Sciencemadness Discussion Board - KNO3 + candle wax => NO reaction ???

KNO3 + candle wax => NO reaction ???

metalresearcher - 21-1-2012 at 13:57

I was just curious. Mixing KNO3 with paraffin candle wax from crushed candles and lighting it.
NOTHING happened except the wax started to burn slowly just as if it were heated without KNO3.

Why ?

Paraffin is a mixture of alkanes ranging from C10 to C20 which is flammable. Why does KNO3 not help ? Other combustible organics (sugar) burn very fast.

[Edited on 2012-1-21 by metalresearcher]

Neil - 21-1-2012 at 14:15

The candle wax melts and cools the KNO3. Sugar has a higher melting point point and chars rather then simply melting

Sugar mixed with wax is used as a smoke formula.

AndersHoveland - 21-1-2012 at 14:20

There would be a self-sustaining reaction if a large quantity of wax mixed with KNO3, in an adequate ratio, was placed inside an intense fire. But wax has difficulty burning, because as it is heated, it melts into a liquid layer which has a relatively low surface area to combust with any oxygen gas. This is why wax is very difficult to burn without a wick. Also, KNO3 is not really an excellent pyrotechnic oxidizer. In my experience, prills of KNO3 added to burning organic material first seem to take time to get hot and melt before they release oxygen. The prills should be crushed into a fine powder for maximum surface area.

Mr. Wizard - 21-1-2012 at 14:27

I agree with Neil.
My best guess is the liquid wax even when melted, keeps the temperature of the KNO3 below the decomposition point, just as the cotton wick of a candle is preserved in a candle flame. When the sugar chars after losing the water in it's make-up, it then allows the heat of the fire to raise it and the nitrate to a point where the reaction proceeds.

Neil - 21-1-2012 at 14:35

Quote: Originally posted by AndersHoveland

There would be a self-sustaining reaction if a large quantity of wax mixed with KNO3, in an adequate ratio, was placed inside an intense fire. But wax has difficulty burning, because as it is heated, it melts into a liquid layer which has a relatively low surface area to combust with any oxygen gas. This is why wax is very difficult to burn without a wick. Also, KNO3 is not really an excellent pyrotechnic oxidizer. In my experience, prills of KNO3 added to burning organic material first seem to take time to get hot and melt before they release oxygen. The prills should be crushed into a fine powder for maximum surface area.

Surface area, for the wax, is not the issue, the low vapor pressure and high boiling point of wax are what limit ones ability to set it on fire. *liquids don't burn* Boiling wax burns and behaves like boiling kerosene.

Bot0nist - 21-1-2012 at 15:31

A bit off topic, but if your looking for a mold-able pyrogen try KNO3 with peanut butter. I know from experience this works really well with KClO3 . Even used it in some small paper rockets. When you get the consistency right it is no longer sticky and really easy to work with.

[Edited on 21-1-2012 by Bot0nist]

AndersHoveland - 21-1-2012 at 17:24

Mmmm, sounds tasty...

http://2.bp.blogspot.com/-79uoAvAip7E/Tr74bwS05bI/AAAAAAAABl...

Adas - 22-1-2012 at 00:36

The wax also increases its volume when heated and boiling temp. of wax is not high enough to release O2 from KNO3 - try adding excess KNO3 (in powder form of course).

As Anders stated before, KNO3 on burning organic material first melts and THEN starts releasing oxygen. And from what I have seen, after it starts releasing the O2, the temperature rises very quickly and the flame on contact surfaces becomes light blue/white. After all O2 is released, the white molten "drop" of KNO3, KNO2 and whatever turns into a black solid in fraction of a second and sticks on the organic material. It is probably K2O. Sometimes you can even smell KCN! That's probably the reaction between NOx released, carbon and K2O.

Endimion17 - 22-1-2012 at 05:24

I bet if there was a barrel of finely ground potassium nitrate impregnated with wax in the correct amount, it would start burning furiously after a while, when the heat builds up in the layers beneath.
Scale of the reaction changes things a lot.

Bot0nist - 22-1-2012 at 07:44

Quote: Originally posted by Endimion17

Scale of the reaction changes things a lot.

This is so true. It has been accidentally demonstrated many times, often to the demonstrators peril. I have heard many stories of someone trying to make a very large smoke-bomb/volcano and greatly scaling up a sugar+oxidizer or even a zinc/iron+sulfur mix, and instead creating a cascading, exothermic catastrophe.

AirCowPeaCock - 22-1-2012 at 12:21

The wax will definitely melt before the KNO3 breaks down. KNO3 breaks down at something like 700C, and have you ever touched melted wax? Its not even 100C.

