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Author: Subject: When Chemistry Goes Wrong
aga
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[*] posted on 15-9-2015 at 15:00
When Chemistry Goes Wrong


jsum_1 made an incredibly good point today : what Can go wrong is rarely documented, just the Successes are publicised.

I suggest we share the knowledge of what actually happens when chemistry is done wrong/badly.

For starters: forget to add boiling chips to the boiling pot when distilling Phenol under vacuum.

What happens is that it boils nicely for a while, then the liquid goes still for a few seconds, then explodes up the column and pukes all over the place before boiling nicely again for a few seconds, then goes silent again etc.

Edit:

We should learn by our mistakes, and that means sharing them.

[Edited on 15-9-2015 by aga]




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[*] posted on 15-9-2015 at 15:04


Forgetting that thermal stress is a thing can easily result in shattered glass.



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[*] posted on 15-9-2015 at 15:06


Share a mistake or actual experience battoussai114 or i shall share my beer-breath while you are trying to eat.



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[*] posted on 15-9-2015 at 15:06


Isn't that what this thread is for? It's a good idea, just a little late;)



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[*] posted on 15-9-2015 at 15:12


Quote: Originally posted by aga  
Share a mistake or actual experience battoussai114 or i shall share my beer-breath while you are trying to eat.

Experimental chemistry lab: Student on the other table forgets that the cold bench-top is really cold in comparison to the beaker he just took of the heating. Blam, shattered beaker and a mess to clean.

My home lab: I'm rushing the preparing of potassium manganate and try to add water before letting it cool properly. A lot of manganese dioxide, potassium hydroxide and potassium manganate spills on my electric stove as the glass broke in an almost perfect line were the cold water/reaction products interface once was.




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[*] posted on 15-9-2015 at 15:12


Similar gdflp, similar.



[Edited on 15-9-2015 by aga]




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[*] posted on 15-9-2015 at 15:15


That's the kinda stuff i'm talking about battoussai114.

What Actually Happens when it goes bad.

Edit:

Maybe how people dealt with it to get a synthesis back on track, or even escape the lab alive ?

Practical stuff about What Can Happen and how to deal with it instead of just 'I got 95 % yield and it was all fine' or 'it gave 20% due to unexpected lizard alien contamination'.

Actual 'it went bad Here when i saw This, so i did This, and got 93% instead on 95 %' - that kind of thing.

Education by actual experience is what i guess i'm looking for.

[Edited on 15-9-2015 by aga]




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[*] posted on 15-9-2015 at 15:25


Quote: Originally posted by aga  

For starters: forget to add boiling chips to the boiling pot when distilling Phenol under vacuum.


When doing a vacuum distillation boiling chips will often not prevent bumping. An ebulliator is usually used instead.

An ebulliator is easy to make using a glass tube (~5mm dia) drawn to a fine tip. Then break off the fine tip to achieve an opening ~0.2mm or so.




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[*] posted on 15-9-2015 at 15:30


Let's not forget that chemistry goes beyond purely mechanical knowledge.

Forgetting to convert gas volumes from room temperature to STP BEFORE using the 22.4 liters/1 mole ratio.
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[*] posted on 15-9-2015 at 15:31


Simple exaple, not documented before, is twice (yes twice) getting carried away with the Proceess and not thinking about the consequences of each step.

One was to neutralise a strong NaOH solution with HCl.

I just dumped the HCl in the pot.

It exploded (both times) which is one reason why my fume hood is a bit stained.

Stupid, yes, however it happened.

I learned from this: the idea of this thread is that Others can do so too, without the inherrernt danger of making that same silly mistake.

[Edited on 15-9-2015 by aga]




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[*] posted on 15-9-2015 at 15:34


Real life example Cou or 38 Mol of aga breath will bathe you as you sleep.



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[*] posted on 15-9-2015 at 15:34


How much Chemistry fucks up clothing
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[*] posted on 15-9-2015 at 15:42


Recount your own experiences or get some agaBreath when you go to kiss your partner.

Repeat offenders get an agaFart, Full Face, just as you're inhaling.

[Edited on 15-9-2015 by aga]




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Little_Ghost_again
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[*] posted on 15-9-2015 at 15:53


30% nitric acid with copper wire in, nothing much happening so decide to heat it up a little on the hotplate. Nothing for a couple of mins then brown gas!!! Not in the fume hood and only around 250ml in a 2ltr flask, so I decide to equickly end the brown gas by grabbing the nearest alkali (magnesium carbonate powder). I dump small amount of powder in flask (didnt get a chance to dump much!!) and woosh foaming nitric acid and magnesium carbonate powder spew from the top and cover by beloved hotplate.
It still stirs but the heater dosnt work anymore :(, not to mention the agro of cleaning up.

