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Murexide
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[*] posted on 25-12-2018 at 19:10
Dichloromethane


DCM is a common solvent, and my purpose is for caffeine extraction from caffeine pills (probably the most common beginner amateur use for DCM), as well as for coagulating AgCl suspensions in certain argentometric titrations (chloroform replacement). Apparently, it smells somewhat sweet, but it is dangerous at levels where it can be smelt.

The downside to DCM is that it is probably carcinogenic. Apparently it is less so than chloroform, which makes it more suitable (as well as significantly easier to obtain in Australia). It is sold as paint stripper 87% dichloromethane, which is apparently a liquid rather than a gel (significantly more convenient for distillation). Separation from ethanol can be achieved with CaCl2/H2O complexation

The other problem is storage and hand protection. Currently, in its paint thinner state it is in a metal can and it can be stored at and slightly above room temperature without explosion or leakage hazards. However, in its pure form it must be stored in either a metal container (risky, due to potential compatibility issues) or glass reagent bottles (explosion hazard unless in a freezer, which is not available, and the type of plastic cap is also an issue). Apparently, DCM creates a strong burning sensation upon contact, so it would be wise to use gloves. Unfortunately, DCM penetrates almost all common glove types. It is interesting that despite the problem of its high volatility and penetration, it is suggested as a chloroform replacement.

If DCM experiments are conducted outside for select experiments, how high is the carcinogenic risk of DCM? It would need to be distilled from a retort connected to a Ahlin connector (I am certainly not distilling a compound bp. 40C with an air condenser!), so some vapours would be released.

[Edited on 26-12-2018 by Murexide]
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DavidJR
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[*] posted on 25-12-2018 at 19:35


Why would glass bottles present an explosion hazard?
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Murexide
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[*] posted on 25-12-2018 at 22:03


DCM is very volatile even at room temperature, as it’s boiling point is 40C. If stored for long periods of time in glass bottles especially at slightly above room temperatures, pressure (of its vapour) can build up and then cause glass bottles to explode.
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Justin Blaise
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[*] posted on 25-12-2018 at 23:46


I don't think you're going to have any compatibility issues with storage in a metal can. It comes in a metal can, for one, and it's not so reactive that the surface of a metal can will appreciably reduce it. Unless your can is made of sodium. You could even just clean out the original container and put the purified stuff back in there.

Hand protection is tough. I've gotten DCM drops on my gloves and then felt burning shortly after. Best solution I could come up with was to work carefully and quickly remove gloves after I notice spills. You get a couple seconds of protection, even if DCM can penetrate, and you can use that time to quickly get your hands out of there. According to this source https://toxnet.nlm.nih.gov/cgi-bin/sis/search/a?dbs+hsdb:@te... there is inadequate evidence to say it's a human carcinogen. So just distill it outdoors or in a fume hood and you'll be fine.
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Murexide
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[*] posted on 26-12-2018 at 02:16


Cleaning the original can is certainly an attractive option given that the formula is liquid and not gel so it will be easier to clean out (water, base would be preferable as it will destroy DCM but metal can will also be destroyed). With some luck, I can probably extract out 250-300mL of the 435mL theoretical DCM, the azeotrope 95% DCM 5% ethanol. The ethanol in fact is probably necessary to keep as a stabilising agent (although DCM is much less risky than chloroform in terms of phosgene formation, it is nevertheless a good idea). So 50% fillled should not provide too much of an explosion hazard, considering it will be used soon after and destroyed after with aqueous NaOH.

For the distillation, I will probably attempt something similar to my nitric acid distillation by using remote switching of the hot plate (of course using a hot water bath) situated outdoors from indoors. This should limit DCM inhalation significantly. Even though it says there is inadequate evidence of it being a confirmed carcinogen and is certainly less so than benzene, it does say it is a probable carcinogen (confirmed for lab animals), so it should probably be treated cautiously.

