Sciencemadness Discussion Board
Not logged in [Login ]
Go To Bottom

Printable Version  
 Pages:  1  ..  27    29    31  ..  66
Author: Subject: Make Potassium (from versuchschemie.de)
blogfast25
Thought-provoking Teacher
*****




Posts: 10340
Registered: 3-2-2008
Location: Old Blighty
Member Is Offline

Mood: No Mood

[*] posted on 17-2-2011 at 09:17


Metalresearcher and condennsa:

The most likely cause of failure in both cases is the refluxer. In the case of MR I didn’t even see any ice or ice/water being used in the condenser (correct me if I’m wrong on that). Remember that that kind of set up (w/o cooling) is used routinely to evaporate liquids without splattering. T-butanol only has a boiling point of about 80 C, it WILL evaporate off in the ‘wrong’ conditions…

Both of you will have to invest in a suitably sized conical or round flask, a fitting rubber bung (nitrile if possible) and a piece of glass pipe (min. ID 5 mm, length min. 25 cm) to better emulate pok’s simple set up.

Condennsa: Nurdrage’s video is inadvertently deceptive. W/o much doubt he kept the reaction covered for most of the time, then exposed it to show the metal obtained. I could be wrong on that…

MR: insulating a thermometer from heat is best done with loosely packed tin foil (aluminium).



[Edited on 17-2-2011 by blogfast25]
View user's profile Visit user's homepage View All Posts By User
peach
Bon Vivant
*****




Posts: 1428
Registered: 14-11-2008
Member Is Offline

Mood: No Mood

[*] posted on 17-2-2011 at 09:41



Isopropyl does indeed appear to be a lost cause


I have read the entire thread and realise isopropyl was mentioned earlier on. But, having some other possible candidates immediately to hand on the shelf, thought I'd try it with isopropyl anyway to check it again. You can click these photos to make them bigger.

Before commenting, please remember I have read this entire thing. I was trying these because they were in front of me.

Given the gigantic length of this thread (a lot of it arguing for no sake), I thought it might be nice to centre align this to make it easily visible as an actual test, as opposed to more arguing.


The paraffin


Checking the EEC code, it appears this is actually kerosene turbine fuel


10ml's of it


Weighs that much


The BP is 180C


To give this the best chances possible, I'm using a German pencil sharpener, and drilling it into a piece of Swiss cheese with a German drill :D


These are the biggest chips I used. Most of them were a lot smaller.


I'm using an excess of magnesium, as I suspect my KOH is rather damp. I have been using it to do the washing up for years, so it'll have picked up moisture


1ml of IPA. An excess again, due to my solvent's BP being a few tens of degrees lower than the D70 I expected it would take significantly longer using the proscribed quantity


KOH. I can see the reading going up as it's picking up moisture


20ml of the kerosene, the Mg chips and the KOH


Blowing dry argon through the glass. The entire thing is sealed. The top of the condenser is going out through an oil bubbler


Ready to go


The alcohol mixed with 5ml of solvent


Warming it up to around 100C. I immediately note the solids at the bottom have clumped into a more homogeneous layer, the cement nurd spoke of


There is a large amount of gas evolving around this temperature and for a period of around 15-30 minutes. The solvent is not boiling, it's hydrogen evolution. After 30 minutes, I raise the temperature and the solvent begins to reflux 10 minutes later


It is now boiling. As I can still see a slow evolution of bubbles, I leave it to do so for an hour and twenty minutes. When I return, the bubbles are now leaving at a rate of one every 20 seconds. I suspect this could go on for a long time at this rate, so decide to add the alcohol. Before doing so, I note what looks like it could be moisture on the upper half of the condenser. Woelen mentioned this on his page. I doubt it is moisture in this case, but blow more argon through. The solvent pushes up the condenser and is miscible with the material on it. So it's simply solvent that's evaporated before I switched the condenser on


The IPA drips in over 25 - 30 minutes. As it goes in, the solution boils more vigorously with the low BP IPA present. However, my condenser is at 10C, well below the BP of either, and neither is making it past the first turn of the coil. The solution has now turned a light grey


An annoying problem of using a high BP solvent and an angled port is that the solvent is condensing in the equalising arm, and blocking it. The slight vacuum the column of solvent creates in the top of the funnel is enough to stop it dripping correctly. Be nice if the funnel was on the other side. I reflux this for 9 and half hours


Some of the spare magnesium burning, after it fell into the sink. I couldn't get the camera in time to show the typical white glow


The result


I can see some unreacted magnesium in there, but no signs of any potassium. I (carefully) empty the flask out and rinse it. Nothing. Thankfully, also no signs that the long reflux with the KOH in there has damaged the glass.


