Hello everyone, this is my first post on the forum.
I've got a bit of theoretical knowledge in general chemistry but not much practice, I'd like to have a bit of fun and learn more while doing it
So I'm getting a basic chemistry setup going and bought a magnetic heater - stirrer.
While the stirring works just fine the heating seems to be really low power or defective, because after 50 minutes I could not get 200 mL of water to
boil.
It's supposed to be 180 Watts...
I should send it back right ? Or does that seem normal for this power output ?Sulaiman - 17-2-2023 at 20:27
180W is good for keeping solutions warm or hot but not for boiling.
The heat loss from the hotplate and the beaker may be more than 180W at 100oC,
So thermal insulation may be required just to reach 100oC (eg aluminium foil)
The heat of vapourisation for water is 2257J/g
So if the hot plate and beaker are well insulated
(all of the heat goes to boiling)
180W could boill off 180/2257 g/s = 0.08 grammes/second,
That is more than 20 minutes to boil off 100 ml (1ml = 1g) of water.
So there is nothing wrong with your hotplate stirrer
it is just under powered for your requirements.
My favourite heaters are heating mantles, but they aren't cheap.
For several years my main heater was one of these https://www.ebay.co.uk/itm/225427887170
A typical generic 1500w electric hotplate.
(after I finally killed it, I bought a cheap used dual hotplate)
It would be better with stirring but it was good enough for several years of experimenting, including distillations.
I would agree that it is underpowered. I've used a hot plate stirrer by IKA before to boil solutions up to 1 L, and I see that that specific model is
1 kW. I probably wouldn't recommend anything below 750 W, or else you could wait a long time for it to get up to temperature.Tsjerk - 18-2-2023 at 07:22
Yes, and when you use insulation to get things to boil you fry the magnet. Cathoderay - 19-2-2023 at 09:00
Yes, and when you use insulation to get things to boil you fry the magnet.
That is not necessarily true.
It depends on the magnet material. Common (and cheap) neodymium magnets can lose their magnetism at as low a temperature of 80 degree C. https://www.jobmastermagnets.com/how-does-temperature-affect...
Most of the time when stir bars are sold the material type is not specified. Mateo_swe - 20-2-2023 at 06:25
So many hotplate stirrers that are just no good.
I have one of these orange Maple Scientific hotplate stirrers and it works ok.
But they cost a bit more, you get what you pay for.
There are probably better ones for more $$$.
An option if you have a variac is to use a heating mantle sleeve, they are cheap.
These are just the replacement heating element for heating mantles with the surrounding glassfiber insulation.
Works perfect to place on a hotplate stirrer and use the stirring function while heating with the sleeve.
But be careful with live AC voltage.