So obviously this topic is relatively amateur, but I found a solution of some sort in an old container. It said on the back that it's contents were a
potassium hydroxide soln, and it has this yellow milky look. What would I do in order to get the potassium out? Just setup for distillation and boil
the water off? Or what. Again I am an amateur, so no nonsense in reply about how I'm a beginner. This is obvious, you are no Sherlock.UnintentionalChaos - 20-10-2012 at 13:15
If the container was glass, you probably now have a solution of impure potassium silicate and the glass has been significantly corroded. If plastic,
the solution certainly shouldn't be yellow or milky. Old alkali hydroxide solutions tend to have quite a lot of the carbonate present from slow
absorbtion of CO2 out of the air. KOH solution should be clear and colorless, so who knows what's in your solution.
KOH holds onto water even if you take a torch to it and bring it to red heat, IIRC. That would be a solid once cooled, but it won't have no water
present.
Your best bet is to just try to rescue the potassium content it as some potassium salt. Add an acid, and recrystallize the result to make KCl or
K2SO4, or some other salt of your choice.kristofvagyok - 20-10-2012 at 13:34
Boil it out in a nickel container and when you got a solid put it in a silver pot and heat it until it boils. Then the most water will be removed.
If you don't have silver/nickel labware then you will have a little problem, because cc hot KOH is more corrosive than cc sulfuric acid and it even
holds water much better....Saganism - 20-10-2012 at 13:49
Cool cool thanks. Alright, also, another question could calcium hydroxide be used instead if I'm trying to isolate pipeline from peppercorn? Lots of
techniques call for KOHSaganism - 20-10-2012 at 13:51
isolation of piperine
place 15g (1) of ... ground black pepper in a 250mL round-bottomed flask,
add 150mL of 95% ethanol and 5 boiling chips (2), and heat at reflux for 2h.
filter the mixture by suction filtration and then concentrate the filtrate to a
volume of 10-15mL by simple distillation or by use of a rotary evaporator.
to 10mL of a 10% solution of KOH in 95% ethanol contained ina 125mL
erlenmeyer flask add the concentrated pepper extract. heat the resulting
solution and add water dropwise. a yellow precipitate forms. add water
until no more solid appears to form and then allow the mixture to stand at
least overnight (3). collect the solid by suction filtration and recrystallize it
with 10-20mL of acetone (4).
(1) this extraction may be scaled up to twice the amounts specified without
difficultiy. if a soxhlet extractor is available, this would be an apparatus superior
to a standard reflux setup.
(2) boiling chips are necessary to prevent serious bumping.
(3) it is best to allow piperine to completely precipitate out by allowing the
mixture to stand until the next laboratory period.
(4) in our hands ca. 0.6g of piperine, mp 127-128°C, was collected upon
recrystallization.
[05, page 527-528]
:::this is what I'm working withkristofvagyok - 20-10-2012 at 14:18
Even a few percent water will ruin the whole isolation. I have done it long ago and accidentally I added KOK solution in water and not in alcohol...
The whole thing hydrolized and I've got nothing.Bot0nist - 20-10-2012 at 14:29
Do a forum search for piperine extraction. There are lots of good threads. Also many good threads on KOH and NaOH reclamation and or aquisition. The
piopering from pepper isolation is very rewarding if you enjoy recrystallizations. I found it to be a lot of fun. Think I even have a thread with
pictures from a while back.hyfalcon - 20-10-2012 at 14:39
I kind of love watching KClO3 and KClO4 fall out of a cooling saturated solution myself, especially if I've brought it all the way from softener KCl
to get it to that point.Mildronate - 20-10-2012 at 14:44
