Sciencemadness Discussion Board

Borosilitate glass broke on heating

underground - 25-5-2018 at 10:01

I bought some battery acid (30% H2SO4) and i was trying to concentrate it. I used a tripod and above it, an iron plate, so the glass will come in contact with the plate and not with the flame. I wanted to do it outside that is why i did that, i could not do it close to my home cause of the fumes and it is a bit populated area.

During the concentration phase, my glass cracked. It was a 5L beaker. Anyone have any idea why this happened? I cant buy nowadays 98% SA without an invoice unfortunately, so that was my only way to get it.

Also if anyone have any page so i could buy chemicals online from Europe, pls share it. It cost me more with that way and it needs to be concentrated too...:mad:

MrHomeScientist - 25-5-2018 at 10:34

Could be anything. Are you sure it was borosilicate glass? Many fake products exist; the story here about the "pyrox" beaker breaking and exploding comes to mind. What is the history of the beaker? Had it been dropped before? Over time tiny cracks can get bigger and bigger until one day the whole thing fails. Was there enough liquid in the beaker, to prevent the glass from developing hot spots? Lots of possibilities, and sadly you'll never know for sure.

weilawei - 25-5-2018 at 10:55

A cheap polariscope (around 25$) would allow you to see strain in glassware for future experiments, in order to select pieces less likely to crack.

I'm also a big fan of sand baths. I can afford to be patient, and I've yet to break anything by heating in 15 years of doing it that way.

Σldritch - 25-5-2018 at 11:01

How big was your beaker? If it was not full the lower part would get much hotter than the part above and crack the glass. I have broken microwave dishes in a similar way. Borosilicate glass is not immune to thermal expansion.

LearnedAmateur - 25-5-2018 at 11:07

In future, I’d recommend using an RBF for strong heating. I’ve broken several top brand beakers using a flame but never a well made RBF, even when immediately hit with a strong oxidising flame from a small brazing torch in order to distill liquids boiling over 150C. The lack of sharper corners, which you obviously get in a beaker, means that heat is better and more easily distributed and stress forces are even and far lower.

Bert - 25-5-2018 at 11:07

You need to spread the heat out evenly, avoiding hot spots and taking temperature up and down reasonably slowly so as to avoid wide differentials in temperature in different parts of the system.

A long time ago I bought a cheap used electrical deep fryer at a garage sale which had a control dial calibrated up to 450F. To dry out 30% acid I would put about an inch of clean sand in the bottom of the fryer, place a 5000ml beaker full of new battery electrolyte on the sand and fill the rest of the space around the breaker with more sand, right to the top of the fryer. I would also wrap the several inches of beaker extending above my impromptu "sand bath" with fiberglass batting to insulate It.

It took an hour to heat up the acid to the point of starting to boil off some water. About half a day to get to the "scary ammounts of dense white fumes are blowing down wind, oh my GOD!" stage.

A couple of observarions:

1: You won't get to 98% like this. After 84% or so, all you do is lose acid right along with the water. Sure does make an impressive fog bank though! Check the density or titrate and see what concentration you really end up with, don't assume.

80% or so sulfuric acid was good enough for most of the things I wanted to to do back then, I usually just had to account for the extra water and use more acid. If it won't do for you- Check the threads on oleum, especially the safety information.

2: Common quartz sand is harder than most glassware. I wrecked a 5000ml beaker by processing about 6 gallons of 30% battery acid, the sand scratched it up to the point I had to retire it for my peace of mind. You REALLY don't want to have the breaker decide to break while handling very hot concentrated acid.

Now, I would use something like Aluminum pellets/BB shot, etc. in place of sand- a "shot bath" to save wear on the glass.

Swinfi2 - 25-5-2018 at 11:13

Quote: Originally posted by weilawei  
A cheap polariscope (around 25$)


I use some polarised sunglasses and my phone, it was free as I already had them ;)

VSEPR_VOID - 25-5-2018 at 11:21

Large beakers and flasks are delicate and break very easily. The bigger the structure the more probable it is there will be a fault.

Quote: Originally posted by weilawei  

I'm also a big fan of sand baths. I can afford to be patient, and I've yet to break anything by heating in 15 years of doing it that way.


I second this. Directly heating glassware, especially really large pieces, can be dangerous. The sand allows for even and gentle heating. It also helps contain things in the event of a spill.

I recently tried distilling sulfuric acid and nearly blew up my distillation rig. The whole thing exploded when the acid flash boiled. My next attempt will not involve distillation. I am not trying that again.