Thick latex gloves seem to be the best option, as they extend the period of time between exposure and contact perhaps from a few seconds to 10 or so seconds. That should be enough time.

Edit: The volatility and capacity of DCM to escape the container when not cooled in a freezer is the main reason I prefer to limit use and destroy soon after

[Edited on 26-12-2018 by Murexide]
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Deathunter88
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[*] posted on 26-12-2018 at 02:53


Stop being so paranoid! The fact that it's sold as a consumer product DESIGNED to be spread over large areas and evaporated means that the exposure you will get from working with it as a chemistry reagent is perfectly safe. I personally wouldn't even bother wearing gloves, since it evaporates so rapidly wearing gloves is just going to trap it against your skin for longer.
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[*] posted on 26-12-2018 at 03:34


You can use vented caps for glass bottles if you want to minimize the risk of explosion. It really depends on the temperature of your lab. If it's at around 20°C you will be fine. Professional labs store DCM in glass bottles at room temperature.

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[*] posted on 26-12-2018 at 03:35


I don't think storing in a metal can will make it explode. I live in a warm place and my DCM is stored in glass beer bottle. The lid is capped loosely and has been sitting there for a year. It's still intact.



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[*] posted on 26-12-2018 at 10:34


where i live temperatures in summer can easily reach 35-40 °C, i expect to be hot as well in australia, so metal or glass container you still need to keep it cool somehow. i'm distilling right now all the solvents i found OTC that contain DCM, i had to wait so long because tadaaa i didn't have the right container (i will be using a glass bottle used for solvents i found while hiking on the italian Alps, really random i know, and to the cap i added a teflon disc).
i think you are a bit paranoid too, sure you don't want to breathe chlorinated solvents all day but a few whiffs won't give you cancer, if DCM does this reaction to you i don't know what benzene would do.
ps gloves are not an instoppable barrier, they are there just to slow contact with skin, if something spills on them, you must change them anyway





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[*] posted on 26-12-2018 at 16:40


Quote: Originally posted by Deathunter88  
Stop being so paranoid! The fact that it's sold as a consumer product DESIGNED to be spread over large areas and evaporated means that the exposure you will get from working with it as a chemistry reagent is perfectly safe. I personally wouldn't even bother wearing gloves, since it evaporates so rapidly wearing gloves is just going to trap it against your skin for longer.


I agree that it's pretty safe to use in a lab situation where you aren't evaporating large quantities into the lab atmosphere. However, I disagree that it's safe as a paint stripper since there have been numerous deaths from people using DCM based paint strippers in poorly ventilated areas. This is why it's banned in paint strippers in many places.

Re gloves, the only gloves which offer real protection against DCM are ones made from polyvinyl alcohol. They aren't suitable for general use though because they are water soluble. Any other kind of glove offers at most a few seconds of protection. Keep this in mind if you're handling DCM solutions of anything that is toxic or otherwise hazardous.
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[*] posted on 2-1-2019 at 07:37


Quote: Originally posted by Murexide  
DCM is very volatile even at room temperature, as it’s boiling point is 40C. If stored for long periods of time in glass bottles especially at slightly above room temperatures, pressure (of its vapour) can build up and then cause glass bottles to explode.


Guess no one has told my glass bottle this information, poor thing will be embarrassed, it's been sitting there and working for a year and some now just doing its job!

HINT: Look up some thing called a PT Chart (Pressure Vs temperature)

Screw it here it is: https://en.wikipedia.org/wiki/Dichloromethane_(data_page)



[Edited on 2-1-2019 by XeonTheMGPony]

[Edited on 2-1-2019 by XeonTheMGPony]
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[*] posted on 2-1-2019 at 12:22


All the DCM I've ever bought came in a glass bottle.
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[*] posted on 6-2-2019 at 10:10


Have you ever simply looked up sellers of industrial solvents in your town? I went to "Buffalo Industrial Solvents" and said that I wanted to buy methylene chloride. The guys said "5 gallons, 60 bucks". I said fine.

