Sciencemadness Discussion Board

Kicks when boiling solutions

Romix - 10-4-2024 at 05:07

Hello Dear members,
Another good question for you lot, what causing kicks when boiling some
of the solutions, some times they are that bad that beaker or flask is jumping up on a stove.
There is a way to prevent them, chuck some ceramic pieces or specially design things for it, I'm not sure how they are called in English, looked up, can't find the translation.
Ok, the question is how to explain this phenomenon why kicking is happening while boiling the solution. And how pieces of ceramic added in is preventing the kicks?



Romix - 10-4-2024 at 05:14

Here's example, beaker was jumping on a stove that bad that it broke, and all my work to produce this solution spreaded around my kitchen. Also maybe it's could be low quality glass, it's them fat walled pyrex beakers with a handle that sells cheap everywhere... Don't know, don't know been boiling in them many times before the incident, when there were no bumping and it was fine.





387532394_1038028993878814_5654219808954642919_n.thumb.jpg.f2c4b5738b81489aa6e45109d3c8d11e.jpg - 88kB






[Edited on 11-4-2024 by Romix]

Sulaiman - 10-4-2024 at 05:17

The word that you are looking for is 'bump' or 'bumping'
but ir seems that you already know the term.
https://www.sciencemadness.org/smwiki/index.php/Bumping
or https://en.wikipedia.org/wiki/Bumping_(chemistry)


[Edited on 10-4-2024 by Sulaiman]

Romix - 10-4-2024 at 05:21

Quote: Originally posted by Sulaiman  
The word that you are looking for is 'bump' or 'bumping'
but ir seems that you already know the term.
https://www.sciencemadness.org/smwiki/index.php/Bumping
or https://en.wikipedia.org/wiki/Bumping_(chemistry)


[Edited on 10-4-2024 by Sulaiman]

Yes, thank you!

Sir_Gawain - 10-4-2024 at 06:28

The best way to prevent bumping is good stirring. Since bumping happens when liquid near the bottom of the container is superheated above its boiling point, stirring helps distribute the heat throughout the whole liquid and keep it at the same temperature.

Texium - 10-4-2024 at 06:56

Also, definitely don’t heat those “Pyrex” measuring cups. They aren’t actually borosilicate, and aren’t designed to be heated on a stove.

[Edited on 4-10-2024 by Texium]

bnull - 10-4-2024 at 09:58

Quote: Originally posted by Romix  
There is a way to prevent them, chuck some ceramic pieces or specially design things for it, I'm not sure how they are called in English, looked up, can't find the translation. [...] And how pieces of ceramic added in is preventing the kicks?

Boiling chips. They facilitate the formation of bubbles in the solvent (https://www.sciencemadness.org/smwiki/index.php/Boiling_chip).

Pumice stone (like those greyish bricks used by pedicures), being both porous and inert, is a good source of boiling chips. Break it in small chunks, about the size of a rice grain or bean.

You can avoid bumping by good stirring or the use of boiling chips. The choice will depend on the setup you're using--boiling chips for a distillation, stirring for the other cases. And, if the liquid is already bumping, do not--never-- add boiling chips to it; use a stirrer instead.

Sir_Gawain - 10-4-2024 at 13:07

Quote: Originally posted by Romix  

Ok, the question is how to explain this phenomenon why kicking is happening while boiling the solution. And how pieces of ceramic added in is preventing the kicks?

Bumping happens when liquid near the bottom of the container is heated above its boiling point, but can’t boil because there is no nucleation sites for bubbles to form on. Broken pieces of ceramic or glass provide places for bubbles to form.

fx-991ex - 10-4-2024 at 13:13

It happen when heating liquid without stirring or without nucleation site.
Quote: Originally posted by bnull  
Quote: Originally posted by Romix  
There is a way to prevent them, chuck some ceramic pieces or specially design things for it, I'm not sure how they are called in English, looked up, can't find the translation. [...] And how pieces of ceramic added in is preventing the kicks?

Boiling chips. They facilitate the formation of bubbles in the solvent (https://www.sciencemadness.org/smwiki/index.php/Boiling_chip).

Pumice stone (like those greyish bricks used by pedicures), being both porous and inert, is a good source of boiling chips. Break it in small chunks, about the size of a rice grain or bean.