Bot0nist - 22-1-2012 at 12:30

No, KNO3 starts to boil and decompose at just over 380C - 400C, IIRC. I have often boiled it in test tubes and dropped bits of smoldering carbon in it as a demo.

http://en.wikipedia.org/wiki/Kno3

Watch.
http://www.youtube.com/watch?v=Y3Jxhbg0k4c

Oh, and melted wax is one thing. Try boiling wax that's surface has exceeded its auto-ignition temperature and is aflame. This, intimately mixed with decomposing KNO3 in med to large scale. Could get scary? I would love to conduct some tests. Cheap materials.

[Edited on 22-1-2012 by Bot0nist]

AirCowPeaCock - 22-1-2012 at 12:37

That low 'ey. Well that would explain why I picked it over KClO4 for the same thing with the test tube. Last time I did a frosted mini-wheat. My brother was perplexed at the ammount of energy the box said one had, I thought it was totally reasonable, and then showed him just how much there was (;

Pulverulescent - 22-1-2012 at 13:04

Quote:

I was just curious. Mixing KNO3 with paraffin candle wax from crushed candles and lighting it.
NOTHING happened except the wax started to burn slowly just as if it were heated without KNO3.

Well try it again ─ this time with an intimate mixture of finely ground oxidiser and sulphur 85/15 and see how that goes!

P

Bot0nist - 23-1-2012 at 09:03

Quote: Originally posted by AirCowPeaCock

That low 'ey. Well that would explain why I picked it over KClO4 for the same thing with the test tube. Last time I did a frosted mini-wheat. My brother was perplexed at the ammount of energy the box said one had, I thought it was totally reasonable, and then showed him just how much there was (;

If you have previously boiled potassium nitrate in a test tube then I would have assumed you knew its decomposition point lay well below 700C, as even good boro tubes start to fail at over 500C.

Mr. Wizard - 23-1-2012 at 09:54

Quote: Originally posted by Pulverulescent

Quote:

I was just curious. Mixing KNO3 with paraffin candle wax from crushed candles and lighting it.
NOTHING happened except the wax started to burn slowly just as if it were heated without KNO3.

Well try it again ─ this time with an intimate mixture of finely ground oxidiser and sulphur 85/15 and see how that goes!

P

Many people don't realize the calorie unit used in food is actually a kilogram calorie or 1000 of the gram calories we speak of. It leads to confused thinking and false ideas such as eating frozen food will significantly lower it's caloric intake.

Neil - 23-1-2012 at 11:05

Quote: Originally posted by Pulverulescent

Quote:

I was just curious. Mixing KNO3 with paraffin candle wax from crushed candles and lighting it.
NOTHING happened except the wax started to burn slowly just as if it were heated without KNO3.

Well try it again ─ this time with an intimate mixture of finely ground oxidiser and sulphur 85/15 and see how that goes!

P

Better hope it has a pretty good flame to flare off the hydrogen sulfide you'd get by boiling wax and sulphur.

Fusionfire - 23-1-2012 at 11:10

Hmm, this got me thinking...what about KNO3 with coal dust?

Adas - 23-1-2012 at 11:20

Quote: Originally posted by Neil

Better hope it has a pretty good flame to flare off the hydrogen sulfide you'd get by boiling wax and sulphur.

How the hell....?

Quote: Originally posted by Fusionfire

Hmm, this got me thinking...what about KNO3 with coal dust?

Would behave pretty much as BP

Neil - 23-1-2012 at 11:22

too hard to get really good mixin with coal dust. Charcoal on the other hand...

Adas - 23-1-2012 at 11:43

But, Neil, can you explain how paraffin can react with sulfur?? I thought hydrocarbons are pretty inert..

Neil - 23-1-2012 at 12:46

Adas, I started answering the above post before yours was posted and thus did not see yours.

Try;

http://www.sciencemadness.org/talk/viewthread.php?action=pri...

Poppy - 23-1-2012 at 12:47

How did you mixed the wax with KNO3 ? Poor mixtures leads to little or simple no efficaccy of the oxydizer. Try melting wax with white gasoline, then pouring this into very finely powdered KNO3. Take care then when igniting it cause it may explode in half ?

