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Author: Subject: Homemade and Repurposed Lab Gear
Sulaiman
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[*] posted on 7-2-2017 at 08:46
Geocachmaster


I have a similar hotplate,
the temperature controller needed multiple re-adjustments :mad:so I used one of the cheap controllers http://www.ebay.co.uk/itm/161843931556?_trksid=p2060353.m274...
In use with a2l flask covered in Al foil
HotplateMod5.jpg - 1MB
Top view after modification
HotplateMod3.jpg - 679kB
The controller in the bottom part of an old plastic box
HotplateMod2.jpg - 623kB
Modified hotplate internals
HotplateMod1.jpg - 1MB

The hotplate now has better control all the way to maximum, which is higher than before..

[Edited on 7-2-2017 by Sulaiman]




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[*] posted on 7-2-2017 at 08:54
Sulaiman


That's a super good idea! I actually just bought a 2000w (I think) ac voltage control for use with my heating mantle (:() and other projects. I think I'll put it to good use now!

The heating control on that hotplate is definitely crap, either too hot or too cold.

[Edited on 2/7/2017 by Geocachmaster]
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Sulaiman
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[*] posted on 7-2-2017 at 09:07


the controller in the photo's was ordered at the same time as a 500ml heating mantle element,
the hotplate died more recently, :P

there is another controller in the post somewhere between China and me
(and a 'spare' heating element, even though construction not started yet :o

P.S. for good performance a batch fractionating column needs very slowly changing temperatures, boil-up rates etc.
I have considered
. a mini-mercury-manometer to control heating based on column differential pressure
. a rex-c100 pid controller
. a £1.24 incl. p&p triac 'dimmer' ... perfect ! for fixed boil-up rates :)

[Edited on 7-2-2017 by Sulaiman]




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tsathoggua1
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[*] posted on 7-2-2017 at 11:13


At least as they come, those hotplates have to bee THE worst I've ever had the displeasure of using.

Had one, and ended up tossing it just recently. If its what it looks like (I can't remember the brand, its been around a while and any lettering had long since been eaten off by various corrosives:P)

But the temperature was thermostatic, and either on or off, cycling in pulses to attempt to regulate the temperature. A real piece of shite and with a tendency to trip the circuit breakers unless very carefully adjusted. Got dumped in the bin the moment another became available again. And the one of those I had was worse than unpredictable. It was the damn devil, and has been responsible for a volcanic unpleasant reaction sudden superheating which resulted in a phosphorus volcano shooting up and out of the condenser, as well as three other times. Once the result was a huge, expensive, if rather pretty, although pretty noxious as well, sodding great gout of subliming iodine vapor, looked as though iodine had been substituted for Cl2 in a damn WWII trench, and the other one ended up starting diethylene glycol smoking and fuming at a roiling boil in a heating bath, which whilst rather, well..not exactly penetrating, and didn't have that sheer carrying or persistency of say, some of the foul-smelling haloalkyl sulfur heterocyclic monstrosities spawned by overheating 1-chloro or 1-bromothiazol-2-ethanes which were just brutal, the diethylene glycol heating bath, which happened to contain salts, CaCl2 and NaCl, due to a former life as a coolant bath with ice and MeOH/EtOH, good god the smell. It was subtle, but odious, a really nasty sickly sweet 'ripe' stench. Not like rot, exactly, but like fruit going rotten without the fruity ester components, and putrid. Stagnant and sickly. Not terribly strong as such, but even faint sensation of that was enough to nearly make one vomit.

The plate eventually grew to be so despised that it went into the trash. The death knell sounded for it the time dipropionyl and dibenzoylmorphine sulfate both almost ended up burnt to a crisp during a sudden temperature spike. Luckily most of the esters were able to be saved, but from 70-something 'C to over 250 'C in no time flat. Luckily the reaction involving the esters was being watched like a hawk due to the preciousness and temporary irreplacability of the substrate and the vessels were snatched, hot as they were, off the place before the substrate was deep-fried in acyl halide. Bugger the hands. The yield had to be saved in that case. Not easy to keep hold of and it had a good go at shrink-wrapping a pair of hands in shrunken gloves. A good deal of swearing followed to say the least, although at least, given the specific activity of the compounds produced, at least the actual pain from grabbing the bloody well hot flask necks stood little chance of standing up to 3,6-dipropionylmorphine. Little yield left afterwards, due to its being needed to sooth the hands that rescued it, but some is better than none. dipropionyl and dibenzoylmorphine turning to carbon..now that would be a sight to make any chemist weep. After that, it went to another hot place. This one with lots of fire and brimstone, from whence it came and where it deserves to be.
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[*] posted on 7-2-2017 at 11:34


These hotplates are definitely horrible for temperature control with the included thermostat. I find it useful for dehydrating stuff that can't decompose/burn. For example if I'm out of anhydrous magnesium sulfate and don't have a lot of time I just throw a bit in a beaker and turn it on full. Also the heating surface is covered with some kind of paint which can stick to glass; it's awful to clean off. I bought a ceramic top hotplate stirrer when I could, but it blew half of this years chem budget.



image.jpg - 867kB

Much better
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JJay
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[*] posted on 7-2-2017 at 13:30


They aren't bad at temperature control if you use a heating bath, but it's easy to burn stuff placed directly on the hotplate's surface. I used a table salt heating bath with mine last week, and it worked great.



