I want to thank you VERY MUCH for this video! I have a very old ingot of Potassium (I'm a chem teacher) that we've probably had since the 60's. It's crusted with much oxidation, but I *never even thought* it could have potassium superoxide on it. Pushing that chemical into pure potassium...you're right. That's such a hazard. And I've been cutting into that metal to portion out pieces for ten years now. Never again! Luckily, I was always doing this in the back room, and not in front of students. At any rate, not only have you warned us about the danger, you've also, in one excellent video, equipped us with the necessary procedure to correct the problem. You sir, are awesome. Thank you again and again!!!
I have plans to. We don't have toluene lying around, though, as it's been identified as a carcinogen. Doesn't mean we can't order it, but we just don't have it normally stocked. I'll have to get that first. Till then, the Potassium we have is off limits.
NileRed is undoubtedly one of the best channels of youtube in its own niche and have always shown the full procedure with security warnings. I'm not a chemist, so performing these experiments would be close to impossible to me, research alone would take ages (and by now i'd been tagged by Security Services for all these chemicals :D ), but watching it here provides me with the amazement i've always enjoyed in chemistry. Truly an excellent communicator for science. So I'm quite happy to learn that chem teachers also do enjoy it; it's a plus both for credit and quality.
Please be sure to read the warnings by research chemists in other comments: isopropyl alcohol is dangerous to use for this, and it will react with the metal as well, somewhat like water does. The gel is identified as potassium isopropoxide, a strong base, and needs to be neutralized by removing the toluene, then slowly adding cold water (what happened to "acid to water"? But I suppose organic chemists know best), producing KOH and isopropanol. The KOH can then be neutralized with vinegar. The alternative offered, likely safer and wasting less potassium, is to use dioxane under argon as a solvent, dissolving the oxides while leaving the metal untouched. You can then heat the dioxane to melt the potassium (still under argon), gathering it one blob, then letting it cool completely. Once it has cooled, you can finally shut off the argon and pick out the solid potassium blob (tweezers are suggested), and transfer it to clean oil for storage.
I'm no chemist, but I do work in industry, and the one thing no one has mentioned - Nitrile gloves are not chemically safe for use with toluene. (notice the gloves getting softer and looser) You all will also observe that the red compound is caused by the toluene coated metal in close contact with the nitrile gloves 14:42
Organic Chemist here. I'm not sure if potassium's oxides will react with alcohols, but I can tell you that alcohols react with alkali metals to form the corrAesponding alkoxide salt and hydrogen gas, much as water reacts to form the corresponding alkali hydroxide and hydrogen gas. (i.e CH3CH2OH (ethanol) + Potassium ==> 0.5mol Hydrogen gas + 1mol CH3CH2O- K+ ) These alkoxides are extremely reactive. Be careful. (How do I know this? I've personally reacted sodium and ethanol before in order to form sodium ethoxide, which is an extremely strong base, for an experiment in my academic research) That stuff left behind in your toluene? Potassium isopropoxide. It's an extremely strong base. The solid gradually turns dark over time because of oxidation. To neutralize it, add cold water to it slowly after removing the toluene. This produces isopropanol and potassium hydroxide. The hydroxide can be neutralized with boric acid solution or vinegar. Again, please be careful. Also, it would be very nice if you add a warning about this to your videos that you clean alkali metals in; they will all react with isopropanol in this manner, and the resulting waste should be neutralized as I described above to prevent accidental harm.
WRONG EXPLAINATION, READ THE EDIT:That sounds about right. Assuming you neutralized with vinegar, alkoxides react with things like vinegar to form esters, which generally smell fruity. Edit: correction many years later... Don't know what I was thinking. Vinegar reacting with the alkoxide will produce the alcohol plus the corresponding salt of the carboxylic acid (e.g., potassium acetate). If there is excess acidity in solution after all this (e.g., a sufficient excess of acetic acid), you may have a slight fruity smell develop after a small amount of the acid is able to react with the alcohol to form the ester, but that would be a VERY slow reaction at best. Thanks to Leo Curious for pointing out this inconsistency!
Alkoxied form esters with organic acids? How is that supposed to work? Reaction mechanism please, because I highly doubt it. It will form the acids salt + the alcohol, eg. CH3-CH2-O-Na + CH3-COOH -> CH3-CH2-OH + CH3-COONa
@@fedorkochemasov4533... and ignited whatever flammable oil it was preserved in, yes. (she was trying to cut off a little piece while avoiding taking the large lump out of the jar, I think)
@@rune.theocracy idk it all sounds cool to me unless someone got hurt, what disgruntled student didn't secretly hope at least once that the school had burned down so they got time off lol
Combining potassium metal with toluene and wet isopropanol is ridiculously dangerous if you don't have an inert gas blanket over the top. It has to be nitrogen or argon to prevent fires. Carbon dioxide does work, but can react to make potassium carbonate which contaminates your potassium. Isopropanol does react with the potassium metal itself (to make potassium isopropoxide and hydrogen), so you risk destroying some of your expensive potassium this way. There is a much better way to make shiny potassium blobs, even from lots of really dirty small pieces. The solvent of choice for this is dioxane, since it can dissolve the potassium oxides without reacting with the potassium metal underneath. Transfer all the dirty potassium to a large beaker about half full of dioxane - you don't need to wash all the oil off first, so if you have a load of small bits, just strain it out with a sieve. Then heat it up until the potassium starts to melt, and it should coalesce. Ideally you should stir it with a magnetic stirrer. This allows you to cover the top of the beaker with a lid and purge the headspace with inert gas while you are heating it, otherwise the risk of fire is rather extreme. The molten potassium floats to the top, while the oxides dissolve and any other insoluble crap sinks to the bottom. Once you have a nice shiny blob, let it cool down while still purging with inert gas. Once solidified, pick it out with tweezers and put it in a clean jar with some fresh oil.
Its really somewhat dangerous. He is also adding way too much alcohole. Just add a few dops and let it sit over night. Use liquid paraffin or some other high boiling hydrocarbon as the solvent and there is no crazy fire hazard.
If someone came in with a bucket of water and some mineral oil... 🔥🔥🔥🔥🔥🔥🔥🔥🔥🔥🔥🔥🔥🔥🔥🔥🔥🔥🔥🔥🔥🔥🔥🔥🔥 Then you try to put it out with water... 🔥🔥🔥🔥🔥🔥🔥🔥🔥🔥🔥🔥🔥🔥🔥🔥🔥🔥🔥🔥🔥🔥🔥🔥🔥🔥🔥 Then the lab burns down
I agree with AmbassadorJJ about caution using isopropanol. Back in the day, I was always advised to only use t-butanol to clean or destroy potassium as it's even less reactive than isopropanol. Another thought: when cutting potassium chunks, never use a metal knife - it can undergo redox with the superoxide and metallic potassium, causing an explosion. I would advise the same for poking a molten blob of potassium too: try using a glass rod instead.
