My teacher did this cheesy little experiment with ethanol, sulfuric acid, and potassium permanganate. She added the ethanol to the sulfuric acid which
floated on top of the acid if I remember correctly. Then she added small amounts of potassium permanganate. Once it sank threw the ethanol, and
contacted the sulfuric acid it reacted with the acid forming manganese heptoxide, which in turn reacted with the ethanol in the form of combustion. It
made like sparkly lights for like an hour. Anyway I have a few questions that I
never seemed to have asked her because she was a dumb "B".
1.) When you first add the ethanol to the H2SO4 does it form some diethyl ether?
2.) Would any organic solvent work for this trick so long as it doesn't react too severely with H2SO4?
3) What is the formula for manganese heptoxide, and how would you right a balanced net equation for the reaction between KMnO4 and H2SO4?
[Edited on 13-12-2004 by tom haggen]The_Davster - 12-12-2004 at 20:56
1.) Concentrated sulfuric acid mixed with ethanol will likely form some diethyl ether, but not enough to be noticeable.
2.) Ethanol doesn't sound safe for this reaction to me so I have no clue what criteria would be necessary to determine if it was safe considering
it doesn't sound safe to begin with. For example, manganese heptoxide can detonate very spontaneously with many organics, I would not risk
trying to change something in a reaction that might risk detonation with the swapping of a reagent.chemoleo - 12-12-2004 at 21:06
I think this is a wellknown chemistry demo experiment, which has the purpose of showing sparks in liquid. If it was that unsafe I guess they
wouldn't be doing it as a demo experiment ... teachers these days being overly concerned with H&S, but completely forgetting that the pupils
get bored with chemistry quickly
I can find the official protocol over christmas if desired.garage chemist - 13-12-2004 at 12:19
A very important thing in this demonstration is that the H2SO4 is NOT mixed with the ethanol. The Ethanol must float on top of the
H2SO4, the less they mix, the better the experiment works.tom haggen - 13-12-2004 at 13:06
Even if the ethanol mixes with the sulfuric acid, wont they separate if you let them sit for a while. Bromic, the reason this isn't that
dangerous is because the manganese heptoxide forms in small amounts and reacts with the ethanol the instant if forms. It gives an effect of all these
mini type explosions underwater.
[Edited on 13-12-2004 by tom haggen]neutrino - 13-12-2004 at 14:14
I’d imagine that you’d be left with a layer of ether and one of acid with some water in it. You might get a little ethanol back, but this is
doubtful. I don’t see why the reaction wouldn’t work with ether, though.tom haggen - 16-12-2004 at 12:22
Just how dangerous is Mn2O7? If I wanted to make like 5 grams of this stuff just for experimentation, would I be putting myself in danger. Can Mn2O7
be stored in any other containers besides those made of glass? I.E. would you be able to put this chemical in HDPE or would it oxidize the polymer?neutrino - 16-12-2004 at 14:20
All I’ve ever heard of anyone making is very small amounts. You should be able to store it in anything noncombustible. Metals would probably
corrode and plastics (except maybe PTFE) would be destroyed. By the way, manganese heptoxide tends to decompose by itself at room temperature. Just
thought you should know.vulture - 16-12-2004 at 15:21
You'd need to store it below -10C. Otherwise it will slowly decompose yielding ozone and oxygen. This can be troublesome in closed vessels as
high ozone concentrations are prone to detonation.tom haggen - 16-12-2004 at 15:57
-10C is pretty cold. Colder than I have capabilties of maintaining. I guess I will just have to make it as I need it. I still am in the dark on
whether or not it will react with HDPE though. I was just thinking of filling small test tubes with Mn2O7 and placing them in a hydrocarbon, and
tossing them for little fire ball type explosions. The only problem is most of the test tubes I have only have lids made out of HDPE. I guess it wont
matter if I use it when I make it
[Edited on 17-12-2004 by tom haggen]BromicAcid - 16-12-2004 at 16:04
I believe Axt has a video on his site of manganese heptoxide reacting with xylene, I'd hardly call it a "small fireball type
explosion". Personally I won't even make the stuff, I've heard sunlight can cause it to detonate as can shock. Plus, as Vulture said,
it decomposes at ambient temperature forming ozone, not good...neutrino - 16-12-2004 at 17:05
Tom: if you have a blowtorch, you can try ampouling it, although it does require a certain degree of skill.tom haggen - 16-12-2004 at 18:28
I'm thinking i'm going to make about 5 grams and use a pipet to drip small amounts on to a puddle of organic solvent. To get a feel for the
chemical. I'm definitely going to use it as I make it though just because I'm paranoid about storing stuff that is dangerous.
I've got a blow torch lying around but I have no idea what ampouling is.
I've also seen axt's video, but I was thinking much smaller amounts, like I said I have to get a hands on feel for how this stuff reacts.
[Edited on 17-12-2004 by tom haggen]neutrino - 16-12-2004 at 18:46
Ampouling is sealing something in an ampoule. First, you take a glass tube and seal one end shut be pulling on the end. You can then heat this to get
a rounded end (like a test tube). Next, you draw the other end out to a thin tube through which something can be added. Add the material and quickly
seal the tube. It’s simple once you get some experience.tom haggen - 16-12-2004 at 20:58
So thats how they seal all those gases like fluorine, NO2, etc. in those glass bulbs in my text bookAxt - 16-12-2004 at 21:03
Before you go playing with your blowtorch, you do realise that Mn2O7 will detonate when heated, dont you.
