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Author: Subject: 300 deg/C oil bath
mechem
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[*] posted on 7-10-2008 at 12:50
300 deg/C oil bath


Hi
Does anyone have any ideas on what substance/liquid could be used in an oil bath, maintained at 300deg/C, without smoking the place out.
Thanks
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sonogashira
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[*] posted on 7-10-2008 at 13:00


-40 to 250° (to 400C under N2)...... D.C. 550 silicone fluid
Up to 340°......... A mixture of 85% orthophosphoric acid (2 parts) and metaphosphoric acid (1 part)
60 to 500C............ Fisher bath wax (highly unsaturated)
73 to 350°.......... Woods Metal*
250 to 800C........ Solder*

* In using metal baths, the container (usually a metal crucible) should be removed while the metal is still molten.

(Source: Armarego, Purification of Laboratory Chemicals. 5th Edition, P35)

Also:

"A fused salt bath consisting of 8.5 parts (by weight) of sodium nitrite and 10 parts of potassium nitrate has a melting point of about 140° and may replace the [Wood's] metal bath." Source.


[Edited on 7-10-2008 by sonogashira]
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jokull
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[*] posted on 7-10-2008 at 13:08


You may use:

Paraffin
Melting point 50º C
Useful range 60-300º C
It is flammable

Dibutyl o-phthalate
Melting point -35º C
Useful range 150-320º C
It is generally used
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chemrox
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[*] posted on 7-10-2008 at 13:19


Dibutyl phthalate is available in 4L containers and has a published boiling point of 340*C. Does it smoke before it gets there? I don't much care for boiling parafin. I'm using silicone brake fluid for up to about 200 but it starts outgassing before. Not sure how it will behave if I run it up higher. Might be something to try and report. Phthalates are pretty cheap although they represent something of an environmental problem. One of my professors had us using hydrolized cottonseed oil and everyone on the floor got a headache. That wasn't even for high temps. I don't care for any kind of waxy material as too hard to clean up.



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mechem
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[*] posted on 7-10-2008 at 13:23


Forgot to mention I need a bath with about 3 to 4 liters of fluid, expense is also an issue otherwise solder or molten metal alloys would be my first chose. KNO3 with NaNO2 sounds interesting but getting hold of NaNO2 might be a problem, any other combinations.
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chemrox
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[*] posted on 7-10-2008 at 14:05


Brake fluid started smoking (nasty) at around 175*C. I'm for trying pthalate esters.

[Edited on 7-10-2008 by chemrox]




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chief
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[*] posted on 7-10-2008 at 14:19


It's probably completely unhealthy to inhale paraffin-smoke ! There's also the wisdom amongst smokers: Not to light a cigarette from a candle; probably because of the unburned paraffine when sucking it through the tobacco, where a small dosage will cool to below the flamepoint.

With vacuum-pumps there is also the issue of not letting the oil-dust (exhalation) get into the lungs, probably it's the same with paraffine. Maybe the body can't get rid of it and it devalues the breathing-effectiveness ...
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tapira1
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[*] posted on 7-10-2008 at 16:15
hightemp bath


Use a sand bath; it is clean, cheap and safe. It performs as the best liquid bath.
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chemrox
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[*] posted on 7-10-2008 at 20:42


The problem with a sand bath or woods metal bath for that matter is you have to heat it with flame. I know the grand old masters heated ether with flames but I like to avoid flame in my lab. The porosity of sand makes it too expensive to heat sand with a hot plate. If you can get one hot enough that is..



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watson.fawkes
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[*] posted on 7-10-2008 at 21:34


Quote:
Originally posted by chemrox
The problem with a sand bath or woods metal bath for that matter is you have to heat it with flame. [...] The porosity of sand makes it too expensive to heat sand with a hot plate. If you can get one hot enough that is..
Why the felt need to use a hot plate? Surely an immersed mantle inside the sand, with the sand held in an insulated container, works just fine, and is just as electrical as a hot plate. For that matter, why not take apart the hot plate and use its element as the mantle?
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Picric-A
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[*] posted on 8-10-2008 at 02:16


Like watson.fawkes said, i made my own mantle by attaching a kettle heating element to the bottom of a metal bowl then filling with fine sand. This is good for refluxing but it can get amazingly hot and is hard to control the temp.
I have used an electric hotplate to heat a sand bath with no probs. Just wrap Al foil around it to keep some of the heat in and its fine.
Remember, the finer the sand the better.
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stoichiometric_steve
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[*] posted on 8-10-2008 at 04:21