@Pietro Tettamanti I'm pretty sure that the potassium superoxide is both highly reactive and a powerful oxidizing agent so the superoxide is where the oxidant comes from in that redox reaction if a metal knife is used to cut potassium chunks
7:06 : that blue color is probably due to thin film interference, similarly to what happens when you anodize other metals such as titanium, hafnium, niobium (that one is the prettiest!), or even when steel is tempered. 13:34 : someone in my lab should have listened to that... He had some potassium in hexane, the whole thing caught fire (we're still not sure why). He freaked out, went to get a fire extinguisher, and knocked the beaker over by firing CO2 on it. He then managed to empty the whole extinguisher without completely extinguishing the hexane. Fortunately, somebody else brought a dry chemical extinguisher, and completely put out the fire. Had he simply grabbed anything to simply cover the beaker, the whole thing would have been over in an instant...
Methoxy Light is an electromagnetic wave. So different thicnesses of oxides refract the light differently. It just happens to be that its the right thikness to make it blue.
At a guess, a uniform thin film forms almost instantly, and this will be about 200 nm thick, giving a blue color. Once the oxide layer forms, the oxidation rate will slow way down as the existing oxide will tend to protect the underlying potassium. Not only that, while the potassium is in the toluene, there is only a trace amount of water available to react with, so the initial oxide formation will tend to deplete the toluene of water impurities. The way to test this, of course, would be to let the beaker sit for a while and see if the apparent color changes. It would also be interesting to cover the top of the beaker and purge the air space with something like nitrogen, to see if that prevents atmospheric water vapor from diffusing into the toluene and thence to the potassium.
I recommend using shellsol D70 for the storing and washing. The potassium doesn't float in it and when adding a drop of isopropanol to the hot mixture the drops coalesce together quite well.
I believe the first safety warning in a textbook comes from a Chinese recipe for gunpowder, and it explicitly mentions people burning their house down.
"What you're seeing now is my normal state" *adds oxygen* "This is a superoxide. And this..." *adds another oxygen* "This is what is known as a superoxide that has ascended past a superoxide, or, you could just call this a superoxide 2" AND THIS IS TO GO EVEN FURTHER BEYOND!!! AHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHH
@Ratko Mladic peroxides and superoxides are molecules where oxygen atoms are bonded together directly. Since this had an extra oxygen, people are joking about it being "more super" than a superoxide.
I found that apart from its medical uses and water cleaning, Potassium Permanganate and glycol make a good fire starter. Doesn't take much either. Stored properly it is handy in your survival kit.
Blue color of potassium is from metallic water witch disolve electrons. You can find ths on yt, just write metalic water, and this is amazing that you find another way to make this.
Alterius Zhang I think it has to do with how straight forward and thorough he is. Like I watch these videos feeling like "man I wish my lab technique was this organized and neat, but NAHH too much work, I'll just watch Nile red instead" lol
The blue colour of pure potassium in toluene is actually solvated electrons, caused by the low first ionisation energy of the element. A similar thing occurs when pieces of sodium and potassium are dropped into liquid ammonia.
No, thats not it. Its just a colloidal suspension. It would be impossible to have water or alcohols and solvated electrons at the same time. But even in pure toluene there are not going to be visible solvated electrons. Oh and toluene is not inert in the potassion/hydroxide mixture... see eg. DOI 10.1021/jo01012a067
Hello Nile! I just wanted to let you know I totally love your videos, man. I'm a chemistry student in Mexico, and if I were already sure that I wanted to become a chemist, your videos always reassure me about it. I would like to ask if you have any book recommendations, as well as studying methods. Again, thanks!
+Itzael Tamayo hello! I am unfortunately not able to help you because I dont really know of any books to recommend. What do you mean by studying methods?
That's ok, I just thought you had a bunch of chem books lying around because you do know a lot! With studying methods I mean if you have any technique to help you understand chemistry things better, and learn about it as a result. Thanks again!
Itzael Tamayo I think the most important thing is to just read about it, be interested in it and try to understand. Over time you will slowly build your knowledge!
To get all the pieces to coalesce you can melt it and use a glass syringe to directly inject the small pieces into the large one. That's what I do anyways. You just have to be sure that you aren't injecting other materials, so you always have that 1 tiny drop where you have to purge the storage liquid and a tiny bit of melted metal comes out.
@@jackychan7758 it depends on the machine you are using. When I was working at the University, we used 50 ml plastic tubes. we removed the cap and replace it with paper towel and put that inside the glass container. I've seen other labs use machines that had many metal racks. It looked like a baking oven but it was some fancy machine for lyophilisation that controled for many environmental conditions. This seems to be the standard now. I seen smaller but similar machines on cooking shows like Guga.
RealChemistry Well not really. I mean, depending on how pure you want it to be. Even dirty potassium is still useful in reactions. It depends on how finicky your reaction is.
+Nile Red Potassium metal is mostly use in organometallic chemistry. Here we need all reagents super super pure and in argon atmosphere... for me it's a waste but i want to see some experiment with your potassium :)
RealChemistry Yeah for some stuff it's not worth it. But organic stuff tends to be pretty robust. We can make potassium tertbutoxide, etc, even if its pretty dirty :)
From my ancient memory, ethanol and sodium react to form the salt sodium ethoxide and hydrogen. It's an acid base reaction and I expect potassium would react in the same way. I imagine isopropanol would be a weaker acid but would react in the same way although with less vigour. The salt that forms might be potassium prop-2-oxide.
I've heard Tertiary alcohols, like Amyl alcohol works far better for cleaning up Potassium than Isopropyl. You should give that a try, even if small scale only. Supposedly it helps it coalesce too.
+Matt „Sigurthr“ Giordano "Amylic Alcohol" isn't a tertiary alcohol, since Amylic alkohol is a synonym for n-Pentanol, which is of course a primary alcohol.
Thanks for the explanation on the potassium superoxide so much!!! I was wondering why it would explode if it got a thick enough oxide layer! Great video! Keep up the good work!
A little tidbit I could add after the whole cleaning procedure is done would be to ad some kind of weight into the mineral oil, just to keep the potassium under the oil and out of contact with the air.
