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Author: Subject: Make Potassium (from versuchschemie.de)
blogfast25
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[*] posted on 1-5-2011 at 12:03


Quote: Originally posted by Eclectic  
I think it's a fairly simple slow distillation from acidified auto anitfreeze....only troublesome bit is getting all the water out of the distillate.


This one here confirms what you say but it’s short on details:

http://www.sciencemadness.org/talk/viewthread.php?tid=55&...

Quote: Originally posted by Organikum  

I prepared DIOXANE several times now from ethylene glycol in very good yields - this solvent is very useful! How to twist this to get acetaldehyde - no clue. For sure simple boiling with H2SO4 gives DIOXANE - and thats fine. ;)

ORG :P



As does plastics... Much obliged, that's pretty unequivocal as a procedure.

[Edited on 1-5-2011 by blogfast25]
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[*] posted on 1-5-2011 at 13:19


BlogFast: Interesting result with the 2 liquid phases. I haven't observed this but then, I don't even get close to 50/50. I don't know if the DOT 4 has anything to do with any of this but if the BF/Kero layer is saturated with kero and it still reacts unacceptably with K then I guess there's not much more to be said about potentially using a DOT 4 blend with K.

My DOT 3 was opened 3 or 4 years ago and left [capped] on a shelf since. No doubt it's wet.

Has naphthalene (moth balls) received any attention? SG ~ 1.14; BP ~ 218*C. No -OH groups to tackle.

Tom
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[*] posted on 1-5-2011 at 14:32


I had a rather left field idea today. It may be possible to get the K to coalesce by applying a very strong electric field - something on the order of 10kV/cm.
Could be done with a neon sign transformer, rectified, with electrodes consisting of sealed glass tubes with wire inside, spaced a few cm apart. Note - I'm thinking electric field, not electrolysis. I would expect the metallic K balls to be attracted into the E-field, creating a bit of a squeeze that would help them coalesce. They wouldn't have to be floating (ending the need for a high density HC) as the E-field would provide all the necessary driving force.
Sorry I can't help with a practical test.

Just ran a simulation with FEMM4.2 - there will be a small force attracting the K balls into the E-field.

[Edited on 1-5-2011 by Twospoons]




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[*] posted on 2-5-2011 at 04:51


Quote: Originally posted by m1tanker78  
My DOT 3 was opened 3 or 4 years ago and left [capped] on a shelf since. No doubt it's wet.

Has naphthalene (moth balls) received any attention? SG ~ 1.14; BP ~ 218*C. No -OH groups to tackle.
Tom


Yes, it is hygroscopic.

I wanted to try naphthalene after Nurdrage’s success with Tetralin ® but it turned out my [url=http://www.sciencemadness.org/talk/viewthread.php?tid=15348#pid199586]’naphthalene’ wasn’t naphthalene[/img]. The idea kind of got forgotten after that. But it’s worth pursuing, IMHO. Just make sure you have the realm McCoy (do an MP test…)

Quote: Originally posted by Twospoons  
I would expect the metallic K balls to be attracted into the E-field, creating a bit of a squeeze that would help them coalesce. They wouldn't have to be floating (ending the need for a high density HC) as the E-field would provide all the necessary driving force.
Sorry I can't help with a practical test.

Just ran a simulation with FEMM4.2 - there will be a small force attracting the K balls into the E-field.

[Edited on 1-5-2011 by Twospoons]


That would work if the K was indeed electrically charged. That seems to be the case with many emulsions. But with K?

What’s FEMM4.2?

Worth considering…
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[*] posted on 2-5-2011 at 07:05


Blog, I tried sodium in naphthalene; briefly outlined here. It's inconclusive for K but thought you might be interested in the results with Na. Based on that, I believe K will float but won't easily coalesce.

Tom
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[*] posted on 2-5-2011 at 14:31


Quote: Originally posted by blogfast25  

That would work if the K was indeed electrically charged. That seems to be the case with many emulsions. But with K?

What’s FEMM4.2?

