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Ramblesthegoat
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[*] posted on 3-3-2012 at 18:02
Sand baths


Hey guys, I have noticed that almost everybody (on Youtube at least) uses mineral oil baths for heating flasks and other things more evenly, but why do I never see sand baths? They are very cheap, reusable, can get to much higher temperatures, and in most cases less messy. Are they more dangerous or significantly less efficient? This might be a really dumb question and the answer is right in front of my face but this has been bugging me for a while.
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entropy51
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[*] posted on 3-3-2012 at 18:18


Quote: Originally posted by Ramblesthegoat  
Hey guys, I have noticed that almost everybody (on Youtube at least) uses mineral oil baths for heating flasks and other things more evenly, but why do I never see sand baths? They are very cheap, reusable, can get to much higher temperatures, and in most cases less messy. Are they more dangerous or significantly less efficient? This might be a really dumb question and the answer is right in front of my face but this has been bugging me for a while.
Click on the "Search" icon in the upper left hand corner. Enter "sand bath" in the search box. Select "Subject only" and "All forums". You will get several hits.

You can also search for subjects such as "heating" or "baths" and so on and find other hits.

If you are really diligent, you can even download several of the practical chemistry lab manuals in the forum library where heating methods and other techniques of the fine art of chemistry are discussed at length.

Wasn't that easy?
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Ramblesthegoat
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[*] posted on 3-3-2012 at 18:39


Well I guess I was more looking for advantages and disadvantages of sand and oil baths. I understand how to set one up and stuff, but I haven't found why exactly sand baths seem to be so unpopular. Is it because they can scratch the flask?
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[*] posted on 3-3-2012 at 18:46


Quote: Originally posted by Ramblesthegoat  
Well I guess I was more looking for advantages and disadvantages of sand and oil baths. I understand how to set one up and stuff, but I haven't found why exactly sand baths seem to be so unpopular. Is it because they can scratch the flask?
That( although hat is a minor concern) and simply because it is messy. At least that is why I don't use sand baths often. Frankly I prefer my Heating mantle but barring that a hotplate , crystallizing dish and the right oil are a good second best. But there are a lot more learned than I here.
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[*] posted on 3-3-2012 at 19:08


I use brine water baths, oil baths, and sand baths. Each in different heating temperatures and situations. I have even used small copper coated shot (BBs) lately a lot, as they have good thermal conductivity and they don't scratch. The method of heating should be tailor fitted to the reaction and apparatus.



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[*] posted on 3-3-2012 at 22:34


One disadvantage of a sand bath is that it takes much longer to heat up than a mineral oil bath. However if you put the container with the sand in the oven, this will heat it up faster than using a hot plate.



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[*] posted on 3-3-2012 at 22:34


Sand baths suck. They're messy, <strong>they're <em>very</em> slow to heat and cool</strong>, and they're opaque. It's also not possible to just lower a clamped setup into a sand bath. You have to dig, shake, or aerate. There are so many better alternatives; <strong>heating mantles</strong>, water baths, metal shot baths, and baths of various oils. You can even use an ionic liquid or eutectic alloy if you're adventurous and reactivity isn't an issue.

[edit]
Sorry, forgot some classics: naked flame & heat gun

[Edited on 3/4/12 by bfesser]




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[*] posted on 4-3-2012 at 00:46


Quote: Originally posted by bfesser  
You can even use an ionic liquid or eutectic alloy if you're adventurous and reactivity isn't an issue.



I once heard of people even using molten potassium nitrate for achieving high temps higher than 300C. That always sounded a bit dangerous and wasteful to me. But supposedly after the nitrate cools it will simply crack and flake off the flask so you don't need to wipe any messy oils off.
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[*] posted on 4-3-2012 at 01:20


Sand baths can be useful in some situations: http://curlyarrow.blogspot.com/2011/03/sand-bath-alternative...
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[*] posted on 4-3-2012 at 01:30


I use a dedicated crock pot filled with sand to heat evaporating dishes (okay, mason jars)
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[*] posted on 4-3-2012 at 03:59


Quote: Originally posted by bfesser  
[edit]
Sorry, forgot some classics: naked flame & heat gun

[Edited on 3/4/12 by bfesser]


Nakes flames are not a classic and never were. They should never be used for heating borosilicate flasks... unless doing some flameworking.

Heat gun is ok, if the temperature is not too high.


Anyway, there aren't methods that fit all the needs...




