nicktoop - 28-12-2006 at 01:13
When I was a schoolboy (early 1960s) I used to spend quite a lot of time playing with electrolysis. I used to pull zinc carbon cells apart for the
carbon rods and then use the zinc as an electrode. After the zinc had dissolved it left a black scum behind. I collected some of this and heated it
in a crucible over a bunsen burner and got a cloud of dense white smoke. I got worried at this point...turned off the bunsen and fled!
What might it have been? At the time I feared it was arsenic oxide.
Sauron - 28-12-2006 at 01:26
ZnO is used as a white pigment. Unless there is As in a Zn-C pile how could you possibly obtain any from it?
Anyway it's 50 years later and you didn't die.
Arsenic is a naughty element.
12AX7 - 28-12-2006 at 02:01
Besides, burnt arsenic smells weird and garlicky. It's a common test for arsenide minerals.
The scum is probably impurities in the zinc, including microcrystalline zinc, which would explain the white smoke at relatively low temperature (zinc
burns at orange hot temperature).
Tim
nicktoop - 28-12-2006 at 04:31
I had assumed that arsenic might be an impurity in the zinc but the microcrystalline zinc explanation seems more likely. Thanks for the explanation.