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Chemorg42
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[*] posted on 13-5-2020 at 16:15
Hotplates


Ok, so here's the deal.
I am thinking of following the tutorial on the wiki to synthesize salicylic acid from acetylsalicylic acid. Only problem is, I need to heat a solvent (acetone or isopropanol), however, I do not have a hotplate right now, nor the money to buy one. So my question is, what should I do, I do not need stirring, all I need is a safe way to heat glassware containing flammable solvents.
Can I just buy a cheep camping hotplate, is there something that makes this impractical, just some things I should know. Or, is there something I can put my burner (home science tools pressurized alcohol) in?, Something I can do with it?
Any help is appreciated.




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stephill92
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[*] posted on 13-5-2020 at 16:40


I have done this reaction using an out door burner attached to a grill, and everything worked out fine. I would recommend using a camping stove however if you have one since they are a bit more mobile. If you do choose to use an open flame make sure you have a plan to put out a potential fire in case something goes wrong.
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Chemorg42
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[*] posted on 13-5-2020 at 21:04


OK, interesting. What solvent did you use? I read that both acetone and isopropanol vapours are heavier than air, is this true? Is it no problem because it disperses in air outdoors?



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mackolol
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[*] posted on 14-5-2020 at 03:01


I strongly recommend just buying cheap electric kitchen hotplates, I would even say, that these are the essential in amateur lab. In my country one costs about 30zł (7Euro), so it is extremely cheap, but they are very durable and can heat very fast to 500C. It is even stronger than my hotplate stirrer (400C) So I use it when I need high temps or just don't need stirring.

It is still way better than burners, because it eliminates (or at least reduces) the risk of fire, and is more precise than just open flame. And come on don't you have 7Euro or whatever currency?

[Edited on 14-5-2020 by mackolol]
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Sulaiman
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[*] posted on 14-5-2020 at 04:16


+1 for the cheap hotplate.

Plenty of power when required
cheap enough to not worry about occasional spills

I also like to use cooking oil in a metal pot on the hotplate for heating flasks
as it is less likely to stress glassware than a bare hotplate.
(hotplate surfaces and glassware bottoms are rarely flat, so hotspots are normal)
but I do prefer my heating mantles for heating RBFs (diy 500ml and a free 5l)




CAUTION : Hobby Chemist, not Professional or even Amateur
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XeonTheMGPony
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[*] posted on 14-5-2020 at 04:27


Quote: Originally posted by Chemorg42  
OK, interesting. What solvent did you use? I read that both acetone and isopropanol vapours are heavier than air, is this true? Is it no problem because it disperses in air outdoors?


I used a butane camping stove with methanol as my solvent first time with a reflux condenser. After getting sick and tired of buying fuel I ordered a heating mantle insert from Deschem, and been happy ever since!

I used an old coffee tin and light dimmer for the control of it, very cheap!

No worry, but I have halon and ABC extinguishers and lots of experience with solvent fires! (I use methanol/Ethanol a lot for starting my wood stove! (Living it up like 1785!))
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DavidJR
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[*] posted on 14-5-2020 at 04:47


Do not use open flames to heat vessels of flammable solvents. It is an accident waiting to happen/
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Chemorg42
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[*] posted on 14-5-2020 at 09:11


OK, I will probably pick up a cheep kitchen hotplate. Now another question, can I put my glassware directly on the hotplate, or should I put wire gauze between them?



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Tsjerk
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[*] posted on 14-5-2020 at 09:28


Use a water bath, especially with these water miscible solvents. If something breaks at least it is contained and diluted with water.

No matter whether you are using a flame or a hot plate, always use a bath of some kind. Water with low boiling stuff, oil or sand with higher boiling stuff. Acetone or IPA on a hot plate will also catch fire.
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Syn the Sizer
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[*] posted on 14-5-2020 at 09:29


Quote: Originally posted by Chemorg42  
OK, I will probably pick up a cheep kitchen hotplate. Now another question, can I put my glassware directly on the hotplate, or should I put wire gauze between them?


I have a stirring hotplate, I stick my glass right on the hotplate. That's what we do in school I have only ever used a gauze when heating with flame and I think that is to spread the heat out more than protect the glass. Though I am sure somebody will come on here with more info.
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Chemorg42
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[*] posted on 14-5-2020 at 13:00


OK, so the last two replies seem to represent two extremes. Is it really necessary to use a water bath with a cheep hotplate or alcohol burner? Is it really safe to place glassware directly on a hotplate?
I don't know the answers to these questions, just not sure what to think.




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Tsjerk
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[*] posted on 14-5-2020 at 13:46


I would use a water bath, it is just safer. It can be as simple as a pot or a pan. If you use hot water from a cooker to fill it it is even faster than waiting for the hotplate to heat your reaction.
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Chemorg42
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[*] posted on 14-5-2020 at 14:11


OK, but how do I keep things like beakers and flasks from floating, or is the water just not that deep.



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B(a)P
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[*] posted on 14-5-2020 at 17:48


Fill the water bath to the depth of liquid in your reaction vessel.
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Mateo_swe
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[*] posted on 17-5-2020 at 06:42


Dont you have a lab stand, the heavy base with a metal rod that you attach clamps for the flasks, condensers etc..?
If not, just make a DIY one.
If the flask is securely held in place you reduce risk off accidents happen.
Preferely the flask is held securely with clamps on lab stand and the heating bath and hotplate is put on a jack so its adjustable in height.
If you dont have the gear just invent some DIY solution that does the same.
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mackolol
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[*] posted on 17-5-2020 at 11:45


Quote: Originally posted by Chemorg42  
OK, I will probably pick up a cheep kitchen hotplate. Now another question, can I put my glassware directly on the hotplate, or should I put wire gauze between them?


For all my chemical life I have always put my flasks directly onto the surface of the hotplate and it went well I didn't have problems just because it was touching its surface. I used sand baths for some time, but I often had the problem of the flask not touching the bottom of the pot, which resulted in not proper heating. Water bath is impractical in most cases as it only has the temperature of 100C which is quite low.
For now, instead of using baths, I insulate my aparature using aluminium foil and it's really working.
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