Dont play with thing without thinking the whole thing through and have what if's in place! I did none of that and lost my heidolph hot plate because of it, I was also lucky with the gas and should have at least expected that!

Oh and two sep funnel mishaps, first check the valve is off when filling :D and secondly I shook one intending to vent but forgot to hold the stopper on as it was tight, splish spalsh splosh chloroform everywhere

[Edited on 15-9-2015 by Little_Ghost_again]




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[*] posted on 15-9-2015 at 16:08


I have enjoyed reading the mishaps thread that gdflp cited. (bad days in the lab and with glassware.) But mishaps and "bad" days are not the only thing -- or not even the main thing.

"When things go wrong" covers situations like lysander's where it is a case of "I am following the procedure and I still can't get the #%$# thing to work." In other words, something other than a mishap and something less than a disaster -- something where the application of bit of specialised knowledge might pay dividends.

"When things go wrong" probably does not include gaseous emissions from aga. From what I understand, that is inevitable. The consequences are largely a matter of proximity: diffusion and the inverse square law being what they are. I am close to antipodal and so feel reasonably secure.

My contribution -- alas, as a beginner it is all pretty lame; but here goes.
My first attempt at purifying battery gunk involved reacting the MnO2 with acid to separate from the carbon powder. The only strong acid I had available was HCl. Of course I had overlooked the fact that the reaction is a redox reaction: the Mn goes from +4 state to +2 and so chlorine gas was going to be liberated. I was kind of expecting a bit of a whiff of Cl2 but I had not thought it through or done any calculations. Anyway, I was working at 20gram scale and it did not take long for me to realise that 3.6 litres of chlorine released into my shed was going to render the air unbreathable for some time. Evacuation procedures worked though. (Hold breath. Run for door. Assess damage in a couple of hours.)
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[*] posted on 15-9-2015 at 16:58


I use a 5% dilute sulfuric acid bath, about 400 ml, to remove flux from cast pure silver bars. I turned on heat to medium low to preheat the dilute sulfuric acid bath then went outside to do something and forgot about the solution on the heat.

About an hour later I went back in and the entire interior of the building was engulfed in a thick sulfuric fog because the water and the acid boiled dry. I've actually done this twice in my 5 year amateur chemistry experience.

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[*] posted on 15-9-2015 at 18:07


My early mistakes can be found here:

http://bromicacid.com/mistakes.htm

For those just looking for the high-points here is a list of the titles:


Neutralization of Sulfuric Acid
Acetone Peroxide
H2SO4 / HNO3
What's In a match head?
Silver Thermite
Phosphorus!
Caustic Nightmare
Chlorinated




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[*] posted on 15-9-2015 at 18:43


^That acetone peroxide story is really scary. EDIT: I just read all the stories...you are very lucky indeed.

The worst I have (I think anyways) is when I grabbed a glass thermometer, dipped it in a solution containing some compound (can't remember which_, and stuck it in an alcohol flame to see the color. I think my line of thought was "well, I'll pull it out before the temp goes to high, just for a brief moment." or if it was "hey its a glass rod there is no problem with this lolz"

It exploded just a couple moments after being put in the flame. Is not the reason I always remember to wear safety goggles or face shield, because I wasn't, and I felt that glass shard fly far to close for comfort.

[Edited on 16-9-2015 by KesterDraconis]
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[*] posted on 15-9-2015 at 20:41


I did some basic garage chemistry as a kid and only got back into it 2 years ago at age 33 but boy do I already have my share of mistakes made:

- Attempting to neutralize ~30% sulfuric acid solution by "slowly" adding 50% NaOH solution. The problem is that it was so viscous and dense that it didn't mix until it sank to the bottom and then bubbled explosively. The fume hood front glass saved my eyes
- Breaking open an ampoule of Bromine using pliers and no gloves, thinking that my hands would be far enough away from the Bromine - not realizing that I was tipping the ampoule horizontal as I did this so about 1mL of Bromine spilled out onto my ungloved hand. I felt a burning sensation immediately but quick dousing with water saved my skin from real damage.
- Drawing Bromine up into a glass pipette with a rubber bulb at the top. Bromine went into bulb and immediately reacted exothermically with bulb, making it too hot to hold and shooting Bromine out the other end. Thank God this was in the hood.
- Boiling a sulfuric acid solution dry in an attempt to recover dissolved solids and ending up with plenty of SO3 gas.
- Testing out about 1 gram of silver nitrate+magnesium flash powder in my kitchen sink - I could not see for about 10 seconds after the flash.
- Having a cheap (but supposedly borosilicate glass) bottle crack when I added approximately 100C sulfuric acid to it. I was wearing gloves but what really saved me is that the bottom didn't fall out until I got it over the sink.
- Storing white phosphorus in a glass bottle of water in an unheated room. Water froze, glass broke. I didn't notice for a week. What I did right was that I had a secondary container so the humidity inside never got low enough (and the temperature was not high enough) for spontaneous ignition of the WP. This was on a shelf next to a bottle of diethyl ether. I don't store the WP near anything flammable now!
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[*] posted on 15-9-2015 at 22:35


