It seems that a rinsing agent helps the dishes in the dishwasher dry much better than they do without it (which I recently noted on my new dishwasher). What molecules are used in the composition of these rinsing agents? How do they help the plates dry?

up vote 10 down vote accepted

According to the MSDS for Jet Dry (a common brand name) it contains:

  • Sodium 2-phenylpropane-2-sulfonate (Sodium cumene sulfonate)
  • Propane-1,2-diol
  • Citric acid

I think it may be safe to assume that the citric acid is in there for a "clean" smell and also to soften the water (thanks to the commenter). The sulfonate is presumably a surfactant to help break the surface tension of the water, and promote evaporation, and the propylene glycol may help serve as a coolant (and is favored due to low toxicity).

  • 3
    Right, the first component is a surfactant. Since presumably this will be used without caring for whether the dishwater is hard or soft, you do not want to use the ester of a fatty acid here. The sulfonate, which is the conjugate base of a relatively strong acid, will tend to be more soluble, and will not form scum with hard water ions. – user95 May 5 '12 at 16:08
  • 2
    The citric acid is there to soften water by converting calcium, iron, magnesium (and others) salts into the more soluble citrates, which also decreases the likelihood of scum. – Ben Norris Aug 9 '12 at 20:03
  • Citric acid does not really smell. I also don't see how propylene glycol would serve as a coolant. – Curt F. Nov 8 '15 at 19:45

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