- Although this wasn't done under ideal conditions (the KOH was probably damper than it should be, and the BP is slightly lower than it should be), this appears to confirm that IPA won't work.

Given the very long reflux time, and slight excess of magnesium, I would have expected to see at least a tiny sparkle from it. The only thing I can conclude, other than isopropyl not working, is that too much of the magnesium has been passivated. Again though, no sign of life.

I posted the pictures of the poppers above, as it would seem to be an easy source of the longer chain alcohols. It is worth noting, amyl and butyl nitrite have largely been removed from the shelves, and there are exactly seven trillion different bottle labels that are all the propyl nitrite. You will need to check the bottles before buying them, and may need to do some searching around for the two of interest. I am not sure why these two in particular where removed, perhaps due to them being sources of naughtiness. However, poppers are potentially good everyday sources as they are simply bottles full of the nitrites with nothing else purposefully added; and you can find them in off licenses, alternatives stores and sex shops (although you may feel the urge to try and explain that you're buying them for 'an experiment' :P). Reducing them back to the alcohol requires only base, which is already part of this process.


- Something worth nothing for anyone wishing to repeat this. IPA forms azeotropes with water. And it is often sold at less than 99% purities (70% for instance). The azeotrope is at 87.9%, and it can be broken by distillation with cyclohexane. I haven't redistilled mine, but I believe it was 99%+ when I bought it, and it hasn't been opened since.


[Edited on 18-2-2011 by peach]




View user's profile View All Posts By User
Picric-A
International Hazard
*****




Posts: 796
Registered: 1-5-2008
Location: England
Member Is Offline

Mood: Fuming

[*] posted on 17-2-2011 at 11:05


Thanks peach, its always worth trying things that may/may not work.... thats what science is all about!

Have you got any t-butyl alcohol to try this with?
View user's profile View All Posts By User This user has MSN Messenger
peach
Bon Vivant
*****




Posts: 1428
Registered: 14-11-2008
Member Is Offline

Mood: No Mood

[*] posted on 17-2-2011 at 11:20


I don't, yet, but I know someone who has and he lives in the UK. :D

I might try the popper method to making the alcohol, but I'd have to find the better ones first. The possible options are n-amyl nitrite, n-butyl nitrite and isobutyl nitrite.

t-amyl 102C
t-butyl 82C

n-amyl 138.5C
n-butyl 117.7C

iso-butyl 107.89C

[Edited on 17-2-2011 by peach]




View user's profile View All Posts By User
mr.crow
International Hazard
*****




Posts: 884
Registered: 9-9-2009
Location: Canada
Member Is Offline

Mood: 0xFF

[*] posted on 17-2-2011 at 11:57


None of those "products" have tertiary alcohols, they are all primary



Double, double toil and trouble; Fire burn, and caldron bubble
View user's profile View All Posts By User
metalresearcher
International Hazard
*****




Posts: 688
Registered: 7-9-2010
Member Is Offline

Mood: Reactive

[*] posted on 17-2-2011 at 12:11


Quote: Originally posted by blogfast25  
Metalresearcher and condennsa:

Both of you will have to invest in a suitably sized conical or round flask, a fitting rubber (nitrile if possible) and a piece of glass pipe (min. ID 5 mm, length min. 25 cm) to better emulate pok’s simple set up.


I already have a 300ml erlenmeyer flask with a drilled stopper and a glass pipe so I can use that. But the problem is : I can't get the lamp oil hotter than 210oC and to initiate the reaction I need higher temp (?) or should I (just like @peach did) wait until the reaction takes place ?
I tried dissolving (paraffin) candle wax but even an 1:1 ratio lamp oil : candle wax boiled at 220 C.
What do you mean with 'reflux' ?
What about KOH attacking (borosilicate) glass > 200 C ?
Should I use IPA ?


