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Author: Subject: Bad days in the lab or with glassware?
j_sum1
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[*] posted on 2-1-2021 at 00:21


I decided I needed some bulk concentrated ammonia for production of ammonium oxalate. I had previously bubbled NH3 into oxalic acid solution but had high losses from solubility. So, this time I decided to begin with ammonia solution and thrn add oxalic acid.

Working on a scale about 4 times larger than I had ever done before, I set up an ammonia generator using Ammonium sulfate and sodium hydroxide in a large filter flask. Unfortunately, it frothed up, blocked the outlet hose, popped the stopper and vented NH3 into the room.

Reaction slowed without proper mixing of the slurry. However, that still left a kilo of unreacted material to clean up. The only idea I had was to immerse the flask in a bucket of water and allow the water to capture all of the ammonia vapour. This worked. However, it felt a bit wasteful. I ran some calculations that suggested I would reclaim much of the ammonia as the oxalate salt if I added oxalic acid to the bucket. I would lose 360g but stood to recover about the same amount.

That started a long day of filtering at bucket scale. And when it was finally done, my product was not behaving as expected. It turns out that I had forgotten to consider the solubility of sodium oxalate: which is similar to ammonium oxalate. I now have several hundred grams of mixed sodium and ammonium oxalate. It will do for my purpose, but I had chosen the ammonium salt deliberately to keep alkali metals out of the situation.

Never mind. I have had a lot worse dsys in the lab than this. Filtering is do unrewarding though.
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[*] posted on 11-2-2021 at 13:19


Yesterday I was using my favourite thermometer to stir a mixture that had become to thick for the magnetic stirrer. I know I shouldn't, but it just looks so robust. Turns out it is not so robust.
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draculic acid69
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[*] posted on 12-2-2021 at 04:04


Wrapped all the joints with PTFE in a dist. Apparatus to attempt
my first vac distillation and ats soon as I attach the receiver
I hear that terrible "tink" sound. The receiver cracks all the way
from the gg joint right down to the bottom of the flask.
I'm only going to use vac grease from now on.
Dam cheap Chinese joints
too little PTFE and it leaks too much and "tink".
Dammed if U do dammed if U dont.
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[*] posted on 12-2-2021 at 11:03


I have used paraffin oil for my joints for a long now. It gets pretty thin in hot joints, but adding a little now and then from a dropper bottle seems to keep it mostly in order.

I started using paraffin oil in my vacuum pump because I couldn't find any vacuum oil and the few I found, were so expensive it was not even a good joke anymore, and as pumps accumulate all the crap that comes over through vacuum outlet, from solvents to water, which emulsifies with the oil and lowers the ultimate vacuum due to increase in vapor pressure, it is good to change the oil pretty frequently, hence the very low price of paraffin oil comes handy. I've changed the pump oil more in the last 4 months than in the last 10 years. I've used it everywhere that needs lubrication, and also add it to distillations to not allow it to run dry. It's cheap and easily available everywhere and has very low vapor pressure and good lubricating properties and does not react with anything, except maybe hot nitric acid and is also odorless (except when heated for long time, but imo the smell is very pleasant, something along candles) and harmless for health. Oh, and I add half a dozen drops in every thermowell to cover the bottom 10mm with oil for the probe.

What this has to do with cracked glass and joints? Nothing, actually, it's on the teflon thread tape side. I wrapped enough layers for 24* thermoprobe to fit into a 29* joint for a flask because with an adapter the probe was way too short, and everything went mostly well - until I stopped the reaction and shut the valve to prevent air entering and oxidizing the hot product. Some time passes, and I go check my stuff, and of course the cooling reaction created a vacuum inside the flask - and right in front of my eyes the probe pops loudly into the flask, crashing through the bottom, and leaking all the contents into the cooling bath. That was 300€ pop for the 3-neck flask. Ironically the probe was fully intact and I still use it on daily basis. Lesson? Never, ever use anything improvised or take shortcuts, unless you want to prepare for extra costs or a huge mess. Funny though, I recovered 100% of the product, which accumulated as a clean layer to the bottom of the bath vessel and it was even washed clean by the cooling bath water, requiring little neutralization afterwards. Sad that I don't do anything for money for the mess-up to be worth it so it's all 100% loss, whatever way it goes.
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[*] posted on 12-2-2021 at 14:23


Fyndium, by paraffin oil, do you mean what they call mineral oil here in the States?



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[*] posted on 12-2-2021 at 15:37


Yep, the liquid stuff that doesn't taste or smell anything and is used on wood, babies and other stuff.

There appears to be two scholars of the stuff:

https://en.wikipedia.org/wiki/Mineral_oil

https://en.wikipedia.org/wiki/Liquid_paraffin_(drug)
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[*] posted on 12-2-2021 at 20:47


ok. i've using PTFE tape, and as a matter of fact I had a neck crack on my 500ml triple neck about six weeks ago....



