Making Potassium Dichromate

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Күн бұрын

In this video I synthesize the highly toxic and carcinogenic oxidizer potassium dichromate from elemental chromium metal. I also quickly show how to make chromic acid and potassium chromate from the dichromate salt.
Sorry my cadence is even more monotone than usual, I'm getting over an illness.
WARNING: This chemical is EXTREMELY toxic and has been proven to cause lung cancer with a 20-year latent delay. It is also lethal through dust inhalation. See disclaimer at the end of the video.
This video was done on request of The Next Guy
#chemistry #science #hydrogen #gas #elements #fire #chemical #industury #color #light #poison #orange

Пікірлер: 60

@experimental_chemistry 11 ай бұрын

This method is so much more comfortable than heating Cr2O3 with KNO3 and KOH in a crucible with a furnace. Well thoughtout procedure, good presentation and explanation - this video will again be a success I guess. Just one thing: as long as no sulfuric acid was added there will be mostly chromate instead of dichromate. Very conc. solutions of chromate also appear slightly orange. And yes: none of your warnings is exaggerated. It's necessary to do this synthesis outside or in a fumehood, always wearing gloves and a particle filter mask (the aerosoles are invisible but as so often the most dangerous aspect!), having a hugh amount of metabisufite solution at hand. Nevertheless: as long dichromate is commercially available I would always prefer to buy it in order to avoid the risks of making it. Fortunately my already 35 years old stock will still be enough for many years because I use dichromate for analytical purposes only, where very small amounts are sufficient. There's no need to use it for making aldehydes, because they are still easily and cheaply available here. So making them by myself wouldn't be oeconomically worthwhile. I haven't much use for them anyways. Now and then I need a little acetaldehyde (dissolved in water) which is easy to make by acidic decompostion of lactic acid (I have a video of that process on my channel). As soon as I make or buy a little aldehyde I try to use it up because they are often also problematic in storage and already harmful on their own. So for example I generate formaldehyde only in situ and semi-microscale.

@integral_chemistry 11 ай бұрын

Thank you! and yeah there are several processes where a furnace would be nearly necessary but given how impossible it would be for me to control toxic vapors/gasses/etc. given off from a furnace I've been trying to figure out wet-chemical methods for different processes that are typically done in a furnace. This worked, and I recently tried potassium permanganate but the final product was too impure for me to obtain the typical "black" crystals (it ended up vaguely dark purple). So I'm going to try that one again before posting and hopefully it works a bit better. And yeah I agree, chromates are extremely cheap especially compared to the extreme hazards associated with making them (which is why I didn't keep anything I made here). I'll have to check out that lactic acid video, sounds fairly neat actually and I'd like to see what types of things you'd actually do with acetaldehyde.

@experimental_chemistry 11 ай бұрын

@@integral_chemistry This was a mistunderstanding: dichromate isn't really cheap here and afaik only one seller is left to buy it from for private individuals in the EU because it's restricted by REACH regulations. Aldehydes are much easier and cheap to get, so it's not worth wasting the last precious stocks of dichromate on making them. In the future it's getting more important for hobby chemist to know how to make dichromate yourself, I guess - although it would be less dangerous if it simply could be bought instead. I already tried the wet route on small scale, using potassium hydroxide and hydrogen peroxide instead of bleach (it's just important then to destroy unreacted peroxide by boiling it out before sulfuric acid is added...) and it worked well, too. The acetaldehyde I made is only a aqueous solution of the vapours and very crude but fairly sufficient for a few typical reactions on test tube scale like detecting it via Schiff's test with fuchsine sulfurous acid. Making potassium permangante in a notable yield and - above all - purity is nearly impossible under laboratory conditions. I tried so many routes but never really succeeded. Fortunately it recently became a little easier again to buy some.

@AmericanWanderers 4 ай бұрын

We used to make up Chronic Acid by the gallon for use as a glassware cleaner. Never a thought to any hazards other than the obvious strong acid/oxidizer. Reminds me of the story one of my chem profs told about being given Beryllium Sulfate as Sugar of Beryllium to taste in his class.

