Alternative heat mantle question

[Phmatt]

Hello all

I was just wondering if anyone had any do it your self heat mantle ideas for round bottom flasks. I would love to purchase an off the shelf unit with a stir bar but at the moment the money could be better spent elsewhere. I think I read somewhere that a water bath runs the risk of cracking the flask and want to avoid the pitfalls that others have overcome. Thanks in advance for your advice.

 

[4metals]

Yes they are pricey. And when you add in the cost of the heat controller for the mantle it adds up quick. A water bath will crack glass only if there is an extreme temperature shift, like if you run out of water when it is hot and refill it with cold water it may shock the glass.

I have made hot water baths for round bottom flasks by heating water in an appropriately deep stainless steel pan in which I cut up an old polypropylene cutting board into a C shape and made 2 with an indexing crosscut so they slip together to form an X shaped 4 ridge support that sits firmly in the stainless pot, and firmly supports the round flask. Make sure the curved cut allows you to lift the vessel out easily enough. If you are doing this for a larger flask, drill some large holes to make circulation more efficient and eliminate hot spots. The pot then sits on a hot plate. Keep the water level high and you should be OK. (Polypropylene is key because it can get hotter than polyethylene without disfiguring.)

I have made hot water baths like described for vessels as large as 50 liters. Never broke one!

Refining acids don't need much over 150ºF anyway.

 

[4metals]

I just realized it may not be easy to get polypropylene cutting boards but I would substitute wood, certain woods, and it would work as well. Oak, Western Red Cedar, Cherry, Maple are all hardwoods with good water resistance.

 

[Phmatt]

Yes they are pricey. And when you add in the cost of the heat controller for the mantle it adds up quick. A water bath will crack glass only if there is an extreme temperature shift, like if you run out of water when it is hot and refill it with cold water it may shock the glass.

I have made hot water baths for round bottom flasks by heating water in an appropriately deep stainless steel pan in which I cut up an old polypropylene cutting board into a C shape and made 2 with an indexing crosscut so they slip together to form an X shaped 4 ridge support that sits firmly in the stainless pot, and firmly supports the round flask. Make sure the curved cut allows you to lift the vessel out easily enough. If you are doing this for a larger flask, drill some large holes to make circulation more efficient and eliminate hot spots. The pot then sits on a hot plate. Keep the water level high and you should be OK. (Polypropylene is key because it can get hotter than polyethylene without disfiguring.)

I have made hot water baths like described for vessels as large as 50 liters. Never broke one!

Refining acids don't need much over 150ºF anyway.

Thank you for your reply. So are all plastic kitchen cutting boards polypropylene or could they be either polypropylene or polyethylene?

 

[Phmatt]

I just realized it may not be easy to get polypropylene cutting boards but I would substitute wood, certain woods, and it would work as well. Oak, Western Red Cedar, Cherry, Maple are all hardwoods with good water resistance.

You are faster than I disregard the reply to your previous post

 

[Golddigger76]

I have a lot of refining equipment but I do not have a round flask mantle.

I use a stand with a adjustable flash clamp to hold my round bottom flasks above the hotplate.
My stand is one that I made out of a 5"X5" & 2" thick piece of steel that has a 16" long piece of rod welded to it and it is heavy enough to hold any of my round bottom flasks when they are full.

I've also seen the insulators that are made for round bottom flasks that can sit directly on your hotplate.
I can't remember the name of these are right now but Amazon should have several different sizes on the cheap.

 

[Martijn]

Hello all

I was just wondering if anyone had any do it your self heat mantle ideas for round bottom flasks. I would love to purchase an off the shelf unit with a stir bar but at the moment the money could be better spent elsewhere. I think I read somewhere that a water bath runs the risk of cracking the flask and want to avoid the pitfalls that others have overcome. Thanks in advance for your advice.

My El-cheapo fix: Use an old stainless steel cooking pan just a bit bigger than the flask diameter, small layer of dried sand in it, put the flask in it, and fill it up with dried sand to evenly distribute the heat. Cover the pan and top of flask sticking out with aluminum foil if needed for insulation. Put the whole thing on a hotplate to heat. There will be loss of heat, but it works fine and no thermal shocks to the glass!