Worth considering…


It works even if the K is not charged, as it is a conductive metal floating in a dielectric sea. As the K moves into the high field region the field energy drops, as the K 'shorts out' the dielectric. The reduction in field energy is what gives rise to the force.
FEMM4.2 is a Finite Element Analysis program for 2D magnetic, electrostatic, and thermal simulations.




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[*] posted on 2-5-2011 at 18:27


Quote: Originally posted by blogfast25  
Actually, after refreshing the concept of surface tension or better, surface energy (dW/dS, the work dW needed to increase the surface area by dS), it’s clear that adding a surfactant to the solvent phase will actually stabilise the ‘K/solvent emulsion’, thereby reducing the K coalescence rate. Much like what happens when you add some detergent to an oil/water emulsion.

In reality we’d have to increase the surface tension, thus favouring minimisation of surface area, ergo larger globules… That’s where other solvents, perhaps dioxane or THF might come into it…
I've found a small section in Physical Chemistry of Surfaces titled "Stabilization of Emulsions by Solid Particles" (p 510 in 6th ed). Given the reports herein of the MgO dust on the surface of the K globules, I'd guess that it's these MgO particles that are stabilizing the interface. The use of a surfactant would be to affect the contact angle between the MgO particle and the K globule. If this contact angle goes to zero, the MgO particles will not adhere to the K.
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[*] posted on 2-5-2011 at 18:59


Wouldn't just the small, slow addition of EtOH to the melted globs lower the surface tension by cleaning it off while generating Alkoxides? I doubt much would be lost and I would think it would allow for nice blobs in the end.




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[*] posted on 2-5-2011 at 19:06


Quote: Originally posted by Twospoons  
I had a rather left field idea today. It may be possible to get the K to coalesce by applying a very strong electric field - something on the order of 10kV/cm.
Could be done with a neon sign transformer, rectified, with electrodes consisting of sealed glass tubes with wire inside, spaced a few cm apart
I had the exact same idea; I should have mentioned it before.

The physics is that conductors self-polarize in an electric field. This is similar to Gauss's law, except here the charge is on the surface and also creating a counteracting electric field until the internal field inside the conductor is zero, at which point no more charge moves. In the present case, a pair of adjacent globules will develop polarizations along the line of (+ -)(+ -), so that the globules are attracted to each other at their poles. This creates a macroscopic pressure of the droplets against each other, a force that might overcome whatever is holding the droplets apart.

The practical difficulties of this instrument are not trivial, although they should be manageable.
  • The glassblowing required isn't too hard for a glassblower, if you are or have access to one. The electrode tips should be arranged so that the greatest field is between the ends; this will concentrate the available polarization in one place. The ends will look sort of like pincers.
  • If you want a wand-shaped device, packing the lead wires with a relatively high dielectric-constant material will also help, essentially by sucking up the field so that the highest remains at the ends. Suitable packings can be liquid, like ethylene glycol, or solid, like TiO2; you could even use water. Remember that the packing goes in the space between the wires, so a liquid packing requires wire support.
  • The power supply for this doesn't need to be particularly high current, so I'd avoid a neon-sign transformer, simply because they create a fairly big hazard when your insulation fails. Much better is a Cockcroft-Walton generator, because they can be designed with high voltages and low internal charge capacity, so their shock hazard is limited. Some experimentation will be necessary to see just what voltages are required, but I don't imagine it will be more than a few kV over, say, a 5 mm gap.
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[*] posted on 2-5-2011 at 20:26


Quote: Originally posted by watson.fawkes  
I had the exact same idea;

Must be a good one then!
The simulation I ran gave forces around 100th of a newton with fields of ~10kV per cm, for a metal ball ~5mm diameter.
I suggested a NST as its a very easy way to get to 20kV. And no more dangerous than playing with blobs of molten K :P
Multipliers are good too- just watch out for the stored charge.

Hell, a Van deGraaf might work, should you have access to one.

The glass work is simple - a 5mm tube will seal on its own if you melt the end in a propane flame.