To the problem of the floating Potassium metal: I was facing the same issue for my Lithium samples and made a kind of a "holding-down-device" which consists of a round plastic disc with a steel screw in the center. The other end of the screw is led through a hole in the lid of my container and kept in position by two nuts. The plastic disk now forces the Lithium pieces to submerge below the oil surface. Nevertheless, my Li got grey all over its surface, in the course of some months. Originally it came (from China) in a sealed plastic bag under Argon and was shiny then.
I found a kind of red stuff on silver crystal 15 years ago as well where I was just a junior high student. It was a single displacement reaction between Cu(s) and Ag+, after I got my silver crystal fully grown on a cooper wire, I pulled it from beneath the solution and found some kind of red-brownish substance covering on the metal surface. It looked like it was the metal itself has some interaction with air but I had no clue at all since no teacher could answer me, nor did I find any literature about it.
could the oxide be blue because of a thin-film effect? I know that when you heat up steel you get an iron oxide layer that's coloured by the thin-film effect, and one of the colours it turns is a blue very like the one in the video
Like most alcohols, isopropyl alcohol reacts with active metals such as potassium to form alkoxides that can be called isopropoxides. The reaction with aluminium (initiated by a trace of mercury) is used to prepare the catalyst aluminium isopropoxide.
You are absolutely correct sir. Potassium is far more reactive than it's counterpart metal of sodium. Might as well combine them to form NaK which is an even more reactive formulation. 😉
The blue color might come from solvated electrons produced by fresh potassium surface. This paper published in Nature Chem might help: "Coulomb explosion during the early stages of the reaction of alkali metals with water" DOI: 10.1038/nchem.2161
The colors on the metal don't need to be the colors of the actual compounds formed. They can very well be caused by light interfering with thin films per se. Remember what happens to stainless steel in flame? Also, remember this is toluene and it's not pure. The red stuff might be an organic compounds which has oxidized and precipitated. Some say it's potassium ozonide. There's really a lot of options. I've been cleaning potassium a long time ago and used same procedure, more or less. It was a pain in the ass. Oh yeah, and use a smaller storage jar. Great video. :)
gygabite I agree. I'm watching the video for a second time, and it definitely appears that the metal is reacting with the gloves. That blue color's just odd though.
Probably Potassium Ozonide. I am not sure if it is caused by the gloves or a contaminant on the gloves, but the color looks just like potassium ozonide. It is normally produced when potassium hydroxide comes in contact with ozone. Not what you want to see xD It is very unstable.
Thanks for this NileRed. It couldn't be more timely. The school where I teach has some potassium that is very old. It is not something replaceable -- schools are not supposed to have it any more. For this reason it has been used sparingly over the years and now has a lot of oxide -- to the point of becoming dangerous. One of those situations where regulation actually makes things less safe. Anyway, I was considering how I might clean it up and to have a tutorial to follow is just great. It helped that the exact moment that I was perusing your channel and found this, the school's work-place safety officer came around with some questions specifically related to the use of potassium and our risk assessment procedures. We watched the vid together. So, a couple of specific questions. Was the toluene dried or did you use it direct from the can? I saw you adding IPA dripwise. How long did this part of the process take? Would other alcohols (ie, ethanol) be equally suitable?
KOEt isn't so soluble in the solvents employed(toluene and mineral oil) so will form a coating over any remaining oxides effectively leaving the hazard behind. IPA is probably the best bet. I have a nice jagged 17 stitch scar on my arm from a NaK still clear up where I didn't use IPA, whatever you end up doing be careful.
+j_sum1 j_sum1 I added it slowly, but I am not sure how long the process took. The toluene was not dried, I just used it directly form the can. The little bit of water in it will actually react with some of the oxides. I am not sure if other alcohols would work, honestly. The commenter below seems to think that ethanol wouldn't be a great choice. If you do this, just remember that a fire can start. To put it out, just cover the beaker with something. Don't use a fire extinguisher or freak out. It can lead to a much bigger problem.
Using anhydrous solvents will be less hazardous (M + H2O - > MOH + H2...) and you wouldn't loose any of your limited potassium stock, but the residual water in toluene won't be available to react/dissolve the oxide species. Your call. Personally I'd use anhydrous to limit the potential hazards but I'm used to working in a lab with an ample supply of them...
Thanks for that MortRotu and NileRed. I'll stick with the IPA then. I'll do a test with the toluene we have available and if it is not to vigorous then I will proceed. If there look to be issues then I will dry it first.
+j_sum1 j_sum1 no problem, I happy to help. If the toluene is too wet you can dry it out reasonably well with some molecular sieves (4A ones for preference, but any size that absorbs water and not toluene would work fine) and not cause your H&S person palpitations by doing a still. It'll still have a fraction of a % H2O in but shouldn't react anywhere near as vigorously as 'wet' toluene would. I hope a PhD in nitride materials synthesis becomes more useful than answering questions on YT...
I think that the red stuff comes from the reduction of the nitrile groups in your nitrile gloves. Then the red stuff is dissolved by the toluene (being an organic substance it will be quite soluble in nonpolar solvents).
Synthetic organic chemist here. I just discovered your channel and I have to say this is pretty great stuff. Keep up the good work. I am currently finishing up my grad work with Nile red and Nile blue analogues. Are you a dye chemist or did you just like the name?
Maybe it's better to leave it to professionals to work with that stuff. Extremely toxic and a environmental hazard. Don't want to see beginners/amateurs messing with it and disposing it incorrectly.
It seems to be some form of reaction with the gloves or their blue color. Its very unlikely KO3 as there is no ozone source and reactive alcohol in the solution.
@@leocurious9919 Ozonide can have enriched over the amount of time and is part of that crust! Especcially in populated areas there can be 'high' amounts of ozone in our atmosphere. Check your parts made out of silver! Regular oxygen cannot corrode it. Next to sulphur compounds, ozone has a big effect on silver, too!
@@knutritter461 Its really obvious that it is a reaction that takes place during his handling that produces this red stuff which is also soluble in the solvent.
"Reactions of ethanol over metal oxides" I've found this old paper published in 2000, discussing the reaction between metal oxides and ethanol, hope it could be useful if you need
I believe that blue oxide color was from some suboxide of potassium. Cesium has many well documented suboxides and are all very strongly colored, and it isn't unreasonable to assume that potassium does the same.
