A post about the possible presence of benzene in denatured alcohol got me reading the Material Safety Data Sheets for various brands of DNA. Some clarification is needed. For example, the MSDS for the StarBronze brand of DNA (StarBronze are also the makers of ZipStrip) shows no benzene listed under Ingredient Composition, yet toward the end of the MSDS there’s a Prop 65 warning, mentioning benzene and toluene.
What gives here? Anyone know? I didn’t find benzene listed in any of about 10 MSDS’s for DNA. Why did it show up in the Prop 65 warning, but not in the ingredients?
forestgirl — you can take the girl out of the forest, but you can’t take the forest out of the girl 😉
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AFAIK, it's not always benzene that's added- I have seen methanol, too. I'll go out and read the can for what I have and see what is in it.
My guess is that one or more of the ingredients are synthesized from petroleum products and that the benzene/toluene are essentially byproduct impurities from those processes. Both probably are present in trace amounts too low to warrant listing on the ingredients.
Noteworthy on that MSDS is the last ingredient - Heptane, which is an Alphatic Petroleum Naphtha. It's possible that the Benzene is introduced this way. Although it is in a completely different class of solvents.
Of course both Methyl and Ethyl Alcohols can be synthesized from petroleum products.
"My guess is that ... the benzene/toluene are essentially byproduct impurities from those processes." Thanks, Kevin. That's the kind of chemistry savvy I just don't have. I've heard recently about benzene in relationship to oil/gas refining. This makes sense.forestgirl -- you can take the girl out of the forest, but you can't take the forest out of the girl ;-)
Would that I could take credit for it. But alas the chemistry savvy isn't mine. I've got an ancient organic chemistry book and a super handy solvent guide published by a supplier which I dug through for about 20 minutes before responding to your post.
I feel like Cliff from cheers posting this, but here it goes anyway....
Benzene is a common additive when one is trying to isolate pure ethanol. Ethanol forms an azetrope with water, meaning that the mixture boils at a lower temperature than either pure substance. So when you try to distill it (purify it), you always end up with a mixture of ethanol and water. The best you can do is about 90% ethanol, (180 proof). By adding benzene, you change the properties of the solution, and can distill off 100% ethanol (which will unfortunately contain traces of benzene, which makes for bad drinking). As a chemist I can get 100% ethanol, but I can be pretty sure that it will always contain benzene, and that the minute I open it, it will slowly start picking up water from the atmosphere on its way to returning to 180 proof alcohol.
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Jamie, I am not aware of benzine being used for denaturing alcohol. But it could be. Here is some info from a chemical dictionary.
Traditionally, the main additive was 10% methanol, which gave rise to its name, but this is not always the case now. There are diverse industrial uses for ethanol, and therefore literally hundreds of recipes for denaturing ethanol. Typical additives are methanol, isopropanol, methyl ethyl ketone, methyl isobutyl ketone, denatonium, and even (uncommonly) aviation gasoline.
If the MSDS shows benzene and toluene, then they are only trace amounts and only dangerous in California.
My impression from reading the various articles that popped up was that benzene isn't used specifically to "denature" (render undrinkable, for those who don't know) the alcohol, at least not these days. I think Rufus and Kevin are on the mark with the chemical processing explanation for what must be extemely small amounts of benzene.
Probably still a good idea to wear the respirator. Darn.forestgirl -- you can take the girl out of the forest, but you can't take the forest out of the girl ;-)
>> Probably still a good idea to wear the respirator. Darn.
That's always true. But, I find that after a session with shellac, I don't need as many martinis before dinner.Howie.........
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