[Edited on 2011-2-17 by metalresearcher]
View user's profile View All Posts By User
peach
Bon Vivant
*****




Posts: 1428
Registered: 14-11-2008
Member Is Offline

Mood: No Mood

[*] posted on 17-2-2011 at 12:59


Quote: Originally posted by mr.crow  
None of those "products" have tertiary alcohols, they are all primary


Sorry, I edited that in a way that made it appear like they were.

You're right, they're all primaries. I included the tertiaries as a reference for the BPs.




View user's profile View All Posts By User
blogfast25
Thought-provoking Teacher
*****




Posts: 10340
Registered: 3-2-2008
Location: Old Blighty
Member Is Offline

Mood: No Mood

[*] posted on 17-2-2011 at 13:17


Peach:

Remember, we strongly believe only tertiary alcohols work. Get 2-methyl-2-butanol (t-amyl alcohol) from here:

http://www.purechemicals.net/buy-2-methyl-2-butanol-2m2b-42-...

… not very expensive and no questions asked, quick delivery. BP just over 100 C. It works (I use it).

Did you see the thread on more specific alcohols for K-‘synthesis’? Here:

http://www.sciencemadness.org/talk/viewthread.php?tid=15171

Nice set up you have, but slightly 'overkill', I feel...

Quote: Originally posted by metalresearcher  
I already have a 300ml erlenmeyer flask with a drilled stopper and a glass pipe so I can use that. But the problem is : I can't get the lamp oil hotter than 210oC and to initiate the reaction I need higher temp (?) or should I (just like @peach did) wait until the reaction takes place ?
I tried dissolving (paraffin) candle wax but even an 1:1 ratio lamp oil : candle wax boiled at 220 C.
What do you mean with 'reflux' ?
What about KOH attacking (borosilicate) glass > 200 C ?
Should I use IPA ?


[Edited on 2011-2-17 by metalresearcher]


210 C is more than fine. At takes about 4 h to complete, including metal coalescence.

Refluxing: in peach’s set up the vertical piece with cooled coil provides the refluxing: any vapours (solvent and /or catalyst) are condensed back to liquid there and flow back into the flask.

No reports of the KOH attacking the glass have been reported: the KOH is suspended in the inert solvent and very little water is present.

IPA? NOOOO!
View user's profile Visit user's homepage View All Posts By User
Picric-A
International Hazard
*****




Posts: 796
Registered: 1-5-2008
Location: England
Member Is Offline

Mood: Fuming

[*] posted on 17-2-2011 at 15:43


Quote: Originally posted by blogfast25  
Peach:

Remember, we strongly believe only tertiary alcohols work. Get 2-methyl-2-butanol (t-amyl alcohol) from here:

http://www.purechemicals.net/buy-2-methyl-2-butanol-2m2b-42-...

… not very expensive and no questions asked, quick delivery. BP just over 100 C. It works (I use it).



@£40 for 100ml... '… not very expensive'... youve got to be joking, right?
View user's profile View All Posts By User This user has MSN Messenger
peach
Bon Vivant
*****




Posts: 1428
Registered: 14-11-2008
Member Is Offline

Mood: No Mood

[*] posted on 17-2-2011 at 19:51


Blogfast
You were complaining about me not using ground glassware in another thread, make yar mind up shipmatie! :P

As people have already shown, it can be done with a whole lot less and still function fine. I'm using the ground stuff since I have it to hand and there is still scope for complaints and errors as a result of the atmosphere and so on. I don't like it when people insist on using [insert expensive item here] when it's not necessary, but we're still working on what is and isn't necessary at this stage, which the people with less equipment will have a harder time working out with the extra variables. Meaning, those with it, should use it to remove the variables faster for the others.

I have noticed nicodem mentioning tertiary alcohols but I haven't seen, or I've forgotten what I've seen over the 28 pages, much in terms of people double checking it. I'm not trying to arrogantly say he's simply wrong, but I'm imagining it from his position that, if everyone takes it for granted, they'll then have a complain if secondaries or primaries are found to function as well. So I'm curious as opposed to trying to prove a point.

