Expert: Profile Closed - 2/18/2010

Question
I would like to make home made soap and my recipi stresses that I must use pure Sodium Hydroxide The best I am able to get is 98% but there is no specification of what is added, or even if the missing 2% is the container! The only additional numbers are UN1823 and EC216-215-185 5 is this the chemicl number for SH or for the plastic container or an additive? HELP!

Answer
Hi there, and thanks for your question.

98% Sodium Hydroxide is as close to pure as is available, and works well for soap-making (which is a hobby of mine too :-). Remember, you're going to be tipping your Sodium Hydroxide in to water as part of the procedure, so it will not be pure for long; as long as the starting material is relatively pure there are no problems.

The Sodium Hydroxide does, in fact, start off as nearly 100% pure, but it absorbs water and carbon dioxide from the atmosphere, meaning that it can't be labelled as more than 98% pure.

The numbers you mentioned are the UN identifiers for Sodium Hydroxide.

As I said, though, it is more than pure enough for soap-making; the reason the instructions specify "pure" is to stop people using things like oven-cleaner, which contains a mix of sodium hydroxide and other chemicals.

Hope this helps, good luck with your soap-making, and please take care to follow all the safety instructions and wear the protective gear suggested; I still have a lovely collection of deep scars on one arm as a result of an accident with 98% NaOH over 10 years ago!

Feel free to ask any follow-ups, best wishes,
George