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Author: Subject: 250 RBF broken
WangleSpong5000
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[*] posted on 26-12-2017 at 18:49
250 RBF broken


Just lost a wall of text. if the following sounds rude i apologize, im just not gonna re write all that again.

Flask broken:

1. Can RBF's be used on hotplates?
2. What temp is required annneal the busted 250
3. does 24/40 = 24/29

Thanks




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zed
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[*] posted on 26-12-2017 at 19:22


Hot plate? Flat bottom flasks work best. Used to be more common.
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[*] posted on 26-12-2017 at 19:53


Quote: Originally posted by WangleSpong5000  
Just lost a wall of text. if the following sounds rude i apologize, im just not gonna re write all that again.

Flask broken:

1. Can RBF's be used on hotplates?
2. What temp is required annneal the busted 250
3. does 24/40 = 24/29

Thanks


24/40 is US standard - 24/29 is international standard. The 40 and 29 is the length of the joint. The 29 will work in the 40 slot.
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WangleSpong5000
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[*] posted on 26-12-2017 at 21:06


Quote: Originally posted by zed  
Hot plate? Flat bottom flasks work best. Used to be more common.


FBF's used to me more common you mean?

Oh yeah, they work best of course but I'm sure I've seen vids of ChemPlayer or someone (can't remember) using a hotplate to heat a RBF. I'm going to do a little experiment and see how it goes... it can't possibly be terribly efficient but anyway...

Cheers

Quote: Originally posted by RogueRose  
24/40 is US standard - 24/29 is international standard. The 40 and 29 is the length of the joint. The 29 will work in the 40 slot.


Yeah I thought so from what I'd read elsewhere, I just wasnt 100% sure.

Thanks

I'm thinking may just have to use my convection hot plate and use it as a water or oil bath for the minute...


[Edited on 27-12-2017 by WangleSpong5000]




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[*] posted on 26-12-2017 at 22:25


Round bottoms work best in a heating mantle, water bath, oil bath, a bath of conductive metal shot (Aluminum works well), air bath- or if you don't care about scratches and sloooooow response time, a sand bath.

Heating a piece of glass strongly on a small point is asking for it, even with borosilicate glass-

So, what brand of glass went crack?




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[*] posted on 26-12-2017 at 23:42


Quote: Originally posted by Bert  
Round bottoms work best in a heating mantle, water bath, oil bath, a bath of conductive metal shot (Aluminum works well), air bath- or if you don't care about scratches and sloooooow response time, a sand bath.

Heating a piece of glass strongly on a small point is asking for it, even with borosilicate glass-

So, what brand of glass went crack?


Unsure of the brand actually. I bought it from a well known quite large Aussie supplier. No brand marked on it that I can see... I'll find out. It was a dumb mistake to try and cool it so quickly but I had a reason. A really dumb one. To try and see what the ginger compound (I thought I had distlled to dryness as i heard a strage sound) was that stunk up my EtOH so much even after I cleaned it to fuck... the irony is there was still water in the flask as that batch of EtOH had only been distilled once so still contained a decent amount of water... i didn't want to overheat the trace ginger mystery material as i thought it may decompose so i quickly cooled that flask and surprise surprise it cracked... as it does. I just didn't think borosilicate glass would crack in this fashion which is pretty fucking stupid now that I think about it. Why would it NOT break... jeez

But the real kicker is I DONT CARE ABOUT MICROGRAMS WORTH OF SOME GINGER STUFF. But I suppose I was curious and keen to experiment due to this curiosity and I think this is the minset that I want to have as a chemist... or just genreally, and I auppose I am like that and now I have the proof... and it's broken... just like my will to live... That last bit was a joke hahahaha... I lost my will to live long before this ;)


[Edited on 27-12-2017 by WangleSpong5000]




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[*] posted on 27-12-2017 at 02:12


The following suggestions will help in avoiding failures during heating and cooling procedures.

