Text 6574, 88 rader
Skriven 2006-10-15 18:41:00 av JOAN MACDIARMID (1:123/140)
     Kommentar till en text av JIM WELLER
Ärende: Vinegar
===============
 Hi, Jim,

 > My parents were chemists and my mom had been known to
 > make pickling vinegar from reagent grade glacial acetic acid

 ML> 98% pure water free acetic acid
 JW>
 JW> That would be technical grade for industrial applications. Reagent
 JW> grade is 99.8%+ pure.

 Good catch, I missed that!

 JM> I think that only means it's easily flammable
 JM> in air if ignited. It doesn't go off spontaneously.

 JW> True.

 JM> Freezing isn't a problem, after all. You warm it
 JM> up, it melts into the same liquid it was before
 JM> it crystallized.

 JW> And unlike water it doesn't expand drastically and break the
 JW> container.
 ML> diluting that to usable levels would require a protective gearing up,
 ML> gloves, respirator, mask, and a measuring utensil that wouldn't get

 JM> Again, nah! Even at 98% purity, acetic acid is
 JM> intrinsically a "weak acid"

 JW> But the fumes are irritating. We always opened the bottle and diluted
 JW> it under a fume hood with the fan on. That was it though: no gloves or
 JW> masks or special equipment.

 It would make you sneeze! Fume hoods are nice things.
 Dave Sac should have one for his horseradish preps!
 Though in fact, he improvises one rather well. I do
 use light gloves when handling glacial acetic acid or
 anhydride, just vinyl. I use rubber or neoprene
 gloves for the strong acids like sulfuric and nitric,
 with vinyl gloves inside because I am contact-allergic
 to neoprene.

 JM> Sulfuric or nitric acids... leave a fearful burn

 JW> Much worse, especially sulphuric.

 JM> Acetic is relatively bland stuff.

 JW> The one I was always extra cautious about was HF. That and making
 JW> glass cleaning solution with sulphuric acid and aqueous Potassium
 JW> Dichromate. Nasty stuff on the skin if it boils over and spits.

 I used to have to do that for our glassware
 cleaning tech. I was VERY careful, full gloves,
 glasses and apron for that job. Now, we don't
 even use that cleaning agent, as someone
 worried about the traces of chromium going
 down the drains of the rinse water.

 JM> Seriously, I think cooks should stick to natural
 JM> vinegar!

 JW> Agreed. I never meant to appear to endorse the practise.

 Understood. It was just a note of interest, of course.

 JM> The glacial is mostly made from petroleum sources[...] who knows
 JM> what stray byproduct molecules are in that 2%?

 JW> Since it's been 30 years since I've read a label I checked an industry
 JW> sales site: grade ACS reagent, 99.8% pure
 JW> total impurities:
 JW> 0.0002% acetaldehyde
 JW> 0.0005% non-volatile matter (mostly metallic acetates)
 JW> 0.002% KMnO4 red. matter (as HCOOH)
 JW> 0.01% acetic anhydride

 Wow! Thanks for the extra information. I just
 write off the top of my head, you actually do
 research! Most of that stuff wouldn't bother
 me much except the mention of metallic acetates;
 I would want to know what metallics? No, I am
 not asking you to find out!

 Joan MacDiarmid
___ Blue Wave/386 v2.30 [NR]
--- Platinum Xpress/Win/WINServer v3.0pr5
 * Origin: Try Our Web Based QWK: DOCSPLACE.ORG (1:123/140)