I wanted to demonstrate that sunlight can be used to ignite things very easily when it is concentrated with a magnifying glass. In order to make it look spectacular I took appr. 500 mg of KClO3 and half of that of red P. Outside, I put the KClO3 on a concrete tile in a small pile. Next, I put the red P on it. I took a dry little twig from a tree (10 cm length or so) and intended to use that for coarsely mixing the two powders. I stick the little twig in the mix and nearly instantly I have a bright flash and have many tiny droplets of molten stuff sprayed around, also on my hand. This was painful!!! The magnifying glass was not needed in this "demo" ;)



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[*] posted on 15-9-2015 at 23:15


Using the wrong vessel as the crucible when calcining bisulfates. Yesterday, I was calcining a big yield of bisulfate and chose a thoroughly washed cat food tin can as the crucible. It turned out that the can still had a lot of trace organics or, possibly, some kind of polymer coating on the inside, resulting in much carbonization of the melt. And part of the can reacted with the melted acid salt, contaminating it with blue-green crap insoluble in sulfuric acid.

Forgetting to empty the waste jar, and forgetting what's there. I had a case when the waste jar contained hypochlorite, and I discarded an HCl-containing solution there. World War I chlorine attack!

[Edited on 16-9-2015 by ave369]




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[*] posted on 16-9-2015 at 04:16


About 12 years back, attempted to duplicate Rosco Bodine's work with Lead azo clathrates. First attempt did not control the (carefully specified!) extremely slow liquid reactants addition rate sufficiently well, failure.

Second attempt with VERY slow addition rate, watched it like a hawk- It took HOURS to do the synthesis/ crystalization... finished well after midnight and done drying product at 03:00. Did a test. FAILED AGAIN! Darn. Just a sad little "poof", NO EARTH SHATTERING KABOOM! THERE WAS SUPPOSED TO BE AN EARTH SHATTERING KABOOM!!!

Next morning before breakfast, and before taking the sad, failed little pile of product out to destroy it... I took a small chunk (half size of a pea! Perhaps 100mg?) off the filter paper and set it on one of the nifty little ceramic glazed cast Iron plates that covered the tops of the burners on my brand new (expensive!) gas stove. Turned burner on low while I made coffee on counter a few feet from stove, range hood was on to handle the Lead fumes. Knew it would just flash and poof like the night before.

Ear (and stove component) shattering KRAAACK!

image.jpg - 374kB

Ceramic covered cast Iron is quite brittle. The shards from that little plate flew at high speeds, impacted Aluminum burner parts and embedded themselves therein... Cost some $'s to fix that dammage. Cleanup was a bitch. Did NOT get to eat the breakfast I was making, glass and Iron "sand" scattered over all the kitchen surfaces.

Lessons learned:

1: A kitchen is not a chemistry lab- OR a materials testing lab.

Don't EVER do tests of energetics in living spaces, MOST particularly, in food prep areas. Even when you "know" it's not going to be spectacular.

2: Don't work with HE chemistry when tired and unobservant/uncoordinated/brain dead from fatigue. 4 hours of sleep after a 20 hour day... Not safe.

3: Don't be in a hurry. The drying time sitting on the filter paper overnight allowed the stuff to show its true nature... I still have the witness plate on which I re-created that impromptu stove top test.

image.jpg - 2.3MB


image.jpg - 2.5MB




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[*] posted on 16-9-2015 at 15:34


Quote: Originally posted by aga  
Real life example Cou or 38 Mol of aga breath will bathe you as you sleep.


Do not have only a mechanical knowledge of chemistry, for that is the biggest symptom of kewlery.

Everyone knows that distillation works by boiling and then condensing in a cold tube. But what about distillation curves?

Everyone knows that you can make cool bubbles by mixing vinegar and baking soda. Can you do the stoichometry?
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[*] posted on 16-9-2015 at 18:49


Bromic, those stories are really frightening, all of them.



Any other SF Bay chemists?
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[*] posted on 16-9-2015 at 19:05


I thought that I had a surprisingly unsupervised childhood of experimentation- Bromic puts my little chemistry, fire and explosion related issues as a kid to shame.



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4. Only then are you permitted to say so much as a word of rebuttal or criticism.

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