1. During evaporation, never leave vessel unattended. Lower the temperature gradually as the liquid level drops, to avoid dryness condition, otherwise glass vessel may crack or explode.

2. Always use caution when placing heated vessel on a cold or damp surface. Sudden temperature may cause the vessel to break.

3. Always cool vessels slowly to avoid thermal breakage.

4. Never apply heat to badly scratched or etched vessel to prevent chance of breakage.

5. Avoid point source of heating to a vessel and always diffuse it by using a metal gauge or air/water bath.
Alternatively ensure uniform heating of the vessel by slow movement of the vessel in relation the heat source.

6. Uniform heat is critical factor for some chemical reactions. For this adjust large soft flame of Bunsen burner to heat slowly but also more uniformly.

7. Adjust the flame contacts and heat the vessel below the liquid level to avoid breakage of the vessel.

8. Always use anti-bumping devices in the vessel, such as pumice or glass wool when rapid heating of the vessel and contents is required and to prevent internal abrasions of the vessels.

9. Thick walled glassware are best heated with the use of an electric immersion heater and should not subjected to direct flame or other localized heat source.

10. Do not heat glassware`s over electric heaters with open elements to avoid localized stress and chances of breakage.

11. Always ensure that the surface of the hot plate is larger in area than the base of the vessel being heated to prevent uneven heating and glassware breakage.

12. When using electrical appliances always ensure to follow manufacturer`s instructions.

The above is from http://www.goelscientific.co.in/care.php

The maximum allowable differential temperature (inside to outside) is usually stated as between 100C and 150 C for boro glass
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[*] posted on 27-12-2017 at 02:40


Cheers wg48.

It was a dumb mistake. I'm just really glad nothing happened while I was doing something a bit more serious.




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27-12-2017 at 17:38
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[*] posted on 31-12-2017 at 15:51


Ummm. I have cracked or broken glassware, very seldom.

Alas, I am mostly accustomed to American made Pyrex, of a bygone era. Heavy, and well annealed.

Sometimes a star-crack would mysteriously appear, but glassware was not only very durable, it was inexpensive and readily available. I remember, heating a heavy duty filter flask to about a kazillion degrees, under vacuum, then putting the flask down, unbeknownst, onto a splash of water. The flask sputtered, cracked, and cost me a few bucks. But, it didn't actually break apart. Just cracked.
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[*] posted on 1-1-2018 at 00:38


I've broken American made Pyrex several times under heating and vacuum and consider it less reliable than modern Chinese boro 3.3. And I have lots of experience breaking glass :)

I've seen star cracks before, but they have always developed almost at random for reasons that I can't explain.

I would not bother repairing a cracked 250 mL flask since you can get a new one from China for around $5, although apparently it is possible to do so with a blowtorch, annealing with a propane weed burner... there are some glass blowers on this forum who could give you specifics....




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[*] posted on 9-1-2018 at 12:13


a little trick for using an actual RBF (and not a flat bottom RBF) on a hotplate is to toss an arms lenght of aluminium foil into a bowl slightly larger than your target RBF, squeeze it down a great deal and then carefully pressing it to a bit higher density with the RBF in mind, if you are lucky you will get a density that will help your poor RBF cope with potential bumping and have quite great heat transfer - plus very large surface area of heating, a layer of aluminium foil can be pressed over the aluminium foil "cup" to give it a bit less "ghetto-look"



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[*] posted on 24-1-2018 at 00:42


Thanks everyone :)

I've ordered another flask... single neck 250ml RBF instead of the 2 neck one I broke. Was surprised how low the price was! $6 or so AUD, free shipping (Deschem). To order the same thing domestically costs about $20 but shipping becomes prohibitive when ordering single items bringing it to $50 in this case. Suppose I shouldn't be surprised really... every item I've bought on eBay thus far has been very reasonably priced but as all my prior purchases have been accessories instead of glassware proper I was ignorant of how cheap these could be.









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