You can avoid bumping by good stirring or the use of boiling chips. The choice will depend on the setup you're using--boiling chips for a distillation, stirring for the other cases. And, if the liquid is already bumping, do not--never-- add boiling chips to it; use a stirrer instead.


Sometime just having a stir bar in there without actually stirring fix the issue(nucleation site). ceramic piece like he said is hard on the glassware.

[Edited on 10-4-2024 by fx-991ex]

[Edited on 10-4-2024 by fx-991ex]

BromicAcid - 10-4-2024 at 13:33

Again, those measuring cups are not meant for direct heat. In addition to boiling chips and stirring you can also sparge gas through the liquid using a capillary tube. If it's non-flammable you can bubble air but to prevent a disaster I'd recommend an inert gas if you're trying to rip off solvent.

B(a)P - 10-4-2024 at 14:57

The good news is that you can use a few of the smaller pieces of your broken jug as boiling chips once you buy yourself some appropriate reaction vessels.
What was it that got spread all over your cooktop and kitchen when the glass measuring jug broke?

Precipitates - 10-4-2024 at 18:25

Pretty bad if pyrex isn't borosilicate as advertised everywhere as this.

I've heated solutions in pyrex jugs for many years and never had any problems.

I've found them to have less bumping than typical beakers, so have preferred them at times for voluminous solutions that I need to boil for a long time - but, with that being said, I never use them for boiling expensive reagents or those that have been hard to synthesise, in case of dramatic failure.

If extreme bumping occurs, boiling chips definitely need to be used, or, the solution needs to be gently heated (without boiling). If the beaker is jumping around the stove it will break, doubtless regardless of the material.

Edit: On further reading it depends if its pyrex (soda-lime) or PYREX (borosilicate)

Will have to check mine when I get home! :o

[Edited on 11-4-2024 by Precipitates]

Sir_Gawain - 10-4-2024 at 18:27

Pyrex used to be borosilicate; they recently changed to cheaper soda-lime glass.

Texium - 10-4-2024 at 18:38

Pyrex branded lab glass is still excellent quality borosilicate. The brand was originally produced only by Corning and was synonymous with borosilicate, but at some point they spun off the kitchenware side of the business, and now Corning only produces Pyrex lab glass and the kitchenware is made by an entirely separate company, confusingly using the same brand name.

Precipitates - 10-4-2024 at 18:56

Yeah that is really confusing! A big difference in quality depending on whether its pyrex or PYREX.

And I'm sure there are lots of people paying more for pyrex, because they think it's a premium product.

Romix - 10-4-2024 at 23:00

Quote: Originally posted by B(a)P  
The good news is that you can use a few of the smaller pieces of your broken jug as boiling chips once you buy yourself some appropriate reaction vessels.
What was it that got spread all over your cooktop and kitchen when the glass measuring jug broke?


Water soluble Potassium compounds out of plant ash after the incineration of salt with MAPP+ to make it colorless. Took me many BBQs to collect all the ash used...

Romix - 10-4-2024 at 23:15

Now I'm evaporating the water off of the salt in the same stainless steel crucible that I've incinerated it in after filtering off all decomposition products. No risk of breaking.

dettoo456 - 11-4-2024 at 06:58

You should have something unreactive in your process vessel in almost any scenario anyways, even if it doesn’t require agitation. Steel won’t fail catastrophically due to thermal shock but boiling liquids in it can still superheat if no nucleation point is made. It’s like boiling water in a clean bowl in a microwave, if there’s no nucleation point in the bowl but the water gets super hot, it’ll instantly flash-boil when even slightly agitated.

I’d either make a good, deep scratch in the steel vessel (less advisable) of just lean a stir rod into it; it could be glass or metal or something generally inert to heat and chemical media.

[Edited on 11-4-2024 by dettoo456]

Morgan - 11-4-2024 at 07:10

I recently got a new borosilicate carafe and PYREX measuring cup in the mail as a gift. Funny though the pint markings are imperial ounces so that it's more than a U.S. pint.
Here's a company that sells PYREX cups.
https://www.pyrexae.com/products/classic-glass-measure-jug-h...

Rainwater - 11-4-2024 at 08:40

If you dont want to use boiling chips, attacking the inside bottom of your boiling vessel with sand paper and making deep scratches will help, its ugly, but cheap, effective and works on more than just glass tho tuffer to clean/collect product from.

