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blogfast25
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Tanker78:
Thanks for the kind words. 
Engine oil is now off the menu: the hope was to improve coalescence (thus reduce process time!) by having the nascent K float to the top but the 10W40
didn’t deliver.
A HC in which sodium would just about float would require a density of d > 0.927 (molten Na at MP) and that’s very high for a liquid
hydrocarbon (plus: they expand quite a lot on heating). To reach above 0.9 with HCs (and stay liquid) you basically need to introduce heavier
hetero atoms into your H and C based molecules. O and Cl, Br, I are obvious candidates but show far too much affinity for alkali metals. (Booom!
potential)
With silicones you’d go above 0.9 easily but it’s a recipe for a brisk alkali metal fire. Yum.
So it really isn’t that easy…
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blogfast25
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Quote: Originally posted by AndersHoveland  | The density of potassium metal is 0.862 g/cm3, whereas magnesium has a much higher density, 1.738 g/cm3.
It is quite possible that the large globules of potassium contain some unreacted magnesium metal particles inside, or perhaps the globule consists of
an alloy of potassium with a lesser portion of magnesium dissolved inside.
It is suggested that you measure the density of the "potassium" you have obtained and do some calculations. The yields from this reaction may be
significantly lower than first thought.
[Edited on 25-4-2011 by AndersHoveland] |
Hi.
The question of contamination of the potassium with either magnesium metal or solid slag particles, which even in very small amounts could tip the
density of the metal slightly over its theoretical density, has already been entertained several times before in this long thread. Very little
information is available on (Mg, K) alloys which makes me believe if any such alloys exist the magnesium content must be very small.
Because of the higher density of Mg and MgO they would drop out of molten potassium very quickly.
Determining the density of potassium would require a picnometer and some argon (the metal oxidises in air very quickly).
The melting point of the metal would probably be noticeable affected by alloyed Mg.
Experience shows that ‘slag’ superficially attached to the skin of the globules can certainly affect apparent density of the product. But
experimenters like Nurdrage, using the precise same method, have obtained floating potassium in HC solvents of less than 0.85, clearly the density is
much in line with the actual density of pure potassium.
I will probably verify any presence of magnesium shortly…
[Edited on 26-4-2011 by blogfast25]
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watson.fawkes
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| Quote: Originally posted by blogfast25 | Well, bizarrely the small ones did float but the larger one didn’t… Heating to about 160 C didn’t change anything… except that the small ones
dived too! At 160 C the density was again estimated to be about 0.834. [...]
I seem to recall nurdrage got floating potassium with Nujol (IR paraffinic oil) and that’s got a density of only 0.838. I just don’t get
it… |
My initial inclination is that these materials generate rather high surface tension energies on
the K globules. That's got to be one reason why coalescence is slow, but it will also play havoc with your intuition about relative density being the
only thing that determines whether something floats or not. The larger the globule, the less important surface tension effects are, so if you're
trying to float and coalesce at the same time, you've got two goals at odds with each other. On the other hand, if it's high surface tension that's
the problem, it's time to consider a surfactant. Unfortunately, I have little idea what to try specifically, because the usual context of surfactant
chemistry is aqueous. I do have a few odd thoughts, though.
One thing is obvious enough, that it will need to be either a non-ionic or charge-balanced (zwitterionic) surfactant, because K is an electron
conductor, and you're not going to get anything with a net charge to adhere to a conductor; the mechanical electrostatic repulsion will just be too
high. Strongly polar molecules will have a similar problem if the can't rearrange their charges either by ionizing two ends or have sufficient
internal electronic mobility. Anyway, try some glycine; it's far from the craziest suggestion in this thread.
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blogfast25
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Watson:
Whatever the cause of poor floating/poor coalescence, it’s a major problem because it increases the process time enormously. The chemistry is
basically over in about 1 h, 1 ½ h tops and could possibly be sped up further with a better catalyst but the coalescing tine is what it is: basically
about 2 h. And the poor coalescence affects yield also: many fine particles are lost, irrecoverably. The last test gave a de facto yield of 55 % for
instance, not great.
