In this video I shall cover the element zinc.
It is a rather boring but very important and
useful element. As the metal, it is a component
of brass, and protects steel via galvanizing.
It is a cheap and easy reducing agent, and
is the go-to for simple metal displacement
reactions. Joined to copper, it forms the
zinc-copper couple, and old-school reducing
agent in organic chemistry. It is also an
important component of batteries.
When it comes to sourcing the metal, Americans
have it the easiest. Pennies, one cent coins,
are a disc of zinc coated in a thin layer
of copper. The zinc inside can be melted in
a flame, and simply by jerking the molten
coin upwards, the liquid can be freed of its
copper shell. An alcohol burner or candle
flame are sufficient to achieve this. No need
for a blowtorch or anything of that magnitude.
This method is rather satisfying, I find,
and I think, though I have not tested as of
the making of this video, that the remaining
copper shells could serve as zinc-copper couples
due to the thin layer of zinc metal remaining
inside the copper shell.
Another source of zinc is batteries. The small
AA alkaline batteries, when new, contain zinc
filings or powder and this can be scraped
out and washed with water. If the discharged
ones are dismantled, one ends up with zinc
oxide, which is a good source of the ion for
zinc chemistry. Zinc-carbon batteries are
an excellent source of zinc too, since the
casing of the battery is a sheet of zinc metal,
and the carbon electrode inside is particularly
useful as an electrode.
However, my main source of zinc is from these
9 V batteries. They consist of a stack of
six alkaline batteries with zinc plates, wrapped
with paper and coated in a sticky waxy substance.
Dismantling the pile reveals each segment
comprises a compressed wad of manganese dioxide
and a sheet of zinc. The paper and plastic
coating can be cut and torn off, and the zinc
sheet removed and washed. The highly impure
manganese dioxide can then be processed as
per my manganese video to a pure form. The
zinc sheets are then useful as technical purity
zinc.
As for the properties of zinc, these are not
particularly interesting. The metal is a white-grey
colour, melts at 420°C, boils at 900°C.
If heated strongly enough, it will catch fire
and burn with a blue-white flame. Anyone that
has melted zinc in a homemade forge will have
learned this the hard way. Restricting the
supply of oxygen is usually enough to control
this burning. The zinc oxide formed is white
at room temperature, but when heated strongly
it turns yellow. This is an unusual property,
and is due to a small of oxygen reversibly
dissociating and leaving vacancies in crystal
structure. This changes the electronic properties
of the material, and hence the colour.
That's all I've got for zinc, thank you for
watching, particularly all the way to the
end. As a bonus for doing so, check out "diethyl
zinc flamethrower" on YouTube to see when
zinc isn't so boring. Until next time!
