Sciencemadness Discussion Board

Glacial Acetic from Vinegar? They did it here

detritus - 18-5-2008 at 13:01

I searched the board, but did not find any other references for this patent that I just happened upon. So I will post it here.

US2422504

Basically, dilute acids such as Acetic and Formic are mixed with activated carbon to take up the acid. This in itself concentrates the acid into the 30% region, and the carbon can be heated a bit to bring it into the 40% region. For those wanting a higher concentration, the carbon can be vac. distilled to take out almost all the water with minimal acid loss. They quote final conentrations of 97% acid for acetic and 75% for formic.

Finally, leach the acid back out of the carbon with acetone or MEK and distill off the solvent.

Seems like a cool way to concentrate acids for cheap, especially for those guys whose moms won't let them buy reagents!

Jor - 18-5-2008 at 13:11

Hmm, but acetic and formic are very cheap and I thought they are readily available via , for example phototography suppliers, or am I wrong here?
I can buy 100% acetic for 14,00 and 99%-100% formic for 8,00 EUR. And these are high purity, from Fisher. So I would guess they can be had very cheap via small suppliers? At least, in Europe.
In the USA, I would expect high shippings...

Jome - 18-5-2008 at 14:04

"That? I just buy it at my local chem-mart"

Damn it.

The world is BIG. Obviously there is going to be differences in availability in different countries.

This method could prove useful.

Formatik - 19-5-2008 at 02:15

You can get acetic acid by heating acetates with H2SO4.H2O or KHSO4. From A Dictionary of Chemistry, pg. 10 found also in the library here.

Jor - 19-5-2008 at 02:22

I was also wondering, for USA members, if Glacial acetic could be prepared from ethyl acetate. Ethyl acetate can be bought pretty easily I think. A good a example was MagicJigPipe, who was offering technical ethyl acetate for a very good price recently. If you could sufficiently hydrolyse this, and distill of the ethanol and ethyl acetate, pretty concentrated acetic acid could be gained. I have no experience with this process whatsoever. I don't know if this has been mentioned before. Does it work?

MagicJigPipe - 19-5-2008 at 03:59

Technically it should work but I haven't been able to get it to work with any kind of practicallity. Surely there is someone out there who knows how to get something like that working!

About the US. In my area NOBODY sells GAA anymore. If I wanted to obtain it I would have to order it one the internet and pay the outrageous shipping/HAZMAT charges which happens to make it not so cheap, anymore. Also, if someone were to sell it locally it would almost certainly be way overpriced because apparently photographers don't really buy it anymore.

ADP - 19-5-2008 at 05:07

Interesting, now if I could just get a good source of activated carbon. I've done this before but did the painstaking task of neutralizing vinegar with sodium bicarb and then boiling the solution down until I extracted sodium acetate. I didn't get a whole lot either. My plan with to distill it with H2SO4 and get the GAA out. I like the method posted though.

I too would have to buy online which really isn't worth it...

detritus - 19-5-2008 at 07:11

I have not tried it yet either, but probably soon. I was thinking of using activated carbon for aquarium refills. The patent says 5-7 mesh, so maybe it would need to be ground up. 5 mesh is about 4mm chunks, in contrast to window screen which is about 50 mesh.

MJP - Can you give any information on your failed trials? Did the carbon not absorb, not dry properly, or not give up the acid? I would certainly like to hear about it.

DJF90 - 19-5-2008 at 09:17

I think MJP was talking about ester hydrolysis of the ethyl acetate. The yeilds would be dependant upon the method used, base hydrolysis (aqueous NaOH) would probably be the higher yeilding method. The sodium acetate formed could then be distilled with conc. sulphuric acid to produce glacial acetic acid.

However it would probably be cheaper to start from sodium acetate as it is fairly accessible (at least on ebay) due to its use in hot ice. This would eliminate troubles with the ester hydrolysis. The sodium acetate used for the hot ice experiment is the trihydrate; to maximise the "efficiency" of the distillation with the conc. sulphuric acid this should be dehydrated by heating to anhydrous quality.

detritus - 20-5-2008 at 22:50

I did a quick test that seems to show it may be worth a try.

