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INTRODUCTION TO CELLS: TERMINOLOGY AND BACKGROUND 283

And finally a word of caution: aluminium ethanoate is toxic, so wash the silver
spoon thoroughly after removing its tarnish.

How does ‘electrolysis’ stop hair growth?

Electrochemical reactions and electrolysis

To many people, particularly the image conscious, electrolysis
Electrochemical means
means removing hairs from the arms and legs – a practice some-
the chemistry of the
times called ‘electrology’. The purpose of such electrolysis is to
electron.
remove the hair follicles temporarily, thereby avoiding the need to
shave. We ‘treat’ each individual hair by inserting a tiny surgical
‘probe’ (in reality, an electrode) into the hair follicle. Applying a
It is wrong to claim
voltage to the hair root for a fraction of a second kills the root. The
a permanent method
electrolysed hair is then removed, and will not regrow for some of hair removal: after
time. This procedure is performed repeatedly until the desired area electrolysis, the hair
is cleared. But how does it work? will grow back, albeit
A voltage is applied to the electrode: we say it is polarized.A thinner and finer.
current flows in response to the voltage, and electrons are consumed
by electrochemical reactions around the electrodes. Electrolysis
The word ‘electroly-
occurs. Each electron that flows through the electrode must be
sis’ derives from the
involved in a redox reaction, either oxidation or reduction. The Greek words lysis,
electrons entering or leaving the electrode move as a result of meaning ‘splitting’ or
reactions occurring in the immediate vicinity of the electrode. Con- ‘cleavage’, and the
versely, electrons can travel in the opposite direction (leaving the root electro, meaning
electrode) to facilitate reduction reactions. ‘charge’ or ‘electric-
In summary, this form of electrolysis is effective because the ity’. Strictly, then,
charge passing through the electrode generates chemicals inside electrolysis involves
the hair follicle. The resultant trauma kills the hair root. A leg or electrochemical bond
cleavage.
arm treated in this way remains hairless until a new, healthy root
regrows later in the previously damaged follicle.

Why power a car with a heavy-duty battery yet use a
small battery in a watch?

Faraday’s laws of electrolysis

A battery is a device for converting chemical energy into electrical
Batteries are described
energy. The amount of energy required by the user varies according
in more detail in
to the application in mind. For example, a watch battery only pow-
Section 7.7.
ers the tiny display on the face of a digital watch. For this purpose,