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Sulaiman
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[*] posted on 8-2-2017 at 01:03


I had a lot of use out of my cheap hotplate before I modified it,
as above, I had two major problems;

the on/off/on/off.. temperature control has a large hysteresis,
so distillations would surge, then die down, then surge, then die down....
OK for a simple distillation but terrible for fractionating.

Possibly due to micro-welding of the switch contacts, the hotplate would occasionally 'stick' on too long and massively overheat for a while.


Converting to a 'dimmer' has transformed the hotplate !
I now feel confident to leave distillations running with very little monitoring,
nice steady boil-up rates.
I recommend this modification to anyone with a little electrical wiring expertise,
even if you think your hotplate is ok ... try a modified hotplate




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JJay
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[*] posted on 8-2-2017 at 03:08


I think I'll definitely pick up some of those dimmers... while I've been trying to cut back on brushed motors, I still have plenty of resistive heating. Why use a $150 variac for your heating mantle....



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tsathoggua1
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[*] posted on 8-2-2017 at 14:48


My current mag stirplate that needed a repair (he's no electrician generally, not with his math) is now thankfully repaired, again with a modification like that, converting the snap-switch (preset levels, without intermediacy, at first) to a dimmer. Still getting used to the hack of the controls. But MUCH better.

The other one had to go though. Was going to rip the resistance wire out of it, but one night, found it had just been thrown out. Fucker was too dangerous to plug back in and once his old man repaired the other one and did that little hack on the controllers, it went before he had chance. Not that he misses it, and not like a bit of nichrome resistance wire is going to break the bank of ever needing to buy any.

First time he knew of that sudden massive overheating. Elemental phosphorus was one of the reagents. doing an RP-I2 reduction of the substrates he was working on at the time, and lets just say, the cleanup wasn't much fun. PI3, I2, burning phosphorus that thankfully, didn't QUITE hit the ceiling. Not far off though, using a long, thin necked flask at the time, a side-arm distillation flask another time was even less pretty (one with an inbuilt long glass side-arm coming off the neck about an inch or two down from the top of the neck. If the top end had been sealed, that would have been...well glad not to be standing too close due to the resulting sideways direction of the jet of reactants:D



[Edited on 8-2-2017 by tsathoggua1]
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[*] posted on 18-2-2017 at 14:58


I had been doing camera work, including a bunch of chemistry videography & photography, using a clamp, stand, and (ugh) selfie stick to hold my camera as a makeshift tripod. It was ok, but still pretty wobbly and inconvenient. I picked up a tripod not too long ago at the local Really Free Market, and decided to retrofit the selfie stick to the tripod so that it could hold my camera phone. Here it is, after sanding down rough edges and epoxying an appropriately-threaded nut onto the phone holder:

IMG_20170214_DIYTripod.jpg - 290kB




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[*] posted on 3-3-2017 at 12:44


My first attempts as making glass pipettes. The top two are made from glass droppers (right) and the bottom two are made from glass tube. The bottom ones are blackened because I pressed the hot glass on a piece of wood to flare the edges, got a nice deposit of soot. Would metal cause cracking?

I heated the last 1.5cm of the tube while rotating until the hole closed and the glass softened enough for it to droop when rotation stopped. Then using a pair of tweezers I grabbed the end and carefully pulled it out. The faster pulled the thinner the tip will be.

image.jpg - 1.6MB



image.jpg - 956kB

My favorite one
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[*] posted on 8-3-2017 at 05:12


Ok. This is worth thinking about.
https://youtu.be/ispolAHB4jA?t=1m56s
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[*] posted on 4-4-2017 at 22:07


Homemade magnetic stirrer 9v bat and computer fan

IMG_20170405_245932954.jpg - 1.2MBIMG_20170405_010043908.jpg - 1.5MBIMG_20170405_245938686.jpg - 1.4MBIMG_20170405_245949082.jpg - 1.3MBIMG_20170405_010038990.jpg - 1.5MB
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[*] posted on 4-4-2017 at 22:09


Homemade magnetic stirrer 9v bat and computer fan

IMG_20170405_245932954.jpg - 1.2MB IMG_20170405_010043908.jpg - 1.5MB IMG_20170405_245938686.jpg - 1.4MB IMG_20170405_010043908.jpg - 1.5MB IMG_20170405_245938686.jpg - 1.4MB IMG_20170405_245949082.jpg - 1.3MB IMG_20170405_010038990.jpg - 1.5MB
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JJay
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[*] posted on 29-4-2017 at 18:15


I made a flexible stir shaft by twisting a length of electrical tape into a core and wrapping several layers of electrical tape around it. It is super ghetto, but it works.




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