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Author: Subject: When Chemistry Goes Wrong
ave369
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[*] posted on 13-7-2017 at 10:39


I had been getting facefuls of ammonia, like, ten times, but it didn't make me quit.



Smells like ammonia....
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[*] posted on 13-7-2017 at 11:01


Squirted myself in the eye with 91% IPA the other day while cleaning the kitchen. Will definitely give up housekeeping now.

Who am I kidding? I gave up in spirit a long time ago.




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[*] posted on 15-7-2017 at 07:37


Bet an eyeful of isopropyl that concentrated stung a bit.
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[*] posted on 15-7-2017 at 07:45


I was heating up a slurry of copper and nickel carbonates in a beaker with manual stirring. A thick slurry. So thick, that when I stopped stirring it instantly started violently boiling on the bottom and made the beaker jump so hard it broke! This was not a thermal stress. The beaker jumped a few times before it cracked and before I could resume stirring or take it off the hotplate.

I didn't even meant to boil the solution, just heat it and cool it a few times to increase particle size to ease up the filtering or decantation.

[Edited on 15-7-2017 by MeshPL]
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JJay
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[*] posted on 31-7-2017 at 12:32


I made the classic blunder of dumping a little too much water into a flask that was half full of sodium hydroxide and ammonium sulfate, resulting in a very stinky and caustic volcano. I managed to escape without any injury, but I am going to be wiping down my fume hood with cleaning vinegar later. Next time I make an ammonia generator, I'm going to use an addition funnel.



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[*] posted on 31-7-2017 at 12:49


JJay: Use a 60Ml syringe, dissolve the Ammonium sulfate in minimal water then drip it in.

Thus no need for addition funnel if you lack one, bit more manual then addition funnel :)

or revers order sodium hydroxide dissolved in water and drip it in to ammonia sulfate slurry.

[Edited on 31-7-2017 by XeonTheMGPony]
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[*] posted on 31-7-2017 at 13:29


I have addition funnels, but I wanted to minimize the number of pieces of glassware to reduce the likelihood of leaks.



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[*] posted on 4-8-2017 at 20:06


Hi everyone, I have been reading on this site for at least a year now, and finally decided to create an account.
I've had one major incident in my lab.
Some Context: I had a chat with NurdRage on youtube about making P-Chlorophenylnitrile via the decarboxylation of Phenylalanine, followed by chlorinating on the Para position, rather than his very long synthesis starting from toluene. I told him I would try it out, and decided to buy my phenylalanine from a seller who marketed it as a ‘health supplement.’

I received a box labelled “Amino Acid” and when I started the decarboxylation (using pyridine and TCCA ), and after refluxing for around two hours, opened the condenser, I got a powerful, lingering, dying rat smell....the Horrific smell of Cadaverine. :(:(:mad:


[Edited on 5-8-2017 by Hypochlorite]
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[*] posted on 5-8-2017 at 12:52


Today while cleaning my 24/40 Buchner funnel I broke the little stem that goes in-between the jointed part of it. It will be missed dearly.
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[*] posted on 6-8-2017 at 23:39


Quote: Originally posted by Hypochlorite  
I received a box labelled “Amino Acid” and when I started the decarboxylation (using pyridine and TCCA ), and after refluxing for around two hours, opened the condenser, I got a powerful, lingering, dying rat smell....the Horrific smell of Cadaverine. :(:(:mad:

For amino acids, purebulk.com usually has very good prices. They're US-based but ship internationally.




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[*] posted on 7-8-2017 at 07:44


When making sodium acetate from ethyl acetate the reflux got a bit energetic and launched the contents into the roof (Spackle) that is now dissolving slowly and I'm just letting it!run its course as I plan to do massive renos to the room (Walls, roof and so on)
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[*] posted on 7-8-2017 at 09:12


Alright this happened quite some years ago, but I remember it everytime I put some water-sensitive reaction into an ice-salt bath again: So I was happening to prepare some EtONa, and the flask was already ready sitting in the cooling bath while I was cutting sodium... with very thick and clumsy gloves, my sodiumgloves... so I wanted to add a(luckily tiny) piece to flask, and one fell into the bath.... hurry, panic, a little sizzling and a wholeheartedly relieved chemists was the only outcome of this potential disaster :D
Since it´s been quite some time now, I can´t vouch for sure if the chemists underpants were richer in a drop of fluid or not afterwards :o :P

[Edited on 7-8-2017 by karlos³]
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[*] posted on 7-8-2017 at 13:43


I, for one, like ammonia. The smell of it tells me I'm not breathing phosgene or acid vapors or halogens, or any number of alkylating agents. With some ammonia vapor in the room, all those nasty gases are visible.

