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garphield
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Chromate/Dichromate thermite
I have a decent amount of sodium dichromate and would like to make thermite using it, aluminium powder, and some calcium fluoride as flux. I do want
to get some decently sized pieces of chromium metal, but im not gonna reduce it to Cr2O3 because I want to know what it will be like and I cant find
any sources online, and I can get the dichromate for $6/lb so will be ok with a lower yield. Would a 3:1 ratio of thermite to flux be ok? I'm worried
that without flux it would just act like flash powder, and although its not gonna be confined that would mean I would get no yield and it would still
be kinda dangerous. Sodium dichromate is sorta deliquescent and forms hydrates, but since I am gonna dry it before doing anything with it and use the
thermite within a few hours of manufacture it should be fine. Im planning on doing this at a 50 gram scale because my Al powder is made from just
putting foil in a blender and I'm using KMnO4/ethylene glycol as my initiator so im worried that at a smaller scale it either won't burn well or the
metal will have more manganese than chromium in it.
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fdnjj6
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Just going to put this here:
https://www.fishersci.com/store/msds?partNumber=S2583&pr...
If you have a potential flash powder mix I seriously hope you know what you're doing. A 4 for the health rating, a confirmed and potent carcinogen,
and a very low LD50 is pretty fucking bad and not something I'd make potentially explosive mixtures out of. You'll need a proper testing area. Don't
do this anywhere where the unreacted materials could be exposed to others and do not let that stuff get into the soil.
I almost ordered some dichromates for my lab which has pretty advanced glassware and good safety in place, but decided against it due to the toxicity.
Please be responsible and safe.
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garphield
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Yeah it might not be the best idea to do this, if it exploded it would be extremely bad (on small scales and unconfined probably not enough to maim me
if im wearing face shield+safety glasses but still), and although the dermal LD50 is ~20 times larger than the oral one because it doesnt go through
skin very well that would change if i was breathing it in/had lots of open wounds. If I do it, I will bring a spray bottle with a sodium sulfite
solution to neutralize anything that gets out, I'm not just gonna dump large amounts of hexavalent chromium into the environment.
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JJay
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Potassium dichromate is better for thermite because it is not hygroscopic. As I recall, it's typically used for starting less energetic chromium
thermites for preparing elemental chromium.
You should have some idea of what you are doing with chromium salts ince they are potentially dangerous and bad for the environment, and they are
carcinogenic. If you just want fire and explosions, I would suggest different oxidizers.
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Whathappensif
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I would second not using chromium as your oxidizer in the thermite, because of its carcinogenicity. Use iron oxide or even copper oxide (less good for
the environment).
Beware though, CuO and Al thermites are explosive, the smaller the particle size the more so.
Also unless your thermite is well contained, you will be sputtering around unreacted reactants and products, which if they are toxic, will pose
problems later.
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Herr Haber
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The Gayest Person on Youtube videos on thermites would be a good start for this kind of project.
I wouldnt have bet a penny on many of his experiments. Sincerely amazing.
The spirit of adventure was upon me. Having nitric acid and copper, I had only to learn what the words 'act upon' meant. - Ira Remsen
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Tsjerk
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Quote: Originally posted by fdnjj6  |
I almost ordered some dichromates for my lab which has pretty advanced glassware and good safety in place, but decided against it due to the toxicity.
Please be responsible and safe. |
Really? You didn't order it because it is toxic? I would understand you being careful not to ingest any because you know it is toxic... but not buying
it is another extreme.
During the first practical course of biology students at my old university they are told to weigh potassium dichromate, some random amount, and make a
solution out of it. They are told it is toxic and to be careful not to spill. We all know they will spill all over, and show them by wiping the place
down with a wet piece of white paper. They are all shocked when we show them the orange paper and tell them it is carcinogenic... Maybe they will pay
a little more attention next time we tell them something is toxic.
| Quote: Originally posted by Whathappensif | | I would second not using chromium as your oxidizer in the thermite, because of its carcinogenicity. Use iron oxide or even copper oxide (less good for
the environment). |
That would beat the goal of producing chromium.... not?
