cnidocyte
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Using hot plates
I have pyrex cookware but I hear glassware will break if you place it directly on the hot plate. How do you usually use you're hot plate? I improvised
a steam bath using a cooking pot and some rocks. I filled the cooking pot with water then placed some rocks and placed the pyrex bowl on the rocks.
Right now I need to evaporate the water in an aqueous solution of ZnCl, obviously the steam bath won't do it since the colligative properties of the
ZnCl raise the BP of the water. Should I put some oil in the pot instead? Oil baths can get pretty dangerous so I don't wanna play with them just yet.
What if I just place the pyrex bowl on the hot plate and raise the heat to about 125C? Would that break the bowl?
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1281371269
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Buy proper lab glassware. It's not all that expensive and you can then heat it with either a hotplate or a burner up to much higher temperatures
without worrying about breakages.
If you're in the UK I can give you some links to websites or ebay sellers who sell lab glassware at decent prices.
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hissingnoise
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| Quote: | | I have pyrex cookware but I hear glassware will break if you place it directly on the hot plate. |
If your cookware is genuine heavy pyrex it should easily withstand being placed on a hotplate and heated to the boiling point of H2SO4. . .
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pantone159
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I have heard that Pyrex brand cookware in the US is often not actually borosilicate glass, the name is just a brand name, not any indication of the
material. For labware this is not true, but if your container is marketed as cookware, beware.
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cnidocyte
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Quote: Originally posted by Mossydie  | Buy proper lab glassware. It's not all that expensive and you can then heat it with either a hotplate or a burner up to much higher temperatures
without worrying about breakages.
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I do have proper glassware but I hear you can't just place FB boiling flasks directly onto hot plates. Pyrex cookware is much thicker than the boiling
flasks I have so I'm guessing its more resilient.
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anotheronebitesthedust
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The general rule I go by is that if it's an ebay glassblower, their glass won't withstand the same pressure/vacuum the the main glassblowers will.
Laboy, UGT, Kantu, Expediglass, and all the upstart chinese companies may be cheap, but there's a reason behind that.
Starting a glassblowing company is an expensive venture not to mention it requires a lot of experience.
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1281371269
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Agreed. But the eBay sellers I was talking about simply sell on (new or used) branded glassware. However, if you aren't buying a big quantity, you
tend to save on shipping and the like such that it's usually more cost effective. But actually I've never had trouble with cheaper glassware - I often
buy unbranded beakers, flasks, etc from educational companies like Rapid (I expect it has to be decent, as it's certified for educational use).
And cnidocyte, yes, but cookware is not intended for dealing with chemicals and proper glassware is. It's seems stupid to use it for something it
isn't intended for when you have the correct equipment at hand.
For boiling down a solution, an oil bath seems like overkill. If you don't want to use the hotplate (though I think it should be fine), do you not
have anything like a bunsen / spirit burner?
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crazyboy
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Putting flasks and beakers directly on a hotplate is fine, just don't do it with Pyrex brand cookware or any cookware for that matter.
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hissingnoise
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I've been using an amber pyrex burner (appropriated from the kitchen) for occasionally boiling water off H2SO4 for years.
It takes gasrings and hotplates in its stride. . .
It's quite heavy and obviously of borosilicate!
So if it fails, it ain't pyrex!
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