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blogfast25
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Yes, the slight polarity is what I hope might just increase the surface tension enough to promote coalescence. I made an unknown blend of mainly
C8/C10 fatty acid ethyl esters today, to be further worked up and thoroughly dried tomorrow.
Surfactants will make matters worse: it’s a bit like adding washing up liquid to a water/oil mixture and hoping the oil will separate out faster
that way: it doesn’t; surfactants promote the formation of emulsions, NOT separation!
HC soluble surfactants would be ideal to make fine dispersions of Na/K in alkanes, like ‘sodium sand’.
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m1tanker78
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I came across another OTC product that caught my attention. It's called "ester oil"  - used in refrigeration systems. The data sheets are a little vague but it's available at automotive stores around here for around $7.00
USD for 3 ounces. It's fairly expensive but may be a reasonable cost considering the required workup for making esters. The reported SG at RT is ~9.5
...
Tank
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Squall181
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So looking at tanks video of floating sodium in the mineral oil and brake fluid mix I decided to try it on thermo-Na. My procedure involved mixing
NaOH with some magnalium powder since that's the only thing I had on hand.
After setting the mixture off and letting it cool, I then broke up some of the slag and filled the container with Mineral oil and heated, when the
oil came to temp I added some DOT 3 brake fluid to the mix and to my surprise there was a lot of bubbling and many brown spheres of slag began to
float to the surface. I then scooped these spheres into a separate container and upon further examination found that they contained tiny balls of
sodium metal covered in brown gunk.
From this result I cannot see how one could efficiently separate these small spheres of sodium from the rest of the material.
Size of the sodium balls was about the size of the ball in a ball point pen.
My next idea is to leave the slag left from the reaction as one big piece and see if any sodium will leach out upon heating in MO.
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blogfast25
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The test with my home made ‘C8/C10 ethyl ester’ shows that long chain esters aren’t suitable for contact with K. This ester product had been
worked up properly, washed amply with water to remove any remaining alcohol or acid and the dried with an ample quantity of anh.
MgSO<sub>4</sub> for over 48 h. Finally it was tested with NaHCO<sub>3</sub> for traces of any acid: no bubbles formed at all.
About 1 ml of the ester(s) was then poured into a dry, clean test tube and a piece potassium added. It floats but even at room temperature there is
very slight reaction. Heating to the melting point of K, white flakes of start peeling off from the metal. It’s very similar to what happened with
the isopropyl myristate.
I suspect that the K snatches the oxygen from the protruding carbonyl group, made more reactive by the long electro-pushing alkyl groups present in
the ester, forming K<sub>2</sub>O (insoluble in the ester).
So esters are out, IMHO, including ‘esterified brake fluid’…
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m1tanker78
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@Squall181: It's possible that the reaction didn't get very far if the sodium bits were that small. I believe heating in MO has been tried before and
found to be of no help. I'd imagine that heating the vessel after the reaction should help coagulate some of the formed sodium. The lid shouldn't be
removed for any reason and oil should not be added until the slag cools to near ambient temp. If I could get my hands on some unadulterated NaOH, I
would personally give this a try but set if off with the vessel sitting on top of some red hot charcoal or embers. I'd remove the vessel from the heat
after about 5 minutes, tapping or jarring the vessel every so often. Just a thought...
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m1tanker78
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| Quote: | | I suspect that the K snatches the oxygen from the protruding carbonyl group [...] So esters are out, IMHO |
Hmm...well, it was put to the test and failed. I purchased a bottle of Castrol branded "ester oil" and noticed a fair bit of reactivity with Na at
ambient temp. I didn't even bother heating it...
Have you had a chance to try the strainer method (for K)?
Tank
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Squall181
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@m1tanker78: You could be right about the reaction not going all the way, because the products always seem like they are too caustic than what they
should be, but I am not really sure. Anyway I will have to try heating for a longer time and see what happens, but that will have to wait till the end
of the week. I'll post the results then.
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blogfast25
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The process of making sodium by reduction of NaOH with Mg or Al will always lead to poor yields, no matter how you play it. Compare it to far more
successful aluminothermic or magnesiothermic processes like Classic Thermite: there the high heat of reaction leads the reaction products iron and
alumina to both form in the liquid state. The hot molten iron then separates out of the hot alumina, sinks to the bottom (it's far more dense than
alumina) where it remains neatly protected by the ‘blanket’ of molten alumina. The whole thing then cools and solidifies with yields of 75 % and
upwards.