About 50ml of 5% vinegar was added to roughly 50ml (in volume, obviously) of activated carbon from the aquarium store and left to sit for an hour or so. Note: a small bit of frothing upon addition, probably due to carbonates perhaps?

Strained the liquid into another beaker and poured an identical amount of fresh vinegar into a second beaker. Neutralized them both with baking soda - the charcoal filtrate took MUCH less to neutralize and the frothing was very weak compared to the fresh vinegar.

I did not think it would be successful, so I did not take careful measurements when I "titrated" out the remaining acid. Very disappointing because I now would like to see the results in numeric form. Maybe later today!

MagicJigPipe - 21-5-2008 at 12:22

ADP, if you want to trade inexpensiveness for accessibility then you could buy activated carbon from Wal-Mart. It's in the aquarium aisle. I have some but it's buried in a box right now. I believe it is ~$5 for a few pounds. Not bad, but not really cheap either. I have noticed that it has very little, if any, "dust", though.

I would like to try this. Normally, it would take a VERY efficient column setup to distill GAA from vinegar and even then you might have to distill it more than once.

ShadowWarrior4444 - 21-5-2008 at 12:53

Quote:
Originally posted by MagicJigPipe
ADP, if you want to trade inexpensiveness for accessibility then you could buy activated carbon from Wal-Mart. It's in the aquarium aisle. I have some but it's buried in a box right now. I believe it is ~$5 for a few pounds. Not bad, but not really cheap either. I have noticed that it has very little, if any, "dust", though.

I would like to try this. Normally, it would take a VERY efficient column setup to distill GAA from vinegar and even then you might have to distill it more than once.


The most convenient way to obtain GAA from vinegar is likely to titrate with sodium bicarbonate, then evaporate to gain sodium acetate and distill with sulfuric acid (or another mineral acid.) Though, the activated carbon method is quite interesting; I wonder if it can be used for other organic compounds. Perhaps hydroxymethylfurfural can be extracted this way!

And as for the Wal-Mart carbon: This is likely the best choice for any activities that do not involve human ingestion. The pharmaceutical one is expensive due to the extensive purification process; anything from a bet store, aquarium supply, etc. should be just as effective and several times cheaper. (If they are large pellets, perhaps grinding a bit in a mortar will increase the surface area.)

MagicJigPipe - 21-5-2008 at 13:55

I wouldn't call it "convienient" but it certainly is the most "OTC". It's a pain in the ass, really. Just think about it. At 100% yield you would get 50mL of GAA out of a liter's worth of vinegar that has been neutralized to sodium acetate. You could probably expect to get 40mL or so.

So, in order to obtain 1L of GAA you would have to neutralize 20L (about 5.25 gallons) of vinegar (assuming 100% yields). That's a lot of work! (not to mention the energy costs of boiling off the water). Damn, now that I think about it, it might actually be cheaper to buy GAA on the internet (after you put the manhours, energy costs, vinegar costs and baking soda costs into it).

I'm going to do a rough estimate while I'm at it.

$1.00 a liter for vinegar x 20 = $20
$2.00 for 450g of baking soda (don't feel like molar calculations now, so let's assume that's enough)
~$15 to boil off about 5 gallons of water (after neutralization)
2L of H2SO4 for $5

Grand total: $42 per liter of GAA (at 100% yield) + work & time

I know that's very rough but do you see what I'm getting at? Sheeeeesh... I'm going to buy my GAA on the internet from now on.

ADP - 21-5-2008 at 14:13

Personally if GAA isn't available in your area, I think the MOST economical route is to purchase sodium acetate from ebay or I believe it can be found in pool supply or something, and distill that with H2SO4. I think that is cheapest with the least amount of work/money involved.

Formatik - 21-5-2008 at 14:25

Quote:
Originally posted by ShadowWarrior4444 The most convenient way to obtain GAA from vinegar is likely to titrate with sodium bicarbonate, then evaporate to gain sodium acetate and distill with sulfuric acid (or another mineral acid.)


