MadSci Network: Chemistry

Re: Dishwashing detergents vs laundry detergents

Date: Thu Aug 5 12:53:34 2010
Posted By: Dean Cliver, Faculty, Food Safety Unit, Uiversity of California, Davis
Area of science: Chemistry
ID: 1278867929.Ch

This is really not my field.  When other sources failed me, I extracted the
following from Wikipedia, under "Laundry detergent" and the "Detergent"
section of the "Dishwasher" entry.  I was tempted to try to paraphrase
these, but thought better of it.

Dean O. Cliver

Laundry detergent

Laundry detergent typically consists of ionic and anionic surfactants which
act as the detergent to remove the dirt from the clothes, perfume,
phosphors which make clothes appear whiter (it is these that show up under
ultraviolet light), and for powders anticaking agents to prevent the powder
becoming one large lump in the presence of moisture. For liquid detergents,
the bulk of the product is water; for concentrated liquids, somewhat less
water, but still the product is mostly water. Biological laundry detergents
contain enzymes which act as catalysts to "eat" the dirt off of the
laundry; these function best at the kinds of body temperatures found in
warm-blooded creatures (30 to 50 C (86 to 122 F)) and will perform no
better, and sometimes worse, at higher temperatures. Detergents may have
other additives such as bleaches and fabric softeners and these are usually
advertised clearly on the packets as selling points.


Different kinds of dishwashing detergent contain different combinations of
the items in the list below. Not all of the ingredients below are used in
some detergents.
o	Dissolves calcium and magnesium ions to prevent 'hard-water' type
limescale deposits. Unfortunately, they can cause ecological damage, so
their use is starting to be phased out. Phosphate-free detergents are sold
as eco-friendly detergents.
	Oxygen-based bleaching agents (older-style powders and liquids contain
chlorine-based bleaching agents) 
o	Breaks up and bleaches organic deposits.
	Non-ionic surfactants 
o	Lowers the surface tension of the water, emulsifies oil, lipid and fat
food deposits, prevents droplet spotting on drying.
o	Breaks up and dissolves protein-based food deposits, and possibly oil,
lipid and fat deposits. Proteases do this by breaking down the proteins
into smaller peptides that are more easily washed away.
	Anti-corrosion agent(s) 
o	Often sodium silicate, this prevents corrosion of dishwasher components.
Dishwashing detergent may also contain:
	Anti-foaming agents 
o	Foam interferes with the washing action.
	Additives to slow down the removal of glaze & patterns from glazed ceramics
	Anti-caking agents (in granular detergent)
	Starches (in tablet based detergents)
	Gelling agents (in liquid/gel based detergents)
	Sand (inexpensive powdered detergents)
Dishwasher detergents are strongly alkaline (basic).

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