I also simply walk into Riverside Chemical Company (a local JTB distributor) and just order what I want, be it PE, toluene, acetic acid, etc. You don't need certification, identification, or company-affiliation to buy these commodity grade materials in NY.





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[*] posted on 7-2-2019 at 04:37


Gloves: nope. It'll go through the gloves yes. But not alone ! So I'd rather avoid gloves at all. The burning is tolerable in the beginning but after a short while the only thing you want to do is wash your hands again and again.
Bottle: Not gonna explode. A media bottle is fine. I have my DCM in a media bottle, it survived last summer 35 degrees without a problem. I've had some years ago from APC Pure delivered in HDPE bottle and THAT is bad.
Someone on the forum used to words "escape artist" for DCM. So true. The HDPE bottle was inside a plastic bag. I stored it, forgot about it and came back months later to find an empty bottle. The bottle and plastic bag were intact and showed no sign 1 liter of DCM had gone through.
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[*] posted on 7-2-2019 at 05:03


I read a lot of fear mongering in this thread.

DCM, stored in glass bottles forms no explosion risk. Period. Not even at very hot summer afternoons, when stored in a normal cupboard in the house or a garage. You may get some pressure buildup in a bottle, but a normal glass bottle withstands quite some pressure. Think of bottled drinks like coca cola in glass bottles. They have MUCH more pressure inside than you will ever get in your bottle of DCM.

DCM hardly is a skin risk. It evaporates very quickly, simply waving your hands for a few seconds removes the DCM. Using gloves is overkill or even adds extra risk.

DCM is toxic, but it is not instant death in a bottle. I would worry about slow long-term release when this is in the same area as where you live on a day-by-day basis, such as was the case with the 1 liter plastic bottle which lost all DCM over a period of a year.
Occassional spills on your hands are no problem. Clean DCM simply evaporates and is not quickly absorbed, because it is not water-soluble. Things may become different if the DCM is used as solvent and contains other toxic compounds. Then a spill on your skin may be problematic, because the DCM is gone in seconds and a thin film of the toxic compound remains on your skin. If that occurs I would wet a piece of tissue with DCM and quickly use that to wipe your skin to get rid of most of the dissolved compound and then wash thoroughly with water and soap.

Again: use common sense, respect the things you work with, but do not fear them!

[Edited on 7-2-19 by woelen]




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[*] posted on 7-2-2019 at 18:22


DCM is a skin irritant for sure though and it would not surprise me if it is absorbed...anyways, my last order of DCM came in typical quart cans, and when I went to jug it up a year later, half the DCM was gone.



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[*] posted on 8-2-2019 at 16:02


Should be sealed tight with an inner metal plug.

Even high boilers, sneak away, if not properly sealed.

Back in the days, when such items were unrestricted in commerce, I weighed a 25lb can of Safrole after several years in storage. ~ 23 Lbs remained!

My theraputic Spray and Stretch, Freon spray bottles, though never used or opened, now stand less than 1/2 full.



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[*] posted on 11-2-2019 at 06:21


Quote: Originally posted by Deathunter88  
Stop being so paranoid! The fact that it's sold as a consumer product DESIGNED to be spread over large areas and evaporated means that the exposure you will get from working with it as a chemistry reagent is perfectly safe. I personally wouldn't even bother wearing gloves, since it evaporates so rapidly wearing gloves is just going to trap it against your skin for longer.


Industries operate based on what their legal department assessment as to acceptable degrees of legal liability. Bottom line, the probability of lawsuits and the expected amount of settlement costs.

This is likely just poorly correlated to actual toxic levels relating to either short term or long term exposure, so don't derive any inferences of presumed safety from the willingness of some local suppliers to sell DCM. A company's variation in behavior across the world is likely a better indicator as to actual safety of a product, in my opinion.

[Edited on 11-2-2019 by AJKOER]
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[*] posted on 12-2-2019 at 20:15


I never had issues with DCM storage even during a hot summer (I use glass reagent bottle with and ABS cap).