If you want to extract the acetate out of solution then try this: precipitate it by shaking and swirling with acetone (some other similar solvents may work), let it settle and then filter the acetate, press dry it and then let it dry in air or faster with a fan. Plus, acetone is already quite volatile (evaporation rate: 7.7; compared with butyl acetate: 1, ethanol: 3.3; ether: 37.5), so it will make the drying process even easier. I just tried this with a (concentrated) neutralized acetate solution and it seems to work well.

[Edited on 21-5-2008 by Schockwave]

MagicJigPipe - 21-5-2008 at 14:28

Yeah, I agree. Because I just did a quick search for GAA online (I haven't done so it quite some time) and noticed that it costs nearly $42/L with shipping and everything.

So, buy that sodium acetate, dehydrate it and distill with H2SO4. That should be the cheapest route if you can't get it locally.

BTW, I did even more searching (a few minutes ago) for a photographic supply store that carried GAA to no avail. None of them would even order it for me and only 2 of them carried 28% (1L of 28% = about 5.6L of vinegar, about $6) but I didn't ask how much. I'm sure it's much more than $6.

not_important - 23-5-2008 at 04:48

Quote:
Originally posted by detritus
About 50ml of 5% vinegar was added to roughly 50ml (in volume, obviously) of activated carbon from the aquarium store and left to sit for an hour or so. Note: a small bit of frothing upon addition, probably due to carbonates perhaps?

Strained the liquid into another beaker and poured an identical amount of fresh vinegar into a second beaker. Neutralized them both with baking soda - the charcoal filtrate took MUCH less to neutralize and the frothing was very weak compared to the fresh vinegar.


You've tried running this in btch mode, which isn't always the best way to do absorption concentration or removal.

Instead if you were to put the carbon in column. a bit like a chromatography column, and slowly flow the vinegar through it, adding fresh at the top as it drips out the bottom, you might be better results.

The charcoal nearer the top will eventually be holding as much AcOH as it will absorb from vinegar, while it is being exposed to fresh vinegar - the most concentrated AcOH you have, right from the feed. As the vinegar flows down the column, AcOH is absorbed from it, so it gets weaker and weaker. At the same time it is encountering charcoal that has absorbed less AcOH, and should be better at pulling AcOH from the weaker vinegar. Finally near the bottom the solution runs through charcoal that has absorbed no AcOH, and should be the best for pulling AcOH from the now very weak solution.

But when you do this in batch mode, the strongest vinegar is first encountering the least 'filled' charcoal, while after awhile the vinegar has gotten weaker while the charcoal holds increasing amounts of AcOH. This is backwards to how you want to do an absorption.

With a column full of charcoal and a slow enough drip rate, you should see very weak acid coming out the bottom until the column is nearly at capacity, after which the acidity of the effluent should rise until it is unchanged vinegar.

Let the column drain, close off the bottom and pull a vacuum on the top, possibly warming the column, until as much water as possible has been removed (multiple experiments, take notes). Then release the vacuum, open the drain at the bottom, and slowly run warm acetone through until it stops showing AcOH content. Use acetone over MEK because its lower boiling point should make it easier to distill away from the AcOH. Finally close the column off at one end and heat it to drive off acetone to be captured and condensed.


BTW, sodium acetate is slightly soluble in acetone, more so in wet acetone, so you'll not get complete recovery of the acetate from the dilute solution. Consider summertime solar driven evaporation of the acetate solution. Perhaps an old wine rack holding bottles with cotton plugs in their mouths and partially filled with the NaOAc solution from neutralizing vinegar. Slow, but you can ignore it with only a occasional peek to see if it's dried out.

Jor - 23-5-2008 at 06:15

Quote:
Originally posted by MagicJigPipe
Yeah, I agree. Because I just did a quick search for GAA online (I haven't done so it quite some time) and noticed that it costs nearly $42/L with shipping and everything.

So, buy that sodium acetate, dehydrate it and distill with H2SO4. That should be the cheapest route if you can't get it locally.

