Ask A Scientist General Science Archive

name         Scott B.
status       student
grade        9-12
location     MD

Question -   I plan to perform an experiment where I will dissolve
sodium carbonate (washing soda) in hot water to remove an olive oil stain
from cotton fabric.  I will use no other detergents and the water is
soft, so the sodium carbonate will not have to concentrate on
"neutralizing" calcium and magnesium deposits.
Per my research, several scenarios should occur:

1) the sodium carbonate should create an emulsion that will lift the stain
from the material;

2) this process is the result of hydrolysis; and

3) a mild saponification could
  occur and convert the stain into "soap."

My research offers no explanation on the process in what happens
"chemically".  I would appreciate an brief explanation on what happens .
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Taking your points one at a time:
1. Sodium carbonate is not a surface active agent, so it will not emulsify
the olive oil. In fact, it may only decrease the already low solubility of
olive oil in water.
2. While hydrolysis of the olive oil will occur, the reaction is slow at
room temperatures.
3. The saponification will produce a carboxylic acid salt which will help
remove the remaining olive oil but I  think you will have to use rather
aggressive conditions of concentration of sodium carbonate and temperature.

Vince Calder
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