Sciencemadness Discussion Board

Mystery oxidizer labeled as KNO3

Gammatron - 23-3-2023 at 12:51

About a year ago I purchased a bunch of "KNO3" on eBay. Yesterday I finally got around to trying to distill some HNO3 with it and got nothing but a bunch of foam and dense white fumes, no reaction... I posted about it here thinking something went wrong with my reaction but it turns out my KNO3 isnt KNO3 at all. It is definitely an oxidizer but can't figure out which so I will just refer to it as Ox.

Here is what I've found out about it:

- It is a fine clumpy white powder, much like KNO3
- It burns hot, bright and fast with sugar in 2:1 - Ox:sugar, very similar to KNO3.
- It does not react with H2SO4, NaOH or NaOCl
- Is somewhat hydrophobic and will not dissolve in water until it is near boiling, recrystallizes as very fine dense particles.
- It melts and decomposes into white smoke over a propane flame but a lighter flame isn't hot enough to melt it. Little to no residue left behind

I made flash powder with it 5:3:2 - Ox:Al:S
- It cannot be ignited with heat as it decomposes
- It is somewhat sensitive to shock and a good blow from a hammer makes a bright and very loud blast, even with just a pinch

I am rather impressed with its pyrotechnical properties but I am completely dumbfounded as to what it might be. Any help is appreciated and big thanks to everyone that helped me thus far on my other post!

[Edited on 3-23-2023 by Gammatron]

Rainwater - 23-3-2023 at 13:28

Is it soluble in ethanol?

Gammatron - 23-3-2023 at 14:02

Not soluble in ethanol or acetone altho it does stay in suspension longer because the solvent is able to get into the clumps of fine powder which water cannot.

BromicAcid - 23-3-2023 at 14:18

No rxn with sulfuric acid makes me rule out chlorate.
Poor solubility in water makes me lean away from most of the nitrates.
What do you mean that flash with it does not ignite with heat? I know you said it decomposes, but how?
Also, when you did the sugar test did you get a hint of color to point to the cation?
The water solubility makes me think it's potassium perchlorate. At least that would be me first guess from all of this.

Parakeet - 23-3-2023 at 14:31

Maybe it’s potassium persulfate.
It is sparingly solubility in water, decomposition, insoluble in ethanol.

Rainwater - 23-3-2023 at 14:36

https://en.m.wikipedia.org/wiki/Category:Pyrotechnic_oxidize...
After reading this list.
White salts with low solubility include

Barium peroxide
Strontium peroxide

This list is questionable. It list ptfe as an oxidizer? Subject for another topic

Gammatron - 23-3-2023 at 14:50

Did a bigger burn test with sugar than I did before and the flame was white hot and it and the smoke was slightly purple so for a while I was sure it was KNO3 or KClO4. I do have KClO4 tho and I compared it with the unknown powder and there were noticeable differences in the burn rate and some reaction tests I did. When I tried to ignite the flash with a flame it basically just melted and smoked leaving a residue of the Al powder.

Wikipedia: Potassium persulfate is the inorganic compound with the formula K2S2O8. Also known as potassium peroxydisulfate, it is a white solid that is sparingly soluble in cold water, but dissolves better in warm water. This salt is a powerful oxidant

This actually seems like a very likely candidate, also because it is a sulfate it would not react with H2SO4. Everything lines up with this so far, does anyone know any specific tests I could do to confirm this?

Edit: the scimad wiki states that HNO3 decomposes it to oxygen and nitrogen but I didnt notice any reaction with it even with heating, altho I wouldn't say that rules it out.

[Edited on 3-23-2023 by Gammatron]

Rainwater - 23-3-2023 at 15:12

https://www.peroxychem.com/media/22874/fmc_peroxygen_talk_20...

Wiki says it decomposes releasing O2 above 100c. You can measure the mass of a sample and heat it. Perform a splint test for O2, then measure the mass afterwards.


[Edited on 23-3-2023 by Rainwater]

ave369 - 23-3-2023 at 15:37

There is a way to determine if it's K2S2O8. Make a wet slush of it and MnO2, and heat to 80-90 C. Then test the resulting slush with pH test paper. If it shows acidic, then bingo! MnO2 catalyzes its decomposition into K2SO4, H2SO4 and O2.

[Edited on 23-3-2023 by ave369]

Gammatron - 23-3-2023 at 15:48

I dont see where it says that but it definitely releases a lot of O2 from burn tests and the white smoke condensed onto the upper end of the test tube. Seems like the melting temp is a good bit higher than 100C but maybe it just takes a lot to get it up to temp like water.