The reaction between NaOH and Mg has none of these desirable features: although it produces a fair bit of heat it’s not enough to melt the resulting
MgO (or Al2O3) but may be enough to vaporise some of the Na. As a result you get a dirty mixture of some elemental Na, MgO slag and reoxidised (air)
Na. Recovering any decent Na from that witches brew is very difficult and no one I know has ever reported yields of more than roughly 10 %.
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blogfast25
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Well, I ran one experiment with a strainer today but it wasn’t hugely successful. Here’s the set up: 4 globules of K in the ‘basket’ of a fine
strainer, submerged in kerosene, at about 80 C (see thermocouple):
After the K had molten completely and taken on its globular form, the strainer was lifted out of the kero and ‘jiggled’ about a bit. The first
attempt actually caused 2 globules to merge (but some smaller ones also formed due to chafing on the strainer gauze). But subsequent tries yielded
nothing to both my surprise and disappointment. The balls do indeed slouch due to gravity and make better contact in the absence of bulk liquid. But
the film of kero that separates them still manages to keep them apart.
Perhaps better results could be obtained with Shellsol D (which is slightly less viscous than kerosene) and I might try that. Also, higher temperature
may help but it’s not viable IMHO to apply this to potassium in the presence of air when both kerosene and potassium are so flammable:
it’s a recipe for a nasty kero/K fire…
Of all the mechanical methods, pressing cold potassium together with some ramming tool still seems to be the most promising to me. I’m thinking of a
larger syringe, capped and with some small holes drilled into the plunger (to allow oil to escape)…
And dioxane remains the one potential coalescing liquid to be tested but I need to synth. some first.
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m1tanker78
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BlogFast, interesting result but not terribly surprising. Try an inert oil next time and take it to a considerably higher temp. If the potassium
begins to burn, it isn't the end of the world or even the end of the potassium, for that matter.  Dunk it in the oil and it will snuff out. Have a suitable cover handy just in case the oil catches fire (needs to be
very hot to do so). I've neglected to get an oil temp reading but will do so next time I fry up some Na. I should also mention that I chose Al because
it doesn't tend to be wetted by Na the way ferrous metals sometimes are. KEEP IT SIMPLE ... AND SAFE!
Tank
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blogfast25
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Quote: Originally posted by m1tanker78  | Try an inert oil next time and take it to a considerably higher temp. If the potassium begins to burn, it isn't the end of the world or even the end
of the potassium, for that matter. Dunk it in the oil and it will snuff out.
[snip]
KEEP IT SIMPLE ... AND SAFE!
Tank |
Kerosene IS inert. No more or no less than any pure HC mixture.
Dunking burning K into a flammable liquid in the presence of air is a recipe for disaster: you may get away with it once, twice, thrice but one time
you’re going to ignite your HC. It’s no basis for a regular, reliable coalescence method, or processing significant quantities….
Higher temperatures? Ditto. Like you said: keep it safe and keep it simple, just DON’T DO IT!
Each time you lift the K out of the bath (even at 80 C) some oxidation takes place, so you're constantly losing some material.
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Neil
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Kerosene does have a habit of holding a surprising amount of water. Have you verified it is dry?
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m1tanker78
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| Quote: Originally posted by Neil |
Kerosene does have a habit of holding a surprising amount of water. Have you verified it is dry? |
Neil: I guarantee the kero is dry; he stores his potassium in it. Water and alkali metals (bar Li) like to hang out in the same zone in oil. 
BlogFast: I have purposely set the sodium and the oil afire. I'm not saying it's safe. If you're prepared for it then it becomes trivial. If
you aren't prepared to deal with the possibilities then, DON'T DO IT! But if you do it, use a metal container to prevent breakage. 
By design, the strainer method can't be used to process large quantities of Na/K/etc. The idea is that smaller (under 5 or 6 gram) quantities are
merged and cleaned then, if desired, one can take the clean nuggets and merge them under a clean HC. I've done this 2 or 3 dozen times with
success.
I can accept some oxidation when the sodium is lifted from the oil as well as from being processed with a BF blend. Although it is a slight loss, I
can't view it as such because the only other option right now is to let the stuff fully oxidize in the waste bin and only collect the clean portion of
the sodium harvest. In your case, the K you collect is already clean so oxidation is probably a bigger concern - not an unfounded one.
BTW, I collect and burn the spent oil in some makeshift tiki torches. They create a pleasant lighting effect when I throw a party or BBQ. The oil is
flammable but I have to pre-heat it quite a bit to get 'em going...
