| Pages:
1
..
36
37
38 |
oceandeep67
Harmless
Posts: 11
Registered: 13-11-2013
Member Is Offline
Mood: curious
|
|
Quote: Originally posted by itsallgoodjames  | | 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
Build your own.? Custom to fit your needs. If I can do it, I'm sure most of you can...
[Edited on 10-3-2021 by itsallgoodjames] |
|
|
|
oceandeep67
Harmless
Posts: 11
Registered: 13-11-2013
Member Is Offline
Mood: curious
|
|
My apologies^
|
|
|
oceandeep67
Harmless
Posts: 11
Registered: 13-11-2013
Member Is Offline
Mood: curious
|
|
Keep in mind I was a child at the time. Like 12 yo. I was performing a combustion reaction in my attic (did not want mother knowing). Anyhow, make a
long story short I burnt the house down.
So yeah, locals think I'm a fanatic about safety/insane but I/we know how dangerous science can be!
|
|
|
BAV Chem
Harmless
Posts: 28
Registered: 9-5-2021
Location: In the middle of nowhere
Member Is Offline
Mood: Thoroughly confused
|
|
A particularly bad week (or two)
So over the past two weeks I've somehow been very clumsy.
For one I made some nitrotetrazole over a week ago and it was all looking good until I managed to knock over the beaker, spilling all of the precious
solution onto the bench. Most of it could be recovered by carefully pipetting it back up (ik this is terrible lab practice) but then the next day the
same thing happened again. At least I managed to recover half of my product somehow...
Yesterday I reached into the cupboard to get out some acetone and knocked down two bottles of formamide and ethyl formate respectively which both
shattered on the floor. After cleaning that mess up (nothing was recovered) I found that acetone didn't work for what I was trying to do and that
ethyl formate would have been much better. 
|
|
|
B(a)P
International Hazard
Posts: 1139
Registered: 29-9-2019
Member Is Offline
Mood: Festive
|
|
So today I was making some ammonium hydroxide using sodium hydroxide and urea. A few minutes in the foam in the gas generation flask started to build.
I switched off the heat and instead of picking up the gas generation flask and receiving flask and carrying it to the sink, I removed the top from the
gas generation flask and the contents immediately flowed over covering my hotplate. Unfortunately this was too much for my hotplate. After I cleaned
everything up i tried the hotplate again. It let out a little smoke and a few sparks and then lights out. I will take it apart in the coming days to
see if can be healed.
|
|
|
arkoma
Redneck Overlord
Posts: 1763
Registered: 3-2-2014
Location: On a Big Blue Marble hurtling through space
Member Is Offline
Mood: украї́нська
|
|
^^^OUCH. My Corning has survived some pretty heinous spills on it, including hot HNO3. Will be a bad day when it quits.
"We believe the knowledge and cultural heritage of mankind should be accessible to all people around the world, regardless of their wealth, social
status, nationality, citizenship, etc" z-lib
|
|
|
B(a)P
International Hazard
Posts: 1139
Registered: 29-9-2019
Member Is Offline
Mood: Festive
|
|
My current hotplate was cheap and is of poor quality. I have had my eye out for years for a good quality one. It seems one of the differences between
a good quality and bad quality hotplate is resistance to spills. This one cost me $50 about 5 years ago and may still be repairable. Still, I think I
might just bite the bullet and lash out on a new good quality hotplate stirer. Sadly their is no used market for them in Australia, at least not that
I am aware of.
|
|
|
arkoma
Redneck Overlord
Posts: 1763
Registered: 3-2-2014
Location: On a Big Blue Marble hurtling through space
Member Is Offline
Mood: украї́нська
|
|
Broke my *&^%%&^%*&%* Claisen adapter. Almost impossible to live without one. *sigh*. Wasn't even doing chemistry, just straightening up
and I bumped it off the edge of my desk. I've got wood floors, so stuff doesn't ALWAYS break, but not that lucky this time.
"We believe the knowledge and cultural heritage of mankind should be accessible to all people around the world, regardless of their wealth, social
status, nationality, citizenship, etc" z-lib
|
|
|
B(a)P
International Hazard
Posts: 1139
Registered: 29-9-2019
Member Is Offline
Mood: Festive
|
|
| Quote: Originally posted by arkoma | | Broke my *&^%%&^%*&%* Claisen adapter. Almost impossible to live without one. *sigh*. Wasn't even doing chemistry, just straightening up
and I bumped it off the edge of my desk. I've got wood floors, so stuff doesn't ALWAYS break, but not that lucky this time. |
Sorry to hear that Arkoma, there is a place just up the road from me that sells used lab gear and they have a heap of glass. If it is an obscure and
hard to obtain shape let me know dimensions, orientation and joint size and I can take a look next time I am in there. If it is fairly standard no
doubt it would be faster to sort out locally.
|
|
|
j_sum1
Administrator
Posts: 6335
Registered: 4-10-2014
Location: At home
Member Is Offline
Mood: Most of the ducks are in a row
|
|
I made some benzaldehyde: just a small amount, about 5g.
After extracting with a solvent I decided to vacuum distil.
I plugged in my brand new, never-used two stage vacuum pump. My entire product evaporated away in seconds never to be seen again. Now my pump smells
like cherries.