I'm sure somebody already answered this better but I did some R&D work for a company about 15 years ago and in my research I ended up learning about anodizing as it was related to the project I was working on and it's basically a process of electrolytically induced and controlled oxidation. I may be wrong but I suspect the blue color of the surface oxide that forms on it is due to the specific thickness that the first order oxide layer as it stabilizes, and that causes some interference effect with light at that wavelength (sort of like the effect of opal and labradorite). From what I remember in my research in to chromic anodizing, the thickness of the oxide layer is what corresponds with a wavelength of light that will be reflected instead of absorbed the most when going through it and that becomes the "color" you see. When you anodize aluminum , titanium or rhodium, you can vary the voltage and electrolytes used to achieve a certain "color" effect on the surface of the metal that in itself is not a dye or tint but yet produces an almost eerie effect of only allowing a specific narrow band of light to escape from it's surface. So by controlling the exact thickness of the oxide layer to reflect or maybe "re-emit" light of that wavelength you achieve an array of surface color effects. The principal is that the potential for oxygen bonds is initially going to be high on a conductive metal surface when no oxide layer yet exists, as seen by the rapid formation of the oxide layer when the potassium was exposed to air, but as that layer of much less electrically conductive oxide thickens, it will quickly reach a point where the potential energy to overcome the oxide layer exceeds the input energy and it stabilizes there. Sorry I can't site a specific source, just spewing something out of memory from years ago.
LCARS43278 it's called the thin-film effect, happens with oxide on steel too. it was and sometimes still is used as a protective finish, and I'm pretty sure it's the reason the black finish on firearms is called gun blue
I want to thank you VERY MUCH for this video! I have a very old ingot of Potassium (I'm a chem teacher) that we've probably had since the 60's. It's crusted with much oxidation, but I *never even thought* it could have potassium superoxide on it. Pushing that chemical into pure potassium...you're right. That's such a hazard. And I've been cutting into that metal to portion out pieces for ten years now. Never again! Luckily, I was always doing this in the back room, and not in front of students. At any rate, not only have you warned us about the danger, you've also, in one excellent video, equipped us with the necessary procedure to correct the problem. You sir, are awesome. Thank you again and again!!!
Gonna clean it now?
I have plans to. We don't have toluene lying around, though, as it's been identified as a carcinogen. Doesn't mean we can't order it, but we just don't have it normally stocked. I'll have to get that first. Till then, the Potassium we have is off limits.
NileRed is undoubtedly one of the best channels of youtube in its own niche and have always shown the full procedure with security warnings. I'm not a chemist, so performing these experiments would be close to impossible to me, research alone would take ages (and by now i'd been tagged by Security Services for all these chemicals :D ), but watching it here provides me with the amazement i've always enjoyed in chemistry. Truly an excellent communicator for science. So I'm quite happy to learn that chem teachers also do enjoy it; it's a plus both for credit and quality.
Please be sure to read the warnings by research chemists in other comments: isopropyl alcohol is dangerous to use for this, and it will react with the metal as well, somewhat like water does. The gel is identified as potassium isopropoxide, a strong base, and needs to be neutralized by removing the toluene, then slowly adding cold water (what happened to "acid to water"? But I suppose organic chemists know best), producing KOH and isopropanol. The KOH can then be neutralized with vinegar.
The alternative offered, likely safer and wasting less potassium, is to use dioxane under argon as a solvent, dissolving the oxides while leaving the metal untouched. You can then heat the dioxane to melt the potassium (still under argon), gathering it one blob, then letting it cool completely. Once it has cooled, you can finally shut off the argon and pick out the solid potassium blob (tweezers are suggested), and transfer it to clean oil for storage.
the teacher has become a student xD
I'm no chemist, but I do work in industry, and the one thing no one has mentioned - Nitrile gloves are not chemically safe for use with toluene. (notice the gloves getting softer and looser) You all will also observe that the red compound is caused by the toluene coated metal in close contact with the nitrile gloves 14:42
And he never reads this
@@davyberson90 That's where you'd be wrong!
@@NileRed finally？
@@NileRed my guy is still active reading comments on a video from 2016, you gotta love that!
@Vox Deus i would like @Nilered opinion, because i am no chemist, but that color was clearly a chemical reaction.
why don't you just scrub it with soap and water
Please tell me this is a joke.
it is a joke
+WeX T laughing ass my off?
Dennis Cordova I know it is supposed to be a joke but because potassium + water = BOOM.
Dennis Cordova Yeah, and disinfect it with chlorine while you're at it
Organic Chemist here. I'm not sure if potassium's oxides will react with alcohols, but I can tell you that alcohols react with alkali metals to form the corrAesponding alkoxide salt and hydrogen gas, much as water reacts to form the corresponding alkali hydroxide and hydrogen gas. (i.e CH3CH2OH (ethanol) + Potassium ==> 0.5mol Hydrogen gas + 1mol CH3CH2O- K+ ) These alkoxides are extremely reactive. Be careful.
(How do I know this? I've personally reacted sodium and ethanol before in order to form sodium ethoxide, which is an extremely strong base, for an experiment in my academic research)
That stuff left behind in your toluene? Potassium isopropoxide. It's an extremely strong base. The solid gradually turns dark over time because of oxidation. To neutralize it, add cold water to it slowly after removing the toluene. This produces isopropanol and potassium hydroxide. The hydroxide can be neutralized with boric acid solution or vinegar.
Again, please be careful. Also, it would be very nice if you add a warning about this to your videos that you clean alkali metals in; they will all react with isopropanol in this manner, and the resulting waste should be neutralized as I described above to prevent accidental harm.
WRONG EXPLAINATION, READ THE EDIT:That sounds about right. Assuming you neutralized with vinegar, alkoxides react with things like vinegar to form esters, which generally smell fruity.
Edit: correction many years later... Don't know what I was thinking. Vinegar reacting with the alkoxide will produce the alcohol plus the corresponding salt of the carboxylic acid (e.g., potassium acetate). If there is excess acidity in solution after all this (e.g., a sufficient excess of acetic acid), you may have a slight fruity smell develop after a small amount of the acid is able to react with the alcohol to form the ester, but that would be a VERY slow reaction at best. Thanks to Leo Curious for pointing out this inconsistency!
Alkoxied form esters with organic acids? How is that supposed to work? Reaction mechanism please, because I highly doubt it. It will form the acids salt + the alcohol, eg. CH3-CH2-O-Na + CH3-COOH -> CH3-CH2-OH + CH3-COONa
@@AmbassadorJJ alkoxides wont react at the carbonyl carbon with carboxylic acids, it will just deprotonate the acid forming carboxylate and alcohol...
@@nolanwilson3021 I stand corrected. Thank you, sir.
no problem Mr Ambassador Dude@@AmbassadorJJ
And *this* was how my teacher burned down the classroom.