Tank
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Neil
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The fact that the kerosene gets exposed to air implies that it is going to pick up moisture. The longer kerosene is in contact with air the more water
vapor can dissolve into it.
It does not seem like much of a stretch to assume that it would interfere with amalgamating the molten metal by forming a very thin oxide coating.
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m1tanker78
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Neil, unfortunately, what you say is true even for mineral oil (to a lesser degree). I'm not sure if 'dissolve' is the right word and I have no way to
know the proportion of air/moisture that gets inducted into the HC's in question. Water will slowly make its way to the bottom of the container and
will even agglomerate with other water pockets to form larger ones.
I take this into account by doing the following: Every so often, when 'garbage time' comes around, I'll make some low potassium (sacrificial) NaK
alloy and use them to prop the rest of the pure sodium nuggets up off the bottom of the container.
A thin oxide layer is a desirable thing to have when the metal is stored in a HC. I actually pre-passivate my Na nuggets by leaving them in oil that's
left open to the atmosphere. That way, the nuggets don't bubble so much when they're in their final storage jar so pressure buildup won't be much of a
problem.
The thin oxide coating sluffs off in hot oil so it doesn't interfere with merging.
Tank
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Neil
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I see, that makes sense.
I found this here.
"Fuel in contact with free water is saturated with water, i.e., the fuel has dissolved all the water it can hold. A typical water-saturated
kerosene-type fuel contains between 40 and 80 ppm dissolved water at 21°C (70°F). If the temperature of the fuel increases, it can dissolve more
water. Conversely, if the temperature of water-saturated fuel decreases, some of the water dissolved in the fuel will separate as free water."
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blogfast25
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Neil and Tank:
Yes, of course something dry will attract some moisture and that’s true of any hydrocarbon based solvent (no less true of ‘mineral oil’, which
kerosene essentially is anyway). The amounts absorbed, unless you actually shake up the HC with water, are small and molten K in kerosene glistens
like pure, unoxidised metal.
Clean hydrocarbons will also dissolve small amounts of air, including oxygen, which explains why over time all alkali metals stored under these media
eventually tarnish. It’s no big deal and certainly no reason to not use them (everybody does).
The method used for making K according the relevant thread generates small amount of water, without it the reaction scheme couldn’t proceed (it's
vital to the part that regenerates the catalyst). But we’re talking small amounts here and they don’t inhibit K coalescence.
Who brought up ‘amalgamating’? Amalgams are alloys of alkali metals with some other metals. Totally inapplicable here…
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watson.fawkes
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Shear forces to break thin film
It's occurred to me that applying a shear force to a thin film might break it. When coalescing K, mostly drained of its hydrocarbon synthesis or
storage medium, breaking the films might be accomplished with a pair of scissors or pair of stirring rods operated like scissors.
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m1tanker78
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Watson, I've toyed with manually breaking the film quite a bit to no avail. So far, the only relatively non-destructive success I've had is to briefly
hold the strainer-ed sodium over the torch. After 2 or 3 seconds, the 'film' covering the sodium begins to smoke and then, BLOOP!
Sodium spheres or nuggets that have never touched BF will slightly stick to one another in hot oil and will merge shortly after; think of a
molecular ball-and-stick model or better, cell division in reverse. Post-BF sodium never shows any degree of 'tackiness' and almost always requires a
flame treatment. I wish I could illustrate this somehow in photos or video...
Tank
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blogfast25
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| Quote: Originally posted by watson.fawkes | | It's occurred to me that applying a shear force to a thin film might break it. When coalescing K, mostly drained of its hydrocarbon synthesis or
storage medium, breaking the films might be accomplished with a pair of scissors or pair of stirring rods operated like scissors.
|
Yeah, I agree and have tried similar things as you suggest, but to no avail...
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Neil
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| Quote: Originally posted by blogfast25 |
Who brought up ‘amalgamating’? Amalgams are alloys of alkali metals with some other metals. Totally inapplicable here…
|
My apologies.
Amalgamate -to combine, unite, merge, or coalesce: The three schools decided to amalgamate.
oh ambiguous language...
Way back a chemist I once knew told me that the reason that potassium metal was removed from all of the High Schools was because of the danger of
thermite reactions causing fires when old potassium is cut after having been stored under oil for long periods.
The obvious solution is to purge the containers of air, but are there any fluids which could be used to store K that would prevent the formation of
oxides all together?