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[*] posted on 3-5-2011 at 04:02


Quote: Originally posted by Twospoons  
Must be a good one then! [...] I suggested a NST as its a very easy way to get to 20kV. And no more dangerous than playing with blobs of molten K :P
Multipliers are good too- just watch out for the stored charge
It's not apparent to me that it's such a good idea. Putting a 7 kV potential inside your hand is not something that the HV crowd does in any kind of regular basis. You have to plan for failure, particularly in this case. It's not like glass never breaks in the lab. I'd say that this tool is significantly more dangerous, at least at first blush, than molten K.

As far as supplies, the difference between a multiplier and a neon sign transformer is that a multiplier has a bit of stored charge, which will dissipate, and the NST has no stored charge, and will keep pumping current indefinitely. You absolutely need an inherently current-limiting supply for this tool to be anywhere near safe. Using an HV transformer pretty much negates that from the start.

Upon further consideration, I'd heartily suggest putting the entire multiplier in the wand on the far side of the handle, so that only the supply voltage of 600 V - 1 kV or so is in the handle. This complicates construction, of course, but seem like a much better idea than running flexible HV cables and having the wand just be passive conductors. At 20 kV potential, it's not an insignificant problem just to source adequate insulation for your wire. In order to avoid corona and arcing inside such a relatively small space, it's necessary to use some kind of potting. Oil or paraffin wax would both work, it seems. You're still going to end up with a thick handle.

Perhaps a much better option is to make this not-a-hand-tool at all. The advantage of a hand tool is that you can wave it around and provide mechanical motion easily. With a fixed tip, you have to move the K, rather than vice-versa, which leads to a whole host of other problems.

The upshot is that this should under no circumstances be anyone's first HV project. There's nothing here which is simultaneously safe and easy.
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[*] posted on 3-5-2011 at 07:04


Sedit:

That’s already been tried (but with IPA), with very mixed results. And it consumes potassium.

Watson and Twospoons:

If Twospoons’ simulation is correct (0.01 N, for 10 kV/cm for a 0.5 cm (5 mm) diameter K ball) then this method should work extremely well: the actual weight of such a ball (unsuspended) is only about 0.0005 N (mass = 0.05 g)! Unhindered by any other forces acting on it (that’s not the case, I know) it would undergo an acceleration of no less than about 200 m.s<sup>-2</sup> ! That really sounds too high to me… :o Way to go if it's true! :cool:

Later on today I'll be testing the more mundane option of using xylene as a coalescing liquid... :)


[Edited on 3-5-2011 by blogfast25]
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[*] posted on 3-5-2011 at 10:51


Xylene (racemic mixture) didn’t really do the trick either. Four pieces of potassium (ca. 5 mm) were cut from a larger piece and added to about 20 ml cold xylene in a 100 ml conical flask. The ensemble was then heated on an electrical hot plate to about 100 C.

At first the pieces were reluctant to assume their normal spherical shape, presumably because of surface impurities forming some sort of ‘skin’.

1 drop of methylated spirits was the added and the pieces immediately took on their ball shape with a silver mirror finish. But no amount of teasing them together could persuade them to merge. I gave up after about 15”.

Next up should be either dioxane or ‘ethyl ester of DOT 4’…
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[*] posted on 3-5-2011 at 16:46


Electrostatic coalescence taken to this thread

I think the forces were more like 0.001N. And they vary according to position in the field.





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[*] posted on 3-5-2011 at 18:21


BlogFast, what did the K do in the xylene? Based on the reported densities, they should have hovered around. What exactly did the drop of methylated spirits do to make 'em ball up? Someone else a few pages back reported success with dioxane so I don't see why it won't work.

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[*] posted on 4-5-2011 at 04:13


Tanker:

Well, the balls weren’t really balls to begin with, as I’d cut off random shapes from a large blob. I fully expected them to assume their spherical shape on melting but they didn’t really: they just kind got more rounded. They were typically blue skinned and I thought the skin was kind of retaining their cut shape. When I added just the one drop of methylated spirits, a bit of reaction showed up and then in seconds they went nice and silvery and popped into their spherical shape. But no floating and no merging either.