Thanks for explaining, I've always wondered what went wrong back then.
You mean he cut into old potassium that had a superoxide on it?
@@fedorkochemasov4533... and ignited whatever flammable oil it was preserved in, yes.
(she was trying to cut off a little piece while avoiding taking the large lump out of the jar, I think)
Imagine having an actually cool chemistry class.
That's cool though, except for the part that the classroom burnt down.
@@rune.theocracy idk it all sounds cool to me unless someone got hurt, what disgruntled student didn't secretly hope at least once that the school had burned down so they got time off lol
Combining potassium metal with toluene and wet isopropanol is ridiculously dangerous if you don't have an inert gas blanket over the top. It has to be nitrogen or argon to prevent fires. Carbon dioxide does work, but can react to make potassium carbonate which contaminates your potassium. Isopropanol does react with the potassium metal itself (to make potassium isopropoxide and hydrogen), so you risk destroying some of your expensive potassium this way.
There is a much better way to make shiny potassium blobs, even from lots of really dirty small pieces. The solvent of choice for this is dioxane, since it can dissolve the potassium oxides without reacting with the potassium metal underneath. Transfer all the dirty potassium to a large beaker about half full of dioxane - you don't need to wash all the oil off first, so if you have a load of small bits, just strain it out with a sieve. Then heat it up until the potassium starts to melt, and it should coalesce.
Ideally you should stir it with a magnetic stirrer. This allows you to cover the top of the beaker with a lid and purge the headspace with inert gas while you are heating it, otherwise the risk of fire is rather extreme. The molten potassium floats to the top, while the oxides dissolve and any other insoluble crap sinks to the bottom. Once you have a nice shiny blob, let it cool down while still purging with inert gas. Once solidified, pick it out with tweezers and put it in a clean jar with some fresh oil.
You are the only sensible person in this commentsection...
Lloyd Evans NO NOT NITROGEN THE K WILL CORRODE
Isn't dioxane gonna act as a chelatant and solubilize potassium metal too ?
@ Alcyne: Where would the electrons go?
Its really somewhat dangerous. He is also adding way too much alcohole. Just add a few dops and let it sit over night. Use liquid paraffin or some other high boiling hydrocarbon as the solvent and there is no crazy fire hazard.
That giant ball of potassium is making me nervous.
@@martynaskerdokas8438 it would be a shame if someone came in with a match
NaK
Is more fluid
If someone came in with a bucket of water and some mineral oil...
🔥🔥🔥🔥🔥🔥🔥🔥🔥🔥🔥🔥🔥🔥🔥🔥🔥🔥🔥🔥🔥🔥🔥🔥🔥
Then you try to put it out with water...
🔥🔥🔥🔥🔥🔥🔥🔥🔥🔥🔥🔥🔥🔥🔥🔥🔥🔥🔥🔥🔥🔥🔥🔥🔥🔥🔥
Then the lab burns down
Shouldn’t
Good thing dog here have a low surface area to volume ratio so the smallest amount of potassium possible is exposed
I agree with AmbassadorJJ about caution using isopropanol. Back in the day, I was always advised to only use t-butanol to clean or destroy potassium as it's even less reactive than isopropanol.
Another thought: when cutting potassium chunks, never use a metal knife - it can undergo redox with the superoxide and metallic potassium, causing an explosion. I would advise the same for poking a molten blob of potassium too: try using a glass rod instead.
Spider Juice redox reaction with what? Where's the oxidant?
@
And how would that change from a metal spatula to a glass rod?
@@pietrotettamanti7239 this man just waited 3 years to add another question.
@@pietrotettamanti7239 I'm no expert but I'm pretty sure that the superoxide is highly reactive and a powerful oxidising agent
@Pietro Tettamanti I'm pretty sure that the potassium superoxide is both highly reactive and a powerful oxidizing agent so the superoxide is where the oxidant comes from in that redox reaction if a metal knife is used to cut potassium chunks
"Okay in this video I'm going to be cleaning some potassium..."
My brain: oh... K
Omg good pun
I was gonna say the same joke
but *Na*
@@DeenBoi Real *Li* dude?
*P Og Ge* r *S*
Beautiful.
3:03 "After a few months of neglect it was coated in yellow." An incredible quote.
yellow chem bad
Just like my liver disease! wow, im like potassium!
That’s what the Coldplay song is actually about
Aeast it's not White
Mellow yellow
7:06 : that blue color is probably due to thin film interference, similarly to what happens when you anodize other metals such as titanium, hafnium, niobium (that one is the prettiest!), or even when steel is tempered.
13:34 : someone in my lab should have listened to that...
He had some potassium in hexane, the whole thing caught fire (we're still not sure why). He freaked out, went to get a fire extinguisher, and knocked the beaker over by firing CO2 on it.
He then managed to empty the whole extinguisher without completely extinguishing the hexane. Fortunately, somebody else brought a dry chemical extinguisher, and completely put out the fire.
Had he simply grabbed anything to simply cover the beaker, the whole thing would have been over in an instant...
+piranha031091 Yup, it's crazy how easy it is to put out but using something like fire extinguisher can make the problem so much worse.
Methoxy Light is an electromagnetic wave. So different thicnesses of oxides refract the light differently. It just happens to be that its the right thikness to make it blue.
thought of the color being due to a thin oxide film aswell but why wouldnt the color continiously change while the oxide film thickens?
That's hilarious, yet plain stupidity.
(I really mean ignorance)
At a guess, a uniform thin film forms almost instantly, and this will be about 200 nm thick, giving a blue color. Once the oxide layer forms, the oxidation rate will slow way down as the existing oxide will tend to protect the underlying potassium. Not only that, while the potassium is in the toluene, there is only a trace amount of water available to react with, so the initial oxide formation will tend to deplete the toluene of water impurities. The way to test this, of course, would be to let the beaker sit for a while and see if the apparent color changes. It would also be interesting to cover the top of the beaker and purge the air space with something like nitrogen, to see if that prevents atmospheric water vapor from diffusing into the toluene and thence to the potassium.
I want to play with that potassium jellyfish thing.
Just not with your finger!
@@eddievanhorn5497 or maybe you want it with your finger,......
“are you going to eat that?”
@@m0w0ss
( ͡° ͜ʖ ͡°)
No...don eat the potassium.
It could explode inside your stomach because there has water and hydrochloric acid in your body.
I recommend using shellsol D70 for the storing and washing. The potassium doesn't float in it and when adding a drop of isopropanol to the hot mixture the drops coalesce together quite well.
