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JJay
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[*] posted on 9-8-2017 at 18:44


@Melgar: Calcium acetate smells like vinegar. That you are not aware of this fact is surprising, but what is concerning is that you're making unwarranted assumptions about the nature of the decomposition products and also making speculation that would require me to waste excessive quantities of chemicals given the level of knowledge on display here.



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Melgar
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[*] posted on 9-8-2017 at 21:26


Quote: Originally posted by JJay  
@Melgar: Calcium acetate smells like vinegar. That you are not aware of this fact is surprising, but what is concerning is that you're making unwarranted assumptions about the nature of the decomposition products and also making speculation that would require me to waste excessive quantities of chemicals given the level of knowledge on display here.

First of all, my calcium acetate has no smell at all. The fact that yours did is what made me speculate. Second of all, virtually all the literature I could find gave the 160˚C decomposition point. For instance, here:

https://pubchem.ncbi.nlm.nih.gov/compound/Calcium_acetate#se...

These figures are for air atmospheres unless stated otherwise. To me, it seemed like a bad idea to heat your Ca(AcO)2 above that, just because you were able to find two different papers that claimed a higher decomposition temperature under very controlled conditions. The one paper went through a lot of trouble to only get the monohydrate in one form, which I doubt you did.

My thought here, is that proving literature wrong is kind of a big deal, and if you're somehow able to prove that it's wrong for amorphous calcium acetate at least, then it's actually something that's worth your time and effort and reagents. Of course, the other option is to assume that it's more or less correct, with some exceptions for certain pure crystalline forms, and dry your calcium acetate below that temperature.




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[*] posted on 9-8-2017 at 22:13


That's not "literature" any more than a library card catalog is literature. It's a compilation. The only source that it cites with a 160 C decomposition temperature is an International Chemical Safety Card, and it gives no information on whether decomposition is production of acetone or simply dehydration. Taking it as gospel, Melgar, is a prime example of how Chemistry Goes Wrong.

In any event, I now have the actual literature that reported formation of traces of acetone at slightly above 160 C, and it concluded that production of acetone was very slight below 400 C.

I'm curious about the purity of your calcium acetate and whether it is the impure commercial form, hydrated, or actual anhydrous calcium acetate but this is not the place to discuss it unless you've had some failed reactions or something.




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[*] posted on 9-8-2017 at 22:32


Quote: Originally posted by nitro-genes  
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...


Nothing like broken glass and sodium hydroxide flying all over the place :) I made an ammonia generator by a boiling strong ammonia solution through a column and running the vapors through a tube of sodium hydroxide and had no problems.




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[*] posted on 12-8-2017 at 11:54


I was weighing out 30g of NaOH and a clump fell out of the bottle giving me about 20g too much. Trying to pour off the extra into a wide necked Erlenmeyer flask and the clump made a bunch spill everywhere. Most of it landed on my scale, getting on the top, under the keys, under the weighing surface, just making a terrible mess in general. Of course its quite humid and all of the beads stick instantly. I think my scale is lost. Oh well, I wanted to get a new one anyway...



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[*] posted on 12-8-2017 at 15:10


I recently ordered some gallium from china. 28g for £8 including delivery a nice price probably a to good to be true price.

It is supposed to be on its way but the listing has been removed so I was concerned in case its restricted. I could find no restrictions on its sale or possession in the uk but its not supposed to be transported by Royal Mail and probably not by air.

I guess I will have to wait (a long time if its by sea) and see if it arrives ok and hopefully I can not get in trouble. It should be the sellers responsibility to ship correctly.

Ok not really "When chemistry goes wrong" but sort of related
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[*] posted on 12-8-2017 at 16:39


I was experimenting with a microwave oven magnetron on my bench. I was careful to avoid significant microwave exposure. When I moved an earthed piece of metal the back of my little finger come too close to a wire connected to the transformer HT output.
.
Ouch zap, about 2kV between my little finger and my earthed index finger and thumb. I cannot say with certainty, as my brain was overload by the sensory input from my hand but it looked like a draw out an arc to several inches with my little finger as I pulled my hand away very very quickly. The were several burn spots on my little finger and big one on my index finger with a smaller one on my thumb. Initially no pain but the fingers where numb and my hand throbbed a lot. All the finger moved ok. Oh and the strange smell of burnt skin. Fortunately and painfully within an hour or so the sensation had returned to my hand and the burns hurt but not particularly so.

