Is saltpeter the same as potassium nitrate?

[nim6us]

The reason I ask if they're the same is I ordered some potassium nitrate online and what I received said it was saltpeter, used for food dehydration. I'm using it to make my own nitrate dosing solution. I followed the ratios on the planted tank calculator website paying careful attention to stay well below the max solubility.

However even after letting it mix for 30min in my magnetic stirrer the solution was still cloudy. When I leave the bottle sit for a while a thin white powder settles at the bottom. I also mixed up some potassium phosphate and that solution is crystal clear.

The package on the saltpeter just says "pure saltpeter" with no other ingredients listed in the composition, but I'm skeptical. So I thought I'd ask the man... any thoughts Randy?

 

[N.Sreefer]

Saltpeter is a mineral form of KNO3 but occasionally (less often) can refer to sodium nitrate NaNO3. Perhaps the mineral form of KNO3 is less soluble than the form its normally sold in?
Curious what
@Randy Holmes-Farley
Has to say about saltpeter

 

[DE FISH]

Yep food grade it’s what I use zero issues so far it’s potassium nitrate

 

[DE FISH]

Here’s a link for a calculator to create your nitrate make sure you use precise scales

http://www.theplantedtank.co.uk/calculator.htm

EDIT: my bad didn’t see you already mixed up your potion your good to go bro

 

[Randy Holmes-Farley Verified Community Expert]

I'd be wary of saltpeter unless it specifically stated it was food grade.

i also don't recommend potassium nitrate unless you are monitoring potassium, as it can rise over time.

Sodium nitrate is a better bet, IMO.

 

[nim6us]

Thanks for the feedback Randy! I am trying to raise potassium a bit and am monitoring with ICP.

@DE FISH Do you find you get the silt settle out when you mix it up or is your solution crystal clear?

 

[DE FISH]

Thanks for the feedback Randy! I am trying to raise potassium a bit and am monitoring with ICP.

@DE FISH Do you find you get the silt settle out when you mix it up or is your solution crystal clear?

no my solution is milky when it’s been sitting in the cupboard for a while I have to stir it up again

 

[Randy Holmes-Farley Verified Community Expert]

no my solution is milky when it’s been sitting in the cupboard for a while I have to stir it up again

How concentrated are you making it?

If you are well below the solubility limit in your dosing solution, I would NOT mix before dosing. The solids are not sodium or potassium nitrate, but some other impurity.

Solubility at 25 deg C:

sodium nitrate: 0.9 g/mL
potassium nitrate: 0.3 g/mL

 

[DE FISH]

How concentrated are you making it?

If you are well below the solubility limit in your dosing solution, I would NOT mix before dosing. The solids are not sodium or potassium nitrate, but some other impurity.

Solubility at 25 deg C:

sodium nitrate: 0.9 g/mL
potassium nitrate: 0.3 g/mL

Hi Randy

I usually make a 30ml solution so times that by two. I’m interested in changing to sodium nitrate just can’t find a calculator for it I can get 99.5% sodium nitrate

 

[Randy Holmes-Farley Verified Community Expert]

I'd leave any solids behind.

 

[nim6us]

Just to close out this thread. I decided to order some potassium nitrate direct from a chemical manufacturer. It cost about triple what I paid on Amazon, however the solution mixes up with zero silt or solids. I gave it three days to ensure there was no settling out.

I can't say definitively that all saltpeter will give you the same experience. However as Randy keenly points out you should probably leave the solids behind. If your KNO3 isn't mixing completely it may be time to find a new source.

 

[Randy Holmes-Farley Verified Community Expert]

Thanks for the update!