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Author: Subject: An accident in my "lab"
greenivan
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[*] posted on 5-7-2012 at 10:18
An accident in my "lab"


I modified my basement as my private and simple lab.... yesterday i tried to make phenylacetone from dry distillation of lead acetate and phenylacetic acid. I have ever tried similiar method using calcium acetate and it worked well except there's cement like residue that couldnt be removed in my boiling RBF. yesterday, I used graham condenser + vigreux condensor (fract column) and "condenser" using large pipe filled by dry ice. After set my heating mantle on maximum heating, i went back to my diningroom for just 10 minutes to get some tea, and i heard strange voices from my basement. OMG. i ran there and found that the reactant was burned vigorously... the "plastic lid + thermometer" throwed away and the fire went out like a butane torch lighter. After that, under panic I threw water and stopped the reaction. All my condenser burned so bad and my RBF broke off... no phenyacetone distilled. Maybe can someone tell me what is my fault?

sorry for my bad english..
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kavu
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[*] posted on 5-7-2012 at 10:26


Lesson learned: Never leave a setup running unless you have first made sure it has stabilized.

It might well be that the dry ice condenser got blocked by moisture/etc. freezing in it. Pressure built up and pop goes the thermometer adapter. Hot gases of organic stuff are allowed to evaporate and can catch on fire quite easily.

[Edited on 5-7-2012 by kavu]
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greenivan
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[*] posted on 5-7-2012 at 10:28


Quote: Originally posted by kavu  
Lesson learned: Never leave a setup running unless you have first made sure it has stabilized.

[Edited on 5-7-2012 by kavu]


yes, I really shocked with the accident and I'm really sure that I will learn from it... But what parts are not stabilized in my setup? Where the fire came from?
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Hexavalent
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[*] posted on 5-7-2012 at 10:56


This is highly irresponsible; as kavu said, never leave a setup on its own until you are certain it is going smoothly at a good rate, all apparatus is working correctly, set to the correct mode/setting etc.

How were you heating the reaction vessel? It is also possible that the dry ice condenser became blocked by moisture/water vapour etc. freezing in it, building up pressure and popping the thermometer joint, being a comparatively weak connection on many ground glass setups. The organic vapour could then have escaped and maybe caught fire that way.

Do you have a proper extinguisher (ABC or AB + C) for your lab?




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woelen
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[*] posted on 5-7-2012 at 11:41


Quote: Originally posted by Hexavalent  
This is highly irresponsible; as kavu said, never leave a setup on its own until you are certain it is going smoothly at a good rate, all apparatus is working correctly, set to the correct mode/setting etc.
I'm even more restictive on this. I never let a powered setup on its own. As long as power is supplied to the setup and for quite some time after power off I babysit the setup. NEVER leave a running reaction alone, not even if it seems to run smoothly and seems to be stable. What now looks stable may be unstable after 5 minutes (e.g. due to evaporation to dryness of your setup). If you need to go to the toilet, then do that before the reaction starts or ask someone else to keep an eye on the setup while you are away.



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Nicodem
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5-7-2012 at 12:30
greenivan
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[*] posted on 5-7-2012 at 19:02


Quote: Originally posted by Hexavalent  
This is highly irresponsible; as kavu said, never leave a setup on its own until you are certain it is going smoothly at a good rate, all apparatus is working correctly, set to the correct mode/setting etc.

How were you heating the reaction vessel? It is also possible that the dry ice condenser became blocked by moisture/water vapour etc. freezing in it, building up pressure and popping the thermometer joint, being a comparatively weak connection on many ground glass setups. The organic vapour could then have escaped and maybe caught fire that way.

Do you have a proper extinguisher (ABC or AB + C) for your lab?