"Don't be crazy and shoot water over it and burn your house down" is the warning I wish was put in every science book. xDDD
I believe the first safety warning in a textbook comes from a Chinese recipe for gunpowder, and it explicitly mentions people burning their house down.
yo nile! red is potassium ozonide... like the superoxide but with an addditional oxygen
+Kye W eyyyyyyyyyy
"What you're seeing now is my normal state"
*adds oxygen*
"This is a superoxide. And this..."
*adds another oxygen*
"This is what is known as a superoxide that has ascended past a superoxide, or, you could just call this a superoxide 2"
AND THIS IS TO GO EVEN FURTHER BEYOND!!!
AHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHH
Jarrod0067 ascended
@@Jarrod0067 megaoxide
@Ratko Mladic peroxides and superoxides are molecules where oxygen atoms are bonded together directly. Since this had an extra oxygen, people are joking about it being "more super" than a superoxide.
Old video of old potassium cleaning. Just what I was looking for.
I found that apart from its medical uses and water cleaning, Potassium Permanganate and glycol make a good fire starter. Doesn't take much either. Stored properly it is handy in your survival kit.
I kinda love how it looks like the metal is bleeding with the red on it.
*Kris, Get The Banana.
*Potassium.
Blue color of potassium is from metallic water witch disolve electrons. You can find ths on yt, just write metalic water, and this is amazing that you find another way to make this.
These videos are strangely entertaining.
Alterius Zhang I think it has to do with how straight forward and thorough he is. Like I watch these videos feeling like "man I wish my lab technique was this organized and neat, but NAHH too much work, I'll just watch Nile red instead" lol
It's chemistry education done right.
nothing strange about it🤷🏾♂️ good content
Human like learn
The blue colour of pure potassium in toluene is actually solvated electrons, caused by the low first ionisation energy of the element. A similar thing occurs when pieces of sodium and potassium are dropped into liquid ammonia.
No, thats not it. Its just a colloidal suspension.
It would be impossible to have water or alcohols and solvated electrons at the same time. But even in pure toluene there are not going to be visible solvated electrons.
Oh and toluene is not inert in the potassion/hydroxide mixture... see eg. DOI 10.1021/jo01012a067
That's some forbidden jello right there.
Running water works best for these things. Just like silverware.
Jake Kim ಠ_ಠ
I also found water works well for cleaning metallic sodium
Water cleans active metals wonderfully😀
All you have to do is add some water, and you instantly clean off everything that was surrounding it.
@@calebbrooks1037 it works well to clean an unknown substance
Me: *looks at potassium*
Potassium: *explodes*
That moment when you realize that even potassium hates you...
i mean basically
"undesirable" is a massive understatement when it comes to potassium fires
"Thats where you'd be wrong. It would burst into flames."
I laughed
Your content is so good because it doesn’t have garbage loud stock music playing
Kris get the metal
Colour is due to unpaired electron present in super oxide, it appears different colour as it absorb different energy and gets excited and de exited.
Kris Get The Banana
*a very undesirable potassium fire*
Good ol'Nile with some epic scientific understatement lol
Hello Nile! I just wanted to let you know I totally love your videos, man. I'm a chemistry student in Mexico, and if I were already sure that I wanted to become a chemist, your videos always reassure me about it. I would like to ask if you have any book recommendations, as well as studying methods. Again, thanks!
+Itzael Tamayo hello! I am unfortunately not able to help you because I dont really know of any books to recommend. What do you mean by studying methods?
That's ok, I just thought you had a bunch of chem books lying around because you do know a lot! With studying methods I mean if you have any technique to help you understand chemistry things better, and learn about it as a result. Thanks again!
Itzael Tamayo I think the most important thing is to just read about it, be interested in it and try to understand. Over time you will slowly build your knowledge!
Tired of having your entire setup burned over again by potassium fires?
*FLEX TAPE!*
Flex tape? Wouldnt that be for sealing stuff and preventing leaks instead of, you know, fire?
@@user-yw8sr3uj1w dude its a meme, and god damn this comment is 2 years old wtf
@@hussam9044 it's on the internet. Age is irrelevant.
@@hussam9044 then make your memes make sense
@@user-yw8sr3uj1w dude flex tape fixes everything, even broken marriages, that was the meme, plus this was 2 years ago, the meme died along your humor
To get all the pieces to coalesce you can melt it and use a glass syringe to directly inject the small pieces into the large one. That's what I do anyways. You just have to be sure that you aren't injecting other materials, so you always have that 1 tiny drop where you have to purge the storage liquid and a tiny bit of melted metal comes out.
Kris get the banana-wait pottasium has metal in it?! still Kris get the banana.
potassium is a metal
at 12:00. To prevent oxidation, you could displace the air out of your jar. You could do that with a vacuum or by adding nitrogen gas in the jar.
But anxiety would increase suddenly for the jar to break under vacuum.
@@jackychan7758 it depends on the machine you are using.
When I was working at the University, we used 50 ml plastic tubes. we removed the cap and replace it with paper towel and put that inside the glass container.
I've seen other labs use machines that had many metal racks. It looked like a baking oven but it was some fancy machine for lyophilisation that controled for many environmental conditions.
This seems to be the standard now. I seen smaller but similar machines on cooking shows like Guga.
Hey, I want to be the first to comment on this video just to say: You make excelent videos about chemistry and keep up with the outstanding job!
+Maxmin Rain Thanks! :)
+Nile Red I think this procedure is a very waste of time and resources. Potassium metal needs a purification under argon to be useful.
RealChemistry Well not really. I mean, depending on how pure you want it to be. Even dirty potassium is still useful in reactions. It depends on how finicky your reaction is.
+Nile Red Potassium metal is mostly use in organometallic chemistry. Here we need all reagents super super pure and in argon atmosphere... for me it's a waste but i want to see some experiment with your potassium :)
RealChemistry Yeah for some stuff it's not worth it. But organic stuff tends to be pretty robust. We can make potassium tertbutoxide, etc, even if its pretty dirty :)
Voting for you to make the N2O video.
+InDmand voting for you to huff the shit off that N2O
only if you huff the shit out of some NO2 first
+InDmand nerds going at it lmao.
+batsman46 look up the definition. You sound like half of the definition.
Rylan Patry ?
I love the safety aspects of this channel. I love, love, love them :)
"Kris get the banana"
13:44 OH GOD AN OIL FIRE! QUICK GET SOME WATER, GET THE "EXTINGUISHING" GASOLINE! GET THE FIRE WOOD! CALL THE PROPANE COMPANY!