The long coalescence times may also cause the MgO to clump together (I feel the larger lumps are the product of some accretion process), which also
makes separating the wheat from the chaff harder….
Surface tension must play a part: I’ve seen quite large globules (> 1 g) dent each other, yet refusing to merge! Len1 claims the lowest metal
viscosity (ergo highest temperature) is beneficial but I’m still not convinced by that argument. Lowest possible solvent viscosity must be
beneficial as lower viscosity reduces the film thickness separating the globules and the film should be easier to pierce.
Do you think glycine has some solubility in hot alkanes?
I also seem to remember someone using dioxane (but at much lower temperatures, obviously). Furan might be a possibility as well…
[Edited on 26-4-2011 by blogfast25]
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watson.fawkes
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| Quote: Originally posted by blogfast25 | Do you think glycine has some solubility in hot alkanes?
I also seem to remember someone using dioxane (but at much lower temperatures, obviously). Furan might be a possibility as well…
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I don't know if glycine is soluble in hot alkanes; just don't know. It's slightly hydrophilic, so it might
not work. On the other hand, there are plenty of amino acids with alkane side chains: isoleucine, valine, leucine, phenylalanine. Really, though, I
doubt there's been much research in surfactants relevant to a K-alkane interaction surface. It's possible there's none at all; it's not like it's a
common combination. All of which means it's time to just try stuff.
Use of dioxane is in the original patent.
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blogfast25
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The only practical area where surfactants in HCs might be used/have been investigated and that springs to mind is in the industrial lube business. I
seem to recall octanoates/naphtenates as agents that help to keep dust particles/metal/metal oxide particles suspended in the base oil. Not exactly
the same, I know, but perhaps at least one avenue of lit research worth taking.
Glycine would be reactive to K, in all likelihood.
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jamit
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Where can you purchase 2 methyl 2 butanol? Is there an OTC source?
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blogfast25
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Remember that t-butanol (IUPAC: 2-methylpropan-2-ol) and 2M2B (t-amyl alcohol, IUPAC: 2-methylbutan-2-ol) are the ones that we know work.
For the UK, this site sells 2M2B, no questions asked (but its fairly pricy):
http://www.purechemicals.net/buy-2-methyl-2-butanol-2m2b-42-...
A 25 ml t-butanol sample was kindly provided to me by a forum member. The vial states “Caesium Laboratories” but nothing else…
I don’t know of any OTC sources, 2M2B was once used in medicine nut has since been phased out (I believe).
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m1tanker78
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What about a high temp. grease?? General compositions are:
-Base oil(s) (mineral/synthetic) .
-Thickener (polyurea in my case).
-Additives - Optional. "The most common additives are oxidation and rust inhibitors"
-Moly and graphite show up sometimes.
What the heck, I have a tub and will probably give this a try later on.
==============
EDIT:
Ok well, the grease didn't react with the sodium but I ran out of gas before all the grease liquified. Seems like a pretty messy way to go (especially
for necked glassware).
Blogfast: I just bought some 85W-140 gear oil. The data sheet indicates that the density @15C is 920 g/ml. I know that oils expand
at higher temps but still seems like a pretty reasonable density for K. I'll take some Na well beyond its melting point in it and post the result
(compared to regular mineral oil).
[Edited on 4-27-2011 by m1tanker78]
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jamit
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I'm in the usa. Where can you get t-butanol or t-amyl alcohol?
