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Sauron
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What topic? The thread author wanted to use ketene to dry the HBr azeotrope to GAA/HBr. That is a foolish ides, in same vein as using phosgene to make
acetyl chloride. Inappropriately toxic reagent to make a single product, when better, simpler and safer methods are at hand. Like generating dry HBr
and running it into GAA.
That having been established the thread has run its course. My remarks about ketene may have based on an old hazard warning but they were on topic.
Meanwhile here is a selected list of OSHA regulated carcinogens, from ocsc.edu, consisting of the ones I already posted, plus benzene, formaldehyde
and paraformaldehyde, along with a long list of inorganic compounds of arsenic and cadmium; also asbestos.
Still no ketene though.
http://ehs.ucsc.edu/lab_research_safety/pubs/chem/OshaCarcLi...
[Edited on 30-5-2008 by Sauron]
Sic gorgeamus a los subjectatus nunc.
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not_important
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`twern't accusing of paranoia, and ketene is unquestionably to avoid inhaling, just got curious and couldn't find a reference. What's on those toxic
lists does fluctuate with the years, I seem to remember n-hexane being Doom itself for awhile but not so much nowadays.
Many things on the current list have been so for some time, beta-Propiolactone (made from ketene and formaldehyde) and sadly but truthfully the useful
chloromethyl ether for example.
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Sauron
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No problem. I am just frustrated because I am having trouble laying hands on the list from Org.Syn c.mid 70s.
Re formaldehyde I thought that IARC decided to delist it as a cancer suspect agent, and it was never a proven carcinogen; maybe no one told OSHA about
that?
Most of the organics on that list are dye intermediates related to benzidine, or vinyl monomers (acrylonitrile, vinyl chloride.) Benzene is sort of
off by its lonesome.
Note the absencee of dimethyl sulfate, reputedly a proven human (brain) carcinogen; ditto iodomethane, the other halomethanes, etc. Are they still in
the suspect category only? This is all very confusing. Why are the alleged authorities waffling? You would think 40 years would be enough time to come
to some conclusions. Instead I am tempted to conclude that it is mostly a crock of shit.
Sic gorgeamus a los subjectatus nunc.
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Ephoton
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Mood: trying to figure out why I need a dark room retreat when I live in a forest of wattle.
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keten is not so bad.
you can smell it for miles so its pritty hard to hurt your self
if your carefull.
plus for the record keten plus a halide acid makes acetyl halides.
e3500 console login: root
bash-2.05#
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Formatik
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| Quote: | Originally posted by Ephoton
keten is not so bad. |
According to this, for ketene: LD50 (oral, rat): 1300 mg/kg.
LCLo (inhalation, rat): 53 mL/m3 (or ppm): 2 hrs.
LCLo (inhalation, mouse): 23 mL/m3: 30 min.
Compared to:
HCN: LC50 (mouse, inhalation): 323 ppm/5 min.
Phosgene: LC50 (inhalation, rat): 5 ppm/1 hr.
H2Se: (LCLo) inhalation in rat: 6 ppm/1 hr.
Cl2: LC50 (inhalation, rats): 293 ppm /1hr .
HCl: LC50 (rat, inhalation): 3124 ppm/1 hr.
Its lethality is about between phosgene, hydrogen selenide and chlorine.
| Quote: | you can smell it for miles so its pritty hard to hurt your self
if your carefull. |
The detectable odor threshold could lie below its lethal dose. Though this isn't too much help because a lethal concentration which is also detectable
by odor can also be reached.
| Quote: | | plus for the record keten plus a halide acid makes acetyl halides. |
Yes, a very useful reagent... acetic anhydride, isopropenyl acetate, acrylic acid, cellulose acetate, acetamide, sorbic and cinnamic acids, etc.
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jarynth
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| Quote: | Originally posted by Formatik
The ketene tube or lamp is tempting as this substance is useful for a variety of compounds. It's hard to find some LC50 or LDLo data on it, but yeah
ketene is very poisonous. According to this, the immediate life dangerous amount is 5 ppm compared to CO: 1200 ppm, Cl2: 10 ppm, H2S: 100 ppm, H2Se: 1 ppm, HCN: 50 ppm, phosgene: 2 ppm,
acetone: 2500 ppm. In addition to ketene another highly flammable is produced, methane: H3C-CO-CH3 -> H2C=C=O + CH4. For sure, nothing for a
beginner or sloppy chemist. |
Same as ozone, further down the list, so what? Nikola Tesla and other HV enthusiasts should all be dead by now.
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Ephoton
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I've made a lot of this in the past. truly not as bad as some think. still very dangerous but no more than a lot of clad procedure.
the hard part is getting the temp right so you don't get methane instead.
nichrome is best for this as the color of the wire tells you
its temp.
tried a heated tube had no success at all.
e3500 console login: root
bash-2.05#
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Foss_Jeane
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| Quote: | Originally posted by Ephoton
I've made a lot of this in the past. truly not as bad as some think. still very dangerous but no more than a lot of clad procedure.
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Ketene is one of those uber-useful chems, and it's quite easy to make. However, that's the big down side since it's a bit too easy for some
yutz to make without an appreciation for just how much care it requires. This is not the time for half fast measures and half fast equipment. A
professional quality ketene lamp would be best, and a good fume hood an absolute must. (Not really all that hard to build one, so no excuse for not
having one.)
| Quote: | | tried a heated tube had no success at all. |
These ghetto preps sound easy, but you still have to take into consideration that you need the acetone vapor in contact with the heated metal long
enough to cause the pyrolisis to ketene, but not so long that you then lose the ketene. It may take some considerable experimentation to get this
right.
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