Later on I’m gonna try to and press them into each other with a test tube and some suitable ramming tool: just trying to press the oil in between them out and the potassium metal into itself…

I’ve no dioxane at hand so’ll probably try and make some from glycol.


*************

The test by squeezing the solid balls together wasn’t 100 % successful either but it worked more or less.

4 balls of about 5 mm diameter were loaded to a standard size test tube and just about covered with kerosene.

A ‘ramming rod’ was fashioned which fitted snugly into the tube while allowing enough daylight for the kero to evade the rod. Pressure was thus applied on the balls, deforming them like hard putty and pushing them into roughly a hemisphere (the shape of the bottom of the test tube). But shaking the tube clearly showed the potassium hadn’t merged yet. So I rammed again and left the ramming rod in place while putting the tube into a water bath of about 70 C.

There partial merge occurred: two pieced welded together quickly while two others were creeping up in the daylight between the ramrod and the tube wall. I hasten to add that this effect was non-capillary: the daylight was far too large for that.

Adding the two renegade pieces to the molten blob and a bit of skilful ramming later all potassium was merged into one single ball.

This method certainly has potential (with some improvements) to fairly quickly merge multiple smallish balls together, say 1 - 5 mm. That size often takes an age to merge into larger units too…


[Edited on 4-5-2011 by blogfast25]
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[*] posted on 6-5-2011 at 12:58


BlogFast, I thought you'd been using kerosene or oil to merge the potassium nuggets all along (separate from the slag). Does the t-alcohol's -OH react with K to form alkoxide? If so, this could be what's making the nuggets stubborn to merge. I had to 'wash' my post-brake fluid Na several times in hot oil before they'd all coalesce. The alk skin seems to linger, causing problems with merging.

Could be the reason for stubborn K in xylene as well?

EDIT: Never mind, I had another look at your proposed reaction scheme and saw that it does produce alkoxide. I'm going to try the strainer method (in the refining thread) and see if that makes things any easier.

Tank

[Edited on 5-6-2011 by m1tanker78]
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[*] posted on 6-5-2011 at 13:39


Quote: Originally posted by m1tanker78  
BlogFast, I thought you'd been using kerosene or oil to merge the potassium nuggets all along (separate from the slag). Does the t-alcohol's -OH react with K to form alkoxide? If so, this could be what's making the nuggets stubborn to merge. EDIT: Never mind, I had another look at your proposed reaction scheme and saw that it does produce alkoxide. I'm going to try the strainer method (in the refining thread) and see if that makes things any easier.

Tank

[Edited on 5-6-2011 by m1tanker78]


Yes, the catalyst reacts with the K but remember that there isn't much catalyst (0.1 mol per mol of K), so that at the end of the reaction all t-alcohol is present as K t-alkoxide. This does not impede coalescence in any way. And presence of the alkoxide cannot be avoided anyway.

I've already removed the solvent (containing the alkoxide) and replaced it with fresh solvent: it makes no difference: K is difficult to get to coalesce, period.

[Edited on 6-5-2011 by blogfast25]
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[*] posted on 6-5-2011 at 14:10


I also removed the Na from -OH and alkoxide source. My point was that the alkoxide (presumably) lingers on the surface of the Na. It doesn't matter if I take the oil to 100 degrees or 300 degrees. As the nuggets become larger, the 'skin' becomes more visible when molten. I never had so much trouble coalescing even the dirtiest Na before.

Quote:
K is difficult to get to coalesce, period.


I disagree (but can't put it to test). I would argue that K that's never been in contact with -OH will merge relatively easily. Like you said, it's not an option here but the distinction should be made, IMO.

Did you ever get around to trying dioxane (from glycol)??

Tank
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[*] posted on 7-5-2011 at 06:15


Quote: Originally posted by m1tanker78  
I disagree (but can't put it to test). I would argue that K that's never been in contact with -OH will merge relatively easily. Like you said, it's not an option here but the distinction should be made, IMO.

