Sciencemadness Discussion Board

Vacuum Filtration Problems

thegrabber - 14-6-2019 at 16:25

I'm following the synthesis of Potassium Dichromate from chemplayer. I have successfully formed the chromate ion based on a slight yellow tinge in my solution. I have a vacuum filtration setup with a ground jointed conical flask and sintered funnel connected to a 12v vacuum pump. I keep trying to filter the chromate from the chromium oxide but the green oxide keeps getting through.

I have tried reducing the vacuum, the solution is filtered at 80 degrees C or so. I have found that initially the chromium oxide gets through, but after a few minutes only the chromate manages to pass through the funnel.

I'm really not sure where the error is. I tried to repeat the filtration by putting the filtrate back through the funnel but the chromium oxide still manages to get through, even though there is a bed of oxide on the sintered glass.

Could it be possible that I need a finer sintered funnel? The one I bought is here https://www.aliexpress.com/item/Kicute-24-40-500ml-Suction-F...

Any help is appreciate, thank you.

Herr Haber - 15-6-2019 at 04:06

This very recent thread might be of interest to you:
https://www.sciencemadness.org/whisper/viewthread.php?tid=15...