Sorry no pics I seem to have lost them or forgot to save them when I viewed them on my pc. It surprisingly how easy it was for me to forget to avoid that wire when I was preoccupied by the experiment. The outcome could have been much worse. I am getting a bit too elderly to chance shock testing my heart. I will not be experimenting with that set up again until the power supply and connections to the magnetron are fully enclosed.

Ok its a "When physics goes wrong" or perhaps a "call me stupid"
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[*] posted on 13-8-2017 at 01:55


I had another incident regarding 'industrial grade' chemicals. I needed some benzophenone and decided to just buy some supposed ">95%" calcium benzoate powder for a thermal decomposition reaction to produce benzophenone. Instead of recrystallizing or purifying the "95%" Calcium benzoate, I felt lazy and decided to just do the decomposition reaction immediately.

I began to gently heat a flask loaded with around 100 grams of Calcium Benzoate and after around 10 minutes, steam began to come off at around 103 degrees, and then continued to gently heat until, after maybe 15 minutes, I heard a very loud "bang" and a very thick black smoke cloud rushed into my condenser, which smelt very strongly like petrol, and I immediately turned on my ventilation. I took the flask off heat and left the area for around 15 minutes.

When I returned, my condenser was coated with a thick layer of black soot that could only be removed by a mixture of Sulphuric acid and hydrogen peroxide, and I had to destroy the reaction flack. Then entire flask was basically filled with carbon foam that would not be removed, as was the glass adapter leading to the air condenser, despite me scrubbing both of them for a good half-hour.

The only 'good' thing is that I now have around 35 mL of Benzene that I don't know want to do with. I have done this reaction before with self-made Calcium benzoate and only got around 2-3 mL of benzene and side products distilling less than 300 degrees in the whole distillation. The moral of this story; Always purify your chemicals, and that I am an idiot for not checking to purity of 'Industrial grade' chemicals... :mad:
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[*] posted on 13-8-2017 at 03:12


If I'd accidentally made benzene a couple of years ago I would have been overjoyed, but the same thing happened to me recently. Benzene tends to give off a lot of smoke when it burns.

There are lots of things you can do with benzene. I would wash it with water, dry it with a suitable desiccant, fractionate it and then store it in a suitable container. Benzene tends to degrade rubber stoppers.




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[*] posted on 13-8-2017 at 03:34


Oh, and I was distilling some benzyl alcohol earlier and managed to melt a screw cap by heating the 14/10 flask directly on a hotplate with a foil skirt. Fortunately, I have two large bags of caps... I was wondering why they included so many in my kit. I managed to rescue the flask by carefully cutting into the cap with a razor knife. I guess next time I should use a heating bath or a vacuum.

It was my first time ever actually using a Hickman distillation head. They seem to work reasonably well.




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[*] posted on 14-8-2017 at 01:40


The thing is, I honestly never use Benzene, or any well-known carcinogens if possible in my lab, so I really don't want the stuff just lying around. I normally destroy any benzene or other unwanted organic compounds by burning a mixture of the benzene and methanol in an old-fashioned spirit burner.

I prefer just burning it as I typically have around 10 mL of some non-dangerous organic compound lying around, so burning it is much, much easier than the ''dangerous waste disposal' as the fee for even small amounts of waste is a nightmare. However, I never incinerate any halogenated or nitrogen containing organic compounds due to the risk of forming small amounts of hydrogen cyanide and phosgene.


Where I live, you can buy liters of 98% Sulfuric acid and 38% HCl from your nearest hardware store, but buying any benzaldehyde or benzyl alcohol will get you a visit from the police.
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[*] posted on 14-8-2017 at 01:53


Oh. Benzaldehyde is like that here (although they let some people get away with buying it). Benzyl alcohol, though, is very easy to obtain.