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garphield
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yeah im gonna be doing it on a large concrete thing and will bring a bottle of sodium sulfite to reduce any dust that comes out to Cr(III), im not
gonna be eating it and will be wearing ppe. main thing im worried about is if it will act like flash powder and explode when im handling it, i will be
mixing it on site by pouring both reagents into one plastic bag before rolling it around inside the bag so no sparks are generated to make sure
there's no way it accidentally ignites but if there's a good chance of it exploding when lit i wont be doing it anyways
Cr(iii) isn't that bad for the environment, copper is def worse than that.
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Syn the Sizer
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I agree, not getting something as a chemist because it is toxic will limit your projects. Just be careful with it, I was pissed off in O-Chem course
when our instructor took the section of a lab out using chromic acid because of its risks. We should learn how to safely use it before entering the
field where employers expect us to know how to use stuff safely.
I am planning on getting 500g of dichromate because it is a strong oxidizer, almost as strong as KMn04 but cheaper and easier to find. You can use it
to turn primary alcohols into aldehydes or further into carboxilic acids, and secondary alcohols into ketones, among many other things.
I am also getting N,N-dimethylaniline to synthesize a few of the methyl dyes, also very toxic but I will be safe in using it.
We walk down the streets breathing auto exhaust, smoke from smokers, all sorts of toxins daily, as long as we are safe using reagents, they are the
least of our worries.
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garphield
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It would still be nice to know if anyone has done this before, or failing that if you think it will burn at a reasonably slow rate or just act like
flash powder.
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Whathappensif
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Sorry, I didn't see the bit about him wanting chromium.
Personally I don't mind so much working with with alkylating agents, oleum, fuming nitric acid....but get nervous around lead, mercury or chromium
compounds.
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Syn the Sizer
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Mercury is the one that I am nervous about.
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Syn the Sizer
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Sorry, we all kind of derailed your thread. My thoughts are if you are unsure and not getting any definitive answers here (I personally have no
experience), maybe try it on a super small scale and see how it turns out.
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Metacelsus
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If you just want chromium metal, you should reduce the dichromate to Cr2O3 first. The reaction will be safer, and also higher yielding because less
aluminum will be needed.
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garphield
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lmao i was making aluminium powder with a coffee grinder and the plastic part with the blades just broke so im not gonna be able to make any until the
replacement parts arrive. it was really old tho so that might have been the reason it broke, but i will put in less stuff at once next time so theres
no chance of it jamming. good thing the replacement part is really cheap lol
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JJay
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Offhand, I see Schlessinger's Inorganic Laboratory Preparations in the Sciencemadness library contains this preparation:
I see another prep in Walton's Inorganic Preparations that doesn't use barium... it uses chromium trioxide, saying that a small amount of chromic
oxide thermite is insufficient to melt alumina. There is at least one other chromium prep in the SM library that I remember seeing.
If you are going to use sodium dichromate, it will have to be thoroughly dried and protected from air, or the mixture will be hard to ignite and will
tend to blow apart prematurely before everything is reacted if it is ignited. Sodium dichromate is usually sold as a dihidrate, and it is
deliquescent.
You should not store chromium-aluminum thermites. The should be prepared immediately before use, and while I don't think they will spontaneously
combust, I'm not so sure about that with sodium dichromate. Also, they should be treated gently (don't mix in a mortar or blender, and don't hit with
a hammer or anything like that).
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garphield
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| Quote: Originally posted by JJay |
...if you are going to use sodium dichromate, it will have to be thoroughly dried and protected from air, or the mixture will be hard to ignite and
will tend to blow apart prematurely before everything is reacted if it is ignited. Sodium dichromate is usually sold as a dihidrate, and it is
deliquescent.