I think that has to be it, it matches almost every characteristic on the wiki and also looks the same as samples on google images for what its worth. I thank everyone for their input on this, it was a fun adventure! Now to figure out what I'm going to do with the kg's I have of it lol

ave369 - 23-3-2023 at 15:53

You can use it to make SO3/oleum. IIRC, you add concentrated sulfuric to it and heat as much as you can. That white smoke, guess what it is.... it is SO3.

[Edited on 23-3-2023 by ave369]

Rainwater - 23-3-2023 at 15:58

Just did some guess work, have not found anything to back this up
But K2S2O8 could react with hcl solution.
Thermodynamics backs this reaction
$$K_2S_2O_8 + 4HCl \rightarrow Cl_2 + 2H_2SO_4 + 2KCl$$
$$KCl + H_2SO_4 \rightarrow HCl + KHSO_4$$

Screenshot_20230323_194949_Microsoft 365 (Office).jpg - 218kB

Gammatron - 23-3-2023 at 16:07

ave369, I didn't see your comment about the MnO2 test before I made my last post, I will do some more tests on it in the morning. I've spent enough time on this today lol

fusso - 23-3-2023 at 20:39

Didn't you also heated it and found it dec into all gasses without residue? Do K2S2O8 do that too?

ave369 - 24-3-2023 at 00:11

Quote: Originally posted by Gammatron  
ave369, I didn't see your comment about the MnO2 test before I made my last post, I will do some more tests on it in the morning. I've spent enough time on this today lol


I've just run the test with my own sample that is definitely K2S2O8. The test was a success, the universal indicator shows pH 4, litmus paper turns red.
Quote: Originally posted by fusso  
Didn't you also heated it and found it dec into all gasses without residue? Do K2S2O8 do that too?


This is what confuses me. As far as I know, K2S2O8 does not do that, but (NH4)2S2O8 does, though solubiluty does not match.



[Edited on 24-3-2023 by ave369]

woelen - 24-3-2023 at 01:35

I don't think it is K2S2O8. I myself have this compound, and it is a strong, but sluggish oxidizer. It is capable of oxidizing silver(I) ions to silver(III), which is impressive, but on the other hand, when it is mixed with a solid fuel (e.g. sulfur, red phosphorus, sugar) and ignited, then it is a really lousy oxidizer. Just smouldering, no vigorous reaction at all.

If you have silver nitrate, a very good test for persulfate ion is the following:
- dissolve a little AgNO3 in 50% HNO3, or in a mix of NH4NO3 and 70% H2SO4
- Add a pinch of the material to be tested for peroxodisulfate to the solution and swirl
If you have peroxodisulfate in your sample, then you get a deep brown solution of silver(III) in the concentrated acid. If you dilute this solution with a lot of water, then the silver(III) hydrolyses and Ag2O3 is formed, which almost immediately decomposes to oxygen and black solid Ag2O2, which is a mixed silver(I)/silver(III) oxide.

Another good test for peroxodisulfate is this:
- Prepare a solution of sodium hydroxide or potassium hydroxide
- Prepare a solution of nickel sulfate, or nickel nitrate (not the chloride).
- Mix the two solutions: You get a pale green precipitate of hydrous Ni(OH)2.
- Prepare a solution of the solid to be tested for peroxodisulfate (heating may be necessary)
- Add the solution to the liquid with the solid hydrous Ni(OH)2 in it.
If the solution contains S2O8(2-) ions, then immediately you get a black precipitate of NiO2, which contains nickel in opxidation state +4. Again, this test is quite specific. Only hypochlorite is capale of a similar reaction, other oxidizers like chlorate, perchlorate, nitrate, do not oxidize the nickel (II).

woelen - 24-3-2023 at 01:46

Maybe your oxidizer is NH4ClO4? This is soluble in water, but not exceptionally well, although it dissolves in water more easily than KClO4. On heating, this decomposes, giving a yellow and fuming gas mix. The yellow color is caused by a mix of Cl2 and a little NO2, and the fuming is due to formation of HCl and water vapor. The decomposition reaction leads to a whole bunch of compounds (Cl2, HCl, H2O, NO2, NO, N2, O2).

I have some NH4ClO4, it is not a free flowing powder, but it also is not overly hygroscopic. It is my only acceptable source of perchlorate ions besides the very expensive HClO4, because KClO4 and NaClO4 are not available in the EU anymore. In mixes with fuels it can burn vigorously, but not as nice as with KClO4. For me, that is no issue, I don't do pyrotechnics, my only application is using it for making interesting metal complexes, with perchlorate as inert counterion.