I've actually taken to using a mixture of ammonia and ammonium ascorbate in water as my go-to neutralization agent, like if I spill something and don't have time to figure out what it was.




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[*] posted on 8-8-2017 at 20:29


A few weeks ago I dry distilled 70 grams of oven-dried calcium benzoate with 130 grams of oven dried calcium acetate. Both were oven dried at around 240 C, and the calcium benzoate did brown in the oven, which was not expected. I pulverized them together in a blender and placed the mixture in a steel can fitted with a copper tube leading to a glass condenser. I heated it strongly to a red heat with a propane flame, carefully venting the vapors. The distillate was a tan liquid that smelled like benzene and boiled at around 80 C, and it did not form a bisulfite adduct. It did not appear to contain any acetone. I am pretty sure it was substantially benzene.

It says on Wikipedia that heating calcium acetate to 160 C causes decomposition, but I haven't been able to verify that with actual references. Anyone know what might have gone wrong?




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[*] posted on 8-8-2017 at 21:23


Were you trying for acetophenone? I thought only a few ketones formed bisulfite adducts.

Quote: Originally posted by JJay  
A few weeks ago I dry distilled 70 grams of oven-dried calcium benzoate with 130 grams of oven dried calcium acetate. Both were oven dried at around 240 C, and the calcium benzoate did brown in the oven, which was not expected. I pulverized them together in a blender and placed the mixture in a steel can fitted with a copper tube leading to a glass condenser. I heated it strongly to a red heat with a propane flame, carefully venting the vapors. The distillate was a tan liquid that smelled like benzene and boiled at around 80 C, and it did not form a bisulfite adduct. It did not appear to contain any acetone. I am pretty sure it was substantially benzene.

It says on Wikipedia that heating calcium acetate to 160 C causes decomposition, but I haven't been able to verify that with actual references. Anyone know what might have gone wrong?


Okay, you just said you oven-dried your calcium acetate at 240˚C, when calcium acetate decomposes at 160˚C. Figure it out yet?

[Edited on 8/9/17 by Melgar]




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[*] posted on 8-8-2017 at 23:39


This ACS reference says that no decomposition occurs at 160 C: http://pubs.acs.org/doi/abs/10.1021/je60012a040?journalCode=...

I've read that small amounts of calcium hydroxide can greatly influence the composition of the pyrolysis products, but I wouldn't expect that to be the case for calcium carbonate. All I can think of is that maybe there were some basic calcium salts present.




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[*] posted on 9-8-2017 at 00:19


Quote: Originally posted by JJay  
This ACS reference says that no decomposition occurs at 160 C: http://pubs.acs.org/doi/abs/10.1021/je60012a040?journalCode=...

I've read that small amounts of calcium hydroxide can greatly influence the composition of the pyrolysis products, but I wouldn't expect that to be the case for calcium carbonate. All I can think of is that maybe there were some basic calcium salts present.

At 240˚C, especially exposed to air in the oven, calcium acetate would decompose quite readily. Its decomposition temperature range is very broad as well, without a sharp line at any temperature where decomposition could be said to begin. CO2 can liberate acetic acid from wet calcium acetate too, forming the carbonate salt.

[Edited on 8/9/17 by Melgar]




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[*] posted on 9-8-2017 at 00:39


I should also mention that in addition to failing tests for acetone, the product appeared to be quite buoyant in water. Yes, I was trying for acetophenone, which unlike most aldehydes and methyl ketones, doesn't form a bisulfite adduct. But acetone does, and it was the only expected product with a density lower than water.



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[*] posted on 9-8-2017 at 00:42


Quote: Originally posted by Melgar  


At 240˚C, especially exposed to air in the oven, calcium acetate would decompose quite readily. Its decomposition temperature range is very broad as well, without a sharp line at any temperature where decomposition could be said to begin. CO2 can liberate acetic acid from wet calcium acetate too, forming the carbonate salt.