Quote:
Originally posted by chiefThere's also the wisdom amongst smokers: Not to light a cigarette from a candle; probably because of the unburned paraffine when sucking it through the tobacco, where a small dosage will cool to below the flamepoint.


sorry, this is totally off topic, but i just had to say it: HA HA HA! does it really matter if you get that small amount of soot from a candle in your lungs when you smoke a cigarette? :D




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Picric-A
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[*] posted on 8-10-2008 at 04:39


Fair point! your lungs are mucked up anyway! a little parrafin wont change much! :D
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chief
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[*] posted on 8-10-2008 at 06:09


The lungs clean themselves regularly, and even formar-smokers can be healthy (some sort of) a whilelater,dependson the dosage. But there is still the parallel with the oil-dust from compressors and vacuum-pumps, usual-safety-issue. And this meant oil-dust is too an mineral-oil-derivative ..

Anyhow I wouldn't subject myself ton any paraffine-smoke.
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[*] posted on 8-10-2008 at 07:54


COMPLETELY off topic:

"Not to light a cigarette from a candle"

I've heard that this is actually quite an old superstition. Apparently sailor's wives would place a lit candle in their windows when their husbands were at sea, and lighting a cigarette off this candle would increase the chances of it going out, which would be seen as a bad omen for the sailor.
Which is why you will sometimes hear that lighting cigarettes of candles kills sailors.
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DNA
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[*] posted on 9-10-2008 at 00:33


I was just about the ask the same question (no not about the sigarettes), I've tried to do a ultra-micro boiling point determination.
I got very pissed of when the oil finally reached the 250*C with my hotplate, then it started smoking a bit and it wouldn't go higher.
The boiling point of the compound was around 260-270*C so that really sucked. Now I'm also indeed wondering what I could use better then the olive oil from the supermarket.
I can get ahold of liquid paraffin oil and silicon oil, ultragrade 19 edwards vacuum pump oil (380*C boiling point :P)
What oil is normally used in melting point apparatus?

DO MIND the autoignition temperature!!!
Just found that for the ultragrade 19 oil this is 355*C!
So the boiling point can nicely be 380 but when the oil will spontaneously catch flames is at 355 that is not really nice if you didn't expect that...

Santovac® 5 Diffusion Pump Oil
Has a boiling point of 476*C and autoignition of 590 so that one is even better, but probably also even more expensive than the ultragrade 19.

Another thing is glycerol/glycerine it has a boiling point of 290*C that is easy/cheap to get and has a nice boiling point...
Also found this:


[Edited on 9-10-2008 by DNA]

oil boiling points.JPG - 52kB
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chief
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[*] posted on 9-10-2008 at 00:42


One other fact: The average livetime of professional cooks is limited to 60years only ! (in Germany), thats statistics. This means: For each one that makes it to 70, 2 passoff at 55 ...
Maybe that comes partially from their oil-dust-breathing too ?


Besides: My version af oil-bath-substitute:
==> I have a hot-air-gun,
==> 2kW, max temp 630 [Cels] (but only 595 can be measured with a thermocouple),
==> temp digitally adjustable in 10 [Cels]-steps, from 50-630 [Cels]
==> and it coasted around 75 EUR

That thing just can be set to any temperature, and will hold it, even if the air-stream has to go through tight areas (higher streaming-resistance ==> less air will pass), due to the digital controller (which rapidly switches on-off the powerat the full 2 kW,net-consumption is less (eg. half-temperature (300 [Cels] @ half air-volume:only 500 W ... )

[Edited on 9-10-2008 by chief]

[Edited on 9-10-2008 by chief]
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chemrox
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[*] posted on 9-10-2008 at 11:23


I like the idea of building a sand bath from parts. One of you said the element he used was hard to control. I use a deep fat fryer as an oil bath and the controller has been spot on to 1-2*C. The only name I can find on it is "Davey." I don't know if it would behave as well if it were filled with sand instead of oil.



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mechem
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[*] posted on 24-10-2008 at 05:53


Does anyone have any experiences of heating Zinc chloride, which melts at 275-C and does not have the explosive drawbacks of KNO3 + NaNO2 if there was a spillage. Mainly need to know if there is heavy fuming at its melting point, as I do not have a sample to test.
Thanks
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