You should not store chromium-aluminum thermites. The should be prepared immediately before use, and while I don't think they will spontaneously
combust, I'm not so sure about that with sodium dichromate. Also, they should be treated gently (don't mix in a mortar or blender, and don't hit with
a hammer or anything like that). |
yeah when I do it I will dry out the dichromate, grind it with the flux in a mortar and pestle, then immediately put it into a ziploc bag. then at the
site i will use it at right before use i will get a premeasured amount of aluminium powder into the bag, close it, and gently shake/rotate the bag to
mix the two powders. water especially could be a concern as if it gets wet the dissolved dichromate might react with the aluminium powder vigorously
enough to start the reaction right there.
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fdnjj6
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Yes, I refuse to bring anything into my home lab that has a health rating of 4 on the NFPA diamond. Nitric acid is the only exception only because I
know it inside and out and have lots of experience with it and it's decomposition products. It would've been 1/4 pound of dichromates. I don't have
proper disposal for chromium products. The reaction should work with KMnO4 anyway, but yea I refuse to do high risk experiments in my home lab.
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Nitrosio
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https://www.researchgate.net/publication/236556739_Theoretic...
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JJay
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It doesn't seem to contain data for any phosphates, but that looks like a good reference.
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Tsjerk
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| Quote: Originally posted by fdnjj6 | | Yes, I refuse to bring anything into my home lab that has a health rating of 4 on the NFPA diamond. Nitric acid is the only exception only because I
know it inside and out and have lots of experience with it and it's decomposition products. It would've been 1/4 pound of dichromates. I don't have
proper disposal for chromium products. The reaction should work with KMnO4 anyway, but yea I refuse to do high risk experiments in my home lab.
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That is perfectly fine, but you don't have to tell everyone every time you see someone talking about something toxic. Unless someone wants to make
dimethyl mercury or clearly doesn't know what they are dealing with, it is fine to assume they will not eat or inhale the stuff.
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symboom
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This might be a little bit of topic but it is a dichomate kinda thermite
caesium dichromate can be reacted with zirconium to produce pure caesium metal
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Tsjerk
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Do you have a source for that?
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symboom
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Well Wikipedia states it due to ceasium and it low boiling point I know it seems like that reaction should not be possible but if is driven forward
and zicronium has a high boiling point so that helps. This is similar in the process to obtain potassium metal from a reaction of lithium and
potassium chloride also works with ceasium chloride
https://en.m.wikipedia.org/wiki/Caesium
Cs2Cr2O7 + 2 Zr → 2 Cs + 2 ZrO2+ Cr2O3
[Edited on 5-8-2020 by symboom]
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fdnjj6
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| Quote: Originally posted by Tsjerk | | Quote: Originally posted by fdnjj6 | | Yes, I refuse to bring anything into my home lab that has a health rating of 4 on the NFPA diamond. Nitric acid is the only exception only because I
know it inside and out and have lots of experience with it and it's decomposition products. It would've been 1/4 pound of dichromates. I don't have
proper disposal for chromium products. The reaction should work with KMnO4 anyway, but yea I refuse to do high risk experiments in my home lab.
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That is perfectly fine, but you don't have to tell everyone every time you see someone talking about something toxic. Unless someone wants to make
dimethyl mercury or clearly doesn't know what they are dealing with, it is fine to assume they will not eat or inhale the stuff.
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I didn't mention it everytime. I mention it here because um, I'm not sure if you read his post, but he is making a potentially explosive mix. So,
while you won't see it under my fdnjj6 profile, I used to be heavily into energetics and I can tell you that when things go boom unconfined, it tends
to send shit everywhere, making it very easy to inhale and expose yourself to it and expose the entire area around you to it. While I know this place
isn't super good on safety, this was something that definitely needed a good word of caution. And to be blatant, there are a LOT of people, especially
kids, on here who do not know what they are doing. So it's fair to assume so.
He also commented on me saying that I just refused to order the dichromate so I figured I'd elaborate.
I help people out all the time with toxic stuff. Mainly on Reddit, however I felt like dropping the MSDS and a good warning was very appropriate. Not
sure why you felt the need to say what you said, it was unnecessary.
[Edited on 5-8-2020 by fdnjj6]
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