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Author: Subject: Green Filter Paper - Chromium, copper, iron, something else?
chemkid
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[*] posted on 13-3-2008 at 16:19
Green Filter Paper - Chromium, copper, iron, something else?


I dissolved an aluminum alloy (actually aluminum rivets) in HCl and left for several days. The solution appeared slight green and also had the usually gray impurities. I filter the solution and got bright green filter paper. So clearly the green tint was not ionic, right? This lead me to think of iron. Fairly insoluble in HCl. I did some research found green iron compounds. Presumably some of the iron dissolved However, I tested the filtered solution with NaOH and got no precipitant of iron hydroxide as expected if there were any iron ions in solution. Copper also seemed like a logical conclusion.

Then i remembered chromium. I really try not to handle any carcinogens at all those this is nearly impossible. I couldn't find any green chromium compounds. But out of mainly paranoia, i didn't want to touch the solution. So know i would rather not touch the thing until i am absolutely sure its not chromium.

So if any one has any assurance that it is or is not chromium it would be much appreciated. Or if some one knows what this might otherwise be that would be fine too. I would check solubility etc. to try and get some more data for you all but if its chromium its going right down the drain or to the hazmat facility.

Chemkid

PS sorry for the ridiculously sized photo

Edit by Polverone: I've removed your jumbo image. Shrink it to no more than 800 pixels wide before attaching it again.

[Edited on 3-13-2008 by Polverone]




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not_important
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[*] posted on 13-3-2008 at 17:17


image size WAY too big go to http://www.irfanview.com/ , download, resize image, upload new size using the 'edit' button on your post.


If the solution was acid, not really likely to be Cu/Cr/Fe. But wash the filter paper in a little strong aqueous ammonia, Cu and Cr will dissolve, Fe won't.

Read up on Al alloys, see what's in them; vanadium and titanium are in some alloys and are green or blue in their lower oxidation states.

What colour were the rivets? It might be nothing more than dye used to colour the surface oxide.
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UnintentionalChaos
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[*] posted on 13-3-2008 at 17:52


Chromium isn't carcinogenic unless its hexavalent...



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[*] posted on 13-3-2008 at 22:48


You couldn't find green chromium compounds? You've got to be kidding, the oxide is green, and so are some Cr(III) salts
Disssolution in HCl doesn't produce hexavalent chromium compounds, so your solution certainly doesn't contain carcinogenic chromium compounds.

Refusing to handle carcinogenic substances is not a good approach to practical chemistry, IMO. A lot of simply unreplaceable substances are carcinogens, and today lots of things are labeled carcinogenic although they don't really pose a significant threat.
If you're going to study chemistry you will handle lots of carcinogens.

I've made and handled lots of potassium dichromate and even chromic acid anhydride. It's nothing special.




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chemkid
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[*] posted on 14-3-2008 at 18:59


I honestly think i get stupider every day, I can't find the edit function now, whatever. Smaller image.

Hmmm....I was under the impression that all chromium compounds are hazardous, stupid 1960s chemical hazard handbook. I did some research outside my little chemical hazard handbook and found that you guys where quite correct that not all chromium compounds are carcinogenic.

However, garage chemist, i really must disagree with you on your view on carcinogens, they're no health hazard now, wait until your 55 and they will be! I strictly refuse to handle carcinogens and attempt to keep my laboratory free of such compounds, (though hypocritically i keep lead, which i never use, and methanol which isn't carcinogenic but isn't exactly harmless). I manage to do plenty of chemistry without carcinogens, mutagens etc etc. Perhaps in the future i will handle them ,in a vent hood and with some heavy duty chemical gloves on.

chemkid

[Edited on 14-3-2008 by chemkid]

[Edited on 14-3-2008 by chemkid]

[Edited on 14-3-2008 by chemkid]

Green Filter Paper (even smaller).jpg - 58kB




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[*] posted on 18-3-2008 at 12:08


I treated the filterpaper with ammonia today. Dilute actually. Whatever it was it appears to have dissolved. The solution was deep blue of copper hydroxide dissolved in ammonia. Then i added sodium carbonate and it changed to the light blue of copper carbonate. Then i took some solution i had not treated with ammonia and treated that alone with sodium carbonate with a large precipitant of insoluble copper carbonate. It appears to be copper which was my impurity.

[Edited on 18-3-2008 by chemkid]




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