Of course I periodically checked and vented the bottles, checking for overpressure.

I used DCM in several extractions, not caffeine but eugenol from clove oil, for example and distilled it many times.

I found that DCM sucked in lots of organic impurities and had to be purified beyond distillation (e.g. shaking with conc. sulfuric acid).

As for the hand spills, you can use two layers of gloves and immediately remove them upon exposure. Although DCM will penetrate them, it takes some time.

The health hazards manifest for people who work with DCM routinely and breathe the vapours in closed areas. If you use it occassionaly with precautions (good ventilation), you will be okay.
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[*] posted on 13-2-2019 at 08:40


Quote: Originally posted by woelen  
I read a lot of fear mongering in this thread.

DCM, stored in glass bottles forms no explosion risk. Period.
[Edited on 7-2-19 by woelen]


I can't remember if it was Dichloromethane or Diethylether... (I get them confused) but I have seen a 2.5L Winchester brown bottle of the stuff on a bench just break apart without any warning at all right before my eyes. It just broke into 2 or 3 pieces right in front of me on the bench. It was a warn day, but still. It did not explode though but would have been very nasty if there had been a naked flame on the bench. The guy using it cleaned it up whilst I waited outside to call an emergency if he passed out from the fumes or sparked an ignition somehow.

It was very strange - as it was evaporating in such a large volume there was massive distortion of vision through the fumes - like looking through heated air that is rising.

I wonder if the claims of explosion were due to the glass breaking as I described whilst there was a Bunsen flame open nearby - that could make it look like the bottle just exploded I suppose.






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[*] posted on 13-2-2019 at 09:36


DCM is not flammable. A bottle that just breaks is faulty to start with, it would break if it was filled with water.

Check this graph: https://en.m.wikipedia.org/wiki/File:LogMethylenechlorideVap...

Even at 50 it's pressure is just at that of water at autoclave running temperature. I can guarantee you I've run many autoclaves and often opened them at running temp because I wanted to go home. Never any bottle exploded or broke while doing so.

Edit: a champagne bottle could hold it at 100.

[Edited on 13-2-2019 by Tsjerk]
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[*] posted on 13-2-2019 at 09:55


Quote: Originally posted by DrP  
Quote: Originally posted by woelen  
I read a lot of fear mongering in this thread.

DCM, stored in glass bottles forms no explosion risk. Period.
[Edited on 7-2-19 by woelen]


I can't remember if it was Dichloromethane or Diethylether... (I get them confused) but I have seen a 2.5L Winchester brown bottle of the stuff on a bench just break apart without any warning at all right before my eyes. It just broke into 2 or 3 pieces right in front of me on the bench. It was a warn day, but still. It did not explode though but would have been very nasty if there had been a naked flame on the bench. The guy using it cleaned it up whilst I waited outside to call an emergency if he passed out from the fumes or sparked an ignition somehow.

It was very strange - as it was evaporating in such a large volume there was massive distortion of vision through the fumes - like looking through heated air that is rising.

I wonder if the claims of explosion were due to the glass breaking as I described whilst there was a Bunsen flame open nearby - that could make it look like the bottle just exploded I suppose.




If it was dichloromethane, then even if there was a naked flame right beside it, you'd have no fire, because DCM isn't flammable.

Diethyl ether, on the other hand.........
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[*] posted on 13-2-2019 at 10:43


Dichloromethane in glass bottles all day long. I dont use anything else. I keep all of my solvents in similar bottles.



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[*] posted on 10-5-2019 at 23:27


I have ordered a litre of pure CH2Cl2 which should arrive to me later this month (it is really cheap, even in a pure form, like €8/litre). I’ll tell you in what type of storage container I get it, if you want.
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[*] posted on 11-5-2019 at 08:28


I paid £9.50 for 2.5L of HPLC grade DCM, and like all of my solvents from that supplier, it came in an amber glass bottle.
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