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[*] posted on 13-2-2021 at 00:54


I've been afraid of the tape because it could concentrate a lot of force on a small area and spreading it evenly and to provide good seal might be tricky. Ready-made PTFE joint sleeves would be ideal, but the cost isn't, as chinese don't sell them for some reason.
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[*] posted on 16-2-2021 at 21:51


I thought I figured out a good way to store my ebulliator tube by placing it in a plastic pipe with paper topping to prevent it sliding. Apparently it wasn't tight enough as I was going through my stuff and grabbed the tube by the end, and the ebulliator dropped out, bleeder head first straight to my finger and broke leaving me with two glass needles sticking out. Luckily they didn't break under the skin, but it still felt nasty pulling out almost a cm long glass needles off my finger.

Gotta draw the bleeder head again. As I just made it perfect last time. I've gotten pretty good at it, actually.
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[*] posted on 6-3-2021 at 02:30


I've truly grown to hate magnetic stirrers.

It seems to be a technology that no one has gotten to work reliably. Their speed control is unreliable, the magnetic coupling is pretty much always too weak and causes decoupling every other time, and it is practical only for minuscule amounts of low viscosity liquids, as the electric motor itself is usually underpowered as well.

I have a stirrer that just simply died during overnight stirring.

My stirplate speed adjustment goes on runaway sometimes and it has caused similar troubles. The heating function isn't neither the best there is, but has been able to complete things so far with constant monitoring.

Overhead stirrer, first the improvised one from hand mixer, and then the actual one have been proven to be the best solution so far, and only limitation seems to be vacuum operation, although there are bearings for that too if necessary. The real overhead has power of 100W with brushless DC so it has a lot of torque, likely not to stall with anything that doesn't break the glassware itself and it's silent. The hand mixer, although being otherwise good, is very noisy and obviously overpowered. Having 500W of power, it is actually dangerous as it can even snap fingers if misused. I turned a coupling for it for ptfe paddle stirrers, and although rudimentary, it does it's job very well.

I suppose the brand plates are good, but their price tags start from $1k so it's somewhat prohibitive. Are there any proven good stirrers/stirplates with reasonable price range?
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[*] posted on 10-3-2021 at 08:00


Quote: Originally posted by Fyndium  
I've truly grown to hate magnetic stirrers.

It seems to be a technology that no one has gotten to work reliably. Their speed control is unreliable, the magnetic coupling is pretty much always too weak and causes decoupling every other time, and it is practical only for minuscule amounts of low viscosity liquids, as the electric motor itself is usually underpowered as well.

I have a stirrer that just simply died during overnight stirring.

My stirplate speed adjustment goes on runaway sometimes and it has caused similar troubles. The heating function isn't neither the best there is, but has been able to complete things so far with constant monitoring.

Overhead stirrer, first the improvised one from hand mixer, and then the actual one have been proven to be the best solution so far, and only limitation seems to be vacuum operation, although there are bearings for that too if necessary. The real overhead has power of 100W with brushless DC so it has a lot of torque, likely not to stall with anything that doesn't break the glassware itself and it's silent. The hand mixer, although being otherwise good, is very noisy and obviously overpowered. Having 500W of power, it is actually dangerous as it can even snap fingers if misused. I turned a coupling for it for ptfe paddle stirrers, and although rudimentary, it does it's job very well.

I suppose the brand plates are good, but their price tags start from $1k so it's somewhat prohibitive. Are there any proven good stirrers/stirplates with reasonable price range?


Get a used brand name hotplate from eBay for a few hundred dollars

[Edited on 10-3-2021 by itsallgoodjames]




Nuclear physics is neat. It's a shame it's so regulated...

Now that I think about it, that's probably a good thing. Still annoying though.
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[*] posted on 10-3-2021 at 12:15


I bought a used Corning PC351 on ebay for $90US, shit, 3-4 years ago? Still works like a charm, and will pull a vortex in my 2 liter erlenmeyer using a large egg stir bar I got from Dr Bob.



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[*] posted on 18-3-2021 at 19:35


Quote: Originally posted by the Z man  

Other accidents:
-In my rookie days (about a year ago ;) ) I had a splash of hot concentrated NaOH soln on my face and in my right eye while making hydrogen adding aluminium. Runway reaction, you know. Luckly for me I was close to the tap. Nothing more that pain to the eye for one day, but I have been scared a lot.
-Sulfuric and nitric acid eruption from a flask upon addition of AN to conc H2SO4 that turned out to be contamined with EtOH. The acid jet passed about 5 cm from my face (obviously without goggles, also see above) and it was strong enough to hit the ceiling. It was a mess to clean before it could damage the wooden floor of my bedroom.
-Fire from 100 ml acetone I was boiling on open fire :o . Half meter fireball :cool:
-The same with ethanol :cool::cool:

Yes, I am stupid.


this is very funny! LOL! and very crazy!!
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[*] posted on 18-3-2021 at 19:55


when I are in a upper floor in the chem school drawing technical in a big, long and heavy table of 6m aprox a big BOOMM happend. I noted the explosion in my ass sitting on a chair. The table jumped! A lot of ambulances come... Some guy in a mortar mix, if I don't remenber bad, phosphorus and nitric acid... and the result, 2 corneal transplants.

