Fair warning to newcomers -- I'm an engineer and a former college-level science and math instructor. If you are not emotionally up to dealing with my engineering professor tone, you should skip this post.
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Firstly, a few people in this thread are confusing IMPURITIES (which is what is being discussed here) with ADDITIVES. They are
not the same.
I have already explained the difference in another one of Don's recent posts, but here is the link for those who are wondering --
http://www.soapmakingforum.com/showpost.php?p=668491&postcount=2 Another explanation:
http://www.soapmakingforum.com/showpost.php?p=631718&postcount=6
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Moving on.
Have you ever looked at a certificate of analysis (COA) for NaOH? For example, hunt up a COA for the NaOH that Essential Depot (ED) sells.
If you do that, you'll see something similar to Don's analytical report. The big numbers on Don's list and on the ED COA are in units of ppm -- Parts Per Million by weight. Don't get spooked by the fact that the numbers seem large, because they're not all that big in reality.
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Don's NaOH has an actual iron (Fe) content of 1.4 ppm by weight and is allowed a maximum limit of 5 ppm.
The ED COA I have for their non-food grade NaOH limits iron to 0.0017% max. That translates to 17 ppm max. Their food grade is 0.0015% or 15 ppm max.
So ask yourself -- which NaOH would you rather use if you're worried about iron? Don's at a max of 5 ppm or ED's at a max of 17 ppm?
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Don's NaOH has an actual nickel content of 0.5 ppm by weight with a maximum limit of 3 ppm.
ED doesn't list nickel on their COA's, but I guarantee there is nickel in ED's NaOH because nickel is a necessary component in the metal equipment used to store and manufacture NaOH.
Since ED's COA is not helpful, let's look at other suppliers' standards for NaOH --
GFS 50% NaOH solution, reagent grade: 0.001% Nickel max (10 ppm max). For grins, the limit on iron (Fe) is also 0.001% max (again, that's 10 ppm max).
But that's a liquid NaOH product. Here's a solid form from Fisher Scientific that's comparable to the solid NaOH that most soap makers use --
Fisher Scientific NaOH pellets, 97%: Nickel 0.001% max (10 ppm max). Iron 0.001 % max (10 ppm max)
And another comparable solid NaOH product from Sigma Aldrich --
Sigma Aldrich NaOH pellets, 97%: Ni: ≤0.001% (10 ppm max) and Iron: ≤0.001% (10 ppm max)
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When you make soap, the trace contaminants in the NaOH are diluted by all the other ingredients in the soap. Picking one of my latest soap recipes, the NaOH is about 10% of the total batch weight. So the iron and nickel are diluted in soap to roughly one tenth the amount present in the original NaOH.
Bottom line --
If you use NaOH made by any reputable company -- and Fisher (distributor), Sigma Aldrich, and GFS are all reputable sources -- your soap will contain as much nickel and iron (and possibly even more) as if you used Don's NaOH.
If you are not having a problem with
your soap doing bad things like triggering someone's nickel allergy or whatever, then Don's soap won't either.
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To Zany -- Where is the COA for the Red Crown Lye you suggested is so much better than Don's product? Did you take the time to compare the Red Crown analysis with Don's NaOH so you know the differences? Do your homework!
To Don -- This NaOH is fine for soap, assuming you actually get what the distributor says you're getting. But my firm advice to you -- next time, ask questions BEFORE you buy. If this was not suitable for soaping, then you would have the problem of disposing of 25 kg of a hazardous chemical, and that is no laughing matter. Do your homework too!