BromicAcid - 25-5-2018 at 12:17

Beakers give a lot of strain at the edges, wouldn't recommend them at high temperatures or if you're just trying to concentrate down a liquid.

underground - 25-5-2018 at 13:02

The beaker was like this one, but ofc not the same brand
https://www.wiltronics.com.au/wp-content/uploads/images/scie...

It actually clearly cracked at the bottom all around separating the bottom from the beaker becoming hollow like a pipe. Hopefully i was doing it outside and i din ton use any electric source :o. It had never before fall down or anything. I thing it was my 1st time doing it with this beaker and i don't remember to have used it again on heat, i bought it for that specific reason. It was almost full, like 3L of liquid inside. I was thinking if clay beaker would be better.


[Edited on 25-5-2018 by underground]

wg48 - 25-5-2018 at 15:05

Quote: Originally posted by underground  
The beaker was like this one, but ofc not the same brand
https://www.wiltronics.com.au/wp-content/uploads/images/scie...

It actually clearly cracked at the bottom all around separating the bottom from the beaker becoming hollow like a pipe. Hopefully i was doing it outside and i din ton use any electric source :o. It had never before fall down or anything. I thing it was my 1st time doing it with this beaker and i don't remember to have used it again on heat, i bought it for that specific reason. It was almost full, like 3L of liquid inside. I was thinking if clay beaker would be better.


[Edited on 25-5-2018 by underground]


The usual recommedation for a flask is to heat atleast up to the top of the liquid.

underground - 25-5-2018 at 15:45

Quote: Originally posted by wg48  


The usual recommedation for a flask is to heat atleast up to the top of the liquid.



Yea but it cracket at the bottom, not at the middle or smthing like that, it cracked exactly at the point where it was heated, at the very bottom

P.S. Anyone got any page here i can buy online H2SO4 in Europe ? e-bay and amazon does not have it

[Edited on 26-5-2018 by underground]

wg48 - 25-5-2018 at 16:13

Quote: Originally posted by underground  
Quote: Originally posted by wg48  


The usual recommedation for a flask is to heat atleast up to the top of the liquid.



Yea but it cracket at the bottom, not at the middle or smthing like that, it cracked exactly at the point where it was heated, at the very bottom

P.S. Anyone got any page here i can buy online H2SO4 in Europe ? e-bay and amazon does not have it

[Edited on 26-5-2018 by underground]


Yes because you did not heat the sides.

Fluorite - 12-11-2020 at 13:36

If I used a sand/oil bath can I boil nitric, sulfuric acid in glass bottle like this?

23718588-empty-glass-bottle-with-plastic-stopper-on-white-background.jpg - 57kB

ArbuzToWoda - 12-11-2020 at 13:39

No. That is a terrible and dangerous idea. Invest 5 bucks in a round bottom borosilicate flask.

Dangerous

MadHatter - 12-11-2020 at 15:02

Fluorite, that appears to be a standard
soda-lime glass bottle. I can't imagine
that standing up to H2SO4's BP of
337C(639F). I agree with ArbuzToWoda, that
an RBF made from borosilicate(BORO 3.3) is
what you really need.

Fluorite, I've seen from some of your other
posts that certain labware is illegal in your
part of the world. Truly ashame because
the powers that be are highly suspicious of
amateur chemistry. I wish you luck.


[Edited on 2020/11/12 by MadHatter]

yobbo II - 12-11-2020 at 16:50


If you heat and cool down very slowly it may be OK. Assume it will break and take necessary precautions.
If you were to put the bottle into an oven and heat to 300C over a period of one hour it would not break.

Its not the actually 'the heat' that breaks glass but uneven heat. The thermal expansion will cause the hot and colder parts to expand a different amount and cause stress which causes the glass to crack.

Yob

Clear_horizons_glass - 13-11-2020 at 02:42

Is it particularly cold where you are at? That can make a difference if you're doing it outside.
The beaker could have not been annealed properly in initial manufacturing, or perhaps it was previously heated unevenly. It could have also been heated up to fast or cooled down to fast. If it has a particularly thick bottom, that would also make sense that it would break at the bottom, as thicker pieces of glass will naturally cool down and heat up at a different rate than thinner pieces. On top of that, any 90 degree angles or less really stresses out glass.
A good RBF is way more ideal for evenly spreading out heat, and the round shape naturally allows for more flexing to relieve stress than a 90 degree bottom to a beaker. The wall thickness will also be more even, which allows for better stress relief.