CrossxD
Hazard to Self
Posts: 66
Registered: 6-7-2015
Member Is Offline
Mood: stainless
|
|
potassium hydroxide?
Hello,
Is possible to make potassium hydroxide from calcium hydroxide and potassium sulphate?
|
|
|
Metacelsus
International Hazard
Posts: 2531
Registered: 26-12-2012
Location: Boston, MA
Member Is Offline
Mood: Double, double, toil and trouble
|
|
Not by precipitating calcium sulfate (if that's what you were thinking). Calcium sulfate is more soluble than calcium hydroxide.
If you had potassium carbonate, you could use that to precipitate calcium carbonate.
[Edited on 9-11-2016 by Metacelsus]
|
|
|
CrossxD
Hazard to Self
Posts: 66
Registered: 6-7-2015
Member Is Offline
Mood: stainless
|
|
Hmm and is there way to make carbonate ftom sulphate? I cant find way :/
|
|
|
NEMO-Chemistry
International Hazard
Posts: 1559
Registered: 29-5-2016
Location: UK
Member Is Offline
Mood: No Mood
|
|
found a patent  http://www.google.co.uk/patents/US1992324
|
|
|
woelen
Super Administrator
Posts: 7977
Registered: 20-8-2005
Location: Netherlands
Member Is Offline
Mood: interested
|
|
Is this
true? As far as I know, Ca(OH)2 is moderately soluble in water, while CaSO4 is insoluble. So, I can imagine that you can make a (dilute) solution of
KOH by mixing stoichiometric amounts of solutions of K2SO4 and Ca(OH)2. Both K2SO4 and Ca(OH)2, however, are only moderately soluble, so your solution
will be dilute. It still will contain a little Ca(2+) and SO4(2-) ions as well and it will be hard to add solutions in exact stoichiometric amounts.
|
|
|
gdflp
Super Moderator
Posts: 1320
Registered: 14-2-2014
Location: NY, USA
Member Is Offline
Mood: Staring at code
|
|
Quote: Originally posted by woelen  | | Is this true? As far as I know, Ca(OH)2 is moderately soluble in water, while CaSO4 is insoluble. So, I can imagine that you can make a (dilute)
solution of KOH by mixing stoichiometric amounts of solutions of K2SO4 and Ca(OH)2. Both K2SO4 and Ca(OH)2, however, are only moderately soluble, so
your solution will be dilute. It still will contain a little Ca(2+) and SO4(2-) ions as well and it will be hard to add solutions in exact
stoichiometric amounts. |
Surprising as it is, it is indeed accurate. Ca(OH)<sub>2 </sub> has a solubility of about 1.85g/L at STP, whereas CaSO4 has a
solubility of slightly over 2g/L according to my CRC. Interestingly, Ca(OH)2 has a reverse solubility curve, as the solubility is well
under 1g/L @ 100°C
|
|
|
CrossxD
Hazard to Self
Posts: 66
Registered: 6-7-2015
Member Is Offline
Mood: stainless
|
|
and how about electrochemical way? is possible to make stoichiometric amount of potassium hydroxide and chlorine? If is than how?
|
|
|
Scalebar
Hazard to Self
Posts: 54
Registered: 6-5-2016
Location: Europe!
Member Is Offline
Mood: Looking for a way out
|
|
Chloralkali process basically, only with KCl instead of NaCl. You just need to keep your electrodes in separate compartments - two beakers, connected
by a strip of wet paper, electrode in each.
|
|
|
ficolas
Hazard to Others
Posts: 146
Registered: 14-5-2016
Member Is Offline
Mood: No Mood
|
|
Electrochemically it is possible from KCl, and KCl is sold as sodium free salt in lots of supermarkets.
Read about the chloralkali process, there is a ton of documentation about in this forum, and even more in the rest of the internet.
The problem it has is that for chlorine free KOH you need mercury and that will produce mercury contaminated KOH
If you can find Ca(OH)2, and K2CO3, its easier that way. Or a very impure and small amount og both KOH and NaOH can be obtained from ashes.
I wanted to try decomposing a calcium carbonate from marble into calcium oxide to get calcium hydroxide, but my "tech" level is still too low for
this. (A bit less than 900 degrees are needed) Its is the way of getting CaOH I know, other than buying it
|
|
|
AJKOER
Radically Dubious
Posts: 3026
Registered: 7-5-2011
Member Is Offline
Mood: No Mood
|
|
Here is a curious path assuming you are willing to may a silver investment:
| Quote: Originally posted by AJKOER | I have been experimenting with Silver salts recently, and I believe I have accidentally demonstrated that one can create a strong base from Ag2O!
Per Wikipedia (http://en.m.wikipedia.org/wiki/Silver_hydroxide#Preparation ):
"It will also react with solutions of alkali chlorides to precipitate silver chloride, leaving a solution of the corresponding alkali
hydroxide.[12][11]"
I prepared some Ag2O, which left in the presence of NaCl and some water, then appears to have reacted as follows:
Ag2O + H2O + 2 NaCl --) 2 NaOH + 2 AgCl (s)
Interestingly, as one can recycle the Silver chloride, it appears that one can create a large amount (by recycling the Silver chloride) of NaOH (or
KOH..) from the likes of inexpensive NaCl (KCl..).
Cool!
The attached picture shows one etched storage jar (I would not recommend repeating this experiment with your expensive glassware!).
[Edited on 4-4-2015 by AJKOER] |
Link to threads picture: https://www.sciencemadness.org/whisper/post.php?action=reply...
Reactions:
Ag(+) + OH- = AgOH
2 AgOH = Ag2O + H2O. (See https://en.m.wikipedia.org/wiki/Silver_oxide )
2 KCl + Ag2O + H2O = 2 AgCl(s) + 2 KOH
Note, the last reaction consumes water in the process of forming the hydroxide. My Silver salt was Silver acetate which one can prepare by mixing
Silver metal, vinegar and dilute H2O2 together with a very small amount of say KNO3 (acting as an electrolyte as the underlying process is
electrochemical in nature). Jump start the reaction in a microwave and periodically add more vinegar and H2O2. Silver acetate is soluble in acetic
acid to which one can add a convenient alkaline to prepare AgOH/Ag2O.
[Edited on 15-9-2016 by AJKOER]
|
|
|
CrossxD
Hazard to Self
Posts: 66
Registered: 6-7-2015
Member Is Offline
Mood: stainless
|
|
Awesome process, but how should I recycle silver?
|
|
|
CrossxD
Hazard to Self
Posts: 66
Registered: 6-7-2015
Member Is Offline
Mood: stainless
|
|
And how about use calcium acetate, react it with potassium sulphate, than filtrate calcium sulphate.
There should left potassium acetate wich I can thermaly decompose to potassium carbonate and from carbonate I can make hydroxide
|
|
|
AJKOER
Radically Dubious
Posts: 3026
Registered: 7-5-2011
Member Is Offline
Mood: No Mood
|
|
There are a few methods to recycle AgCl. A few years ago, my recollection was boiling AgCl with NaOH in a microwave which eventually changes color to
Ag2O. Then, I beileve I used as a sugar glucose source (which acts as a reducer) some molasses.
Here is a link to another method by dissolving the AgCl in conc ammonia and then employing ascorbic acid as the reducer: https://www.google.com/url?sa=t&source=web&rct=j&...
An interesting exercise that I would recommend performing at least once.
[Edited on 17-9-2016 by AJKOER]
|
|
|
![[*]](images/xpblue/default_icon.gif){kind=icon}
