Sciencemadness Discussion Board

Kitchen Hot Plates

DangerousStudent - 11-4-2013 at 13:34

Hi,
I need a hot plate, but as I am on a very tight budget, I was thinking of just using a kitchen hotplate off eBay to start with. Does anyone have any experience with these el cheapo hotplates, or is it worth investing in a more expensive one, and leave less cash for other stuff?
Thanks,
Ben

Mailinmypocket - 11-4-2013 at 13:45

They work okay for heating, they just aren't very stable in their temperature control (in my experience anyways) but for the most part, they do an okay job, considering the cost. You might be able to snag a real one on eBay or on the forum for a reasonable (albeit higher) cost....

I have an older PMC hotplate stirrer combo that I'm willing to give away. All I ask is that whoever wants it pays the shipping, which... Given its heavy duty build, might be quite a bit. If love to give it to somebody here but I'm afraid of how much shipping would be...

DangerousStudent - 11-4-2013 at 13:49

How Much for shipping to the UK?

Mailinmypocket - 11-4-2013 at 13:53

Quote: Originally posted by DangerousStudent  
How Much for shipping to the UK?



Ill have to weigh the darn thing, the body is very heavy, but it lasted me for years before I bought my new one. In the UK... Ouchhhh... Ill check

It does look used, but it's tough as nails.



image.jpg - 60kB

chemcam - 11-4-2013 at 13:55

I would be interested as well. I'm in USA, specifically Oregon.

DangerousStudent - 11-4-2013 at 14:04

Oi, This one's Mine.:D By the way, Do you have any idea as to why it would be so heavy. Really big magnets?

Mailinmypocket - 11-4-2013 at 14:04

Okay, well I will weigh it later tonight and then see what costs you guys would be looking at. It's been sitting on my shelves for almost a year unused now, the only reason I've not put it up on SM yet is that I'm afraid of shipping costs. US would be cheaper than overseas but ill let you know either way.

Mailinmypocket - 11-4-2013 at 14:07

Quote: Originally posted by DangerousStudent  
Oi, This one's Mine.:D By the way, Do you have any idea as to why it would be so heavy. Really big magnets?


You've got dibs on it no worries, just wait until I look into shipping though, you may change your mind. The body is made of cast metal(not aluminum). It's just built really heavy duty for some reason.

DangerousStudent - 11-4-2013 at 14:08

Industrial usage maybe?

chemcam - 11-4-2013 at 14:10

Quote: Originally posted by DangerousStudent  
Oi, This one's Mine.:D By the way, Do you have any idea as to why it would be so heavy. Really big magnets?


I know you have first dibs. I'm just letting my interest be known. I currently use a kitchen type hot plate and it works like it should but temperature control is awful.

Mailinmypocket - 11-4-2013 at 14:11

It came from a lab closing sale (government operated oilseed research lab)

Edit: the weight is a bit under 10lbs. With packing and all, I'd say perhaps around 11ish lbs. I still need to determine costs, for anyone interested u2u me your address (or approximate address) and I can give a fairly good idea of the cost.


[Edited on 11-4-2013 by Mailinmypocket]

elementcollector1 - 11-4-2013 at 14:38

Quote: Originally posted by chemcam  
I would be interested as well. I'm in USA, specifically Oregon.

Hey, I'm in Washington!
Already borrowed a hotplate from the school, so...

DangerousStudent - 11-4-2013 at 14:49

With these kitchen hot plates, the problem is temperature control. My guess is they are passing AC straight through a variable resistor into some nichrome wire, potentially with some very basic logic to maintain a constant temperature. Do you think that a homebrewed temperature controller would be hard to design?

chemcam - 11-4-2013 at 15:49

Mine certainly does not maintain any temperature it fluctuates up to a certain point then switches itself off until it reaches another set point and goes back on. Its never at one temp more than a minute so I am constantly adjusting the knob. I would think if I installed a more sentitive pot and temperature gauge it would greatly improve its functionality. I knew that for $15 it would suck but it is barely better than holding a magnifying glass up to the sun.

Mailinmypocket - 11-4-2013 at 16:14

To the UK...I think You might be better off on eBay or with a good kitchen hotplate! Wow... Ridiculous price, $82.11 for regular parcel, after that? $142.00 for 4 day delivery.

Of course, if you want it it's yours. I personally wouldn't though, that's the smallest best packed box I could make and the shipping seems very high.





[Edited on 12-4-2013 by Mailinmypocket]

Sciocrat - 11-4-2013 at 21:20

I use a kitchen hot plate for most of my experiments, however there is almost no temperature control, except for manual turning on and off, along with monitoring the temperature closely. I would love to have a real lab hot plate, but these are unfortunately very expensive where I live.

DangerousStudent - 12-4-2013 at 00:56

I think I'll leave it. Thanks for your time. With these kitchen hotplates, do they have a microcontroller?
If so, it shouldn't be hard to reprogramme to stop it cutting off? Has anyone here tried anything like this?

Finnnicus - 12-4-2013 at 01:01

Oh man, I forget the guy, but someone had 'the best Hotplate' or something. Turned out to be an upside down iron (like for clothes), anyone know who? I loled.