BTW, I did even more searching (a few minutes ago) for a photographic supply store that carried GAA to no avail. None of them would even order it for me and only 2 of them carried 28% (1L of 28% = about 5.6L of vinegar, about $6) but I didn't ask how much. I'm sure it's much more than $6.

Hmm, I'm not sure, but in USA, there is a standard HazMat right, no matter if you buy 1 or 5L? If that's the case, consider buying in bulk, saves shippings.

Formatik - 23-5-2008 at 10:19

Quote:
Originally posted by not_important BTW, sodium acetate is slightly soluble in acetone, more so in wet acetone, so you'll not get complete recovery of the acetate from the dilute solution. Consider summertime solar driven evaporation of the acetate solution. Perhaps an old wine rack holding bottles with cotton plugs in their mouths and partially filled with the NaOAc solution from neutralizing vinegar. Slow, but you can ignore it with only a occasional peek to see if it's dried out.


Don't use a dilute solution for solvent extraction, concentrate it by boiling or longer, evaporation. From there use a solvent to extract it so you don't have to wait long for an evaporation, and then to recover the rest one can allow this to evaporate. But if you evaporate it, you can use an excess acid (should work with dilute acid too) and form the diacetates which when heated (like the potassium salt around 200ºC) give off acetic acid. Do you have a reference on solubility in acetone? I've looked for data on solubility in acetone but found none. Though the line between insoluble and slightly soluble can be quite thin and a matter of opinion, e.g. KNO2 is very slightly soluble (J. Anal. Ch. 6, 184) or insoluble (Chem. Centralbl. 1899, II. 1014; Ber. 1904, 37. 4329) in acetone.

A more adventurous way

kalacrow - 23-5-2008 at 14:27

Hey all. :)

I have this method (adapted from industrial process), which is bang on as far as OTC chems, and a route to GAA. The down side is that it also produces acetic anhydride, which is scheduled in the US, however you can add a bit of water to get it back to GAA. I leave it to you to work out the details for your case, and I don't think I have to mention that Ketene is poisonous, and that acetone is flammable, and that everything should be GAS TIGHT (test with light pressure) before you light a freaking burner. You could substitute an electrical element for the burner.. it would need to be very powerful.

So if you plan to try this, make sure you plan it out VERY CAREFULLY in advance if you want to avoid very nasty surprises, like poison gas or explosions.

That said, it makes gallons of the stuff. Very quickly. Dont worry about the Ketene in solution.. it will break down into acetic anhydride and then acetic acid again once it gets diluted. You may want to run fresh water along with the aspirator exhaust water down the drain. If you really wanted to be clean, you would close the sink (or just the aspirator drain tube and the water drain) off with plexi and put a small hole or two in it with rubber flap valves on the inside.

Also, to shut this down, first turn off the propane burner on the tube and wait for it to cool. Then turn off the heat source for the acetone and wait for it to cool. Make sure you have a way to relieve pressure, like a T pipe with a valve on it that you use only for this purpose. Also have a gas valve on your Ketene inlet pipe so you can shut this before you turn off the burner, and have another valve to allow air into the vessel, or make the gas valve two position Y. Make sure you WAIT a bit (a noticable temp drop) before you open a relief valve. Now that everything is cool and you don't have Ketene floating around, you can turn off the aspirator and CAREFULLY open the vessel with the product. There may still be some ketene in there, but I doubt it since you have been running the aspirator for t least 30 minutes, and the vessel vented to the air right? :)

Basically, make sure you have cleared the system of any ketene or acetone vapor before you expose yourself to it. And make sure you dont crush the vessels by stopping them up before they have cooled, without a relief valve.

I don't have the reaction times.. they vary (because its not incredibly controlled.. no measurement of Ketene vapor, pressure control, and less than great temperature control) and I usually just let it run for "Awhile". I encourage folks with the patience for it to figure out more detailed methodology and results.

Enjoy!
Quote:

Another way to GAA

Admitted, this is not so fast and and easy as the IPA - salting out method or the sodium acetate, but it has some other advantages....

