Mabus
Wiki Master
Posts: 238
Registered: 3-11-2013
Member Is Offline
Mood: Energetic
|
|
Does zinc peroxide form while melting zinc?
I recently melted some car stick-on wheel counterweights made of zinc. During the melting process, the resulting slag turned yellow. After I poured
the molten zinc into another can, I let the slag to cool, and as it cooled, it turned white.
Was the yellow color from zinc peroxide?
|
|
|
BromicAcid
International Hazard
Posts: 3248
Registered: 13-7-2003
Location: Wisconsin
Member Is Online
Mood: Rock n' Roll
|
|
As I recall zinc oxide is thermochromic and changes color due to heating alone. Usually peroxides are unstable at higher temperatures so it would
surprise me to find out that a transient peroxide was the cause of the color change.
|
|
|
Mabus
Wiki Master
Posts: 238
Registered: 3-11-2013
Member Is Offline
Mood: Energetic
|
|
I believe you are right:
<iframe sandbox width="640" height="360" src="http://www.youtube.com/embed/cEIujFx2Mro" frameborder="0" allowfullscreen></iframe>
Mystery solved.
|
|
|
chemrox
International Hazard
Posts: 2961
Registered: 18-1-2007
Location: UTM
Member Is Offline
Mood: LaGrangian
|
|
This could also be due to Fe impurities in the weights. Maybe they're an alloy?
"When you let the dumbasses vote you end up with populism followed by autocracy and getting back is a bitch." Plato (sort of)
|
|
|
Pumukli
National Hazard
Posts: 705
Registered: 2-3-2014
Location: EU
Member Is Offline
Mood: No Mood
|
|
Bromic is right, ZnO changes its color depending on the temperature. I heated pharmacy grade ZnO in a small ceramic crucible and it became yellow when
was on fairly high heat. Upon cooling the original white color came back.
If you have some known pure ZnO you can see that even at room temperature it is not 100% WHITE, as snow white or TiO2 white (tooth paste white). It
has a bit yellowish tinge!
|
|
|
MrHomeScientist
International Hazard
Posts: 1806
Registered: 24-10-2010
Location: Flerovium
Member Is Offline
Mood: No Mood
|
|
Correct! I also saw the thermochromism when decomposing zinc hydroxide into the oxide. Since both are white powders, I used the yellow color change as
an indicator for when the conversion was complete. Cooling turned it back to nice and white.
|
|
|
![[*]](images/xpblue/default_icon.gif){kind=icon}