Edit: was the 'worlds most famous', I nearly fell off my chair.

[Edited on 12-4-2013 by Finnnicus]

DangerousStudent - 12-4-2013 at 02:38

Ha, suppose it would work.

confused - 12-4-2013 at 03:23

...i dont mind it, but my parrents don't approve of me spending so much cash(even if its just shipping) on my hobby
Btw, what would the shipping be like to singapore?

DangerousStudent - 12-4-2013 at 04:34

I have a cashcard from HSBC, and have my bill sent by email. Thus way, my parents have no say on what I can buy with my own money (I.e, they don't know). You might want to do the same, confused. You can get one when you are 13. They are awesome:cool:

Carharttguy - 12-4-2013 at 05:13

If you're just a starter, it shouldn't be to expensive. Altough it's indeed harder to control (or maintain) temperature.

I got my first boiling plate from a second hand store, paid 8 euros for it. It does the job :) (but I'm also a beginner)

confused - 12-4-2013 at 05:17

I have one, but the statement still comes via mail at the end of the month...thats when they kick up a fuss
...also, im sort of hesitant to spend so much cash...already used up $200+ on a fractional distillation setup...shipping's a killer:(

DangerousStudent - 12-4-2013 at 06:50

If you sign up for Internet banking, I think you no longer receive a statement. I'm also building a distillation rig. I am hoping to distill limonene.

confused - 12-4-2013 at 07:05

you mean something like this?
part 1 http://www.youtube.com/watch?v=fVZRnVKqkgw
part 2 http://www.youtube.com/watch?v=bMFt1lOmlQ4
what do you think the anti-foaming agent is?

DangerousStudent - 12-4-2013 at 09:01

It all depends what limonene is soluble in, because there are water and oil based anti-foaming agents.

Quick Note. Say we had some substance that needed distilling, If we put a thick layer of less dense liquid on the top with a higher boiling point, would it stop the bottom liquid from forming bubbles. Might need to do something about the less dense liquid splashing out. Any thoughts?

confused - 12-4-2013 at 09:38

i dont think so, the bubbles is the gaseous state of the substance that you are distilling...so i dont think that it'll work

or i may be completely wrong...its late and i might not be thinking straight:D

[Edited on 12-4-2013 by confused]

DangerousStudent - 12-4-2013 at 10:33

Sorry, not bubbles, foam. I was thinking that the top liquid (naturally not foaming, say oil) would stop the liquid layer around the gas from forming. I did prepare an experiment with oil and water (with fairy liquid as a foaming agent), but all I got was an emulsion:mad:.

confused - 12-4-2013 at 10:42

because soap emulsifies the oil, making it soluble in water

I'm pretty sure the emulsion will still distill though, if you put a few drops of mineral oil into the substance, it will probably stop, or at least reduce the amount of foam in the substance

[Edited on 12-4-2013 by confused]

DangerousStudent - 12-4-2013 at 11:16

Confused, I believe that we are talking about two completely different things.

confused - 12-4-2013 at 11:24

sorry...what were you asking again?:P

[Edited on 12-4-2013 by confused]

DangerousStudent - 12-4-2013 at 13:48

About using a secondary liquid, on top of the liquid to be distilled, to prevent a foam from forming.

confused - 12-4-2013 at 18:21

That should work although you can just as easily use a few drops of silicon or mineral oil to reduce the surface tension thus inhibiting the foam from forming

Edit: found another post discussing the same thing
https://www.sciencemadness.org/whisper/viewthread.php?tid=23...

Edit, did a few experiments, oil seems to work to a certain extent, but alcohols like isopropanol and ethanol seem to work well, of course there may be a few flaws in my setup, so you might want to try it out for yourself

[Edited on 13-4-2013 by confused]

DangerousStudent - 13-4-2013 at 00:19

I fear that alcohols will have a too low boiling point.

confused - 13-4-2013 at 00:56

or you could just distill it twice

DangerousStudent - 13-4-2013 at 01:15

Ethanol forms an azeotrope with water. You distillates might get contaminated.

confused - 13-4-2013 at 01:26

well, stream distillation appears to work well as long as you watch the heat and boiling chips are used to prevent bumping, if you want to further purify it just distill it further
http://goo.gl/eXFLs

[Edited on 13-4-2013 by confused]

DangerousStudent - 13-4-2013 at 01:32

No good for inorganic stuff

confused - 13-4-2013 at 02:07

well, steam distillation appears to work well as long as you watch the heat to prevent foaming and boiling chips are used to prevent bumping, if you want to further purify it just distill it further

http://goo.gl/eXFLs

DangerousStudent - 13-4-2013 at 03:58

Just wondering, how long is your condenser and fractionating colum.

confused - 13-4-2013 at 07:42

well, my glassware hasnt been delivered yet,
i ordered a 400mm liebig condenser and 300mm vigreux column
but in the meantime, my school's lab tech has been kind enough to let me use some of the glassware that he has:D

[Edited on 13-4-2013 by confused]