A coppertube of about 70cm length and about 3mm inner diameter is connected to a vessel/flask where acetone is brought into a gaseous state of matter (aka boiling). A batwing propane-burner is installed under the part of the tube at the outlet side which heats the tube to a dull red glow. (The burner is positioned at about 50cm from the tubes inlet). The outlet of the tube leads straight into a big vessel with vinegar. This vessel should be halfway filled with broken glass and be hold at a temperature of about 70°C. The vessel has to be closed except for an outlet connected to an smoothly running aspirator.

Operation:
The acetone is brought to an straight boil and the tube is purged by the acetone. The burner is started and soon after the tube reached a dull red heat direct over the burners flame ketene will be formed by thermal decomposition of the acetone. The ketene reacts with the acetic acid in the vinegar to form acetic anhydride which reacts with the water to form acetic acid. It is possible to use straight water from start instead of vinegar but this is unfavorable as the reaction of water and ketene is rather slow and ketene would escape. Ketene is poisonous so the aspirator which must run down the drain - no aspirator-station like design here.
After some time you will have a mixture of GAA and acetic anhydride which can be separated by simple distillation. The GAA will be absolute anhydrous. The ridiculous acetic anhydride may be converted to GAA by the addition of water. This should be done ASAP as acetic anhydride is a scheduled compound and might cause legal trouble.

This is a little bit a piggy-setup as the unreacted acetone is washed down the drain and not recovered. But it spares all these washbottles and scrubbers and condensors and stuff, and acetone is cheap and not regarded as enviromentally dangerous. (at least the bottles I buy carry no such warning)

Yields: At least 50% from theory, up to 80% with some finetuning.
Ok, it is some work included. But once the work is done you have a neverending source of GAA....



PS: I know you folks whom are advanced chemists will know about this route! You'll also know how to do this in a much more sophisticated fashion. I was posting this for those whom may not be aware of this simple process, and who may not be able to get their hands on large amounts of GAA cheaply.


[Edited on 23-5-2008 by kalacrow]

Formatik - 28-5-2008 at 23:28

I have found a simple method of extraction of acetate out of solution, although it may take a little longer. A saturated solution of calcium acetate has either ethanol or isopropanol (methanol doesn’t work) added and this will form a gel, the gel is removed and allowed to dry for a few days or also under the fan (faster), or maybe even under the sun (though this gel is flammable) and there is already a thread on it here. The gel reduces in volume after evaporation of the alcohol and what is left behind is the powder. It doesn’t necessarily take a few days if a fan is used. And for another topic, but this compound is also useful as it gives off acetone at around 160ºC, below that its monohydrate loses the H2O. This is just another alternative to boiling down or evaporating all of the way, I really hate scraping for powders. I used more or less stoichiometric vinegar and CaCO3 and then boiled it until saturated (around three times less the starting volume), then EtOH for the gel.

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.

Sauron - 29-5-2008 at 19:15

Ketene is also a proven human carcinogen, one of the really very few. Not a suspected one, not an animal one, not a "reasonably anticipated to be" one. A known human carcinogen. That means if it does not get you from an acute exposure, it may still kill you from cancer.

It shares this distinction with really charming compounds like benzidine and aminonapthalene.

not_important - 29-5-2008 at 21:02

Note that there is an extensive thread related to ketene, given the obscuring title of "keten lamp":

http://www.sciencemadness.org/talk/viewthread.php?tid=8148
Quote:
Originally posted by Sauron
Ketene is also a proven human carcinogen, one of the really very few. Not a suspected one, not an animal one, not a "reasonably anticipated to be" one. A known human carcinogen. That means if it does not get you from an acute exposure, it may still kill you from cancer.


While there is no denying that ketene is quite toxic, and not to be used without considerable care, your repeated statements as to its carcinogenic properties don't seem to be widely held. For example, the NIOSH Pocket Guide to Chemical Hazards, Risk Management for Hazardous Chemicals (Vincoli), and 2007 Exposure Limits for Air Contaminants (PELs, TLVs & STELs), all do not indicate ketene as being a suspected carcinogen, much less a proven one.