Did you ever get around to trying dioxane (from glycol)??

Tank


It’s simply not true, Tank: in the several tests I’ve carried out of late all my coalescing experiments were with pieces of K with perfectly clean skin (bar that thin blueish film you always get with freshly cut K), cut from a much larger blob (about 2 cm wide) and they show clearly show that that K too is hard to get to clump together, no difference.

It’s mentioned also higher up by people like len1 as a property intrinsic to K, not to how it was produced. It has no ‘memory’ of the latter.

Dioxane? Give us a chance, man! I’ve yet to synthesise some because it’s quite expensive. That’ll be sometime next week. Synth will be time consuming to get rid of the last bits of water/acid in it. And I don't expect miracles from dioxane eithr, just an improvement, see also the patent itself.

The other solvent that interests me is the ‘ethyl ester of brake fluid’ but I’ve no glacial acid at hand. Because of the multiple ether functions in the brake fluid an esterified version would be a bit ‘dioxane like’…


[Edited on 7-5-2011 by blogfast25]
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[*] posted on 7-5-2011 at 09:24


BlogFast: I don't know how the following translates into chemical/scientific terms so bear with me a little bit. ;)

I have no reason to doubt that the film that forms on post-BF treated Na is sodium alkoxide so I'm running on that basis. This alkoxide film is 'repelled' by the molten sodium and by the oil. If either of those were to fail then the film wouldn't be a .... well, film. With that in mind, if you take some sodium (assume K too) nuggets, cut them in pieces and bring them to MP in a HC, the alkoxide film is going to 'extend' to cover the entire metal/HC interface once again. You'll now have fragments of the stubborn metal (counter intuitive to the goal which is merging).

Pressing the solidified K obviously disturbs the [immobile] film so that's why some of your pressed K successfully merged.

According to the net, alkoxide begins to decompose from 100 to 300 degrees C. But would it truly decompose in contact with a reactive metal?? I believe not, especially not at higher temps.

This is my basis for wanting to differentiate coalescing alkali metals produced by catalytic t-alcohol and alkali metals in the general sense. This may also help me further understand what the hell's taking place in this alcohol-catalyzed reaction. As I said before, I never recall having much trouble merging Na that has never seen brake fluid which reinforces the above stated. Sodium oxide forms a not-so-subborn crust or easily diffuses into hot oil then settles out after cooling.

++++++++++++++++++++

Two relatively easy experiments pop into mind with K. One is to take two large-ish spheres of K and cut out a cube with each (or somehow 'peel' the outer layer). Immediately place the cubes in HC and attempt to coalesce.

The other is very dangerous but may be worth a try sometime. Take 2 or 3 K globs and give each one a very quick dip in ice water. Quickly plunge them in HC, preferably with an intermediate dip in a non-flammable HC.

Both of these procedures should produce K that's mostly free of alkoxide, only ordinary oxides, and will probably merge much more easily.

Just thinking out loud here....

Tank
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[*] posted on 8-5-2011 at 08:30


Tank:

You claim that you have ”no reason to doubt that the film that forms on post-BF treated Na is sodium alkoxide” yet I see no reasons to underpin that claim.

Let’s start with the potassium alkoxides of t-butanol and 2M2M (the t-alcohols we know work). These do not ‘form a film’. We know these to be effective because they HAVE to form alkane-soluble potassium alkoxides. Without alkoxide solubility, no sustained reaction could take place. So forget about a film of K alkoxide on the potassium. It ain’t there.

How about the sodium alkoxide formed when sodium reacts with the brake fluid polyether ester hydroxyl functionality? Well, I can’t vouch for it but in all likelihood the resp. alkoxide will be highly soluble in the brake fluid. Why not test this with a nice, clean cut piece of sodium and some fresh (and dry) DOT 3? The potassium dissolves without leaving a trace in DOT 4.

The experiments you prescribe are interesting but IMHO simply not necessary. ‘Cleaning’ the potassium with a quick dunk in ethanol has already been tried: it makes no difference. Freshly prepared, cooled potassium (using our method) looks precisely like you would expect it to: typically blueish.

