# Grey sludge with pgm blacks



## bpc1987 (Apr 18, 2012)

Hi guys, I have just extracted my first pgm blacks from my hcl-cl leech solution as per lazersteve's dvd , however once the black pgm powder had been filtered off from solution, I have noticed a small amount of grey sludge amongst it. At first I thought it might have been a bit of unactive zinc, however I added that batch to another leech and the grey sludge still remains so I am presuming that it isnt zinc and somehow some of the cermaic/carbon cat material has somehow got through the two stage filtration process :?: If this is the case- would the pgm blacks dissolve back into a straight solution of 36% hcl. I could then filter the solution through a fine filter paper and then re cement the pgm's using zinc again after of course having increased the ph. Any help would be much appreciated.

Regards

Ben


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## lazersteve (Apr 18, 2012)

If you are using powdered zinc it may have Cab-O-Sil added as a stabilizer.

Check the powdered zinc by dissolving a few grams in HCl and see if any solids remain.

Search the forum for more information on Cab-O-Sil.


Steve


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## bpc1987 (Apr 19, 2012)

Thanks Steve-I will look into this!

Regards

Ben


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## bpc1987 (Apr 29, 2012)

It would seem that the undissolved grey sludge was infact cab-o-sil! I think next time I will be using turnings instead of powder!

Ben


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