 ml water, then it's not KNO3.
If you can't, then it's not Ammonium Nitrate/Calcium Nitrate/Magnesium Nitrate/Sodium Nitrate.
Should be valid I think...
 

Jim

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My first batch of KNO3 was very white and after 5 years I'm coming to the end of that batch.

I recently bought another 5 kilos and it's an off white colour a most definate off white colour. I mixed a small quantity with some sugar and it burnt like what I would expect KN03 to burn like.

Why would it be off white? Any thoughts?
 

dw1305

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Hi all,
It is probably a purity issue, the lab. grade (and some of the liquid fertiliser grades) will be pure white and over 99% pure. The ordinary fertiliser grade will often be "off white" because it will not be as pure, but it will still be c. 98% pure.

As long as you aren't trying to dispense the solution through a micro-dispenser it makes no difference.

cheers Darrel
 

GPHowell

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I'm new to this forum (and like it a lot by the way) and I'm also a professional chemist so I thought I'd throw my two-pence-worth in...

Personally, I'd be very wary of purchasing KNO3 from I supplier I wasn't entirely sure of. I'm genuinely not trying to scare or worry anyone but I wouldn't be too happy having 5 kg of potentially low-grade KNO3 in my house.

It's important to realise that most small-molecules containing nitrogen/oxygen combinations (nitrates, nitrites, nitroso etc) are potentially explosive and potentially strong oxidising agents. In general terms, the higher the nitrate content, the more risk there is of running into trouble.

As stated in the OP, KNO3 is a good fertiliser because it has ~60% nitrate and 40% K, so you get a lot of usable N/O per gram of fert. It's also a good oxidising agent and is a principle component in gunpowder (with carbon and sulfur).

But, if you push the nitrate content up higher (e.g. NH4NO3 ammonium nitrate), you get even more useable NO3 but you now have a very potent explosive. Ammonium nitrate is also a contact explosive, meaning if you drop it you're potentially in trouble.

The important thing to realise here is that many methods for the production of KNO3 go via ammonium nitrate or other hazardous compounds and these are the most likely contaminants in any low-grade KNO3 you might buy from the internet...

My advice would be to get it from a reputable supplier, with a C of A if possible and don't be tempted to save two quid by shipping it in from a dodgy-looking supplier :)
 

dw1305

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Hi all,
I'm genuinely not trying to scare or worry anyone but I wouldn't be too happy having 5 kg of potentially low-grade KNO3 in my house.
I hadn't really though about storage in those terms, although we had a post about the possible explosive dangers of nitrates before, I'll see if I can find it. I'm pretty sure one of our continental members wasn't able to buy KNO3 etc without a license. If I want any oxidising agents (to make up reagents etc.), they have to be signed in and out by the chemistry technician, from a double locked explosive proof box in the Chem store.

cheers Darrel
 

Alastair

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skeletonw00t said:
http://www.ebay.co.uk/itm/Empty-bag-Potassium-Nitrate-Cheapest-Ebay-VALUE-L-K-/110799210293?pt=UK_BOI_Medical_Lab_Equipment_Lab_Supplies_ET&hash=item19cc25c735#ht_817wt_1139

will this really be an empty bag ?
ha ha possibly not. But whether it's pure kno3 is a different question.
Or it could be that they are stating they are selling 'the bag' as they aren't legally allowed to sell kno3 but haven't indicated what contents are in the bag lol.
ORRRR it could genuinely be an empty bag


Sent from my iPhone using Tapatalk
 

John S

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Well they've got 100% feedback, so quite a few people happy with 'empty bags' :lol:

As Alastair says though, I'd be wary if its genuine KNO3 on reading this thread.
 
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What is the situation with dry ferts these days? I have plenty left over from my previous purchase so haven't been looking to buy any for a while. I'm aware ebay no longer allow you to sell it although they do sell plenty of empty containers with kno3 labels on :rolleyes: If certain sponsors still sell it how come they get round the supplying of dry ferts where other don't, is there actually a law at the moment preventing certain people selling it or not? There is a bulk supplier of garden fertiliser next to my office who deals in half ton sacks of various fertilisers I keep meaning to have a chat with.

@ GP Howell what is the chemists policy on supplying ferts and what would your average chemist think if someone came into the shop looking to purchase of them out of curiosity? I've often wondered, looking at James solubility table on the bottom of here http://www.theplantedtank.co.uk/calculator.htm 36gram of kno3 will dissolve into 100ml of water so why don't people just sell one litre of water that's known to have 360 gram of kno3 in and let the buyer do their own maths, the safer chemicals can come in dry form. I know it would be a touch more expensive but surely that would get round the pyrotechnic thing as it is rendered useless as an explosive when mixed with water.

Just thinking out loud :)
 

deepak267

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I believe, there is a lot of restriction on selling KNO3 because it is used in making explosives. So it will be worth knowing the source of good KNO3 supply
 
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