From my ancient memory, ethanol and sodium react to form the salt sodium ethoxide and hydrogen. It's an acid base reaction and I expect potassium would react in the same way. I imagine isopropanol would be a weaker acid but would react in the same way although with less vigour. The salt that forms might be potassium prop-2-oxide.
“superoxide” sounds like the name of an indie rock band
Me who failed he chem 1: hmmm very interesting. (only has a basic concept of what's happening)
Just remember when looking out for potassium superoxide, you can always spot it by the cape and the tights.
I've heard Tertiary alcohols, like Amyl alcohol works far better for cleaning up Potassium than Isopropyl. You should give that a try, even if small scale only. Supposedly it helps it coalesce too.
+Matt “Sigurthr” Giordano Cool. Unfortunately I dont have any :(
+Matt „Sigurthr“ Giordano "Amylic Alcohol" isn't a tertiary alcohol, since Amylic alkohol is a synonym for n-Pentanol, which is of course a primary alcohol.
+196Stefan2 I was referring to this one; en.m.wikipedia.org/wiki/Tert-Amyl_alcohol
You can make some, for exemple Chlorobutanol, by mixing Chloroform and aceton ;)
Matt then you have to say that. Tert. Amyl alkohol is something completely different to amyl alkohol...
One of the best videos you have ever made
An idea for future videos: A Wittig reaction (use of phosphonium ylide).
Please do more metal cleaning videos!!! They are so satisfying to watch ❤️
Thanks for the explanation on the potassium superoxide so much!!! I was wondering why it would explode if it got a thick enough oxide layer! Great video! Keep up the good work!
A little tidbit I could add after the whole cleaning procedure is done would be to ad some kind of weight into the mineral oil, just to keep the potassium under the oil and out of contact with the air.
I could never be a chemist, that jello looked way too tasty
Pretty sure it’d give you heartburn…
How to clean you Potassium.
Step one: throw it in a lake
Step two: watch
To the problem of the floating Potassium metal: I was facing the same issue for my Lithium samples and made a kind of a "holding-down-device" which consists of a round plastic disc with a steel screw in the center. The other end of the screw is led through a hole in the lid of my container and kept in position by two nuts. The plastic disk now forces the Lithium pieces to submerge below the oil surface. Nevertheless, my Li got grey all over its surface, in the course of some months. Originally it came (from China) in a sealed plastic bag under Argon and was shiny then.
I love your sarcasm when you pour some water into the beaker with potassium residue
“Kris get the banana”
I was thinking the same thing
I wish this channel was available when i was in school. I was curious of so many this shown in the videos. Glad to know about them now. 😌
kris get the bannana, potasium
yes
“When it just sits there you can see how blue it is”
*why you gotta attack me like that my dude*
I found a kind of red stuff on silver crystal 15 years ago as well where I was just a junior high student. It was a single displacement reaction between Cu(s) and Ag+, after I got my silver crystal fully grown on a cooper wire, I pulled it from beneath the solution and found some kind of red-brownish substance covering on the metal surface. It looked like it was the metal itself has some interaction with air but I had no clue at all since no teacher could answer me, nor did I find any literature about it.
Did you use those blue gloves?
cuprous oxide perhaps
The spheres are beautiful.
Next - Cleaning old Cesium metal
No old francium
Sam T lolllll, it only last 22 seconds
+Jinyu Dai no. It lasts much longer than that. It has a half life of 22 minutes
+Josh Lukowicz huh really?
To make cleaning easier, you could use argon in a fish tank to make an inert atmosphere. You can get argon from a welding supply store.
I always use potassium fire when i light my candles
The blob is so satisfying to watch!!!!
could the oxide be blue because of a thin-film effect? I know that when you heat up steel you get an iron oxide layer that's coloured by the thin-film effect, and one of the colours it turns is a blue very like the one in the video
thought of that aswell but why wouldnt the color continiously change while the oxide film thickens?
Like most alcohols, isopropyl alcohol reacts with active metals such as potassium to form alkoxides that can be called isopropoxides. The reaction with aluminium (initiated by a trace of mercury) is used to prepare the catalyst aluminium isopropoxide.
How do you dispose of your chemical waste like the contaminated toluene?
You are absolutely correct sir. Potassium is far more reactive than it's counterpart metal of sodium. Might as well combine them to form NaK which is an even more reactive formulation. 😉
Amazing how much we don't know even when it comes to basic reactions
About 1 year late, but what part of this video do we not know about any basic reactions?
It's such a simple video but so satisfying
13:00 Yet another example of how things can go from really good to really bad really fast.
The blue color might come from solvated electrons produced by fresh potassium surface. This paper published in Nature Chem might help: "Coulomb explosion during the early stages of the reaction of alkali metals with water" DOI: 10.1038/nchem.2161
Couldn't you eliminate a lot of the risks by using a cylinder of Argon and putting a tube beaker?
+MaxRay16 that would require a cylinder of argon!
MaxRay16 argon is expensive.
@ eddie van horn its cheap
1m^3 is about 20$ in hardwarestores
its the cheapest noble gas because its released by the radioactive decay of 40^K
The colors on the metal don't need to be the colors of the actual compounds formed. They can very well be caused by light interfering with thin films per se. Remember what happens to stainless steel in flame?
Also, remember this is toluene and it's not pure. The red stuff might be an organic compounds which has oxidized and precipitated. Some say it's potassium ozonide.
There's really a lot of options. I've been cleaning potassium a long time ago and used same procedure, more or less. It was a pain in the ass.
Oh yeah, and use a smaller storage jar. Great video. :)
the red stuff seems to appear when it touches your glove, maybe it's reacting with the glove or something?
gygabite I agree. I'm watching the video for a second time, and it definitely appears that the metal is reacting with the gloves. That blue color's just odd though.
Probably Potassium Ozonide. I am not sure if it is caused by the gloves or a contaminant on the gloves, but the color looks just like potassium ozonide. It is normally produced when potassium hydroxide comes in contact with ozone. Not what you want to see xD It is very unstable.
Makes me wish I would have done more in school growing up, I love your videos
Potassium.
You should make audio versions of your videos, because I can fall asleep to these videos. Your voice is very soothing.
Thanks for this NileRed. It couldn't be more timely.
The school where I teach has some potassium that is very old. It is not something replaceable -- schools are not supposed to have it any more. For this reason it has been used sparingly over the years and now has a lot of oxide -- to the point of becoming dangerous. One of those situations where regulation actually makes things less safe.
Anyway, I was considering how I might clean it up and to have a tutorial to follow is just great. It helped that the exact moment that I was perusing your channel and found this, the school's work-place safety officer came around with some questions specifically related to the use of potassium and our risk assessment procedures. We watched the vid together.
