From part of an earlier question:

My question:
D. What filtration device would you use to isolate 2.0 g of crystals from about 50 mL of solution after performing a crystallization?
My answer was a Buchner funnel

Your answer:
It would need to be a SMALL Buchner funnel. And 2 g of crystals can get lost on a large sheet of filter paper. Using a regular piece of filter paper and funnel would concentrate the 2 g in the center of the cone. The filter-tip pipette might work ok here too. Most of these answers are personal preferances, of course, but I would not go with a Buchner, even a small one.

How about using a Hirsch funnel?

Sheryl

I think that is a step in the right direction. I think some Hirsch funnels are as small as 10 mm diameter at the small end, where the filter paper fits, and 2 g probably wouldn't get lost on that. However, you will lose some of the crystals because they will collect on the sides of the funnel (not so with paper because you can wash any solid down to the center of the cone). You can wash the sides of the Hirsch funnel down, too, but some will ALWAYS be lost when the filter is removed from the device. I expect a Hirsch funnel will do what you want it to do if you have a propensity to use vacuum filtration. My philosophy always was that 200 or 300 mL to be filtered required some thinking about how I wanted to do it but 20-50 mL I just let time take its course and I kept busy with other parts of the procedure. I didn't think it was worth the trouble of getting the funnels, suction flask, hoses, paper, etc. and putting all of it together. Another thing I had to contend with was this: About half-way through the filtration, someone would flush a commode in another part of the building, suddenly the pressure in my flask was too low, and water from the aspiration system filled the flask, sometimes completely full. That meant that I had to add a second vacuum flask, in the future, in series so that my material was not contaminated. Funny now but definitely not funny then.

here is a good colorful link to vacumn filtration techniques.]]http://orgchem.colorado.edu/hndbksupport/filt/filtration.html

Using a Hirsch funnel could be a suitable option for isolating 2.0 g of crystals from about 50 mL of solution after performing a crystallization. However, there are a few things to consider.

Hirsch funnels are available in different sizes, with small diameters at the small end where the filter paper fits. With a small Hirsch funnel, 2 g of crystals would not get lost on the filter paper. However, some crystals may still collect on the sides of the funnel, and when removing the filter, some crystals may be lost.

If you choose to use a Hirsch funnel, you can wash the sides of the funnel to try and minimize crystal loss. But it's important to note that some crystals will always be lost during the filtration process.

It's worth mentioning that using a vacuum filtration setup with a Hirsch funnel requires additional equipment like suction flasks, hoses, and filter paper. This might be more suitable for larger volumes to be filtered, like 200-300 mL. For smaller volumes like 20-50 mL, it might be more convenient to let gravity filtration take its course and focus on other aspects of the procedure.

Lastly, it's important to be aware of potential fluctuations in the vacuum pressure. For example, flushing a toilet in another part of the building could cause the vacuum pressure to drop, leading to water from the aspiration system filling the flask and potentially contaminating the material. To prevent this, you could consider using a second vacuum flask in series to avoid contamination.

If you would like to learn more about vacuum filtration techniques and see visual examples, you can visit the following link:

[http://orgchem.colorado.edu/hndbksupport/filt/filtration.html]