Furboffle
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waterbath vs. steambath
I'm performing an experiment soon that requests a steam bath. I don't have a proper steam bath apparatus but with my assortment of glassware I figure
its not so important. first off what is the major difference between a steam bath and a boiling water bath? can they be substituted effectively? I
would assume they wouldn't vary much. water shouldn't get hotter than 100°. steam coming off it should be right there at 100° or slightly above. so
for the sake of temperature control I feel like they're the same. If I effectively replace the steam bath with a boiling water bath then I guess the
rest of the thread is voided.
But if there is an advantage to a steam bath which I need to employ, as I don't have one what would be the most adequate means of making one? I want
to say I recall back in gen chem using a beaker of boiling water for steam generation and a watch glass on top as the reaction vessel on top. is there
something better than this to do?
perhaps use a 100mL RBF on top of a 50mL beaker of boiling water?
It crossed my mind maybe use two filtration flasks connected with a hose. stopper the first flask with the boiling water, in the second flask insert a
test tube for the reaction.
any advice or perhaps confirmation of boiling water bath?
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Mailinmypocket
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Quote: Originally posted by Furboffle  | I'm performing an experiment soon that requests a steam bath. I don't have a proper steam bath apparatus but with my assortment of glassware I figure
its not so important. first off what is the major difference between a steam bath and a boiling water bath? can they be substituted effectively? I
would assume they wouldn't vary much. water shouldn't get hotter than 100°. steam coming off it should be right there at 100° or slightly above. so
for the sake of temperature control I feel like they're the same. If I effectively replace the steam bath with a boiling water bath then I guess the
rest of the thread is voided.
But if there is an advantage to a steam bath which I need to employ, as I don't have one what would be the most adequate means of making one? I want
to say I recall back in gen chem using a beaker of boiling water for steam generation and a watch glass on top as the reaction vessel on top. is there
something better than this to do?
perhaps use a 100mL RBF on top of a 50mL beaker of boiling water?
It crossed my mind maybe use two filtration flasks connected with a hose. stopper the first flask with the boiling water, in the second flask insert a
test tube for the reaction.
any advice or perhaps confirmation of boiling water bath? |
I have never had a problem heating a flask for example on a hot water bath as opposed to a steam bath. The only time I could see this being
problematic is if you are trying to dry a sample in an evaporating dish and the water boils and bumps some liquid into your sample.
I will very often submerge a flask in hot/boiling water though, never had issues.
Here is an image of when I was distilling DCM from an extraction of carvone from caraway. The procedure called for a steam bath but hot water
worked better anyways. Steam would seem too hot for DCM at any rate.
[Edited on 20-1-2013 by Mailinmypocket]
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SM2
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Usually you can substitute, as long as the conditions calling for the steam bath are respected in the 1st place. You will have to make sure your flak
is properly coddled, almost as if poaching. a double boiler might not be a bad idea. Hope this small amount of advice can help in some small way!
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Furboffle
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awesome this cleared up some uncertainty. Once my reagents arrive Tuesday I can get this underway. I'll definitely give some thought to a double
boiler. but at least I'm confident about just an RBF in a hot water bath.
thanks for the advice.
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kadriver
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Sorry, a newbie here, what is an RBF?
When moisture getting in the sample being heated is a concern, I have used mineral oil instead of water.
This eliminates the moisture problem, but the temperature of the oil must be monitored with a thermometer because the temperature of the mineral oil
can exceed the temperature of boiling water.
The boiling point of mineral oil is around 300 degrees c.
kadriver
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elementcollector1
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| Quote: Originally posted by kadriver | Sorry, a newbie here, what is an RBF?
When moisture getting in the sample being heated is a concern, I have used mineral oil instead of water.
This eliminates the moisture problem, but the temperature of the oil must be monitored with a thermometer because the temperature of the mineral oil
can exceed the temperature of boiling water.
The boiling point of mineral oil is around 300 degrees c.
kadriver |
RBF = Round Bottom Flask
It confused me too at first.
Good idea about the mineral oil, I wouldn't have thought of that. Although, hot oil splashing around...
I think that when you're choosing what bath to use, you have to think about in what 'range' your compound-to-be-distilled boils off. For example:
50-100 C: Water
101-300 C: Min. oil
300+ C: Sand
I used hot water to distill acetone (BP = 56 C), and it worked wonders. The support for the RBF was actually the Keck clips on the condenser, and it
held to the beaker fairly well, suspending most of the flask inside the bath.
Elements Collected:52/87
Latest Acquired: Cl
Next in Line: Nd
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UnintentionalChaos
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| Quote: Originally posted by elementcollector1 | | Quote: Originally posted by kadriver | Sorry, a newbie here, what is an RBF?
When moisture getting in the sample being heated is a concern, I have used mineral oil instead of water.
This eliminates the moisture problem, but the temperature of the oil must be monitored with a thermometer because the temperature of the mineral oil
can exceed the temperature of boiling water.
The boiling point of mineral oil is around 300 degrees c.
kadriver |
RBF = Round Bottom Flask
It confused me too at first.
Good idea about the mineral oil, I wouldn't have thought of that. Although, hot oil splashing around...
I think that when you're choosing what bath to use, you have to think about in what 'range' your compound-to-be-distilled boils off. For example:
50-100 C: Water
101-300 C: Min. oil
300+ C: Sand
I used hot water to distill acetone (BP = 56 C), and it worked wonders. The support for the RBF was actually the Keck clips on the condenser, and it
held to the beaker fairly well, suspending most of the flask inside the bath. |
In practice, the bath should be a fair bit hotter than what is being distilled or the rate of distillation will be utter crap. I probably wouldn't try
a hot water bath on anything boiling over 80C. Plus, the condensation on everything is miserable.
Mineral oil starts fuming badly in the neighborhood of 200C, so trying to distill anything over 170-180C is probably a bad idea.
For anything boiling higher than that, you should really consider vacuum distillation if possible.
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'In organic synthesis, we call decomposition products "crap", however this is not a IUPAC approved nomenclature.' -Nicodem
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Hexavalent
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Placing a sheet of Al foil around the edges of the waterbath significantly reduce this, in my experience.
"Success is going from failure to failure without loss of enthusiasm." Winston Churchill
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