Try adding a little of your solid oxidizer to solid NaOH, mix the solids, and add a drop of water. If you smell ammonia, then it most likely is NH4ClO4.

[Edited on 24-3-23 by woelen]

Gammatron - 24-3-2023 at 04:21

Unfortunately I don't have any nickel or silver compounds. I attempted the MnO2 test with a random amount of reagents, heated to just under a boil and there was no ph change. It also does not react with NaOH, or any other reagent I have tried and the only one it dissolves in is hot water. Other than being a really good oxidizer it seems chemically inert. I was also convinced that it was a potassium compound because of the purple tint of the flame, are there other cations that can make said color?

Nitrate

MadHatter - 24-3-2023 at 07:43

KNO3 has a sweet smell to it. If you dare give it a taste test this is what you
should expect: At 1st it will taste cool then turn bitter. It's the 1st test I give to
comps made by people that fail to detonate in salutes.

ave369 - 24-3-2023 at 08:16

Quote: Originally posted by Gammatron  
Unfortunately I don't have any nickel or silver compounds. I attempted the MnO2 test with a random amount of reagents, heated to just under a boil and there was no ph change.


For how many minutes did you keep the temperature?

Gammatron - 24-3-2023 at 10:04

When I burned it with sugar it smelled like KNO3 rocket candy but maybe that's just the sugar I smelled. It had almost no taste at all, probably due to its insolubility but what little there was tasted kinda like sodium bicarbonate.

I only heated for a few seconds in a test tube. Sadly I'm at work until the end of the day so I'll have to wait a while before I can try again.

ave369 - 24-3-2023 at 10:26

Keep it for two or three minutes to perform the test properly.

Nitrate

MadHatter - 24-3-2023 at 10:38

Probably not a nitrate then. The cool/bitter taste happens with every nitrate I've
ever tasted. As for solubility most nitrates, with some exceptions such as the
barium salt, are very soluble in hot water. For the potassium salt the solubility
range, in 100 ml water, runs from 13.3g at 0C to 246g at 100C. I used to obtain
potassium nitrate in the metathesis reaction of sodium nitrate and potassium
chloride both obtained at a garden shop. These days it's just cheaper to buy it
from a reliable supplier.

Sir_Gawain - 24-3-2023 at 11:59

Quote: Originally posted by Gammatron  
When I burned it with sugar it smelled like KNO3 rocket candy but maybe that's just the sugar I smelled. It had almost no taste at all, probably due to its insolubility but what little there was tasted kinda like sodium bicarbonate.

I only heated for a few seconds in a test tube. Sadly I'm at work until the end of the day so I'll have to wait a while before I can try again.

Tasting unknown compounds has not been standard procedure since the 1700's (for good reason!).

Rainwater - 24-3-2023 at 17:01

When stuck I make list and think out loud.please correct any mistakes ive made

Observations

  1. Slightly solubility in cold water
  2. Low but Increased in hot water
  3. Insoluble in ethonol
  4. Insoluble in acetone
  5. Decomposes upon heating into O2 ( needs clarification. Did it relight a splint?)
  6. Decomposes into white fumes which solid at room temp.
  7. Leaves no residues after thermal decomposition in air
  8. No visible reaction with 96% H2SO4 at stp
  9. Reaction at +180c when mixed with sulfuric acid.


Documented experments and observations

  1. Distillation with unknown + sulfuric acid producing distillate @ 180c-210c
    foaming upon heating
    yellow fumes observed
    Distillate has low ph, no smell
    Distillate does not react with copper metal
    Distillate reacts with aluminum metal

  2. combustion of unknown and sugar
  3. unknown + H2SO4 + Cu = No reaction
  4. energetic reaction: 5:3:2 - unknown:Al:S
    flame causing melting/decomposition
    Impact causes explosive decomposition

  5. Unknown + HNO3 = no reaction


The exact values would be a great asset to this problem

Melting point ?
Decomposition temp?
Density?
Any reaction between unknown and HCl?

Not sure what your capabilities are
Density will be the easiest to measure if you have a volumetric flask and scale
Weigh the dry flask.Throw in some powdered unknown. Weigh again.
Add water and mix to remove air bubbles. Top off to the fill line and weigh again.
Density = weight of the powder ÷ (size of the flask in ml - weight of the water added
In grams)

Can you tell us more about the distillate collected.
Density, boiling point.
you mentioned a ph 4. How much base to bring a known volume to netural?

ave369 - 24-3-2023 at 22:14

It was I who mentioned pH 4, in a wholly different context.

