Why does amazon reccomend three items that do not go together, so mad i bought the recommendation, the rubber does not fit the buchner funnel

Yeah it's more like "frequently returned together" than anything.I'm going to try drilling a hole in the stopper that's big enough for the funnel, but that's the only solution I see. I don't see a way to flag the recommendation, but hopefully people will read these comments.The spout on this funnel is about 2cm wide. The hole in the stopper is closer to half a centimeter.The stopper fits the flask (barely) but not the buchner funnel it's recommended with.

what size rubber stopper do i need for this ?

I'm not sure. It is too big for a#8. I use one of a set of funnel adapters to make it fit the flask that would take a #8. See e.g. https://www.sks-science.com/funnels-p-6442.html.Phil

Is this something that will help me with gold refining?

Hi Ray,If you are recovering microfine product, you will need this, a vacuum pump and very fine Whatman filters. You need to make certain however, that the edges of the filters do not lift up during the vacuum process, or your product will go under the filter, with the possibility of throwing it away. It is not necessarily for refining, but rather for collection after processing, before the refining step. It is invaluable for determining recovery weights. You have to run a parallel filter that is a blank so to speak through the rinse and vacuum process for an accurate weight of the filter paper. They lose weight after all of that rinsing and vacuuming, so the beginning weight will not be the correct weight of the filter paper, when determining recovery amounts. I prefer the plastic models over the ceramic as sometimes the ceramic catches your product, as this product sometimes sticks to glass, especially if the particles are very small things. I use Whatman 387 filters, which retain material down to around 1.5-2.0 microns in size. They are pricey and slow, if you do this without a vacuum pump, but they work very well. So, to answer your question, after all of that, yes, you need something like this, but not for refining. It is necessary for recovery. It also depends on what your lixivant is that you are precipitating your product from. Some lixivants are harsher than others and will ruin your pump; it depends on your process.

Is the pore plate flat? I keep ordering different ones and they all have a convex (curved) pore plate and the filter papers never seal properly.

Yes, the " bottom" or pour plate is flat. I really like these funnels. I have several sizes and they all have a flat bottom. I especially like the fact that the funnel separates just below the floor so you can use a wash bottle or whatever to do it redeem all of your solution, and clean the underside and tape Ed area thoroughly. I cut circles out of fiberglass cloth about 2 cn smaller than the filter paper and place it in the funnel first. This gives you a "stand off" or lifting area which prevents the paper from clogging directly over the holes and GREATELY INCREASES the filtering area.

ASIN	B00BHLE6MO
Best Sellers Rank	#51,051 in Industrial & Scientific ( See Top 100 in Industrial & Scientific ) #2 in Lab Buchner Funnels
Brand	EISCO
Brand Name	EISCO
Capacity	5.1 Inches
Color	White
Customer Reviews	4.6 out of 5 stars 295 Reviews
Global Trade Identification Number	00849230023218
Item Dimensions W x H	5"W x 8.25"H
Manufacturer	Eisco
Material	Polypropylene (PP)
Material Type	Polypropylene (PP)
Product Dimensions	5"W x 8.25"H
UPC	849230023218
Wide End Diameter	13 Centimeters

13cm Dia. (5.1") Filter Funnel, Buchner Style - 2 Parts, Polypropylene, Designed for 11-12.5cm Filter Paper

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