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blogfast25
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@Watson:
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…
Wiki’s data table clearly shows that polar solvents have higher surface energies than less polar ones, water being a real case in point…
**********
As luck would have it, I stumbled on this neat little table with surface tensions (ST) of some common liquid chemicals:
http://www.surface-tension.de/
Name CAS Ref.-No. Surface tension @ 20 °C in mN/m Temperature coefficient in mN/(m K)
n-Decane (DEC) 124-18-5 23.83 -0.0920
n-Dodecane (DDEC) 112-40-3 25.35 -0.0884
n-Heptane 142- 20.14 -0.0980
n-Hexadecane (HDEC) 544-76-3 27.47 -0.0854
n-Hexane (HEX) 110-54-3 18.43 -0.1022
n-Octane (OCT) 111-65-9 21.62 -0.0951
n-Tetradecane (TDEC) 629-59-4 26.56 -0.0869
n-Undecane 1120-21-4 24.66 -0.0901
Toluene 108-88-3 28.40 -0.1189
Water (WA) 7732-18-5 72.80 -0.1514
o-Xylene 95-47-6 30.10 -0.1101
m-Xylene 108-38-3 28.90 -0.1104
Tetrahydrofuran (THF) 109-99-9 26.40 -0.1277
Furfural (2-Furaldehyde) 98-01-1 41.90 -0.1225
Benzene 71-43-2 28.88 -0.1291
1,4-Dioxane 123-91-1 33.00 -0.1391
Note how the ST of n-alkanes goes up with MW.
Of the others water clearly stands out (but not as much as mercury!  )
Also highish values for dioxane and furfural (fairly OTC). Very OTC are toluene, benzene and xylene. Not very high for THF, the one I was
looking for when I found this web page…
[Edited on 27-4-2011 by blogfast25]
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m1tanker78
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Blog, have you given the heavy oil mentioned above any consideration? Initial tests provided me with floating Na spherelets (<= 1mm dia.) at around
Na's MP. I observed circulating spherelets 'riding the current' at the oil's BP but no coalescing. 
Initial tests also indicate Na being stripped from the block residue (GOOD!) but the oil is extremely opaque after boiling (BAD!). I still have much
testing to do but I'm almost certain this oil will float K.
One more thing, some gas octane boosters mention 'amyl' on the label but no specifics. Any hope there for an OTC K catalyst?
Tank
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Twospoons
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Would it be possible to get to t-butanol from MTBE (methyl tertiary butyl ether)?
Helicopter: "helico" -> spiral, "pter" -> with wings
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blogfast25
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| Quote: Originally posted by m1tanker78 | Blog, have you given the heavy oil mentioned above any consideration? Initial tests provided me with floating Na spherelets (<= 1mm dia.) at around
Na's MP. I observed circulating spherelets 'riding the current' at the oil's BP but no coalescing.
Initial tests also indicate Na being stripped from the block residue (GOOD!) but the oil is extremely opaque after boiling (BAD!). I still have much
testing to do but I'm almost certain this oil will float K.
One more thing, some gas octane boosters mention 'amyl' on the label but no specifics. Any hope there for an OTC K catalyst?
Tank |
Coalescence of small globules in viscous liquids will always be problematic. For now my priority is testing dioxane and/or xylene as ‘coalescers’.
High liquid surface tension and low viscosity are what we must look for to promote coalescence.
OTC K catalyst? We’re working on things in the relevant thread (see my response to Twospoons). Progress is decidedly slow, I must say…
No idea. Questions about the synth. of t-alcohols are better placed in this thread:
http://www.sciencemadness.org/talk/viewthread.php?tid=15171
… where there’s a chance the organo wiz kids pick up on it.
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blogfast25
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Following Tanker’s suggestion to look at polyglycols (such as found in brake fluids) as coalescing liquids, I purchased some DOT for a simple test.
Well, I couldn’t get DOT 3 but got DOT 4 instead, which states ‘contains polyalkylene glycol ethers and ether esters’. I believe these brake
fluids are highly anhydrous because moisture would reduce the desired high boiling points and could lead to ‘spongy’ brakes.
A globule of 0.5 cm diam. of clean K was placed in a few ml of the liquid and the assembly immersed in a water bath, starting at RT. The K floats
right away and at RT there isn’t much reaction going on. But as temperature increases and bubbles started to form on the surface of the metal. At
about 40 C the reaction is brisk (but contained) and the metal dissolved in the DOT 4 in matter of a minute or so.