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Ramblesthegoat
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[*] posted on 4-3-2012 at 04:10


So it seems to me like sand baths are better for higher temperatures, but bad with heat transfer and spills are a pain. I will try some metal bb's because they seem to be the way to go, but different baths are good for different situations and temperatures. Thanks for all the advice guys!
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[*] posted on 4-3-2012 at 06:35


I've said it in other threads and I'll say it again. If you ever read the instructions for your hotplate it will usually have a warning about sand baths. Sand is a very good insulator and hence the instructions will warn you not to use sand baths for high temperatures as the insulating effect can burn out the coils. Since most people only want to use sand for higher temperatures this means that the utility of a sand bath becomes next to nothing.

This information is not just in the manuals, my hotplate has the same warning written on the tag on the cord not to go above 3 / 10 when using a sand bath and it was mentioned a few times during my college years.

sandbath.jpg - 156kB

Edit: Of course all of this assumes you want to use a sand bath on a hotplate. They work well to diffuse the heat of an open flame.

[Edited on 3/4/2012 by BromicAcid]




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[*] posted on 4-3-2012 at 06:41


I think peach, or somebody here, melted there hotplate by covering it tightly with foil. The heat built up inside the plate and destroyed it.

[Edited on 4-3-2012 by Bot0nist]




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[*] posted on 4-3-2012 at 09:27


Quote: Originally posted by Endimion17  
[Naked] flames are not a classic and never were. They should never be used for heating borosilicate flasks... unless doing some flameworking.
I disagree. Although, perhaps, I shouldn't have said <em>naked</em> flames. If you're heating a florence flask with a non-flammable liquid, for example, you'd typically want to put a ceramic coated wire mesh between the flame and the flask. But it's not always necessary. Especially if the flame is low, and you're heating gently.

<hr width="300" />
I have a personal hatred of sand baths. The ceramic top of my favorite hot plate cracked cleanly in half because I was slowly heating a small sandbath. Even if you're careful, which I was, they're a pain. If you do choose to use a sand bath, as some procedures implicitly call for, be very careful. And don't use a ceramic top hot plate!

I forgot to mention a good one: steam baths/cones.




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[*] posted on 4-3-2012 at 09:32


I also use "air" baths to good success. All that's needed is a foil skirt around the RBF. lower it until in is just a few cm from touching the hotplate. Works fine for many lower boiling point refluxes and distillations.



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[*] posted on 4-3-2012 at 13:31


I also hate sand baths. Many of my expensive flasks have been severely scratched using them - personally, these days I use liquid paraffin/paraffin oil or sunflower/corn oil bath, the former which I buy in glass bottles from the pharmacy for treating diarrhoea(!) and the second, of course, from the supermarket, both very cheaply.

I have never tried mini copper BB pellets, although I may give them a go in the future. I am however, a big fan of air baths using aluminium foil (the Baco-foil thick stuff is the best).

My two cents, for all its worth:)




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[*] posted on 4-3-2012 at 14:48


Quote: Originally posted by Endimion17  
Nakes flames are not a classic and never were. They should never be used for heating borosilicate flasks... unless doing some flameworking.
Well that is news to all of us who learned organic back in the 1960's when Bunsen burners were the only heat sources used in the undergrad labs, including organic chem. Not to mention to guys like Liebig, Wohler, Hoffman, Perkin, Gatterman, Fischer and so on.

Flame free labs are a relatively new phenomenon.

So I think the Bunsen flame is indeed classic, if sometimes a little risky.

I have about 8 mantles, 2 stirring hotplates and several oil baths but I still sometimes use a Bunsen flame if I want to be able to immediately remove the heat at the first sign of trouble. (But I do always feel a little naughty when the solvent is flammable,)
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[*] posted on 4-3-2012 at 15:33


I don't think I've ever used a sand bath. Setting up a mantle seems so much easier. If I think I need an even heating high temperature bath I use silicone oil. If I need it even and kept below 100° I use a steam bath (especially good for low boiling flammable solvents like ether). I also use a Bunsen burner if I need heating with a quick response, and always use a screen with the ceramic center, unless just spot heating the glassware. My wife recently gave me a hot air gun for Christmas, and I'm finding I use that more than expected. It is the only heater I would use for certain applications.



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[*] posted on 5-3-2012 at 04:43


Quote: Originally posted by bfesser  
I disagree. Although, perhaps, I shouldn't have said <em>naked</em> flames. If you're heating a florence flask with a non-flammable liquid, for example, you'd typically want to put a ceramic coated wire mesh between the flame and the flask. But it's not always necessary. Especially if the flame is low, and you're heating gently.