AirCowPeaCock - 23-1-2012 at 15:07

It's not going to explode. Maybe if one used potassium chlorate, but not with the nitrate.

aaparatuss - 23-1-2012 at 19:51

now in google E book Chemical & metallurgical engineering, Volume 22 page 806
under wax bleaching they describe passing ozone threw molten wax

then of course at nasa
http://science.nasa.gov/science-news/science-at-nasa/2003/28...

they are trying to use wax mixed with the correct oxygen ratio as a nice rocket....

so ozone impregnated wax seems at first neat, but not stoichiometric

the chlorate idea is interesting i must admit

Bot0nist - 23-1-2012 at 20:26

I once saw a mythbuster's show where they made a "rocket" with a steel pipe filled with solid paraffin and cored. N2O was injected through the core and ignited at the nozzle by pyrogen (cellulose nitrate I think). It failed to achieve lift but made a lot of noise. Once again, Jamie and Adam where embarrassingly hokey, as per usual.

NOTE: I am thinking about trying to do some tests with wax and KNO3. I was thinking in an old 50ml beaker as a "barrel", as Endimion17 put it. I will make a composition of pure paraffin candle wax and finely divided potassium nitrate with a small percentage of sulfur to hopefully lower ignition temperatures. (I will burn under proper ventilation to avoid the slight H2S risk) I will try my best to make the composition stoichiometrically optimal. For mixing I was thinking of slightly dissolving the paraffin in kerosene and making a slurry with the oxidizer and sulfur. I would then try and evaporate off the volatile kerosene while thoroughly mixing. But in the end I may have to melt the mix with a boiling water bath and pour into the beaker. For ignition, I was thinking a candle wick would be perfect. I'll try and have something up by this weekend. I have everything on hand. Just gotta get to it.

Does anyone have any suggestions for my little planned experiment. I'm still in the contemplative/brainstorming phase.

[Edited on 24-1-2012 by Bot0nist]

Neil - 24-1-2012 at 05:09

You really need something for the nitrate to bite, something that can serve as a fuel and withstand being heated to the point where the nitrate starts to oxidize, perhaps adding some starch or just a bit of sugar?

Bot0nist - 24-1-2012 at 07:05

Ok, I'll try one with powdered sugar proportion, and one with lamp black. I thought the sulfur may help in this aspect.

Fusionfire - 24-1-2012 at 09:07

Quote: Originally posted by Adas

Would behave pretty much as BP

What was I thinking, *facepalm*. Of course, but less sensitive without the sulphur.

Sorry I am learning a foreign language ATM and my chemistry thinking cap is dusty

Fusionfire - 24-1-2012 at 09:32

Quote: Originally posted by Neil

You really need something for the nitrate to bite, something that can serve as a fuel and withstand being heated to the point where the nitrate starts to oxidize, perhaps adding some starch or just a bit of sugar?

What about magnesium powder?

Let the KNO3 + wax be the bulk of the redox reaction, but the Mg powder would serve as hot spot nucleation sites.

Sadly I don't think the more common/cheaper aluminum powder would work, unless it is prepared in an anaerobic ball mill, because of the very strong oxide layer.

Bot0nist - 24-1-2012 at 19:44

3 small scale attempts tonight. All fail. Working in sub gram scale though. Will try variations on sugar, sulfur, carbon, and maybe pyro-Al (German blackhead, 5 micron) if it comes to it, in a larger scale this week.. I just feel that wax as the primary fuel wont work. It's too hard to ignite, even when melted together with a lot of or sulfur or carbon. This wiki excerpt doesn't give me much hope. Maybe when I make the 50-100 ml in a beaker and try to burn it as a normal candle I will get a reaction after some time, if things heat up enough. I'm having doubts though.

Quote:

Paraffin wax (C25H52) is an excellent material to store heat, having a specific heat capacity of 2.14–2.9 J g−1 K−1 (joule per gram kelvin) and a heat of fusion of 200–220 J g−1.[10] This property is exploited in modified drywall for home building material: it is infused in the drywall during manufacture so that, when installed, it melts during the day, absorbing heat, and solidifies again at night, releasing the heat.[11] Paraffin wax phase change cooling coupled with retractable radiators was used to cool the electronics of the Lunar Rover.[12]
~wiki

Neil - 25-1-2012 at 08:38

Quote: Originally posted by Fusionfire

Quote: Originally posted by Neil

The oxide layer gets fluxed by Potassium oxide and is actually broken as the Al heats and expands in the flame front.

Fusionfire - 25-1-2012 at 08:51

Quote: Originally posted by Neil

Quote: Originally posted by Fusionfire

Quote: Originally posted by Neil

The oxide layer gets fluxed by Potassium oxide and is actually broken as the Al heats and expands in the flame front.

Yeah but the problem is initiating the reaction in the first place.