# Need help on filtering...



## DNIndustry (Nov 30, 2008)

I am having an issue on filtering.
I did some research and The particle size im dropping with I2 is 5 micron.
I have a gallon of liquid that has been filtered 5x. coffee filters and vaccum filtered with Watman #4 filters. Does anyone know about ceramic filters or have any recommedations. I need to change things up. I need a bigger filtering flask as well. Ive been working with various plastics but some of them actually have a porosity or a charge to them that makes it worse, the gold sticks.


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## qst42know (Nov 30, 2008)

Whatman #4 is 20-25um. I suspect the porosity of coffee filters varies widely as what is required for a good cup of coffee has nothing to do with capturing PM's. I have not had much success with the java filters from around here except for pre filtering coarse wastes, I find too much in my stock pot. 

There are finer standard paper grades that can still be burned to recover trapped values. Numeric values of Whatman grades do not follow sequentially the porosity of the filter.

http://www.whatman.com/QualitativeFilterPapersStandardGrades.aspx


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## qst42know (Nov 30, 2008)

As far as the filtration vessel is concerned this rig allows me to use any glass jar, pint to gallon. Just add a ceramic funnel and a piece of sheet rubber gasket.


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## lazersteve (Nov 30, 2008)

DNIndustry,

After precipitating your gold there is no real need to filter. 

Let the gold settle and siphon off the liquid. Rinse several times with water letting settle and siphoning after each rinse. The gold never leaves the flask it is precipitated in until it is completely rinsed, washed with hot HCl, water two more times, hot ammonium hydroxide, and finally rinsed with water twice more.

The throughly washed and rinsed gold powder is then heat dried in the flask with swirling to prevent any steam explosions or sticking.

The dry gold is then easily poured out of the beaker/flask.

Here's a detailed post of the process:

Filterless Wash Process

Steve


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## Harold_V (Nov 30, 2008)

DNIndustry said:


> I am having an issue on filtering.


I refined for more than 20 years and would use nothing but Whatman #2 for my gold chloride solutions. When re-refining, I switched to a Whatman #5, which is more retentive. Very clean solutions, such as the ones that came from the second refining, had no problems going through a #5, but it is dreadfully slow for dirty solutions. 

I also had a policy of incinerating everything before it got put into solution, plus, depending on circumstances. some of my lots were given a boil in HCl and water before dissolution. This wash was followed by no less than two rinses, with the solution decanted, not filtered. That often removed substances that made filtration difficult. 

If you're wise, you'll pick up on the two things I've told you here that make a world of difference in filtration. 

I did not use coffee filters. I was refining precious metals, not brewing coffee. To me, it was worth the price of the right size and grade of filter. 

S&S makes what they call Sharkskin. It's excellent for filtering very dirty materials, such as separating gold chloride from processed polishing wastes from the jeweler's bench. 

Harold


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## qst42know (Nov 30, 2008)

I just ran into that name S&S Sharkskin is part of Whatman. And both are part of General Electric. I was brousing yesterday though I don't recall where.


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## Harold_V (Dec 1, 2008)

qst42know said:


> both are part of General Electric.



Interesting. My last purchase of filters was prior to '94. I don't believe they were under the flag of G.E. at that time. Fact is, I think Whatman is (was) British in origin. Just a hunch----I stand to be corrected. 

Harold


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## qst42know (Dec 1, 2008)

Looks like Whatman bought S&S in 04. And GE bought them in 08.

The Sharkskin line is still available.


http://www.whatman.com/ViewPressRelease.aspx?PID=92

http://findarticles.com/p/articles/mi_m0EIN/is_/ai_n14862501

http://www.medibix.com/company.jsp?company_id=29436


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## DNIndustry (Dec 1, 2008)

I GOT ur drift. I was really thinking out loud. A duh moment. Shor recommends coffee filters... 
Duh..
In my organic days i used to use .22um filters that handle 125L each. Not easy to get at the goods though 

I picked up some United 12.5cm #1. No info but definitly smaller pore size.
The Iodine precip creates the smallest possible particles, Now that its monday i will look into shark skin and some Whatman 5's

And lazersteve...Not sure if my methods will ever be accepted, but with any Iodine process adding a step to boil with H20+ H2O2(30%) removes any iodine in your precipitant. Iwould love to provide more details to be added ]
Thakns guys.


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