Ask A Scientist Chemistry Archive

name         F. W.
status       educator
age          30s

Question -   Hi - What is the compound in laundry detergent which
makes the suds?  Is it the phosphate?  I'm curious to know whether the
detergent marketed as for "front loaders" are similar to those with "no
phosphate"?
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Most laundry detergents these days are phosphate-free, in contrast to
automatic dish washer soaps that usually contain phosphates. Phosphates
generally do not foam very much, that is why they are used in automatic
dishwashers, where suds is a disaster. Phosphates are also good detergents
despite the lack of foam.

The consumer for decades has associated "suds" with cleaning ability,
because that was true decades ago.  The myth lives on, so manufacturers add
some non-ionic and anionic surfactants (detergents) to laundry detergents
that produce a controlled amount of "suds". There are literally hundreds,
maybe thousands of substances to choose from. Also, historically good
laundry soaps required "hot" water. With modern surfactants that is no
longer universally true. None the less, automatic clothes washers all have
"hot", "warm" and "cold" cycles.

The distinction between "front loaders" and "top loaders" is only indirectly
related to the composition of the detergent. Top loaders, because they
tumble more vigorously than top loaders, require a different balance of
surfactants. Too many "suds" actually interferes with the ability of a
detergent because it hinders the movement of the water.

Vince Calder
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