Ask A Scientist Chemistry Archive

name         Jocelyn R.
status       student
age          13

Question -   How does lemon juice remove stains?  What is the
chemistry?
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Jocelyn,

There are two likely possibilities. (1) Stains, being organic in nature are
more soluble in lemon juice then in water owing to the fact that lemon juice
contains organic substances that can more easily dissolve similar organic
compounds. (2) Stains react with the acids and/or oxidizers in lemon juice
-since ascorbic acid is not only an acid, but is also an oxidant- which
convert the stains into substances that are more soluble in water or the
lemon juice.

Greg (Roberto Gregorius)
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There are several chemical processes that can occur as a result of
substances contained in lemon juice (some other citrus fruits too). Any of
these alone or in combination can affect the staining of a given material.
1. The juice is acidic, so there is a substantial lowering of the pH when
the juice is applied to a stain. If the staining substance is acid-soluble,
reducing the pH increases its solubility and helps remove it. If the
staining substance is base-soluble and acid-insoluble, the opposite effect
occurs.
2. Lemon juice contains ascorbic acid (vitamin C). Ascorbic acid is
an active reducing agent (as opposed to an oxidizing agent). If the
staining substance can be reduced by ascorbic acid, and the reduced product
is not colored, then the lemon juice bleaches the stain.
3. The skin of lemons and other citrus fruits contains oils (lemon oil, 
specifically). If
the staining substance is soluble in the oil, the juice will help remove
the stain by dissolving the offending substance. These are just a few of
the chemical processes that could occur.

Vince Calder
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