You’re looking too far a field. I’d really try and esterify the brakefluid if I was you, then remove all traces of excess acid and water and see where that leads.

The real causes of the difficult coalescence of K and Na are:

1. Surface tension not high enough: much higher surface tension would favour small globules merging into larger ones because for the same volume, one larger globule has less surface area than several small ones. Hence looking at more polar solvents like dioxane, which have higher surface energy.

2. The almost weightlessness of the metals when suspended insolvents of similar density. Imagine how quick mercury would coalesce: the globules congregating at the lowest point of the container would exercise considerable force on each other. Not so with K and Na...

[Edited on 8-5-2011 by blogfast25]
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[*] posted on 8-5-2011 at 12:17


BlogFast, I'd already dissolved Na in 'dry' DOT 3 (thanks to my neighbor - had an unopened bottle and donated to me). Indeed, it fizzled away in the warm BF without a visible trace. I see your point about alkoxide being soluble in BF. With that out the way, I still maintain that there's a stubborn 'film' on my post-BF Na which apparently is NOT alkoxide and makes coalescing said Na much more difficult.

A few points to keep in mind before dismissing the film claim:

I. Na treated with BF was finicky to merge even after 5 rinses in hot, clean mineral oil. I discarded the oil after each cycle - replenishing with fresh oil.

II. Na that has never been in contact with BF merges extremely easily under oil in spite of it pulling into a tight ball and having surface oxides/crust.

III. Correct me if I'm wrong. Rinsing/dipping K in ethanol isn't much different from dipping in BF in terms of avoiding -OH. Both provide a primary alcohol function, no? If so, the ethanol dip you mentioned was irrelevant, possibly counter-productive if my theory is correct.

I haven't had a chance to look over the complete ingredient list for the particular BF's I've used. There may be something else (unrelated to alcohol function) that causes the annoying film. I recall a similar effect when I experimented with a synthetic heavy oil.

If I can rig something up to safely make an attempt at 'brake fluid ester', I'll give it a try. I need to read up on the process and try to adapt.

Tom

[Edited on 5-8-2011 by m1tanker78]
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[*] posted on 9-5-2011 at 03:13


Again though, the ethoxides and methoxides of K and Na are highly soluble in the respective alcohols. You can even test that with their hydroxides:

(K, Na)OH(s) + (Et, Me)OH(l) === > (K, Na)(Et, Me)O(sol) + H2O(l)

The pure alcohols act as weak acids also towards these strong hydroxides and they dissolve completely, as alkoxides.

For the esterification of DOT 3/DOT 4 you need some glacial acetic acid and some conc. H2SO4.

Another potential coalescing fluid I’ll be testing shortly is isopropyl myristate:

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

Very OTC (but not cheap), from Dentyl pH. With that end ester group this may have enough polarity to work. I’m drying some now.


[Edited on 9-5-2011 by blogfast25]
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[*] posted on 9-5-2011 at 13:54


DentylPH, huh? May be worth the investment if a) it works and b) it's at least somewhat resistant to decomposition at elevated temperatures. That being the case, it could be reused at least several times.

Brake fluid ester: I have conc. sulfuric (~98%) but no glacial acetic. Still, I did some tinkering with first blending H2SO4 with BF, then blending that with mineral oil that contained a few small sodium pieces and some block residue. Adding a little bit of H2SO4 to BF at RT reduced reactivity with sodium by half compared to sodium in straight BF in a side-by-side (at RT). I was anticipating an angry reaction with the acid blend but the contrary resulted.

No gas evolved from BF + H2SO4 however, a little warming did occur. Not sure how big a part moisture in the BF played. Hot (Mineral Oil + (BF + H2SO4)) spared and cleaned the small sodium pieces but created some black sludge which hampered my attempts to coalesce. I suppose some of the glycol component was carbonized (dehydrated).

Could IPM be a candidate for conversion to a t-alcohol?

Tank

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