Sciencemadness Discussion Board

Unusual gas from Mg in Citric acid

FragranceLover89 - 27-10-2020 at 10:01

I was trying to smooth a Mg ring I carved with citric acid. The Mg started bubbling and began producing a slight garlic smell, which freaked me out a lot because H2 is supposed to be odorless. I am worried my Mg is contaminated with MgP or MgAs. Does anyone know what happened?

njl - 27-10-2020 at 10:16

Garlic smell could be H2S, so maybe a sulfide? Also contaminants could even be other metal cations.

woelen - 27-10-2020 at 10:41

Garlic smell is not H2S. Could be PH3, but in these small quantities I would not worry at all. PH3 has no long-lasting effects and the amount is way too small to pose a direct risk.

No need to worry about AsH3. Nowadays, arsenic contamination of metals like Mg, Al, Fe is not at all common. Around 1900 things were different, but nowadays, unintended As-contamination of commercially available materials is uncommon.

valeg96 - 27-10-2020 at 13:40

OT: Woelen I agree, but sometimes cheap stuff is contaminated. A friend of mine purchased a roll of cheap solder from china, and found out it was exceedingly radioactive (I assume the production plant improperly melted some radioactive lead). So I wouldn't be surprised if a cheap block of Mg from china had relevant amounts of As.

Then again, I've found that most metals give off a garlic-y smell while being dissolved, or at least their acid aereosol stinks a bit. Iron is a prime example.

Herr Haber - 27-10-2020 at 14:07

Quote: Originally posted by valeg96  

Then again, I've found that most metals give off a garlic-y smell while being dissolved, or at least their acid aereosol stinks a bit. Iron is a prime example.


Oh so true. I sometimes wondered what kind of contaminants were in the steel I was trying to restore with sulphamic acid.

And the cell to remove silver plating from silverware... Yuk!

FragranceLover89 - 29-10-2020 at 15:59

Thanks! It is good to know this is probably common/not hazardous.

Fluorite - 31-10-2020 at 09:43

You can try the marsh test if you're concerned