@keisisqrl 11 ай бұрын

If not friend, why friend colored?

@integral_chemistry 11 ай бұрын

right? All the coolest chemicals seem to be the deadliest...

@keisisqrl 11 ай бұрын

@@integral_chemistry annoyingly dichromate is *really* good for photographic processes, there are only mediocre alternatives. a lot of photographers who work in that are not super responsible with it... but it's so easy to mitigate the waste!

@mythics791 11 ай бұрын

I remember my grandfather using potassium dichromate for his mahogany woodworking projects. thank you for the video

@integral_chemistry 11 ай бұрын

No problem! And yeah I was actually going to comment on its use in woodworking and leather tanning but I couldn't think of a good place to fit it. He safe with it? Several decades ago we didn't know yet how dangerous this stuff was

@Drjtherrien 11 ай бұрын

Oh yes! I used that back in high school to darken some mahogany chairs I made. I had no idea how bad the stuff was and I'm sure I got it on me. Thirty years later and no extra limbs. 🤞 Funny enough I got the dichromate from my dad who got it from a person he knew at the town water treatment plant! Let that sink in. Boy how times have changed.

@AmericanWanderers 2 ай бұрын

@@integral_chemistry No doubt that it is carcinogenic but was there a mass die off of chemists and woodworkers, 30 years ago? Most seems to live to old age. Despite handling daily many now labeled deadly chemicals. So are we exaggerating the hazards? We are alive in a risk adverse time.

@hellothere3163 11 ай бұрын

Nicely done! Stay safe with the cleanup!

@integral_chemistry 11 ай бұрын

Thank you! and yeah cleanup of this stuff is always a very nervous unpleasant time

@metiscus 11 ай бұрын

@@integral_chemistrywould love to see a video on cleanup and safety

@inglewooddoktor92 7 ай бұрын

Possibly plan to make that clean-up video for Potassium dichromate?

@RohanLoomis 11 ай бұрын

Amazing, this is probably one of the only good quality videos on the subject.

@integral_chemistry 11 ай бұрын

Thanks man! I'm glad you like how it turned out. And right? I'm surprised there isn't more given how commonplace this stuff is.

@chemicalmaster3267 11 ай бұрын

@Apoptosis 2:00 Chromium chloride regardless of its hydration state is deliquescent, which means it absorves so much water from the air that it dissolves into a poddle of concentrated solution. Sodium hydroxide, magnesium chloride, calcium nitrate and iron(III) chloride are also good examples of deliquescent compounds.

@Energetics_Testing 10 ай бұрын

Or hygroscopic.

@barrymayson2492 4 ай бұрын

They used it basic breathalyser when they first became a thing end of 1960s . A friend at school and me decide to see what would happen if we mixed with pure alcohol. It was a energetic to say the least. Took us ages to clear up the mess.

@undernetjack 11 ай бұрын

Wow. Very well done. I've learned a few things. Thank you.

@derchromebacher4366 11 ай бұрын

Thank you for your service.

@clintongryke6887 11 ай бұрын

Really interesting and balanced.

@danielwshingtondasil 11 ай бұрын

it always creep me out to remember doing my bachelor degree and we were doing experiments with potassium dichromate without even gloves. Brazil is a crazy place to live in lol.

@woopwoopboopboop47 11 ай бұрын

Really ? That's wild

@danielwshingtondasil 11 ай бұрын

@@woopwoopboopboop47 I wish it wasn't true but it's mostly because of government funding because it's a public university.

@antonschollum3128 11 ай бұрын

Nice one brother👍used to work with dichromate ie: pretty orange death

@evandunkley292 11 ай бұрын

By far my favourite carcinogen.

@jonhoyles714 11 ай бұрын

great video 😊

@integral_chemistry 11 ай бұрын

thank you! :)

@vladislavshepel6389 4 ай бұрын

To easify of the filtration it needs to heat fresh precipitate for an hour and give it to cool down to room temperature. Super micro cristasl will be recrystallised to micro crystals and then you can filter 'em out without problems.