Is very dangerous work with others persons, stupid egos pop up, alpha idiotic males, or simple assholes with no neurons :-)
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[*] posted on 19-3-2021 at 10:50



Quote:

Is very dangerous work with others persons

I'd contend with that and say that for some things, having another person around incase something goes wrong is basically a must. Just as long as that other person acts responsibly




Nuclear physics is neat. It's a shame it's so regulated...

Now that I think about it, that's probably a good thing. Still annoying though.
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[*] posted on 6-6-2021 at 03:04
the chemistry stories thread


on SM there a lot of different stories from different users about failed experiments, stupid things done during an experiment, improvised apparatus, experiments done as teenagers and so on. I thought that a thread about these stories would be great, so one doesn't have to search into different threads. For example i once wanted to electroplate things with nickel, and since i didn't have any acid strong enough for dissolving it, i scraped some of the nickel coating from a few magnet and dissolved it in a concentrated solution of copper sulfate. But on contact with various metals, such as magnesium and zinc they were plated with a grey substance. That's an example of a failed experiment. Any story is welcome!
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[*] posted on 7-6-2021 at 04:39


As a teenager (15 years old-ish) I made a flash powder with Mg powder/KNO3. I was using a piece of wire with a loop at the end to scoop small amounts out and place into a flame and get small flashes and poofs of smoke. It was great fun until the wire got hot and when I dipped it into the vial of flash powder. WHOOSH! A blinding white flash exploded the vial but not before a jet of fire shot out and completely torched the thumb and finger holding the wire.

I ran to the washroom to rinse off the melted chemical on my skin, I peeled it off and realized this was not melted chemical but actually cooked skin. It was leathery in texture and the burn itself was a deep hole in my finger.

Very painful, took forever to heal and the wound kept sticking to the bandages which added to the nightmare.

Lesson learnt. Don't dip hot metal wires into flash powder and expect nothing to happen :)




Note to self: Tare the damned flask.
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7-6-2021 at 05:27
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[*] posted on 7-6-2021 at 05:38


Quote: Originally posted by BauArf56  
on SM there a lot of different stories from different users about failed experiments, stupid things done during an experiment, improvised apparatus, experiments done as teenagers and so on. I thought that a thread about these stories would be great, so one doesn't have to search into different threads
To that end, I’ve merged it with an existing long thread that already serves that purpose well.

To add my own recent story… A few days ago, my friend at work was running a column. He had the compressed air line clipped in place, but the clip failed, causing the glass adapter to pop out, ruining his column as the sudden change in pressure caused the packed silica inside to expand and mix together. The adapter swung like a pendulum, directly into a 250 mL Erlenmeyer flask, cleaving it cleanly in half. The fritted funnel that was sitting in the flask fell out and broke into many pieces on the bench, and the silica gel that was inside of it became dispersed all over the inside of his hood that he had just got done cleaning that morning.




Come check out the Official Sciencemadness Wiki
They're not really active right now, but here's my YouTube channel and my blog.
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[*] posted on 7-6-2021 at 06:28


Quote: Originally posted by Fyndium  
... The hand mixer, although being otherwise good, is very noisy and obviously overpowered. Having 500W of power...

The motor is a simple brushed dc type so can be used with a low voltage dc supply, allowing slow speed while maintaining full torque availability if required.
eg one of my crappy videos https://www.youtube.com/watch?v=ziRxiFSaZsA




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[*] posted on 7-6-2021 at 09:48


Sulaiman, making the stirrer from hand mixer is really good idea. I definitely need it and will do it also.

Brushed motor can be a problem when working with flammable vapours but the risk can be reduced by enclosing the motor in casing. Need to check if how much heat will it generate and if isolation will not cause any issues. Motor can be also moved somewhere and the force can be transferred via belt.
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[*] posted on 26-6-2021 at 21:43


Leaking glass joint in chlorine generator. Annoying and unpleasant.
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[*] posted on 26-6-2021 at 21:48


Hope it was noticed quickly and dealt with before it caused unpleasantness
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[*] posted on 27-6-2021 at 04:44


Quote: Originally posted by draculic acid69  
Hope it was noticed quickly and dealt with before it caused unpleasantness

Well, the good thing about using an addition funnel sliwly dripping as that you can just turn off the acid and let the production die down. Then the only thing to deal with is the gas in the volume of gas in the system. So, it's not out of control. But it does mean stopping what you are doing.

A bit of teflon tape does wonders. In this particular case it helps a lot to fix the right joint though. Hence the post.


For those who want a useful takeaway...
I keep a spray bottle of sodium thiosulfate solution in the lab. Really useful when working with oxidisers: including cleaning up permanganate spills.
This time around, a squirt on the joints helped diagnose the problem. The droplets go cloudy when exposed to Cl2.
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[*] posted on 12-10-2021 at 00:09
D'oh !


I just received two new thermometers, 0 - 50 and 0 - 100 red alcohol.
I decided to calibrate them against water and my two mercury thermometers.

melting ice ..... all read 0C
boiling water .. POP! ... D'oh! ... 50C thermometer did not like 100C :(

how dumb/careless of me.




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