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[*] posted on 20-8-2017 at 17:30


Unhooking the water lines to a condenser. Easy enough to do, except when you forget to turn off the flow of water first! I tried to clean up and grabbed a towl, but I forgot it was one that I had spilled methylene blue crystals on...



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[*] posted on 20-8-2017 at 21:31


You've got a good reason to feel blue now / you've entered your blue phase ?

This is what happens when you have a nice new shiny lab ! :P




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[Edited on 21-8-2017 by Sulaiman]




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[*] posted on 20-8-2017 at 23:20


Hey, at least it wasn't silver nitrate!

There are safe limits to benzene exposure, and its carcinogenic properties tend to be from occupational exposure. It's not in the same category as say, dimethyl sulfate. If it were up to me, the alarmists that study what causes cancer would have to rank everything on their list from most to least carcinogenic, just to give some perspective. And forcing mice to breathe 200 ppm of a chemical for their entire lives should not be enough evidence to label something as a carcinogen. Most carcinogens only cause cancer when they or their metabolites accumulate faster than your body can remove them or repair the damage they do.




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[*] posted on 21-8-2017 at 00:44


I know, but I still don't want to work with any potential carcinogens in my garage lab, but I definitely agree that the current epidemic of Chemiphobia has gotten out of control. Anyways, I would just not work with dimethyl sulphate in my current lab, but I would see no problems working with Dimethyl carbonate.

In other news, I managed to spill around 10 mL of saturated K2MnO4 that I was trying to crystallize without decomposing to brown MnO2 muck, and it landed on the carpet. Now I have to deal with several holes in my carpet and a large brown stain to clean up.
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[*] posted on 24-8-2017 at 17:38


I learned today that solutions of NaOH in alcohol are not compatible with HDPE. After two days I noticed that my 500 mL HDPE ethanol recovery bottle was cracking at the top and had warped and became soft at the bottom. I had poured ethanol which contained excess sodium hydroxide in and didn't think about it because HDPE is compatible with both of those chemicals. For now I placed the bottle in secondary containment and I will dispose of it tomorrow.

On another note I was trying to do a fractional distillation using a 1 meter packed column, it had massive flooding issues (I checked under the aluminum foil when I heard bad noises and more than 2/3 of the column was full :o). I will have to rethink my design. I'm thinking larger diameter column and slower heating rate.




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[*] posted on 26-8-2017 at 11:01


Quote: Originally posted by wg48  
I recently ordered some gallium from china. 28g for £8 including delivery a nice price probably a to good to be true price.

It is supposed to be on its way but the listing has been removed so I was concerned in case its restricted. I could find no restrictions on its sale or possession in the uk but its not supposed to be transported by Royal Mail and probably not by air.

I guess I will have to wait (a long time if its by sea) and see if it arrives ok and hopefully I can not get in trouble. It should be the sellers responsibility to ship correctly.

Ok not really "When chemistry goes wrong" but sort of related


I am pleased it arrived today via Royal Mail. Not packed very well. It had apparently melted and leaked from its container. The whole package weighed 36g so the weight of the gallium is about correct.



gallium-metal.jpg - 143kB
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[*] posted on 26-8-2017 at 17:21


Quote: Originally posted by BromicAcid  
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


LOL that phosphorus story is crazy. Had me laughing and made me realize this is something I never want to do.
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[*] posted on 5-11-2017 at 15:53


Yesterday I decided to generate some ammonia gas for a separate project of mine. I had the whole gas generating setup built and so I mixed the reactants and started gas generation. By the way I was making ammonia via ammonium halide salt + alkali metal hydroxide. Any way, the reaction started and a lot of gas was coming off. There was also a good deal of moisture coming with it. Little did I notice that some (a great deal) of ammonia gas was leaking from the tubing that I used to make the gas generating setup. Before I realized what was happening I lifted the sash of the fumehood up and got a huge whiff of ammonia gas. I had forgotten to turn my fume hood on. I quickly turned it on and ran to the other side of the lab. I walked over to the hood every few seconds and within 2 minutes there was no detection of ammonia gas.
This wasn't a super dangerous situation but it did give me somewhat of a scare considering that ammonia isnt the greatest stuff to inhale.

