[Bushinryu]

I'm not sure if this section is the appropriate one to put this question in, but it seemed like the right place so I hope no one minds.

I've always used digital hotplates in my work rather than heating mantles due to the price difference, but I've decided to try purchasing a mantle or two in different sizes to make use of the benefits they carry over hotplates--such as avoiding scorching certain heat-sensitive matters, for instance--now that I've found some suppliers here in Asia that have some decent prices.

However, as I'm a complete noob when it comes to heating mantles and the use thereof, I need to ask some elementary questions that may seem somewhat silly in here. But please bear with me and my lack of experience with this equipment thus far.

The newly arrived mantle which I set up in the lab today appears to be a bit big for its flask size. It's a 500 ml flask mantle and it may just be my misunderstanding, but I was under the impression that heating flasks are supposed to fit rather snugly into a heating mantle, thus resulting in as much physical contact between the mantle and the flask body to ensure good, even heat distribution. However, upon placing a 500 ml round-bottomed boiling flask into the mantle, I immediately noticed how former actually did NOT fit snugly into the latter; there's quite a bit of "air" around the body of the flask and the inside of the mantle and I'm wondering if this is normal and it's supposed to be like this, of if this is actually due to a poorly designed heating mantle or a flask of "incorrect" standard body-sizing with relation to its capacity.

I've added a couple of photos to try and show you what it looks like...

Is it supposed to have this much "air", or space, around the body or am I right and the entire body of the flask is supposed to be in direct contact with the inside of the heating mantle?

Any help will be greatly appreciated!

[tomek]

From my perspective heating mantles should accommodate RBF (round bottom flask) rather snugly. Otherwise you're not getting efficient heat transfer and you probably will need to set it up to much higher temperature. I assume it will to the job fine though. If you're planning on purchasing more of these I highly recommend getting those that come with stirring. In my work we use Heidolph stirring hot plates that allow you to use different heat-on attachments to accommodate different sizes of RBF, set up stirring rate and heating temperature (digitally). They're bit pricey but worth every penny. I only wish they come with a cooling feature

[Bushinryu]

From my perspective heating mantles should accommodate RBF (round bottom flask) rather snugly. Otherwise you're not getting efficient heat transfer and you probably will need to set it up to much higher temperature.

Exactly what I was thinking, too. I contacted the company that sells these heating mantles and the guy in charge told me that the inside dimensions of the heating mantles in China are all of a standard size and so it should technically fit. So I'm considering the possibility that the flask I put in the mantle might be of "non-standard" dimensions (though I'm unsure on exactly how much "off" a 500 ml round-bodied flask can be). So I'm thinking of possibly purchasing another 500 ml RBF and see if that changes anything.

I assume it will to the job fine though.

That's what that Chinese company said, too, so I'm gonna give it a test run next week, once I've had time to go to the local electronics store to pick up a plug adapter (I purchased the mantle they sell that uses the same voltage as here in Japan, but the Chinese plugs are still different so I'll need an adapter before I can try it out). Then I'll report back what the results were.

Incidentally, I've seen some various college lab videos in which demonstrations have been carried out with flasks that appeared to be way too small for the mantles (such as a 250 ml flask in a 500 ml mantle), so apparently this is not uncommon practice. But still... like you said, for optimal heating efficiency, a snug fit should be the case for maximum contact surface and thus uniform heating.

If you're planning on purchasing more of these I highly recommend getting those that come with stirring.

Well, I've never purchased hot plates or any other such with a stirring function as I've always used porous boiling chips and I assume that the general purpose of a stirrer & stirring rod is the same as any kind of anti-bumping means. Is there any other reason why a hot plate or heating mantle with a stirrer is better than one without?

In my work we use Heidolph stirring hot plates that allow you to use different heat-on attachments to accommodate different sizes of RBF, set up stirring rate and heating temperature (digitally). They're bit pricey but worth every penny. I only wish they come with a cooling feature

Thank you very much for the tip, as well as for your overall comments on this thread. I greatly appreciate it. I'm gonna take a look at the Heidolph stirring hot plates.

[curiouscat]

Well, I've never purchased hot plates or any other such with a stirring function as I've always used porous boiling chips and I assume that the general purpose of a stirrer & stirring rod is the same as any kind of anti-bumping means. Is there any other reason why a hot plate or heating mantle with a stirrer is better than one without?

If you have a two phase reaction or solid catalysts or solid reactants or a viscous medium stirring becomes essential.