Same day. The joint-seize I hate most. I broke another sep funnel. Glass stopper was stuck and I attempted to loosen with a heat gun. Anyone else
familiar with that high-pitched "tink" sound that lets you know your glassware is destined for the bin. I should just have sprayed with WD40 and left
it for a week.
|
|
|
wg48temp9
National Hazard
Posts: 786
Registered: 30-12-2018
Location: not so United Kingdom
Member Is Offline
|
|
| Quote: Originally posted by j_sum1 | I made some benzaldehyde: just a small amount, about 5g.
After extracting with a solvent I decided to vacuum distil.
I plugged in my brand new, never-used two stage vacuum pump. My entire product evaporated away in seconds never to be seen again. Now my pump smells
like cherries. |
If you have not done so already, as soon as possible drain the pumps oil then flush with clean oil , drain that and fill with fresh oil. There is a
good chance your benzaldehyde will gum the pump up.
I am wg48 but not on my usual pc hence the temp handle.
Thank goodness for Fleming and the fungi.
Old codger' lives matters, wear a mask and help save them.
Be aware of demagoguery, keep your frontal lobes fully engaged.
I don't know who invented mRNA vaccines but they should get a fancy medal and I hope they made a shed load of money from it.
|
|
|
j_sum1
Administrator
Posts: 6335
Registered: 4-10-2014
Location: At home
Member Is Offline
Mood: Most of the ducks are in a row
|
|
| Quote: Originally posted by wg48temp9 |
If you have not done so already, as soon as possible drain the pumps oil then flush with clean oil , drain that and fill with fresh oil. There is a
good chance your benzaldehyde will gum the pump up. |
I am not terribly worried. Running the pump for a couple of minutes seems to have eliminated the smell. And if the worst does happen, fixing it will
be identical to the preventative you have prescribed.
|
|
|
Lionel Spanner
Hazard to Others
Posts: 168
Registered: 14-12-2021
Location: near Barnsley, UK
Member Is Offline
|
|
A little while back, I attempted to prepare sodium nitrite by hydrolysing bronopol with caustic soda. As far as I'm aware there is no written record
of this procedure, so I was working entirely blind.
On the first attempt I tried adding caustic soda to an aqueous solution of bronopol, which caused a runaway exotherm, making it boil over and spill
hot greasy orange water everywhere.
On the second attempt I pre-dissolved caustic soda in water and slowly added bronopol to it, while keeping the temperature fairly constant. This
worked perfectly, producing a yellow solution. My intention was then to heat the solution to reflux, but on heating, as the mixture reached about
70-80 °C it darkened from pale yellow to orange and heated up very rapidly, causing the solution to boil, and a runaway exotherm occurred again,
violently ejecting a jet of hot greasy orange water through the condenser.
Fortunately I was using a long Allihn condenser, and I'd instinctively removed the heat and moved far from the apparatus as soon as I saw it starting
to boil, so no damage was done other than a load of annoying greasy orange stains.
To add insult to injury, once the remaining solution had been refluxed, I couldn't separate the organic products by extraction with ethyl acetate, as
it was miscible with them, and the dark red colour of the solution made any kind of phase separation impossible to discern.
|
|
|
beta4
Hazard to Self
Posts: 56
Registered: 3-2-2019
Member Is Offline
|
|
It was cold outside so I tried stick welding in the chemical fume hood.
I thought the aspirator could get rid of the fumes and the tiles surface is fire proof.
Don't. The slag sprayed when welding etches the glaze of the tiles leaving permanent black spots.
|
|
|
Lionel Spanner
Hazard to Others
Posts: 168
Registered: 14-12-2021
Location: near Barnsley, UK
Member Is Offline
|
|
I recently tried repeating a procedure I'd previously had success with six months ago - reduction of GABA to its alcohol - with the idea of making a
video about it.
The first step was heating it with finely powdered sodium borohydride in dry THF until they form an acetoxyborohydride salt. Both are insoluble in THF
and the reaction is otherwise very slow, so the mixture needs to be heated nearly to reflux.
At reflux, everything was going smoothly for the first few minutes, until the mixture started boiling vigorously, a load of smoke (dust?) was ejected
through the condenser and the suspended white solids in the mixture started turning brown, orange and pink. This has not happened before, and it's
fair to say the reaction was ruined, so I abandoned it and later recovered the THF by distillation - that stuff's not cheap.
It had been six months since I'd last carried out this procedure, and the temperature had not quite been as high - 50 °C rather than 65 °C. It's
possible GABA had drawn water from the air in the container during that time, and/or a self-cyclisation reaction occurred at the higher temperature,
forming the lactam. Either way, it's not doable with GABA straight out of the jar.
[Edited on 21-2-2024 by Lionel Spanner]
|
|
|
Sulaiman
International Hazard
Posts: 3723
Registered: 8-2-2015
Location: 3rd rock from the sun
Member Is Offline
|
|
(carefully calibrated pycnometer) vs (gravity + concrete floor)
it is not the cost (<$2) but the time and patience calibrating it
[Edited on 23-12-2024 by Sulaiman]
CAUTION : Hobby Chemist, not Professional or even Amateur
|
|
|
| Pages:
1
..
36
37
38 |
![[*]](images/xpblue/default_icon.gif){kind=icon}
