Sciencemadness Discussion Board

Solvent for Potassium synthesis

ReaktionChamber - 16-11-2018 at 02:50


So I want to perform the potassium synthesis, by the alcohol catalyzed magnesium reduction approach. I already have the alcohol (tert-amyl alcohol) and the Mg+KOH. I'm now questioning which solvent might be the best to use.
I have some octane, hexane, pentane and several other on hand.


regards

rC

artemov - 16-11-2018 at 03:12

Hypoallergenic *baby oil? According to nurdrage, in his sodium synthesis series on YouTube.

[Edited on 16-11-2018 by artemov]

12thealchemist - 16-11-2018 at 03:52

Hypoallergenic baby oil will be the best that is readily available. You're after a hydrocarbon solvent with a boiling point of at least 180°C; aromatics are ideally to be avoided. For potassium, you may be able to get away with it, but it's a little risky, and that's for tetralin (tetrahydronaphthalene).

zed - 16-11-2018 at 15:26

Yup. We normally think of Aromatic Hydrocarbons, as being inert to Alkali Metals.

But, in this case, our thinking is wrong.

Nurdrage, seems to have failed, using most common solvents.

Found success, utilizing a Walmart Brand of hypoallergenic baby oil.

https://www.youtube.com/watch?v=oiZf-O6vvbE

[Edited on 16-11-2018 by zed]

GrayGhost- - 16-11-2018 at 16:15

Hi, my question is, what if you use paraffin wax have boiling point more 370°C ?

j_sum1 - 16-11-2018 at 18:48

I recall in the potassium thread some people having some success with paraffin wax. I also seem to recall Nurdrage experimenting with various solvents and mentioning differences between sodium and potassium.

12thealchemist - 17-11-2018 at 02:01

The problem with paraffin/candle wax was that it is solid at room temperature. This makes recovery of the potassium metal extremely difficult, and so is a poor choice of solvent. Also, NurdRage only ever got "potassium sand" - tiny balls of potassium, never large globules using wax as a solvent.

The main difference between sodium and potassium is time. Sodium is about 25x longer than potassium (give or take), and so you'll need to react it for at least 24 hours. As a result of this, aromatic solvents like tetralin are degraded into tar, and destroy all the yield. It's possible to use tetralin for potassium, but only because the reaction is relatively so fast. Additional alcohol catalyst must be added, however, to clean the potassium of the tar formed.

elementcollector1 - 20-11-2018 at 21:51

Kerosene lamp oil was the solvent that ended up working for me. Mineral oil was a bit annoying to deal with - despite my attempts to dry it, something would always prevent the reaction from even starting. Also, it bubbled and foamed up into the condenser.

MrHomeScientist - 21-11-2018 at 07:57

I used lamp oil as well. Mine had a blue dye, so I "decolorized" it by heating with hydrogen peroxide (IIRC). I succeeded in making K spheres, but only a few mm in diameter. Coalescence was my problem. I bought tetralin to try to solve this but that reaction failed because my hotplate overheated, and I haven't tried it again since. Also nobody told me how overpowering an odor tetralin has!

As I always say whenever these threads come up, go read the main potassium thread. It's incredibly long, but I bet every question you have is answered in it. If you must skim, look for posts with pictures since those usually include actual results.

12thealchemist - 21-11-2018 at 12:07

Quote: Originally posted by MrHomeScientist  
As I always say whenever these threads come up, go read the main potassium thread. It's incredibly long, but I bet every question you have is answered in it. If you must skim, look for posts with pictures since those usually include actual results.


It wasn't until today that I read the forum guidelines (Nicodem's current signature), and encountered the concept of cross-posting. However, I feel this rather short thread may be of great help follow your comment, MrHomeScientist

http://www.sciencemadness.org/talk/viewthread.php?tid=104576

MrHomeScientist - 21-11-2018 at 13:08

Excellent summary! That included a lot of theoretical discussion I don't recall seeing in the thread.
I made my own summary somewhere in the middle of the thread, but good luck finding it :) Mine was more focused towards experimental concerns as I prepared to try it myself. I definitely want to try this again using tetralin, but I really don't want to use it without a fume hood. I also probably need a better heating setup than the sand bath that damaged my hot plate.

12thealchemist - 22-11-2018 at 00:56

My aim was to condense everything that was known about the reaction into a single document, including the recent work by NurdRage and my own thoughts on the reaction.

I do remember finding your summary; I went through the entire thread picking out all the relevant information. Were there any experimental details that you would include that I've missed?
And on a purely curious note, what does tetralin smell like?