Alkoholvergiftung - 25-3-2023 at 02:24

Is it Guanidinnitrate? Solubility like KNO3, Burns without remanents. Bad Solutions would be over ph 7.

Gammatron - 25-3-2023 at 08:21

The distillate just turns out to be dilute H2SO4, boiling around 150C, it slowly attacks copper while hot but adding NaNO3 accelerates the attack and releases NO2. As I expected, the powder never reacted with the acid and instead that is what I was actually distilling over. I added a little water to help with the foaming so thats why it is dilute.

The powder is not affected by HCl, ~40% HF acid, 40% acetic acid or 10% NH4OH.

It will be difficult to measure density because when added to water, about half of it floats and the rest of it seems like it has air trapped in it... But now that I think of it, it does go right into ethanol without trapping any air so I could just measure it with that.

Edit: that didn't work at all. I thought I could adjust for the density difference of using alcohol instead of water but im also not the greatest at math, maybe someone else can figure it out.

Measured density of alcohol: 0.78g/ml
Flask size: 25ml
Flask weight: 49.94g
Powder added: 0.84g
Alochol to fill to 25ml: 19.24g


Guanidine nitrate is flammable and an explosive in itself according to wiki and this is not.


[Edited on 3-25-2023 by Gammatron]

Rainwater - 25-3-2023 at 09:04

barium thiosulfate doesnt react with any of those chemicals
This post
http://www.sciencemadness.org/talk/viewthread.php?tid=152049
List a paper which describes how to test for the thiosulphate ion using reagents of iron, copper and nitric acid
Quote:
Reaction of iron(III) with Thiasulfate
Prepare some Fe(NO3)3(aq)-a few tenths molar-and put some into each of three beakers. Prepare some Na2S203(aq)--a few tenths
molar; also prepare some Cu(N03)2(aq)-a few tenths molar-in a
smalI bottle with a medicine-dropper top. Add a small amount of
Na2S203(aq) to one of the beakers containing Fe3+(aq). The solution
will immediately turn a deep violet color. During the next few
minutes the violet color will gradually fade away and the color will
return to that characteristic of Fe3+(aq). Next add a small amount of
Na2S2O3(aq) to each of the remaining two beakers containing
Fe3+(aq). To one of the beakers add a few drops of Cu(N03)2(aq).
The violet color in the solution containing the Cu2+(aq) catalyst will
fade very rapidly, whereas the violet color in the uncatalyzed solution
will again take several minutes to fade away.

That did not coppy well from the pdf.
By replaceing the sodium thiosulphate(Na2S2O3 with the unknown, any result would be something.
Edit: fixed the bad copy

[Edited on 25-3-2023 by Rainwater]
0.84÷(0.78×25−19.24) = 3.2307692308 g=cm³
https://m.chemicalbook.com/ChemicalProductProperty_EN_CB8131...
Density of BaS2O3 3.45 g/cm³
Decomposition temp 220c
Melting point 220c
Sounds like a good candidate to me. Pricey stuff to

[Edited on 25-3-2023 by Rainwater]

Gammatron - 25-3-2023 at 09:21

I dont have time to do another test right now, going to meet up with Dr. Bob to get some lab supplies :cool:

However, it doesnt seem very likely it would be a barium compound because as far as I can tell they are somewhat uncommon and expensive. I think I got like 10lbs of this stuff for $30 or somewhere around that neighborhood. I bought it so long ago and just never even did anything with it until now. I wish I could contact the seller but I don't see the listing on ebay anymore. I'm starting to think this is going to require the help of a mass spectrometer lol

ave369 - 25-3-2023 at 10:40

What about the rerun of the MnO2 test with proper timing? The fact that the distillate was confirmed to be just sulfuric acid speaks in favor of the persulfate hypothesis.

Texium - 25-3-2023 at 10:55

Barium salts also generally give a quite strong lime green flame test, so it’s unlikely to be the case given that you didn’t observe that (and luckily for you too, considering you tasted it, given that barium is highly toxic…) They aren’t all that uncommon or expensive, though, and they are commonly used in pyrotechnics to impart a green flame color.

Gammatron - 25-3-2023 at 12:00

Oh yeah, I did try the MnO2 test again for several minutes and there was no change in ph.

well, the few times ive looked for them on eBay they were quite expensive but they were also high purity samples.

