Precipitation help needed please (1 Viewer)

[matt161989]

Hi, I done a prac involving determining the sulfate content of fertiliser and it involved making a barium sulfate precipitate and filtering it, it was a very milky and not very solid precipitate which didn't filter particularly well. I was wondering whether anyone has any ideas on how I could have made it filter better, without using a different filter. I have heard that boiling it makes the clumps bigger, how does this work and also someone in my class used hydrochloric acid and his precipitate was more powdery and filtered much better.
Please post anything you have and please explain why it would work.
Thanks evry1 in advance

 

[Riviet]

I was wondering whether anyone has any ideas on how I could have made it filter better, without using a different filter.

If you used filter paper, you could improve the effectiveness of the filtering using 2 or 3 pieces instead of one.

 

[A l]

We used something called a Buchner funnel. This is a a cylindrical often porcelain filtering funnel that has a perforated plate on which the filter paper is placed and that is used usually with a vacuum. This funnel uses tubing attached to a side arm flask and a running tap to create a suction under the filter paper above the funnel. This suction ensures faster filtration as there is extra indirect downward force being applied.

Heating it also helps. The precipitate particles form larger solid clumps when kept warm but do NOT boil it, as you will lose some content through evaporation.