I was referring to the process of heating a flask with visible flame (the hotter it is, the greater the danger), i.e. immersing it into the flame. That is something that should never be done. It doesn't have to crack at all. It just introduces stress inside the glass, and if you do it again, and again, and again, the stress builds up and one day CRACK, or if ether is inside, WHOOSH/BANG!.

It is a rule. Period.


Quote: Originally posted by Bot0nist  
I also use "air" baths to good success. All that's needed is a foil skirt around the RBF. lower it until in is just a few cm from touching the hotplate. Works fine for many lower boiling point refluxes and distillations.


Yeah, that's a convenient way, too, though it isn't recommended it for things like ether. Non-flammable halogenated hydrocarbons, that's ok.
If the flask cracks, and they do occasionally, ether will fall on the hotplate and catch fire. Such fires are quite spectacular. :D
It's always better to use a water bath for ether, as it boils at around 36 °C.

Foil skirt or not, it's always bad to lower the flask to the metal of the heating pad, but if the setup is heavy, and you don't want to clutch it too hard with clamps, you can put a small cushion of asbestos mat (2x2 cm) between. Asbestos is soft, so this works great.
Sometimes I do it with 4 cushions, placed at four corners, like here.


Quote: Originally posted by Hexavalent  
I also hate sand baths. Many of my expensive flasks have been severely scratched using them - personally, these days I use liquid paraffin/paraffin oil or sunflower/corn oil bath, the former which I buy in glass bottles from the pharmacy for treating diarrhoea(!) and the second, of course, from the supermarket, both very cheaply.

I have never tried mini copper BB pellets, although I may give them a go in the future. I am however, a big fan of air baths using aluminium foil (the Baco-foil thick stuff is the best).

My two cents, for all its worth:)


Sunflower oil fan right here! :D
I heated it to 280 °C. No smoking occured. Great stuff.
Paraffin tends to smoke and catches fire rather easy if you go that high.


Quote: Originally posted by entropy51  
Well that is news to all of us who learned organic back in the 1960's when Bunsen burners were the only heat sources used in the undergrad labs, including organic chem. Not to mention to guys like Liebig, Wohler, Hoffman, Perkin, Gatterman, Fischer and so on.

Flame free labs are a relatively new phenomenon.

So I think the Bunsen flame is indeed classic, if sometimes a little risky.

I have about 8 mantles, 2 stirring hotplates and several oil baths but I still sometimes use a Bunsen flame if I want to be able to immediately remove the heat at the first sign of trouble. (But I do always feel a little naughty when the solvent is flammable,)


I doubt the mentioned guys were stressing their equipment like that.
The heat of the naked flame was always used together with an asbestos mat, or a bath of some kind.
One of the rare things that can be immersed into a naked, blue flame are thin porcelain crucibles, after they were preheated above the sooty yellow safety flame for a few minutes.
And of course, quartz vessels can be immediately heated in the blue flame.


You're playing with the devil. Keep building stress in the glass and one day an accident will happen...




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[*] posted on 5-3-2012 at 17:02


Seeing as the original post's questions have been thoroughly answered, discussed, and elaborated upon at this point; I see no harm in taking this thread a little more off topic.

Quote: Originally posted by Endimion17  
You're playing with the devil. Keep building stress in the glass and one day an accident will happen...


Says the man who experiments with large volumes of liquid mercury, causes white phosphorus to luminesce, images mercury vapour with ultraviolet lamps, dips his fingers in molten lead, intentionally starts mock laboratory fires, microwaves assorted metallic and glass objects, surfs on elevators . . . need I go on?

I don't think your <em>opinion</em> has much value. The <em>fact</em> is that naked flame is a <em>classic</em> heating method, even for borosilicate glassware. Flame heating has been associated with chemical (or material, elemental, phlogistical, whatever) manipulations since pre-Lavoisier chymistry and even alchemy. Besides, I never said that flame heating was superior, simply that it's a classic.

I'd like to add that, from my personal experience (which I'm sure mirrors that of others here), vintage borosilicate glassware, although it is typically thinner-walled and of lighter construction, will take more abuse than it's modern day equivalents. I've dropped old 'green stamp' 500 ml Erlenmeyer flasks from shoulder height to a rough concrete floor and watched them bounce at least a meter into the air and continuing until at rest with no damage observed whatsoever. These flasks were heavily used before they ever came into my posession--with FLAME! Try doing that with your 'unstressed' glassware. Your arrogance does not lend support to your opinion, nor does it cause reality to reflect your opinion.