Metal Researcher
Reflux is continually boiling a solvent, then condensing it as it tries to leave the flask. All of my kerosene would have been gone in minutes had I not been condensing it at the same time, making the volume remain the same after a very long period of boiling.

I would not recommend you use IPA. If I get one of the known alcohols to work under the same conditions as I used above, I will know for sure it was the IPA causing it to fail. I can not be 100% sure until I do that, but I suspect IPA is unsuitable.

--------------------------------------------------------------------------------


Len will enjoy this - KOH mass changes


Method. Open KOH tub, empty some out onto dish in balance. Wait. Empty, wash and dry dish. Empty some more KOH out, crush it, add to dish. Wait.

Result. The pile of powder picks it up quicker, at first, but they both end up the same provided they're left alone. Likely as a result of the bulk of the crushed material not being in direct contact with the atmosphere.

The line for the crushed KOH appears to be decelerating, whereas the flakes are close to a straight line. It doesn't look like it makes much difference. The important thing would be not to get it out and then go for a 2 hour lunch break before using it, which Len will undoubtedly already know. Powdering is also not necessary, as Pok pointed out and some have discovered first hand. But here's a graph that shows it's perhaps not such a lethal mistake as was suggested towards the beginning of the thread.

{edit}Oh... I left all the doors open on the balance doing this, so the samples had the same amount of access to the atmosphere as they would normally. The balance wasn't particularly happy about that, but you can still see the trend clearly enough.


Flakes straight out the tub



Crushed





There is still some muck stuck to the glass, after a 12h soak, but it's slowly coming back off. A wash with some acid got most of the rest off after this photo. No signs of a chewed up surface after 9 1/2h reflux at 180C.


[Edited on 18-2-2011 by peach]




View user's profile View All Posts By User
blogfast25
Thought-provoking Teacher
*****




Posts: 10340
Registered: 3-2-2008
Location: Old Blighty
Member Is Offline

Mood: No Mood

[*] posted on 18-2-2011 at 07:22


Quote: Originally posted by Picric-A  
@£40 for 100ml... '… not very expensive'... youve got to be joking, right?


Not unless you can come up with a better price, Picric!

100 ml 2M2B makes an awful lot of K, even more so if you can recycle the alcohol...

Peach: 6 significant digits, eh? Talk about overkill! :D
View user's profile Visit user's homepage View All Posts By User
DJF90
International Hazard
*****




Posts: 2266
Registered: 15-12-2007
Location: At the bench
Member Is Offline

Mood: No Mood

[*] posted on 18-2-2011 at 08:40


I've seen it sold for 15£/500ml commercially, and £12/L on ebay as a "5-off" BIN sale.
View user's profile View All Posts By User
metalresearcher
International Hazard
*****




Posts: 688
Registered: 7-9-2010
Member Is Offline

Mood: Reactive

[*] posted on 19-2-2011 at 03:20


Another try of my experiment:

I heated the beaker in a sand bath and kept it at 190 C (to prevent boiling) During heating up it bubbled when 80-100C: is that the reaction ? Refluxing is done by a porcelain crucible on top of it and the thermocouple wire through the spout which kept virtually all oil inside. It had been running for 45 minutes. Or should I stop heating further when it bubbles (not as a result of boiling).

Here a picture : I cannot recognize the K metal did it form ??


IMG_4472.JPG - 40kB

[Edited on 2011-2-19 by metalresearcher]
View user's profile View All Posts By User
Picric-A
International Hazard
*****




Posts: 796
Registered: 1-5-2008
Location: England
Member Is Offline

Mood: Fuming

[*] posted on 19-2-2011 at 06:46


Quote: Originally posted by DJF90  
I've seen it sold for 15£/500ml commercially, and £12/L on ebay as a "5-off" BIN sale.


£49 for 1 litre off Acros. As previously mentioned i have seen it come up on Ebay a couple of times..
View user's profile View All Posts By User This user has MSN Messenger
blogfast25
Thought-provoking Teacher
*****




Posts: 10340
Registered: 3-2-2008
Location: Old Blighty
Member Is Offline

Mood: No Mood

[*] posted on 19-2-2011 at 08:09


Quote: Originally posted by metalresearcher  
Another try of my experiment:

I heated the beaker in a sand bath and kept it at 190 C (to prevent boiling) During heating up it bubbled when 80-100C: is that the reaction ? Refluxing is done by a porcelain crucible on top of it and the thermocouple wire through the spout which kept virtually all oil inside. It had been running for 45 minutes. Or should I stop heating further when it bubbles (not as a result of boiling).

