Sciencemadness Discussion Board

Mechanical stirrer

Odyssèus - 4-11-2006 at 17:55

I am having trouble finding any suppliers of mechanical stirrers. I need one that will fit to a ground glass joint. I dont know what size yet because I havent bought the flask yet.

I am trying to put together a distillation apperatus, this is what I'm looking at buying:

2-neck RB flask 500ml
500ml heating mantle
RB flask 250ml
200mm Liebig condenser
Vacuum adapter
3 way adapter
Thermometer adapter
0 - 400 C thermometer
Mechanical stirrer

I am leaning towards going with 14/20 joints. I would rather have a 1-neck flask and a heating mantle with a built in magnetic stirrer but I cant find that either.

This is frustraiting... I'm alredy going to have to order this stuff from 4 different suppliers just to get everything.

Magpie - 4-11-2006 at 21:02

Since this is a fairly sizeable and longterm investment you are contemplating, I would try to make it as generally useful as possible.

14/20, in my opinion, is pretty small for a general setup. I recommend 19/22 or 24/40 joints. Also, getting a shafted stirrer that will fit down a 14 mm hole might be tough.

I have never really required a mechnical stirrer on a shaft. I use a magnetic stirrer driven by a stirrer-hotplate. I can even use this for stirring by resting a heating mantle on the hoplate and leaving the hotplate off.

Odyssèus - 4-11-2006 at 21:33

Hmmm, so even if the hotplate is a couple inches away from the stirbar it still works? I wouldve thought the range would be much shorter.

Magpie - 5-11-2006 at 10:27

Yes. I just made a test using a 1" stir-bar, a 500mL mantle, a 250mL flask, and a Corning PC-320 stirrer-hotplate. The bar was spinning fast (in air) up to a distance of about 2 inches between the hotplate and the bar. But in practice you don't need it anywhere near that far away.

bio2 - 5-11-2006 at 10:34

...... if the hotplate is a couple inches away from the stirbar it still works? ........

Yep, except the torque and speed control suffer the farther
away it is.

My 12' stirrer/hotplate will spin a magnet 4-5 inches away
but the torque is pretty useless at that point.

armo - 9-11-2006 at 15:31

Hi bio2, sometime ago I made a small mechanical stirrer by using the electric motor inside the credit card machines. I found several on a surplus store. If you find one, you will need just a variable 12 V power supply. Changing volotae changes speed and torque. As they are bilt with a small reduction gears you have a fair amout of torque.
armo
Quote:
Originally posted by Odyssèus
I am having trouble finding any suppliers of mechanical stirrers. I need one that will fit to a ground glass joint. I dont know what size yet because I havent bought the flask yet.

I am trying to put together a distillation apperatus, this is what I'm looking at buying:

2-neck RB flask 500ml
500ml heating mantle
RB flask 250ml
200mm Liebig condenser
Vacuum adapter
3 way adapter
Thermometer adapter
0 - 400 C thermometer
Mechanical stirrer

I am leaning towards going with 14/20 joints. I would rather have a 1-neck flask and a heating mantle with a built in magnetic stirrer but I cant find that either.

This is frustraiting... I'm alredy going to have to order this stuff from 4 different suppliers just to get everything.