Foeskes
Hazard to Others
Posts: 156
Registered: 25-2-2017
Member Is Offline
Mood: No Mood
|
|
Filtering and washing calcium fluoride
I made some CaF2 for a source of F for my collection. I bought some HF glass enchant and mixed it with CaCl2 to make CaF2. I I found the precipitate
to be very fine and the excess CaCl2 started to crystallize out and needed to be washed out.
My Büchner funnel is really big(7cm diameter)and I most likely only have like 3-10 grams of CaF2. Any tips?
I also don't have any centrifuges otherwise it would be easy.
|
|
|
Deathunter88
National Hazard
Posts: 508
Registered: 20-2-2015
Location: Beijing, China
Member Is Offline
Mood: No Mood
|
|
Add lots of water to the reaction mixture, wait a few hours for the CaF2 to settle, decant. Repeat a few times, then on the last go after decanting
let the resulting slurry dry. A tall container works best.
|
|
|
wg48
National Hazard
Posts: 821
Registered: 21-11-2015
Member Is Offline
Mood: No Mood
|
|
Quote: Originally posted by Deathunter88  | | Add lots of water to the reaction mixture, wait a few hours for the CaF2 to settle, decant. Repeat a few times, then on the last go after decanting
let the resulting slurry dry. A tall container works best. |
and takes the longest time to settle.
|
|
|
LearnedAmateur
National Hazard
Posts: 513
Registered: 30-3-2017
Location: Somewhere in the UK
Member Is Offline
Mood: Free Radical
|
|
Calcium chloride is highly soluble in water whereas the fluoride is barely soluble at all. For 3-10g you shouldn’t need more than 20-50mL water to
dissolve all of the chloride (@ 20C, solubility is 745mg/mL - PubChem), and I’d recommend a paper filter folded into a funnel to minimise losses in
the Buchner. As a general rule of thumb, use paper if you care about the precipitate, or use a Buchner if you care about the filtrate. It will take a
long time without vacuum either way as the fine precipitate clogs the filters, but it’ll undoubtedly be quicker than waiting for 2-3 washes to
precipitate, since just one won’t be adequate if you want to avoid CaCl2 contamination upon drying, as well as whatever else may be in the etchant,
unless it’s pure? Haven’t ever needed to use it myself so I have no idea on the additives.
In chemistry, sometimes the solution is the problem.
It’s been a while, but I’m not dead! Updated 7/1/2020. Shout out to Aga, we got along well.
|
|
|
![[*]](images/xpblue/default_icon.gif){kind=icon}