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m1tanker78
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| Quote: | | [...] any fluids which could be used to store K that would prevent the formation of oxides all together? |
Possibly pure, cryogenic liquid argon? In realistic terms and at STP, I don't think so. Much can be done to thoroughly dry a HC, as well as purify,
dry and purge the ambient (glove box?) and fully vac, backfill, and seal the storage container. I'll bet 1 ppb or ppt of oxygen will still remain.
Probably not enough to create the explosive superoxide within 100 years. Good enough for an element collection but realistically, the container would
need to be opened every so often.
++++++++++++++++++++++++
To drive home the subject of air/moisture diffusion in a HC, I observed and photographed a pure sodium nugget in various stages of surface oxidation
for 4 days after cleaning it in pure mineral oil - no BF blended in at any point. Upon cooling, the nugget was transfered to a glass vessel
which was left open to the [humid] ambient air throughout.
~ 2 hours after cooling to ambient temp; essentially a sodium mirror. You can see the reflection of the cell phone and my fingers cradling it.
I think those are my eyes at the lower part of the nugget ...
@ ~ 4 hours, some light oxide patches have begun to form around the top...
@ 24 hours, I can see the gamut of colors that I mentioned in another thread. There are some peculiar patterns that go around the mid section that
remind me of hieroglyphs. The bottom half is still mostly mirrored and there's a mirror island at the top of the nugget...
At the top, the familiar blue-grey crust is beginning to appear and engulf what's left of the mirror finish. You can see the reflection of the camera
lens in this one...
Day 3: In spite of the appearance, the surface of the nugget is mostly smooth (except where uneven cooling distorted the surface and maybe bruising
with the tongs). The bottom half is still mostly reflective from about 10 degrees North to around 80 degrees South (latitude)...
Day 4:
++++++++++++++++++++++++++++++
It's not a huge surprise that the top portion of the nugget and the bottom point oxidize much more rapidly than the bottom half. Presumably, moisture
and possibly air that diffuse into the oil slowly cascade downward and the portion that doesn't 'land' on the nugget collects at the bottom and reacts
with the the bottom point. Conversely, this transformation probably would have taken weeks or months - maybe years if the nugget were placed in a
'dry', inert solvent and sealed properly. On the other hand, if this were a post-BF nugget, the transformation would have taken minutes to a couple of
hours.
Tank
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blogfast25
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| Quote: Originally posted by Neil | Way back a chemist I once knew told me that the reason that potassium metal was removed from all of the High Schools was because of the danger of
thermite reactions causing fires when old potassium is cut after having been stored under oil for long periods.
|
Tell him he’s getting his facts jumbled up.
Over long periods of time alkali metals, even if stored properly, can develop dangerously explosive superoxides.
The ‘thermite’ thingy is something else. It’s recommended to cut alkali metals with a non-steel knife (e.g. clean wood) because oxide surface
blemishes on the knife could lead to the alkali metal reducing the oxide, with great release of heat. But you’d have to use quite a rusty knife for
that to happen, IMHO. I use a clean, sharp Stanley knife for cutting K.
‘Thermite style’ accidents have occurred quite frequently. Not long ago a fire in a factory was caused by clean titanium metal in contact with an
easily reducible metal oxide: the titanium then played the part of aluminium in thermite! Beware of so-called ‘chemical incompatibilities’…
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Neil
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@Tanker, that was very helpful and an interesting documentation, that you for sharing.
@ Blogfast, I haven't seen him for years. I always assumed he meant the K metal would thermite the over oxidized K oxides when a knife pushed them
into the metal. If he did mean someone had literally cut potassium with a rusty knife... Well a that's thoroughly disappointing comment on the High
school teachers who did so. I'd be hard pressed to see how shoving rust into K would make sense on any day of the week.
Thanks for the clarification from both of you.
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m1tanker78
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Neil, glad ya liked it. I don't think you have to go as far as contemplating a 'thermite' reaction (iron oxide). I don't have any practical hands-on
experience with pure potassium yet so I could be wrong. I believe the greater danger with KO2 is simply strong oxidizer + fuel(HC) = combustion which
produces some water. It isn't hard to imagine a runaway reaction running its course very rapidly there (explosion). According to literature,
alkali metal superoxides/hyperoxides are fairly stable when dry and undisturbed. They can, however be decomposed by friction or heat - exacerbated by
impurities which could initiate an explosion.
The good news is that alkali superoxides can be distinguished by color so you can pretty safely dispose of the metal if it becomes tainted. I don't
know what lab SOPs say about potassium, for example. I would assume that it should be inspected every year or 6 months??
The bad news is that there isn't any safe way to remove the MO2. The tainted metal must be [safely] discarded.
Tank
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