Source
r/DMTlab•
Lagrange91

Questions regarding the heating of glass

NSFW

Due to a recent incident I experienced where the bottom of a glass beaker broke off (luckily during the acid phase, a big mess nonetheless) I want to expand my knowledge regarding the proper use of glassware. So if you have some best practices you can share I would be very happy. Furthermore I now bought more expensive quality glass beaker (Schott Duran). Reading deeper into their specs I found some guidelines. It is written that the Temperatur for long heating periods should not be above 350deg C. Though for short spans one might go up to 500deg C. But the maximum temperature difference between two points of the beaker should not be bigger than 100deg C. My heated stirrer allows to set the temperature of the heating plate. But for an aqueous solution one can hit a maximum temperature of 100deg C obviously. So should I raise the Temperatur of the heated stirrer correspondingly to the temperature of the aqueous solution with a maximum difference of 100deg C (up to maximum of 200deg C)? Or can I heat at 350deg C from the beginning? I just want to make sure to keep the glassware as long living as possible. Thanks for any input.

Posted Mar 6, 2021, 11:23 AM UTC

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ExplorerOfLife•

I read you should put an old towel or some material with poor thermal capacity in between, when the inside is very how and it stands on a stone table for example that would be a problem. Just avoid big gradients for example a cold table and a hot soda lye inside.

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Lagrange91OP•

Thats a good idea, thanks for the input.

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norolindaModerator•

Schott Duran is marvelous glass, good choice. u/grammorphone can personally attest to its quality.

The temp recommendations are really more geared towards heating mantle use on an empty flask, not hot plate with a filled beaker. Your hot plate will probably never heat the glass past 350 C on its best day, and definitely not if there’s liquid in there.

Your hot plate really has TC? I just finally bought a (digital) stirplate with true TC and a probe and it cost me $600 used. I’d keep an eye on the temp of the plate with an infrared thermometer.

But breaking beakers with plates definitely isn’t unheard of; it’s pretty common actually, even in real labs. Most plates easily hit 500 °C at max and can totally shatter glass if you don’t wind it up slow-ish.

Setting to 350 C seems a little high, try like 275. Make sure it’s actually 275 with a thermometer. It takes one hell of a plate to get good TC.

For reference on my TC plate, i set it without the probe to 150 °C (it hits probably 140-165 °C at the center in practice), then after it heats the glass for a bit I put in my immersible probe, otherwise it just sets the heat to max and shatters glass. Set it to like halfway maybe until the solution is warm, then bump it up until it hits the temp you want.

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Lagrange91OP•

Thanks for your elaborations, I guess I may have been a bit optimistic on what plate temperatures are fine for my beaker. I will try out your suggestions and keep the temperature a bit lower. Btw this is the hotplate setup I recently bought: https://www.ika.com/en/Products-Lab-Eq/Magnetic-Stirrers-Hot-Plate-Lab-Mixer-Stirrer-Blender-csp-188/C-MAG-HS-7-Package-cpdt-9015900/ It works really well and feels like it is pretty accurate with the temperature. One can even buy a probe with an integrated ph meter additional to the temperature meter but that would really have blown my budget.

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norolindaModerator•

Shit that’s actually a really good stir hot plate, nice purchase. Better get some good use out of that; you can’t give up on chemistry now!! I don’t doubt the temperature is accurate on that. I have a friend who has I think that exact model, good stuff.

I have a Corning PC-620D https://chemglass.com/pc-620d-hot-plate-stirrers-digital-10in-x-10in-corning

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Lagrange91OP•

I’m very happy with that purchase and love to work with it. Yours looks very nice as well! From the background of my studies I just love good laboratory equipment (though it’s expensive as hell). And no worry I really developed a deep intrinsic interest in the process. I may not have studied chemistry but come from another corner of natural sciences. Therefore I love to optimize and this is why I love this sub. One can get detailed information on every step from nice people. You and the other mods (as well as other people around here) are really competent. Thanks for that.

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grimlid•

When does DMT require these temps? Ive never gone over 50 or 60c except on a boil out.... maybe I'm missing something, or is this just hypothetical info...?

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Lagrange91OP•

Its just the temperature of the hot plate and defines how fast the aqueous solution is heated up. A separate thermometer tells the hotplate when the target temperature is reached and it stops heating. So for acid boils I aim for a maximum temperature of 100deg C of the aqueous solution, above would not be reachable anyway ;). Most of the time I used it at the same temperatures you mentioned. If I set the temperature of the hotplate to „only“ 50deg C it would take mich longer to reach it as when I heat up the aqueous solution to 50deg C with a temperature of the hot plate for example at 100deg C. The rest of my question is to get a feeling what is possible to reach using proper glass ware without to damage it.

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grimlid•

Thanks for the clarity. I appreciate the reply. I've been using water baths my hot plate is still in the box.

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Nataschrist•

Pyrex is where it’s at as far as I know.

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norolindaModerator•

Pyrex is a kind of glass, much like Kimble-Kimax, but not a brand. Schott-Duran has their own kind of glass distinct from Pyrex and Kimble.

I think there is an actual brand called PYREX, and Corning advertises themselves as “Corning Pyrex,” but it’s so confusing tbh. I like Kimble glass personally, I go for ChemGlass brand. I like Ace glass a lot, they use Duran glass. Not a huge Pyrex fan, but I do have a custom solvent still that’s Pyrex and I love it.

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Nataschrist•

Ahhh. I just said Pyrex because every lab I’ve ever worked in has pretty much had all Pyrex glassware.

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norolindaModerator•

Generally brands that use Pyrex glass write it on their glass. Some are unbranded but have Pyrex written on it too? Pyrex is so confusing, it’s one of the reasons I stick with Kimble-Kimax.

A lot of labs have Pyrex because the glass is so widely renowned. But Ace and ChemGlass are big names in labs too

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Nataschrist•

Thank you for the info, I really appreciate it actually. Looking to purchase some new glassware. What would you recommend? If that question is not allowed please strike it from the record.

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wheresmywanksock•

PYREX (note the capitalisation) is indeed borosilicate glass. Pyrex may not be.

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norolindaModerator•

Pyrex is a kind of lab glass used by many brands. There is a brand of kitchenware called Pyrex, but it’s not made of Pyrex lab glass. Many brands use Pyrex lab glass, such as Corning, but it’s not a brand itself. PYREX is a brand that uses Pyrex glass, which is really confusing. Corning is a good example of a quality Pyrex manufacturer.

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wheresmywanksock•

It gets confusing because US, South America and Asian Pyrex is different from European PYREX. You goddam Yanks, haha.

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