Archive for February 20th, 2015

February 20, 2015

A difference worth noting…

by Janie Jones

So, when you are using a hotplate that also functions as a magnetic stirrer, and you *think* the instructor says set the heat to high, but you notice that your dial reads degrees, and you are wondering what is considered ‘high,’ it is worth noting that your neighbor, who the instructor has already helped set her hotplate temperature, has the heat setting knob on the right, instead of on the left like yours. So when you glance over to see what temperature hers is on, you are actually looking at the speed of the magnetic stir. Of course you think it is a bit strange that your heat only goes to 550, when your neighbor’s is set to 700, but maybe that’s not degrees but just numbered settings. After all you’ve had stoves that are numbered with settings 1-10, and not showing degrees. And, the instructor has moved on to talk about something else so you just turn the knob all the way up and turn your attention to what ever else is going on.

Now, it’s not until after the 1 liter flask goes all Mt Vesuvius that you realize that it wasn’t the temperature knob you were looking at at all. While it was pretty cool to see 500 mL of solution spew a good 10 feet into the air, it’s not so cool to be the one responsible.

How.  Very.  Embarrassing.

I suppose it could happen to anyone. And yet, it never happened before in all the years that lab has been taught.  Thankfully no one got hurt.

So, learning experience.  A ‘high’ heat setting is not the same as 700 rpm.

Also good to note:  our lab has 3 different types of hotplates with magnetic stirs. Two of them are even made by the exact same company and look almost identical, but their knobs are reversed.

You all see the important difference now?

You know I do.