I heated my vessel using a heating mantle. My heating flask is 2000 ml one necked RBF, the condenser is 1 graham + 1 vigreoux, cooled by dry ice in a pipe wrapped around it.
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greenivan
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[*] posted on 5-7-2012 at 19:14


I just really wondered if the lead (II) acetate + phenylacetic acid is actually really easy to burned ?
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kavu
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[*] posted on 6-7-2012 at 00:34


Not as such, but when heated strongly organic compounds tend to decompose to smaller readily volatile molecules.
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edgecase
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[*] posted on 6-7-2012 at 18:17


Quote: Originally posted by greenivan  

I heated my vessel using a heating mantle. My heating flask is 2000 ml one necked RBF, the condenser is 1 graham + 1 vigreoux, cooled by dry ice in a pipe wrapped around it.


2000ml is a *very* large scale, especially for something you are trying for the first time. You mentioned that you did a *similar* reaction before... how about using say 250ml when trying something for the first time? I have gotten in trouble by having too large a scale; when things get away, it can get ugly really fast. Now I think smaller, at first.
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greenivan
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[*] posted on 7-7-2012 at 01:14


Quote: Originally posted by edgecase  
Quote: Originally posted by greenivan  

I heated my vessel using a heating mantle. My heating flask is 2000 ml one necked RBF, the condenser is 1 graham + 1 vigreoux, cooled by dry ice in a pipe wrapped around it.


2000ml is a *very* large scale, especially for something you are trying for the first time. You mentioned that you did a *similar* reaction before... how about using say 250ml when trying something for the first time? I have gotten in trouble by having too large a scale; when things get away, it can get ugly really fast. Now I think smaller, at first.


If I have the stuffs more than enough, I prefer do large scale so the product is in larger amount and easy to identified.

Anyone know how to recognize the vapour of phenylacetone? I mean how is the colour, etc...
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Hexavalent
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[*] posted on 7-7-2012 at 04:17


Pay a little more attention, greenivan.

When we say do a reaction on a small scale first, we mean to try it using <250ml, possibly <100ml amounts, just to test how it goes, if the reaction goes smoothly, any unexpected results etc. If a reaction is unexpectedly vigorous, it's better if it occurs with 2ml or even 20ml of chemicals in a small flask or test tube as opposed to 2L in a large flask. If nothing unusual is noted and the reaction proceeds fine, THEN you can scale-up if you want.

It is not a waste of time, just an important safety consideration. Professional labs never experiment with 2L of chemicals the first time, usually under 500ml: when they stumble across something they like, then they scale it up.




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maxpayne
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[*] posted on 7-7-2012 at 06:45


Can I ask you how you made phenylacetic acid?
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woelen
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[*] posted on 8-7-2012 at 23:04


Quote: Originally posted by greenivan  
If I have the stuffs more than enough, I prefer do large scale so the product is in larger amount and easy to identified.

Anyone know how to recognize the vapour of phenylacetone? I mean how is the colour, etc...
This is bullshit, even if you have hundreds of liter of "the stuffs" then still you don't want to start an unknown reaction on a liter scale. This kind of posts makes me pissed off. Why are you here? You want some advice? Then at least try to listen to the people who respond to your questions.

Test tubes and small scale glassware exist for a good reason. They allow you to test things on a relatievely safe and small scale and I strongly urge you to use that option before proceeding to larger scale. This is important from a safety point of view, but it also can safe you a lot of losses. What if the reaction does not work at all and you have 2 liters of mixed crap? What are you going to do with all the waste?




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hissingnoise
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[*] posted on 9-7-2012 at 06:22


Quote:
What are you going to do with all the waste?

Not to mention the product, if he actually gets it, that is?

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maxpayne
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[*] posted on 9-7-2012 at 09:38


I also agree with scaling up, but only AFTER trying small/test scale in chemistry as everyone here said.

Here greenivan claims that he want to go large scale because of the massive product for easier identification, he gets fire only, but he do not specify what is the amount expected from his try. So, if this reaction produce so little product from 2000ml flask it is not worth discussing.

Another question is the nature of the product and how he (if) made the reagents. Maybe the source of fire lies in the impurity of the reagents.
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Hexavalent
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[*] posted on 9-7-2012 at 09:48


Maybe, that is certainly a possibility.

Why are we even still discussing this topic now?




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