There is this:
Quote:
...Ketene was one out of 21 chemicals selected as a suspect chemical ...However, due to this limited number of cases and potential exposure to other compounds, no conclusions can be dawn with respect to an aetological role of ketene


Ketene
(CAS reg no: 463-51-4)
Health-based Reassessment of Administrative Occupational Exposure Limits
Committee on Updating of Occupational Exposure Limits,
a committee of the Health Council of the Netherlands

Note that the Netherlands tightly regulates various toxic and carcinogenic materials. For example they prohibit a cadmium content greater than 100 ppm except in a few applications related to electronic and other equipment used in maritime settings. Anything containing cadmium must have provisions for recycling and recovering its cadmium content. You can't consider them slackers on regulation of nasties.

And I found a couple of other sites that listed ketene as a possible carcinogen. However these were just lists with no attributions, as they also included such things as advising to avoid consumption or contact with foods containing malic acid, and stating that SO2 is derived from coal tar, I don't assign too much weight to their assesments.

So as someone else asked, could you provide links to this rating of ketene as a carcinogen?

Sauron - 29-5-2008 at 21:53

The list of compounds stated to be proven human carcinogens was published in Organic Synthesis more than thirty years ago. I believe this was a regurgitation of the OSHA list of 21 "proven human carginogens". I put brackets around that only because it appears that a whole lot of backpeddling and obfuscation has been going on ever since.

If current occupational safety and IARC have gainsaid that list, then I stand corrected. Chemical carcinogenicity is not a particular interest of mine, and I do not pay much attention to the ebb and flow of official opinion on the subject. I had thought that in the case of the Org.Syn. published list the matter was settled, but, apparently I was mistaken.

I will retrieve the warning statement from Org.Syn. and post it here as a matter of information, and to demonstrate that I was not engaging in hysteria. Error, perhaps, but not hysteria.

The list is certainly in the hardcopy annual OS volumes and Collective Volumes, but is apparently not on the Wiley OS website. I know I have the hardcopy annual volume it is in because I well remember seeing it. Finding it however will be a bit of a chore as I have about 20 annual volumes scattered around in various places.

Any help I can get in finding the OSHA list will be appreciated.

Here's FWIIW a list of 13 OSHA "carcinogens" which I would take to mean proven human carcinogens, most or all of these were I believe on the list published in Org.Syn. a few decades ago, but the list there was longer and included ketene.

4-Nitrobiphenyl, Chemical Abstracts Service Register Number (CAS No.) 92933;
alpha-Naphthylamine, CAS No. 134327;
methyl chloromethyl ether, CAS No. 107302;
3,3'-Dichlorobenzidine (and its salts) CAS No. 91941;
bis-Chloromethyl ether, CAS No. 542881;
beta-Naphthylamine, CAS No. 91598;
Benzidine, CAS No. 92875;
4-Aminodiphenyl, CAS No. 92671;
Ethyleneimine, CAS No. 151564;
beta-Propiolactone, CAS No. 57578;
2-Acetylaminofluorene, CAS No. 53963;
4-Dimethylaminoazo-benzene, CAS No. 60117; and
N-Nitrosodimethylamine, CAS No. 62759.


My question now is, if the OS list (from OSHA) were not proven human carcinogens, then show me a list of what ARE proven human carcinogens, and not merely compounds surrounded by weasel words like "suspect" or "reasonably anticipated to be" that sound more like lawyerly "deeming" than science.



[Edited on 30-5-2008 by Sauron]

S.C. Wack - 30-5-2008 at 02:39

If ketene was a carcinogen then toxnet would have lots of references to such. It doesn't. See, this is what happens when we get off-topic.

Sauron - 30-5-2008 at 03:35

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]

not_important - 30-5-2008 at 05:17

`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.

Sauron - 30-5-2008 at 08:01

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.

Ephoton - 9-6-2008 at 00:18

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.

Formatik - 9-6-2008 at 04:47

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.

jarynth - 8-10-2008 at 13:52

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.

Ephoton - 13-10-2008 at 00:48

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.

Foss_Jeane - 26-10-2008 at 18:39

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.


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.)
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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.