@ac281201 11 ай бұрын

Looks yummy! 😋

@spiderdude2099 5 ай бұрын

You know Chromium trioxide is bad when you can ONLY WASH IT with azeotropic nitric acid (or higher concentrations), because it oxidizes everything else. And nitric acid is relatively volatile and will not leave too much contamination. And as an added benefit tho, whatever glass fritt you use will be IMMACULATELY clean due to the chromium trioxide and chromic acid that destroys any lingering organics. That’s actually the textbook method for cleaning glass within an inch of its life without needing some fancy plasma cleaner.

@Zen_Ft5e 11 ай бұрын

Very nice. Is there any way to remove the K2SO4 from the chromic acid in order to get pure trioxide?

@lemoncheesecake4880 11 ай бұрын

Reminds me of a demo I saw on highschool with ammonium dichromate

@AndresRamirez04 Ай бұрын

Hey. Great video, man. How'd you get your hands on 5lbs of K2Cr2O7? Im looking for some for an oxidation of Etoh for an aldol condenstation to cinnamaldehyde. Thanks!

@integral_chemistry Ай бұрын

Thanks man! I've considered that reaction too, but as you might have gathered from the video I'm pretty wary of chromates lol. The company I got the K2Cr2O7 from is called US Pigment Corporation. Just Google that and the site should come up. They mostly sell pottery/pigment supplies but also a lot of bulk chemicals at very low prices. I think the craziest thing they sell is arsenic trioxide 💀

@AndresRamirez04 Ай бұрын

@integral_chemistry Thanks man! Just ordered a pound.

@HighEnergeticEnthusiast 11 ай бұрын

Cancer Juice!!!

@integral_chemistry 11 ай бұрын

Tbh I feel we should make that its official IUPAC name

@HighEnergeticEnthusiast 11 ай бұрын

For sure only problem would be that ther would be several red/orange liquids with the same name

@lautaromorales2903 11 ай бұрын

with stainless steel sodium chloride electrolysis using the steel as anode gives the oxides instead of the hydroxide. This makes the filtering and handling easier compared to the hydroxides.

@196Stefan2 10 ай бұрын

Have you ever considered to start with easily commercially available chrom alum [KCr(SO4)2* 12H2O] instead of CrCl3? I expect Chromiumhydroxide precipitates the same way after adding NaOH, as is does with CrCl3 and the potassium and sulphate ions should not be a reason for concern. Chrome alum is a quite cheap source of Cr3+

@gsmontag 11 ай бұрын

I would've loved to have seen an ammonium dichromate 'volcano', could've been a fun way to dispose of it?

@integral_chemistry 11 ай бұрын

I actually didn't realize how insoluble ammonium dichromate is when I made this (typically I think of ammonium salts as being super soluble). I did read recently that its pretty easy to precipitate it so I do plan on doing that for a video of chrome green pigment I'm working on

@QuantumAsesorias 11 ай бұрын

How do you know is only K2Cr2O7 and not NaCr2O7, why only potassium dichromate precipitate ?

@integral_chemistry 11 ай бұрын

Mostly because the sodium salt is super soluble and doesn't easily precipitate

@DangerousLab 11 ай бұрын

Did you just add the disclaimer page at the end after our discussion?😂

@integral_chemistry 11 ай бұрын

LMAO yep! That is actually exactly what happened. These videos take long enough to make I would be quite annoyed if one got taken down

@DangerousLab 11 ай бұрын

@@integral_chemistry IMO the addition of that disclaimer page is a wise move👍

@amateur_chemistry232 Ай бұрын

Can i use an excess of potassium dichromate to oxidize 2-nitrocinnemaldehyde to 2-nitrocinnamic acid?

@chemicalmaster3267 11 ай бұрын

@Apoptosis It would have been better if you added some sodium hydroxide to the mixture of chromium(III) hydroxide and sodium hypochlorite since it helps in the conversion of chromium(III) to chromium(VI).

@kevinwoodruff9431 10 ай бұрын

What are you gonna do with it? And what was the Can you sell it? You really know your stuff and where do you get hold of All these chemicals. where do you get The idea of😮 these things Where do you get hold of these chemicals?