[Edited on 6-11-2017 by TheNerdyFarmer]
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[*] posted on 6-11-2017 at 11:45


Several months ago I was playing with some sodium metal, first thing that came to mind was the addition to water since it's always exciting to watch the little fiery balls dance across the surface. At first I was using little cubes about 2mm each side which lasted a few seconds and quickly got boring. 'Why not scale it up?' I thought, so I doubled the dimensions to 4mm. A lot more in the way of sparks and acrid fumes, so I stepped back and the little chunk exploded, sending specks of the flaming metal upward about 1.5m where they still exist to this day as a collection of black dots on my ceiling. Glad that it ended that way and not in my eyes or mouth, I've since well warmed up to the necessity of PPE even on such a micro scale.



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[*] posted on 6-11-2017 at 11:57


Sodium, especially, illustrates that in chemistry scaling up amounts does not always mean scaling up the reaction at the same rate. Small bits fizzle and occasionally catch fire, but larger pieces explode and can splatter flaming sodium everywhere. Even larger pieces can explode violently, launching the majority of the sodium intact into the air to land who knows where and explode again. See the videos of people throwing sodium into lakes - there are always many explosions after the initial one as bits hop around the lake. Scary!
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[*] posted on 7-11-2017 at 05:02


I have not had bad experiences particularly with sodium, but with making it. I was using the magnesium oxide aggregate method that nurdrage used. I had a small crucible that I could not find the lid to. Somehow I decided that a large, oblong rock would serve as a good lid. So I stuck it on top and lit up the reaction. Of course, it tipped over sending the flaming mixture onto my fume hood bench. Luckily, the bench was made of a relatively flame retardant so it just left a large char Mark.

Mistake number 1: Rushing into a reaction that I wasn't ready for.
Mistake number 2: Performing a reaction that involved fire and very high temperatures indoors.

I do intend on trying this reaction again except I will be using proper equipment and performing it outdoors.
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[*] posted on 7-11-2017 at 18:50


Quote: Originally posted by owie  
Quote: Originally posted by BromicAcid  
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


LOL that phosphorus story is crazy. Had me laughing and made me realize this is something I never want to do.


Bromic Acid's website, along with Woelen's and AX10whatever his name is (Tim, sorry...)'s websites, are what made me join Sciencemadness. And I got a huge laugh out of his stories, too...definitely told well, they're Max Gergel quality...




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[*] posted on 9-11-2017 at 09:48


Quote: Originally posted by wg48  
I was experimenting with a microwave oven magnetron on my bench. I was careful to avoid significant microwave exposure. When I moved an earthed piece of metal the back of my little finger come too close to a wire connected to the transformer HT output.
.
Ouch zap, about 2kV between my little finger and my earthed index finger and thumb. I cannot say with certainty, as my brain was overload by the sensory input from my hand but it looked like a draw out an arc to several inches with my little finger as I pulled my hand away very very quickly. The were several burn spots on my little finger and big one on my index finger with a smaller one on my thumb. Initially no pain but the fingers where numb and my hand throbbed a lot. All the finger moved ok. Oh and the strange smell of burnt skin. Fortunately and painfully within an hour or so the sensation had returned to my hand and the burns hurt but not particularly so.

Sorry no pics I seem to have lost them or forgot to save them when I viewed them on my pc. It surprisingly how easy it was for me to forget to avoid that wire when I was preoccupied by the experiment. The outcome could have been much worse. I am getting a bit too elderly to chance shock testing my heart. I will not be experimenting with that set up again until the power supply and connections to the magnetron are fully enclosed.

Ok its a "When physics goes wrong" or perhaps a "call me stupid"


Found one of the pics

files.php.jpg - 11kB
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