What is your source for this information?




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[*] posted on 9-8-2017 at 01:52


Quote: Originally posted by JJay  
What is your source for this information?

If your oven was hot enough to brown calcium benzoate, then it was definitely hot enough to decompose calcium acetate. In air, it wouldn't decompose into acetone anyway, it'd decompose into CO2, methyl acetate, methanol, etc. The references you have also appear to be anaerobic conditions, and the temperatures specified on Wikipedia and elsewhere (every MSDS for calcium acetate) are for aerobic conditions.




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[*] posted on 9-8-2017 at 04:00


I think it's more likely that impurities caused the browning of the calcium benzoate, not an excessively high temperature. The first five SDS results for calcium acetate on Google do not mention decomposition in the manner that you suggested. It is of course possible to determine the exact temperature at which a reaction begins to proceed spontaneously using the thermodynamic properties of the substances involved in the reaction. And I don't think the paper above specifies anaerobic conditions, although they certainly wouldn't hurt.

The effect of calcium hydroxide on the pyrolysis of calcium salts of organic acids is well known: http://pubs.acs.org/doi/abs/10.1021/j150183a002

I used an excess of calcium carbonate to make my calcium salts, but I think it's reasonable to suppose that this could result in contamination with small amounts of basic calcium salts and that these had a similar effect to that of calcium hydroxide. Very little is known about basic calcium salts, but the theory is straightforward, and I think this is a sound hypothesis that could be verified or ruled out with further experimentation.

While I'm reluctant to rule it out at this point, I'm not seeing any theoretical basis or empirical results in the information you've provided, but I'll try doing the reaction with inert gas or a vacuum next time I get around to running it.




[Edited on 9-8-2017 by JJay]




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[*] posted on 9-8-2017 at 05:14


Quote: Originally posted by JJay  
And I don't think the paper above specifies anaerobic conditions, although they certainly wouldn't hurt.

It doesn't say strict anaerobic conditions, but it specifies putting the salt in an RBF with a slight vacuum. So there's a tiny amount of air that decomposes a little bit of the salt, but nothing like the convection cell that goes through a typical oven.

I did find a paper showing that decomposition for calcium acetate went first, endothermic dehydration. The second step was endothermic unless oxygen was present, in which case it was exothermic, meaning that it's two different reactions depending on the availability of oxygen. I have no idea where to find that paper, but I remember that much.

edit: you understand that I'm saying that I think you had calcium carbonate, not calcium acetate, when you took it out of the oven, correct?

[Edited on 8/9/17 by Melgar]




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[*] posted on 9-8-2017 at 05:32


Yeah, but I'm saying that I don't think so. It still smelled like calcium acetate. I didn't notice any noxious fumes coming off of it while it was in the oven. And there seems to be a serious lack of good references suggesting that calcium acetate decomposes at low temperatures.

Also, that's just one small part of the paper, and it says *slight* vacuum. No vacuum is mentioned in the oven drying procedures. This is not the first time I've read a paper that discusses oven-drying calcium salts, and they generally don't mention a vacuum or inert gas for that step. In short, your assertion that they used anaerobic conditions is not supported even though they did use a slight vacuum at one point in the paper.

In addition, even if decomposition did occur, a small amount of calcium carbonate is unlikely to seriously interfere with the reaction.




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[*] posted on 9-8-2017 at 13:40


Also had an incident with an ammonia generator using diammoniumphosphate instead of ammoniumsulfate, which I normally use. The generator had been running fine for about 15-30 minutes or so, when suddenly a thick amorphous cake (mono/disodiumphosphate?) formed on top of the reaction mixture, which was pushed up by the ammonia still produced, clogging the neck and hose. Heard some loud hissing before the 250 ml erlenmeyer exploded from the overpressure, which was impressive to say the least...
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[*] posted on 9-8-2017 at 17:49


Quote: Originally posted by JJay  
Yeah, but I'm saying that I don't think so. It still smelled like calcium acetate. I didn't notice any noxious fumes coming off of it while it was in the oven.

Calcium acetate isn't volatile, you know, so any smells you associate with it are probably decomposition products.

You could know for sure by oven-drying calcium acetate, then reacting with acetic acid again. Fizzzing would imply decomposition.




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