Here a picture : I cannot recognize the K metal did it form ??
[Edited on 2011-2-19 by metalresearcher]


Preventing boiling isn’t really a solution to anything. Even at 190 C the vapour phase of the catalyst/solvent mix contains a lot of the alcohol. Also, the actual potassium forming reactions are likely to be very temperature dependent, thus slower at 190 than they are at 200 or 210 C.

The initial bubbles you see at 80 – 100 C are the removal of moisture in the KOH by Mg. Actual metal formation starts (we believe) much later and at higher temperatures. They are slow reactions, requiring several hours to complete. 45 minutes is really nothing.
View user's profile Visit user's homepage View All Posts By User
condennnsa
Hazard to Others
***




Posts: 217
Registered: 20-4-2010
Location: Romania
Member Is Offline

Mood: No Mood

[*] posted on 20-2-2011 at 18:31


Merck offers 2-methyl-2-butanol (t-amyl alcohol) for 35 euro/ litre. http://www.merck-chemicals.com/romania/tert-amyl-alcohol/MDA...
View user's profile View All Posts By User
Picric-A
International Hazard
*****




Posts: 796
Registered: 1-5-2008
Location: England
Member Is Offline

Mood: Fuming

[*] posted on 21-2-2011 at 02:58


Ok, I tryed this reaction using 2-methylpropan-2-ol and paraffin as the solvent. The only form of magnesium that was available to me was ribbon so i spent ages cutting it up into little pieces hoping it would suffice.


40ml of paraffin was added to a RBF along with 3.11g magnesium and 6.12g KOH. The mix was then boiled for one hour. Here gas evolution was obvious. I captured some of the gas over water and sure enough it burned with a squeeky pop but strangely a luminius orange flame. My quess is it contained some methane/ethane/propane which was dissolved in the paraffin before.

After the initial boil 0.6g t-BuOH dissolved in 1ml of paraffin was injected into the mix slowly, ensuring none was lost to flash evaporation. The mix was then refluxed gently for a furthur 9 hours. I checked on it roughly every hour.


Result:
No potassium was formed. The KOH seemed to form a white crusty material but the magnesium seemed unaffected. The paraffin was decanted off and water was added. No bubbling was observed.
The paraffin solvent had changed from a light yellow colour to a dark brown colour which is an observation i cant explain.



[Edited on 21-2-2011 by Picric-A]
View user's profile View All Posts By User This user has MSN Messenger
condennnsa
Hazard to Others
***




Posts: 217
Registered: 20-4-2010
Location: Romania
Member Is Offline

Mood: No Mood

[*] posted on 21-2-2011 at 05:55


Picric, did your magnesium change color? perhaps to a dark grey, slight brown? Because, I for one, strongly suspect that anyone who doesn't succeed with this synthesis has the wrong magnesium.
Do you have the purity specifications of your Mg ribbon?

I always see potassium form right at the beginning, after the violent reaction, but then the magnesium stops reacting, and takes a dirty appearance.
I'm not giving up, i'll order some grignard magnesium turnings to see if i'm right.
View user's profile View All Posts By User
blogfast25
Thought-provoking Teacher
*****




Posts: 10340
Registered: 3-2-2008
Location: Old Blighty
Member Is Offline

Mood: No Mood

[*] posted on 21-2-2011 at 08:28


Strange result, Picric-A, the discolouration too. But 9 h is a long time. You didn’t mention type of reflux or temperature.

