teodor
National Hazard
Posts: 872
Registered: 28-6-2019
Location: Heerenveen
Member Is Offline
|
|
How to wash very fine crystals?
Like Fe(OH)3 or CuCrO4. The latter is even harder. I use a buchner funnel and vacuum. After the first water removal the mass becomes very dense. It is
impossible to mix it with water in the funnel itself - it sticks to a glass rod and doesn't want to become less dense, forming clots. So, I put it
into the flask to mix with water but transferring is a very messy process, it sticks to everything. It's not possible to remove it from a flask neck
or spatula without a paper towel.
Is there any technique, any way that can help to wash such fine powders?
|
|
|
Ubya
International Hazard
Posts: 1232
Registered: 23-11-2017
Location: Rome-Italy
Member Is Offline
Mood: I'm a maddo scientisto!!!
|
|
by boiling the solution for prolonged amounts of time the particles coalesce in bigger particles, making it easier to filter.
for the washings, use a beaker, wash the powder with lots of water inside the beaker, let it settle, filter the water without letting much of the
powder in the funnel, repeat the washings as needed.
---------------------------------------------------------------------
feel free to correct my grammar, or any mistakes i make
---------------------------------------------------------------------
|
|
|
teodor
National Hazard
Posts: 872
Registered: 28-6-2019
Location: Heerenveen
Member Is Offline
|
|
Thank you, Ubya, I like your method.
[Edited on 2-7-2019 by teodor]
|
|
|
Tsjerk
International Hazard
Posts: 3022
Registered: 20-4-2005
Location: Netherlands
Member Is Offline
Mood: Mood
|
|
You could try washing it with acetone after the first water is pulled of by the vacuum, that dries your material, possibly not making it sticky
anymore.
[Edited on 2-7-2019 by Tsjerk]
|
|
|
DavidJR
National Hazard
Posts: 908
Registered: 1-1-2018
Location: Scotland
Member Is Offline
Mood: Tired
|
|
For materials that are a pain in the ass to filter - avoid filtering!
Instead, you can often just allow to settle and then decant the supernatant. Repeat as needed for washings.
Or, if you have less patience, get a centrifuge. I got a cheap one on eBay which has been very useful for work on phthalocyanines which are an
absolute nightmare to filter.
|
|
|
teodor
National Hazard
Posts: 872
Registered: 28-6-2019
Location: Heerenveen
Member Is Offline
|
|
Quote: Originally posted by Tsjerk  | You could try washing it with acetone after the first water is pulled of by the vacuum, that dries your material, possibly not making it sticky
anymore.
[Edited on 2-7-2019 by Tsjerk] |
I also thought about another solvent, but in the case of washing CuCrO4 acetone possible will not work. The main impurity is K2CrO4. According to
wikipedia K2Cr2O7 is insoluble in acetone, I think the same should be true for K2CrO4. Also some solvents will be oxidized. But of course I can try
several and select which works.
Or do you mean to make one wash with water and one with another solvent to remove the water and to make the mass more sparse and remove cracks, and
than again with water and so on? I will try that, it could be interesting.
[Edited on 3-7-2019 by teodor]
[Edited on 3-7-2019 by teodor]
[Edited on 3-7-2019 by teodor]
|
|
|
teodor
National Hazard
Posts: 872
Registered: 28-6-2019
Location: Heerenveen
Member Is Offline
|
|
| Quote: Originally posted by DavidJR | For materials that are a pain in the ass to filter - avoid filtering!
Instead, you can often just allow to settle and then decant the supernatant. Repeat as needed for washings.
|
Another problem that fine powders are also good absorbents. Washing with the method of settling in water could be endless especially if I need the
material for analytical purposes.
| Quote: Originally posted by DavidJR |
Or, if you have less patience, get a centrifuge. I got a cheap one on eBay which has been very useful for work on phthalocyanines which are an
absolute nightmare to filter. |
Yes, the time matters. I am thinking about a centrifuge. May be I will buy or make one if will not find another solvent which will work.
[Edited on 3-7-2019 by teodor]
[Edited on 3-7-2019 by teodor]
[Edited on 3-7-2019 by teodor]
|
|
|
![[*]](images/xpblue/default_icon.gif){kind=icon}