I gave some of the powder to Dr. Bob to run through his mass spectrometer at work. He wasn't sure if his machines would be calibrated correctly to detect such a compound but he said he could give it a try. I'm running out of chemicals to test this against and it just blows my mind that it wont react with anything except to burn with sugar and explode in flash powder and even if I never figure out what it is, it is at least useful for that lol

clearly_not_atara - 25-3-2023 at 12:22

More importantly, BaO2 reacts readily with sulfuric acid. We are narrowed down to a very short list of compounds based on oxidizer + does not react easily with sulfuric acid. And yellow fumes, which to me sounded like chlorine. And it is almost entirely volatile.

One test that seems tempting is to reduce it with formic acid and analyze the residue. If any. What a strange compound.

ave369 - 25-3-2023 at 13:19

Sounds like a pretty good idea to me. If it's an oxidizer, try various reducing agents at various pH.

Gammatron - 25-3-2023 at 14:47

Just going to post my current update, I haven't tried changing the ph with any of the solutions below but it has no reaction with any of them.

Oxalic acid, K dichromate, NaBr, KI, H2O2, NaF

Now I haven't been very scientific with any of these and have just dissolved a random amount in water and added a tiny spoonful of the powder, I also didn't let them sit for very long but if it was going to react then I would expect to see something immediately. But there hasn't been the slightest hint of a reaction with anything I've tried and im running out of new things lol

HOWEVER! I mixed a little with some ground up charcoal and it was sparking like it wanted to burn but went out. So I added a little more as well as a little sulfur and it went up in bright flame with tons of smoke, just like black powder! The smoke had almost a slight sting in the nose when inhaled as if there was some Cl or SO2 in it but it was too faint to make any guess. It could have just been from the sulfur I added. So I also tried burning soaked with alcohol and I was finally able to get some good pictures of the purple flame and also found that once most of the alcohol has burned away and the powder can heat up to decomposition it greatly accelerates the burning within that chunk of material until its gone, but it does not spread.

[Edited on 3-25-2023 by Gammatron]

Gammatron - 25-3-2023 at 14:54

Firstly, the colors are much more vivid in person but still clearly seen in the pictures. The picture where the flame is small and bright is what I meant when it accelerates the burning near the end. It also gets some yellow and orange color in it but I can't be sure if where thats from, possibly contamination or maybe it has some Na in it? It only appears when the powder starts getting hot.

edit: did some more flame tests, I tried dumping dry powder on the burning alcohol and the clumps would melt into little beads that burned with spectacular and powerful flames even though all the fuel was in the form of alcohol vapors external to the powder.

334193853_915932389455193_2557720559168829692_n.jpg - 288kB 334256447_3600098306875623_8970375468184705893_n.jpg - 347kB 334541896_508533427960767_8392115735395328251_n.jpg - 351kB 336942381_1014940123044539_2964150462406503954_n.jpg - 314kB

[Edited on 3-25-2023 by Gammatron]

Texium - 25-3-2023 at 16:05

That does look like a potassium flame.

Gammatron - 25-3-2023 at 16:27

A little more interesting finds, when mixed 50/50 with either sulfur or carbon then it will explode with a strong impact (both mixtures were about the same in power), I was unable to set it off by itself. Id say its about 10% as powerful as ETN by weight just based on the sound but obviously thats very subjective. The flash powder with Al and S is probably 2 or 3x more powerful than with the S or C mixtures.

Burning with the sulfur mixture looked like regular burning sulfur until it was hot enough to decomp the powder at which point the whole pile went up in a blinding blue flame. The carbon mixture lit a little more easily and burned with an equally bright white flame. (I added more Ox than the previous test I tried with carbon)

At this point with these results Im kinda glad I received this mysterious powder instead of KNO3 cause its a lot more fun to play with :D

[Edited on 3-26-2023 by Gammatron]

fusso - 26-3-2023 at 01:00

Could it be a mixture mostly of something volatile with a little K?

Herr Haber - 26-3-2023 at 11:44

The suspense is killing me :D

Among all the properties you described, it's the "water repellent" aspect that puzzles me the most.

Gammatron - 26-3-2023 at 19:59

For me its the unreactiveness to literally everything unless burned or hit with a hammer, it just doesn't make sense to me. I also suspect that the hydrophobicity might be hindering it from reacting to certain solutions but I figured I'd at least see some indication that somethings happening.

ave369 - 27-3-2023 at 00:08

You did mention is dissolves a little bit when water is heated to boiling temp. Why not try reactions with reducers at boiling temp?

ave369 - 29-3-2023 at 11:44

The mystery remains...

Rainwater - 25-4-2023 at 14:56

Any updates?