Precipitates - 12-4-2024 at 06:10

I second (or third?) that. Part of the reason my PYREX jugs don't really bump is probably because they are getting old, and are heavily scratched now. Yeah looks horrible compared to a nice shiny new jug, but seems to do the trick.

Sulaiman - 12-4-2024 at 23:53

Bumping can be pretty violent sometimes,
but I don't think that was the main cause of failure.
I suspect that thermal stresses were the primary problem.
Try using a shallow pan with less than an inch deep sand,
Heating up and cooling down will be much slower,
Boring, but better for the glass.

PS If there is a future breakage the pan can hold the spilled liquid.

Also,
If you have a small air pump, (eg aquarium type)
bubbling air via a small/capillary opening (to give a continuous stream of tiny bubbles)
helps to prevent bumping and gives some mixing.
Not suitable if atmospheric oxygen, moisture or carbon dioxide would interfere with the experiment.
and
I found that using boiling chips for a second run is not very effective unless the chips are dried between batches.
May just be an anomaly that I had, but it makes sense, so probably worth doing.

Not least - I don't like scratching my glassware.

[Edited on 13-4-2024 by Sulaiman]

bnull - 13-4-2024 at 06:17

Quote: Originally posted by Sulaiman  
I found that using boiling chips for a second run is not very effective unless the chips are dried between batches.
May just be an anomaly that I had, but it makes sense, so probably worth doing.

"Boiling chips cannot be re-used since the pores inside these stones become filled with liquid on cooling."[1] Honestly, it's more like "should not" than "cannot". Unless you're boiling something that generates tar as the procedure nears the end or you want to reuse them in other different procedures, letting the chips rest overnight under a bit of the same solvent, drying and heating them to drive off the liquid rejuvenates them. You're right, it makes sense.

By the way, what kind of chips do you use? Store bought or homemade? (Edit: Nevermind.)

Are you still using stones from the garden?

[1] https://orgchemboulder.com/Technique/Procedures/Distillation...

[Edited on 13-4-2024 by bnull]

Sulaiman - 13-4-2024 at 07:02

Quote: Originally posted by bnull  
By the way, what kind of chips do you use? Store bought or homemade? (Edit: Nevermind.)

Are you still using stones from the garden?

Yes, and for sulphuric acid distillation I used some of those stones,
the ones that tested inert to cold sulphuric acid.
I noticed no obvious loss of mass after distillations.
It was those stones that failed during a second distillation.
Scared the cr@p out of me!
(no harm done but I imagined what could have happened - terrifying really)
Nevertheless, I have another H2SO4 distillation planned for 'quite soon'

bnull - 13-4-2024 at 15:25

Have you ever tried sand? Fine silica sand, after a digestion with hot concentrated acid to remove attackable impurities, should work well.

Edit: Vogel's take on superheating, bumping, and boiling chips is attached.

Attachment: Vogel's - Superheating and bumping.pdf (555kB)
This file has been downloaded 198 times

[Edited on 14-4-2024 by bnull]

Conure - 26-7-2024 at 07:45

I had a bump yesterday when trying to evaporate my first solution of NH4NO3! I got scared! :o

fx-991ex - 26-7-2024 at 08:10

For NH4NO3 i drive most water out on hotplate with stirring then when almost all the water is out(usually temp start rising), i just set the hotplate to keep the sln at around 90-95C with a fan blowing on it.
It take a few hours but i get a very dry product this way.(i usually do that in the cold canadian winter, when humidity is very low.)

Its best to manually mix it once in a while on the last stage, dont want a solid cake at the bottom of beaker that you cant take out and have to redissolve.
Or use evaporating dish.

[Edited on 26-7-2024 by fx-991ex]

Deathunter88 - 26-7-2024 at 21:56

Lots of terrible advice being thrown around this thread, I must say. You should never intentionally scratch your glassware just to avoid bumping, you are just asking for your glassware to break (ever looked into how glass is "cut", you score the glass and then it breaks like crackers). In fact, my lab throws away any beaker or flask that is scratched.

No matter if a measuing cup is made of borosilicate or soda lime, it should never be heated on the stove because the shape is not made to handle the thermal stress and the glass itself is too thick to expand evenly.

Finally, using any old broken ceramic or glass for boiling chips is also not recommended, since they themselves can scratch the bottom of your glassware leading to the same issues as mentioned before.