I have a test tube full of the stuff, from a failed naphthalene diozonide attempt. Sits up the back in a large 1/4" steel vessel, too scared to
go near it
[Edited on 17-12-2004 by Axt]tom haggen - 17-12-2004 at 01:09
I still have my hands now, and if I were going to lose them they would be gone by now.neutrino - 17-12-2004 at 03:27
That's the point of having a narrow neck the pipette can fit through: it doesn't get any liquid on it and can be sealed quickly. If
you're worried about this, you might want to leave a lot of extra space in the ampoule.Saerynide - 17-12-2004 at 04:26
What if later, when you wanna open the ampoule to get the stuff out, and when you crack it, the shock causes it to detonate? You'll be impaled
with glass shards cyclonite4 - 17-12-2004 at 04:49
Thats only if you can blowtorch the tube shut without the heat setting it off.
Mn2O7 doenst evaporate easily does it?
Whats wrong with storing it in a glass-stoppered glass bottle, and if it doesnt react with PTFE, use teflon thread sealing tape (from a hardware
store) to make an airtight seal around the stopper?
Then again, why store it at all?Saerynide - 17-12-2004 at 05:09
It does.
"The oil is green by reflected light and reddish-purple by transmitted light. It's fairly volatile, also, and hydrates to a purple fog if
you're brave enough (or stupid enough) to breathe over a container of the stuff. "cyclonite4 - 17-12-2004 at 05:17
Damn, why are all the cool compounds volatile , jk!
Well, someone mentioned before that it probably doesnt react with PTFE, so a glass bottle + glass stopper with PTFE tape to form an airtight plug, is
a good option for storage (although storage isn't a good option).The_Davster - 17-12-2004 at 06:15
A couple of months ago I made a small ammount of manganese heptoxide in a 50mL beaker. I got the pure green Mn2O7 liquid(very little of it) floating
on top of the sulfuric acid and a very dark green solution of Mn2O7 in sulfuric acid.
The day it was prepared: When the pure liquid was dripped onto a kleenex instant flash and the kleenex caught fire. The solution of Mn2O7 in sulfuric
took abot 10s to catch the kleenex on fire.
The next day: Pure liquid took 5-10s to catch the kleenex on fire. Less "fwump" upon ignition than the previous day. The solution of Mn2O7
took almost a min to catch the kleenex VERY weak "fwump"
2 weeks later: The pure liquid has dissapeared. The contents of the beaker were brown and gooey. Nothing in the beaker was able to catch kleenex on
fire.
[Edited on 17-12-2004 by rogue chemist]neutrino - 17-12-2004 at 10:24
The tape used for plumbing is not always impervious to vapors. IME, the stuff is either impure or permeable to gases and vapors. If you want to make
some chemically resistant vials, get some decent sheet. As always,I recommend trying ebay.tom haggen - 17-12-2004 at 15:16
Do you guys think that isopropyl alcohol will work in that demo in place of ethanol?cyclonite4 - 18-12-2004 at 05:22
@tom haggen: Probably. They are both alcohols, but don't take my word for it, try it out.
@neutrino: Also from my local hardware store, you can get "Thread Sealing Compound, which is a paste composed mostly of PTFE (teflon). Don't
worry, it wont dry out. It's usual use is similar to the tape, just put it all over the threads, and tighten. This may work, the only problem
being if you use too mush, some may fall into the Mn2O7, which i wouldnt expect to be very convenient.
Manganic Acid
Endo - 6-1-2006 at 07:25
While reading through the HF thread I saw the +7 oxidation experement with permanganate.
It got me to thinking about a demo I have heard of where manganic acid is produced under a layer of alchol. It supposedly is produced at a constant
slow rate and it oxidizes the alchol and makes for a pretty light show... I also remember that the setup was not to be agitated or disturbed because
it could go out of control and start a fire/explode.
Of course as a high school student at the time the details were kept from my devious ears. Now as an irresposible adult I would like to figure out
what was used in this demo, but I have had very little sucess in my very sporadic research attempts.
Thanks
Endo12AX7 - 6-1-2006 at 07:45
Woelen also has an example of that experiment. Permanganic anhydride, BTW (Mn2O7).
There actually already is a thread about that particular demonstration. It sounds fairly interesting though I have never seen it myself.
Permanganic anhydride? Yes, that is Mn<sub>2</sub>O<sub>7</sub> but Endo specifically stated the acid, a solution of
HMnO<sub>4</sub> not the anhydride. The solution of the acid is less dangerous, though easily dehydrated to the anhydride. Never the
less I think the procedure does indeed involve manganese heptoxide considering the way the steps are carried out.
[Edited on 1/6/2006 by BromicAcid]Endo - 10-1-2006 at 19:51
Sorry about that... It took me some time to figure out where the post had gone...
It looks like I had been mis-informed all those years ago about what the actual substance formed was...
This kinda hindered my search and led me to post something that had already been gone over in depth.
By the way...
It seems like around 90% of the stuff I think of posting has already been posted about... Kinda refereshing!quantumcorespacealchemyst - 14-1-2015 at 05:13
The tape used for plumbing is not always impervious to vapors. IME, the stuff is either impure or permeable to gases and vapors. If you want to make
some chemically resistant vials, get some decent sheet. As always,I recommend trying ebay.
i have read that all the PTFE tapes but the green (for potable water) have an oil on them. if these are non fluoropolymer/PTFE they may be
flammable/able to react with the Mn2O7.
although they may be able to be leached out and washed by solvent. there is PTFE sheets sold online that are thin enought to make buffers between
stoppers
also wikipedia says "Mn2O7 can react further with sulfuric acid to give the remarkable cation MnO3+, which is isoelectronic with CrO3" which sounds
interesting to me
[Edited on 14-1-2015 by quantumcorespacealchemyst]
. Anyway I have a few questions that I
never seemed to have asked her because she was a dumb "B". 