<a href="http://www.ch.ic.ac.uk/video/linstead/" target="_blank">[video featuring classic organic chemistry utilizing flame heating]</a>




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[*] posted on 5-3-2012 at 17:17


Quote: Originally posted by bfesser  
I'd like to add that, from my personal experience (which I'm sure mirrors that of others here), vintage borosilicate glassware, although it is typically thinner-walled and of lighter construction, will take more abuse than it's modern day equivalents. I've dropped old 'green stamp' 500 ml Erlenmeyer flasks from shoulder height to a rough concrete floor and watched them bounce at least a meter into the air and continuing until at rest with no damage observed whatsoever.
I can second that. Some of my Pyrex is older than I am and has seen many a flame applied.

I think it is the rate of temperature change and not the heat source that causes glassware to fail.

I have to shake my head when I read about some of the "unexpected" catastrophic glassware failures that people report on the forum.
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[*] posted on 6-3-2012 at 00:48


Quote: Originally posted by bfesser  
Seeing as the original post's questions have been thoroughly answered, discussed, and elaborated upon at this point; I see no harm in taking this thread a little more off topic.

Says the man who experiments with large volumes of liquid mercury, causes white phosphorus to luminesce, images mercury vapour with ultraviolet lamps, dips his fingers in molten lead, intentionally starts mock laboratory fires, microwaves assorted metallic and glass objects, surfs on elevators . . . need I go on?



I see no problems with those experiments. They were done with a great deal of ventilation, and sometimes mask was used. Mock fire was made in an almost completely empty room made of concrete, with one wooden shelf and a water main exactly behind the camera. Molten lead is a trick, and so is the elevator surfing. Microwaving a CFL immersed in a glass of water is one of the safest tricks you can do with such oven.


Quote:
I don't think your <em>opinion</em> has much value. The <em>fact</em> is that naked flame is a <em>classic</em> heating method, even for borosilicate glassware. Flame heating has been associated with chemical (or material, elemental, phlogistical, whatever) manipulations since pre-Lavoisier chymistry and even alchemy. Besides, I never said that flame heating was superior, simply that it's a classic.

I'd like to add that, from my personal experience (which I'm sure mirrors that of others here), vintage borosilicate glassware, although it is typically thinner-walled and of lighter construction, will take more abuse than it's modern day equivalents. I've dropped old 'green stamp' 500 ml Erlenmeyer flasks from shoulder height to a rough concrete floor and watched them bounce at least a meter into the air and continuing until at rest with no damage observed whatsoever. These flasks were heavily used before they ever came into my posession--with FLAME! Try doing that with your 'unstressed' glassware. Your arrogance does not lend support to your opinion, nor does it cause reality to reflect your opinion.

<a href="http://www.ch.ic.ac.uk/video/linstead/" target="_blank">[video featuring classic organic chemistry utilizing flame heating]</a>



On the other hand, heating a glass vessel with a naked blue flame will introduce stress buildup. That's a fact mentioned in pretty much every lab manual I've read, and it's something glassblowers/flameworkers always talk about when asked about the chemists' worst habits (that, and stucked glass joints). They usually do an assortment of facepalms while discussing it.

Thinner glass or thicker glass? It depends. For new glass (boro 3.3) thicker is the option. Old Jena glass (boro 3.1 I believe) prefers thinner. Nobody works with 3.1 anymore, and if you have a broken part, repairing it is a nightmare.

You think your flask that fell on the floor is safe as ever? Sorry, but you really don't know much about glass. I don't, but you know way less.
Flasks that fell on the floor and managed to survive have either microfractures or local stress. They're prone to bursting more than a brand new.

If I'm arrogant, then my flameworker is arrogant, too. I'm just repeating his words.


@entropy51: It's not just the temperature change rate, but the geometry of heating. There's a reason why mantles and baths exist.

[Edited on 6-3-2012 by Endimion17]




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[*] posted on 6-3-2012 at 01:52


I use sand baths on occasion. Back with my homelab, I'd use them to do some moderately high temperature reactions. I didn't have access to good silicone oil at the time. I wish I had known about sunflower oil back then. In the academic lab I currently work in we use sand baths to activate things like silica and alumina. The temperature we activate them at (250C) is on the upper end of the useable range of even the high temp silicone oil and much cheaper.
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[*] posted on 9-3-2012 at 09:57


Quote: Originally posted by bfesser  
<a href="http://www.ch.ic.ac.uk/video/linstead/" target="_blank">[video featuring classic organic chemistry utilizing flame heating]</a>


Sorry, I noticed that this video doesn't seem to load from the original site. I've uploaded the film segment to YouTube.

http://www.youtube.com/watch?v=5PcrVsYxAYs




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