I think cut up ribbon should do it: that’s usually quite pure Mg. Fineness should of course play a role since as at least one of the proposes reactions is a solution/solid reaction…
View user's profile Visit user's homepage View All Posts By User
metalresearcher
International Hazard
*****




Posts: 688
Registered: 7-9-2010
Member Is Offline

Mood: Reactive

[*] posted on 21-2-2011 at 11:28


I think that inducing the reaction requires a higher temp. Heating it to 500-600 C induces a quick reaction leaving lots of white smoke which is probably K2O as I left the mixture unprotected in a steel tube.
I repeated the same in a Schott Duran test tube which also lighted up suddenly and left white smoke and purplish flames. The test tube survived the experiment.
View user's profile View All Posts By User
blogfast25
Thought-provoking Teacher
*****




Posts: 10340
Registered: 3-2-2008
Location: Old Blighty
Member Is Offline

Mood: No Mood

[*] posted on 21-2-2011 at 13:24


The reaction 2 KOH + Mg --> 2 K + MgO + H2 works, we know that both from theory and experiment. But just heating a mixture of KOH and Mg (with or without some solvent) until initiation starts is not what this thread is about. Heating KOH + Mg yields the indicated reaction products and much reaction heat, enough to cause a near-explosion (because the low BP of K will be reached very quickly). To contain the reaction, a bomb type (oxygenless) reactor could be imagined but that’s likely to have the formed K and H2 to recombine to KH (2K + H2 --> 2KH).

But in the present of the catalyst it’s possible to run the reaction in a controlled way at quite a low temperature (approx. 200 C). Pok, len1, woelen, Nurdrage and myself have all done it w/o particular problems.
View user's profile Visit user's homepage View All Posts By User
Picric-A
International Hazard
*****




Posts: 796
Registered: 1-5-2008
Location: England
Member Is Offline

Mood: Fuming

[*] posted on 21-2-2011 at 14:07


One thing i forgot to mention- before use i dryed the paraffin overnight with sodium metal.

My magnesum was 99.9% from Acros. It did indeed turn from light silvery to greyish brown tinge however i suspected the parafin had something to do wth this.

Indeed 9h is a long reaction time, i kept checking hourly to see if any K had formed however i did not want to give up so i kept it refluxing at around 180-200degC in the hopes of a successful reaction.

Any ideas how i can guarantee a successful reaction next time? I did everything pretty much by the book par the magnesium...
View user's profile View All Posts By User This user has MSN Messenger
blogfast25
Thought-provoking Teacher
*****




Posts: 10340
Registered: 3-2-2008
Location: Old Blighty
Member Is Offline

Mood: No Mood

[*] posted on 21-2-2011 at 14:23


Picric-A:
Bar not being able to see what precisely you’re doing I’d say you’re doing everything right. 180 – 200 C may be borderline but you should certainly have obtained some K at that temperature and duration…

The discolouration of the paraffin oil is a little strange but I believe that even if it’s caused by small amounts of some degradable impurity that that should not really impede reaction, unless the contaminant was really something very specific. People have had success with Shellsol D70, kerosene, parffinic oil (IR grade), paraffinic oil (vet grade), candle wax and Tetralin: so quite a broad range.

Are you sure you’re refluxing system is keeping all the alcohol in the system?

If so, I’d try another grade of Mg: a medium fine (50 - 100 mesh) pyro grade should do it. Try and get the temps. to > 200 C during all of the run. Temp. fluctuations are OK, IMHO…
View user's profile Visit user's homepage View All Posts By User
Picric-A
International Hazard
*****




Posts: 796
Registered: 1-5-2008
Location: England
Member Is Offline

Mood: Fuming

[*] posted on 22-2-2011 at 02:55


Im not sure the t-BuOH is being kept in the system, i will test the decanted paraffin later and see if there is any t-BuOH still in there.
Im going to buy some powdered magnesium and hope for a successful reaction, will let you know how it all goes.
View user's profile View All Posts By User This user has MSN Messenger
blogfast25
Thought-provoking Teacher
*****




Posts: 10340
Registered: 3-2-2008
Location: Old Blighty
Member Is Offline

Mood: No Mood

[*] posted on 22-2-2011 at 07:56


Quote: Originally posted by Picric-A  
Im not sure the t-BuOH is being kept in the system, i will test the decanted paraffin later and see if there is any t-BuOH still in there.
Im going to buy some powdered magnesium and hope for a successful reaction, will let you know how it all goes.


You seem very cagey about your reflux system. If you're not sure the t-butanol is being kept in the system you're basically gambling...
View user's profile Visit user's homepage View All Posts By User
 Pages:  1  ..  27    29    31  ..  66

  Go To Top