This reaction, assuming I’m right about the water, must come from terminal OH groups present in the brake fluid, thus rendering it unsuitable for
contact with (warm) K.
This defect could possible be remediated by esterifying the -OH groups. But that’s not so simple either: any excess carboxylic acid not used is
likely to be miscible with the brake fluid, as would also reaction water. These would then be fairly difficult to separate from the bulk of the
liquid…
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m1tanker78
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BlogFast, straight brake fluid reacts briskly with Na as well. I assume you used straight BF for your experiment? My experiment which I briefly
outlined in the t-alcohol thread used a blend of mineral oil and BF!
May I suggest you retry the experiment beginning with a small K glob in clean HC in which it should sink. Warm the oil slightly and add the BF
dropwise, if need be, to the oil until you achieve the desired SG.
K should require less BF which I think should offset K's higher reactivity than Na. Also note that I used food grade mineral oil which I think has a
higher SG than kerosene. I haven't read up on the differences between DOT 3 and 4 BF but they presumably should have similar results.
Good luck!
Tank
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blogfast25
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To further evidence that the DOT 4 does contains alcohol functionality I tested the substance as follows (it’s a little test I devised some time
ago): to two test tubes was added 5 ml of 1 M K2Cr2O7 in 1 M H2SO4. To the first was then added 8 drops of ‘methylated spirits’ (ethanol,
essentially) and to the second 8 drops of DOT 4. (Dichromate oxidises primary alcohols to carboxylic acids and secondary alcohols to ketones (it
doesn’t affect tertiary alcohols) and is itself reduced to green/blue Cr3+.)
At about 70 C the ethanol control reacted fastest of the two but the DOT 4 tube really wasn’t far behind: within minutes both tubes had their
dichromate reduced to Cr3+ COMPLETELY. This shows strong alcohol functionality present in the brake fluid…
Tanker, to carry this further means to me to have to eliminate the alcohol functionality: it's no good using a liquid that react with the metal, even
if reactivity was much smaller than it currently is.
Like I said, it might work better for Na.
I will seriously consider esterifying the DOT though: these polyglycol ether esters are interesting liquids and could indeed be good coalescing
agents, if modified. I might raise a note in the organics section about it...
[Edited on 30-4-2011 by blogfast25]
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m1tanker78
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Blog, I won't twist your arm but still feel like your experiment was inconclusive for the purpose of a coalescing medium. In fairness, I haven't
provided any compelling evidence to suggest that it could have a favorable outcome with K. If I had any potassium metal, I'd test it myself. I realize
that if you tested every single theory that's proposed, you'd be K-poor 
If my 'glass' will withstand a 500W heat lamp, I may do a side-by-side experiment (Na in BF/MO blends) and post the vid.
Tom
[Edited on 5-1-2011 by m1tanker78]
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blogfast25
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Ok, just because it's you  I'll run a test with 50 kerosene/50 DOT 4 and K, even
though I can guess the outcome: blending doesn't make the alcohol functionality go away and K remains more electropositive than Na.
Should be later on this day...
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m1tanker78
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| Quote: Originally posted by blogfast25 | Ok, just because it's you I'll run a test with 50 kerosene/50 DOT 4 and K, even
though I can guess the outcome: blending doesn't make the alcohol functionality go away and K remains more electropositive than Na.
Should be later on this day...
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Blog, I believe 50/50 (v/v) is too much BF - certainly for K! Slowly adding the BF to warm HC seems to help remove some of the moisture by flash
boiling. One thing I haven't accounted for in my own experiments is the fact that the block residue might somehow have a favorable impact by
pre-drying or pre-reacting with the BF.
Still too many 'X-factors' for comfort that I need to iron out. Blog, I won't blame you if you want to hold that experiment for a later
date. Keep in mind that this procedure is intended to give Na and K a medium to float in. This would obviously facilitate separation of the
metal from heavier residues and MIGHT help with coalescing the same.
