Deo - 15-12-2024 at 17:56
I recently purchased one of these hotplate stirrers for a pretty hefty discount.
https://www.amazon.com/FOUR-ES-SCIENTIFIC-Magnetic-100-1500R...
Although I have noticed that it is quite slow at boiling water. It certainly is powerful enough to boil the 200 mL of water I was testing it with,
after all it has a 600W heating element. But after waiting like 20+ minutes it wasn't boiling. Does anyone else have experience with one of these
hotplates? Are yours also this slow
or is mine broken?
BromicAcid - 15-12-2024 at 18:56
It has good reviews but honestly sounds pretty weak and like it was written by someone that has never used a good hotplate before:
"Tips: Put a glass or tinfoil lid over the mouth of a beaker before heating to speed the heating. Please keep the room temperature above 25 ℃ / 77
℉ during heating. Please note the lid, or tinfoil, needs to be left with a cooling hole to prevent cracking "
"Long-lasting equipment: Brush DC motor is maintenance-free and ensures a long lifetime. Continually run for 168 hours." I routinely leave things
overnight, sounds like it would burn out in a week.
"If requiring a high temperature above 100℃, we suggest a smaller capacity under 500ml liquid to heat. 500ml water can be boiling to 100℃ from
room temp in about 1 hour." An hour to boil, is that on high? Seems to be inline with what you said above.
They also have a chart of Stirrer Experimental Test Data which looks like nonsense. Like it takes 70 minutes to make 1000 mL of water homogeneous.
Deo - 15-12-2024 at 19:36
Tbf I got this hotplate for 40 bucks off an auction on eBay, so I can’t really complain. I did notice that it actually heats up really quickly like
from RT to 80 is degrees then it spends the majority of the time trying to get it up to boiling. I dont think it’s an issue with the heating element
Itself but maybe the heating algorithm or sensors
[Edited on 16-12-2024 by Deo]
BromicAcid - 15-12-2024 at 20:16
If it works then it works. Water can be a chore for most heating elements - the specific heat of water is 4.186 J/g°C which is about double of most
solvents. I hate stripping off water after a reaction because it just takes so much to get it going. I've had mantles glowing red before due to my
impatience.
Assuming you're using a beaker so you get a lot of surface contact and not just suspending a flask over it with a clamp? I mean, I cover pans when I
am boiling on the stove or use a watch glass to cover a beaker to keep in the liquid so it might be worthwhile to cover it. If you really want to
push things along get some fiberglass mat and wrap it around the beaker and put some wire around it to hold it in place to insulate it.