B(a)P
International Hazard
Posts: 1139
Registered: 29-9-2019
Member Is Offline
Mood: Festive
|
|
What yields more
What is the reaction? I would have thought more solid on the bottom of the reaction vessel would reduce bumping as in would provide gas nucleation
sites? The more you filter the more mechanical losses that you have so that will reduce yield.
Your only question is about volume, of course if solid is removed then volume decreases, what do you mean by this?
I see no reason why multiple filtrations would improve yield if that is your question. It may depend on the specific reaction though.....
|
|
|
Texium
Administrator
Posts: 4580
Registered: 11-1-2014
Location: Salt Lake City
Member Is Offline
Mood: PhD candidate!
|
|
On this forum we appreciate clear language and references to procedures.
When those aren’t provided, it’s a lot harder to help, and it gives the unshakable impression that you’re up to something unsavory. You can’t
expect anyone to advise you on a problem so vague. The answer could go either way depending on what it is specifically that you’re making, so either
enlighten us, or this will go to Detritus.
|
|
|
Yttrium2
Perpetual Question Machine
Posts: 1104
Registered: 7-2-2015
Member Is Offline
|
|
Wikipedia says:
"K2HPO3 + 2 HCl → 2 KCl + H3PO3
In practice aqueous potassium phosphite is treated with excess hydrochloric acid. By concentrating the solution and precipitations with alcohols, the
pure acid can be separated from the salt."
Now, I have heard that it is best to remove precipitation, reduce the solution, remove more precipitate, reduce the solution, remove more precipitate
-- I've heard its best to do this like six times in order to reduce bumping, but it seems like an awful lot of work, mess, smell ect. Is this the best
way to produce the H3PO3?
What about boiling it almost all the way, till it stops precipitating and then filtering, and then reducing the mixture? Will this have more
mechanical loss since you are filtering very little liquid through a lot of KCL or would there be more mechanical loss through filtering a lot of
liquid through a little KCL mutliple times? -- Nothing was said about the mechanical losses, just the bumping.
What about freeze distilling the h3po3 out of solution?
What about setting up for distillation, reducing the mixture till all the precipitate forms, and then vacuum distilling out the H3PO3?
I am not up to anything unsavory
P.S. - I would like my name changed to IUPAC
[Edited on 7/3/2020 by Yttrium2]
|
|
|
SWIM
National Hazard
Posts: 970
Registered: 3-9-2017
Member Is Offline
|
|
This is an unusual case since the solution is in phosphoric acid.
As you boil the water out it'll get thicker and thicker, and the thicker solution will make it harder to filter the KCl.
The extra filtrations may be to avoid winding up with a whole lot of KCl in a thick phosphoric acid syrup because filtering this might be tough.
Do you have a vacuum filtration set-up?
Could save a bit of time.
|
|
|
Yttrium2
Perpetual Question Machine
Posts: 1104
Registered: 7-2-2015
Member Is Offline
|
|
I guess the alcohol is used to wash the phosphorus acid / water off of the KCL
isopropyl alcohol
In addition, it forms an azeotrope at certain levels (how much again?) - with water and helps to dry the phosphorus acid at lower temperatures.
[Edited on 7/3/2020 by Yttrium2]
|
|
|
Yttrium2
Perpetual Question Machine
Posts: 1104
Registered: 7-2-2015
Member Is Offline
|
|
Just confused about the bumping,
is it true that stirring is always recommended and boiling stones never? I heard this somewhere
|
|
|
Yttrium2
Perpetual Question Machine
Posts: 1104
Registered: 7-2-2015
Member Is Offline
|
|
Quote: Originally posted by SWIM  |
As you boil the water out it'll get thicker and thicker, and the thicker solution will make it harder to filter the KCl.
The extra filtrations may be to avoid winding up with a whole lot of KCl in a thick phosphoric acid syrup because filtering this might be tough.
|
does this make it easier, in practice?
|
|
|
draculic acid69
International Hazard
Posts: 1371
Registered: 2-8-2018
Member Is Offline
|
|
So r u making h3po3 from a potassium phosphite solution? Is that what this post is about?
|
|
|
mackolol
Hazard to Others
Posts: 459
Registered: 26-10-2017
Member Is Offline
Mood: Funky
|
|
I totally don't agree with you that if you have more solid on the bottom, the reaction doesn't bump. Lately, I'm performing decarboxylation of
aminoacid by boiling it in turpentine. The aminoacid has quite low density and it is required a lot of this to get few grams, so the solvent layer is
just above. All I can tell you is that it bumps as fuck.
If I had to tell how to prevent bumping, the solid should be dense and hard, something like sand and just a thin layer to cover the bottom.
@Yttrium2 is right, stirring is always recommended.
|
|
|
Yttrium2
Perpetual Question Machine
Posts: 1104
Registered: 7-2-2015
Member Is Offline
|
|
| Quote: Originally posted by mackolol | I totally don't agree with you that if you have more solid on the bottom, the reaction doesn't bump. Lately, I'm performing decarboxylation of
aminoacid by boiling it in turpentine. The aminoacid has quite low density and it is required a lot of this to get few grams, so the solvent layer is
just above. All I can tell you is that it bumps as fuck.
If I had to tell how to prevent bumping, the solid should be dense and hard, something like sand and just a thin layer to cover the bottom.
@Yttrium2 is right, stirring is always recommended. |
who were you disagreeing with, swim wasn't sure.
and
what do you mean by "If I had to tell how to prevent bumping, the solid should be dense and hard, something like sand and just a thin layer to cover
the bottom"
-
If anyone else feels like chiming in I am waiting
|
|
|
draculic acid69
International Hazard
Posts: 1371
Registered: 2-8-2018
Member Is Offline
|
|
I'm still not sure what this post is about
|
|
|
B(a)P
International Hazard
Posts: 1139
Registered: 29-9-2019
Member Is Offline
Mood: Festive
|
|
Yttrium2 appears to have deleted the original post, which makes this very confusing.
Yttrium2, why not try both and compare yields then report back? That would answer your question and contribute to the forum.
|
|
|
Yttrium2
Perpetual Question Machine
Posts: 1104
Registered: 7-2-2015
Member Is Offline
|
|
My last question is how come the KCL does not stay in the water / H3PO3 / acid after it has been reduced down, and filtered off.
I know a lot of KCL precipitates at first, but doesnt some of it stay dissolved and make its way into the final product?
Unless one is boiling it all the way down, and just filtering off the H3PO3 -- but there is usually a minimal amount of water in it at this point,
which I suspect would contain some dissolved KCL
Is the alcohol addition essential to get the dissolved KCL to precipitate from the trace amounts of water in the H3PO3?
|
|
|
Yttrium2
Perpetual Question Machine
Posts: 1104
Registered: 7-2-2015
Member Is Offline
|
|
and what about the phosphite solutions that have dyes in them? I heard that the main source changed their label, but did not change the formulation,
-- can anyone comment on that? I forgot the color of the original solution and dont know if it had dye in it.
[Edited on 7/6/2020 by Yttrium2]
|
|
|
![[*]](images/xpblue/default_icon.gif){kind=icon}