So, a couple of specific questions.
Was the toluene dried or did you use it direct from the can?
I saw you adding IPA dripwise. How long did this part of the process take?
Would other alcohols (ie, ethanol) be equally suitable?
KOEt isn't so soluble in the solvents employed(toluene and mineral oil) so will form a coating over any remaining oxides effectively leaving the hazard behind. IPA is probably the best bet. I have a nice jagged 17 stitch scar on my arm from a NaK still clear up where I didn't use IPA, whatever you end up doing be careful.
+j_sum1 j_sum1 I added it slowly, but I am not sure how long the process took. The toluene was not dried, I just used it directly form the can. The little bit of water in it will actually react with some of the oxides. I am not sure if other alcohols would work, honestly. The commenter below seems to think that ethanol wouldn't be a great choice.
If you do this, just remember that a fire can start. To put it out, just cover the beaker with something. Don't use a fire extinguisher or freak out. It can lead to a much bigger problem.
Using anhydrous solvents will be less hazardous (M + H2O - > MOH + H2...) and you wouldn't loose any of your limited potassium stock, but the residual water in toluene won't be available to react/dissolve the oxide species. Your call. Personally I'd use anhydrous to limit the potential hazards but I'm used to working in a lab with an ample supply of them...
Thanks for that MortRotu and NileRed.
I'll stick with the IPA then. I'll do a test with the toluene we have available and if it is not to vigorous then I will proceed. If there look to be issues then I will dry it first.
+j_sum1 j_sum1 no problem, I happy to help. If the toluene is too wet you can dry it out reasonably well with some molecular sieves (4A ones for preference, but any size that absorbs water and not toluene would work fine) and not cause your H&S person palpitations by doing a still. It'll still have a fraction of a % H2O in but shouldn't react anywhere near as vigorously as 'wet' toluene would.
I hope a PhD in nitride materials synthesis becomes more useful than answering questions on YT...
I think that the red stuff comes from the reduction of the nitrile groups in your nitrile gloves. Then the red stuff is dissolved by the toluene (being an organic substance it will be quite soluble in nonpolar solvents).
Synthetic organic chemist here. I just discovered your channel and I have to say this is pretty great stuff. Keep up the good work. I am currently finishing up my grad work with Nile red and Nile blue analogues. Are you a dye chemist or did you just like the name?
+Vincent Martinez hey! I am not a dye chemist at all. I just randomly chose the name
+Nile Red I thought it would be interesting to see some chromatography
Logan Mante Probably would. I might do it in the future but i am honestly not a fan of it. It is usually pretty tedious.
Vincent, he has beakers with the channel name on them - you should get some. :D
Your videos are so mesmerising. I've watched the sodium cleaning 3 times.
You don't know why the oxides are blue? They are being removed, that's why they are blue. :(
That's got to be the cleanest sample of a group 1 metal that I've ever seen!
KCN/NaCN synthesis.
Maybe it's better to leave it to professionals to work with that stuff. Extremely toxic and a environmental hazard. Don't want to see beginners/amateurs messing with it and disposing it incorrectly.
little did he know nurdrage posted a video one week later
Nurd rage did it
I wonder how many people attempted this and died..
@@NextGenAge What? Sodium cyanide is not that dangerous. You probably can pour it down the drain. It's way safer than some chemicals
**sees potassium**
*NICE*
Cody’s lab rambles on trying to demonstrate the fire while Nilered is just avoiding
Slow clap
5:23 add light axle grease, make it cry, burn it, and let it swim /ref
the red stuff appearing when clean potassium is exposed to air should be potassium ozonide (KO3)
It seems to be some form of reaction with the gloves or their blue color. Its very unlikely KO3 as there is no ozone source and reactive alcohol in the solution.
@@leocurious9919 Ozonide can have enriched over the amount of time and is part of that crust! Especcially in populated areas there can be 'high' amounts of ozone in our atmosphere. Check your parts made out of silver! Regular oxygen cannot corrode it. Next to sulphur compounds, ozone has a big effect on silver, too!
@@knutritter461 Its really obvious that it is a reaction that takes place during his handling that produces this red stuff which is also soluble in the solvent.
You can tell this is the old and more responsible NileRed, mostly because he didn't cut the potassium while it was still dirty.
The red stuff almost seems to appear where you touched it, could it be reacting with the gloves?
"Reactions of ethanol over metal oxides"
I've found this old paper published in 2000, discussing the reaction between metal oxides and ethanol, hope it could be useful if you need
Potassium
I believe that blue oxide color was from some suboxide of potassium. Cesium has many well documented suboxides and are all very strongly colored, and it isn't unreasonable to assume that potassium does the same.
Queen would love this video, though knowing her she'd use bananas and battery acid, which probably is a bad idea.
I'm sure somebody already answered this better but I did some R&D work for a company about 15 years ago and in my research I ended up learning about anodizing as it was related to the project I was working on and it's basically a process of electrolytically induced and controlled oxidation. I may be wrong but I suspect the blue color of the surface oxide that forms on it is due to the specific thickness that the first order oxide layer as it stabilizes, and that causes some interference effect with light at that wavelength (sort of like the effect of opal and labradorite).
From what I remember in my research in to chromic anodizing, the thickness of the oxide layer is what corresponds with a wavelength of light that will be reflected instead of absorbed the most when going through it and that becomes the "color" you see. When you anodize aluminum , titanium or rhodium, you can vary the voltage and electrolytes used to achieve a certain "color" effect on the surface of the metal that in itself is not a dye or tint but yet produces an almost eerie effect of only allowing a specific narrow band of light to escape from it's surface. So by controlling the exact thickness of the oxide layer to reflect or maybe "re-emit" light of that wavelength you achieve an array of surface color effects.
The principal is that the potential for oxygen bonds is initially going to be high on a conductive metal surface when no oxide layer yet exists, as seen by the rapid formation of the oxide layer when the potassium was exposed to air, but as that layer of much less electrically conductive oxide thickens, it will quickly reach a point where the potential energy to overcome the oxide layer exceeds the input energy and it stabilizes there. Sorry I can't site a specific source, just spewing something out of memory from years ago.
LCARS43278 it's called the thin-film effect, happens with oxide on steel too. it was and sometimes still is used as a protective finish, and I'm pretty sure it's the reason the black finish on firearms is called gun blue
Around 10:00, the potassium looks like some kind of sea urchin with all the bubbles surrounding it.
I really, really, really like this video.