Question: Can copper sulfide and copper oxide products be precisely visually identified?

gretchengehrke asked on November 09, 2017 00:00
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I'm interested in using the copper pipe method for detecting hydrogen sulfide that Lionel Milberger has been developing (here: https://publiclab.org/wiki/hydrogen-sulfide-copper-pipe). Copper is subject to oxidation and sulfidation, and a lot of folks are curious how well we can distinguish cuprous oxide (Cu2O, which has a reddish color), cupric oxide (CuO, which has a black/brown color), and cupric sulfide (CuS, which has a black color). Can we distinguish them visually? What are other methods for distinguishing them?



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1 Comments

Ag8n 4 months ago

Hi Gretchen. Out of curiousity, what progress has been made on this question? Thanks.

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1 Answers

Copper and copper (I) oxide can be determined visually, based on color.

Copper (II) oxide and copper sulfide, both of which are black, cannot be easily determined visually. Copper sulfide should be insoluble in most common liquids. On the other hand, copper (II) oxide is soluble in many acids and some bases.

Try scraping the black material from a copper test rod onto weighing paper. Then Transfer that into a test tube. Add some dilute hydrochloric acid and shake (you might be able to get by with distilled white vinegar...Don't know). Take a look at the residue on the bottom of the test tube. I don't know how long it will take for copper (II) oxide to dissolve, but it should. If you are using white vinegar, it could take along time ( maybe weeks). Copper sulfide should stay black and not dissolve.

This is an educated guess only, based on published data. I haven't tried it. And Murphy's law seems to be as strong as many others.


gretchengehrke 3 months ago

That is such a good idea, @Ag8n!! We should definitely try this. @sara, what would you think about trying this with copper strips that are colocated with Purafil coupons, and we could look at the dissolution rate and extent alongside Purafil's reported oxide/sulfide ratios.

warren 3 months ago

@Ag8n -- would you like one of our prototyping kits? We're almost ready to start shipping them out, and @asnow and @bronwen can get one over to you if you're interested. Thanks!

Ag8n 3 months ago

Let me do a little more research and get back to you.

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