I wonder if boric acid could be used to 'tie-up' some of the alcohol functionality. I believe the active portion of the BF is a C10 so boric acid may
not even tickle it. One other thing to consider is that a HC/BF blend would probably remain hygroscopic so an additional warm HC dip would be
necessary prior to storing either alkali metal.
Tom
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Eclectic
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It should be easy enough to distill dioxane from Glycol antifreeze with a little sulfuric acid added....why not use that?
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blogfast25
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Well, well: the result of the DOT 4/kerosene (50/50 V/V) was a bit unexpected. Firstly the liquids don’t mix completely and form a two phase system,
kerosene on top (obviously). Dropping a small piece of clean potassium in it, it settles at first at the interphase. But then, as temperature rises
the K starts reacting with the DOT 4 and it shoots up into the kerosene phase because of the hydrogen which ‘carries’ it. The reaction then
subsides and it sinks back into the interphase where it starts reacting again, then shoots up into the kero, etc etc. Here it is currently floating in
the kero (this is a 1” test tube):
As a result the potassium lasts much longer and I lost only about 50 % (still way too much) or so after cooling.
Interestingly this two phase approach could be useful because the kero protects the metal from air oxygen. The activity of the DOT 4 remains too high
for K though.
As a sideshow I’ve estimated the -OH functionality of the DOT 4 semi-quantitatively with a simple experiment. To 3 test tubes was added 15 ml of 0.1
N K2Cr2O7 in 0.1 M H2SO4 each (note: this was 0.1 normal dichromate, not as previously used 0.1 molar dichromate - it’s 0.1/6 M). To the first (the
control) was added 1 ml of methylated spirits (this reduced all dichromate quickly to Cr3+) and to the two others resp. drop by drop
methylated spirits and DOT 4. All tubes were kept on water bath (about 90 C) and plenty of time was allowed between drop additions for the reaction to
proceed (it’s slow at these concentrations). By comparing the colours of tubes 2 and 3 with the control it could be estimated how many drops of
alcohol and DOT 4 were needed to achieve complete reduction of the dichromate.
The methylated spirits took about 9 drops, the DOT 4 about 17 drops. So in essence and approximately to completely esterify the same volume amounts of
methylated spirits and DOT 4, the brake fluid would require about half the quantity of an (identical) alkanoic acid (no wonder it reacts vigorously
with Na and K!).
This approximate result could also be used as a basis for back titration of an excess of dichromate which should allow precise determination of the
molarity of the -OH functionality of the brake fluid.
Tom:
For me, to carry on with this promising development means terminating the hydroxyl groups. I doubt boric acid could do it: boric acid does react with
methanol but that’s quite a different alcohol. Glacial acetic acid, a few drops of conc. H2SO4 and mild heat would do it though. You’re then left
with the task of removing any reaction water, the H2SO4 and any excess acetic acid but that’s doable.
In fresh brake fluid a priori moisture must be very low: these liquids are designed for high boiling points; bubbles of steam would mean spongy brake
responses.
[Edited on 1-5-2011 by blogfast25]
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blogfast25
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| Quote: Originally posted by Eclectic | | It should be easy enough to distill dioxane from Glycol antifreeze with a little sulfuric acid added....why not use that? |
Ecclectic, I’d use dioxane if I had any (I can get some quite easily but it’s fairly pricy). Someone on this forum somewhere claimed converting
glycol to dioxane was seriously messy. Will have to search the board again, could be wrong on that...
This proposed esterified brake fluid may be quite ‘dioxane like’ (the ‘poor man’s dioxane’? ) with some added advantages (much higher BP).
All to play for…
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Eclectic
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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.
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plastics
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For dioxane:
http://classic-web.archive.org/web/20071011001804/www.frogfo...
is what you want
I can personally vouch for the fact that removing the water is a right royal pain in the a**e and leaves you with a lot less than you think!
However having a small quantity of the real McCoy to compare with, it does work
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