Sciencemadness Discussion Board - Using table salt in heat bath?

Using table salt in heat bath?

chucknorris - 17-12-2012 at 14:53

I have tried couple of different options:

water - only good up to 100c
sand - damn good heat insulator - slow
brake fluid - the smoke....
food oils - FUCK! IT AUTOIGNITED!

So, how about table salt, maybe as fine powder? Dont have enough at hand and though to ask quickly wether anyone at here have tried or used it and found it better than the previous ones?

kristofvagyok - 17-12-2012 at 15:45

Table salt has a similar problem to sand, it is slow as hell.

Try out silicone oil, it is usually good up to 300 Celsius.

VitaminX - 17-12-2012 at 15:57

Triethylenglycol or higher Polyethylenglycols which are fluid at RT would be an option as well (good to use until about 240 °C I'd say)

chucknorris - 17-12-2012 at 21:09

Ok thanks for giving me chance to pass that salt test.

Silicone oil is ok but the high price sucks.

On the other hand, I gave a thought for 4.5mm steel or copper bb:s which are sold everywhere - it would cost probably even more. Anyways, when using large vessels like 4L, 10L and 20L, the amount of oil and BB needed are tremedous.

Oscilllator - 17-12-2012 at 21:12

Your cooking oil auto ignited?! according to the below website the auto-ignition temp of vegetable oil is 424 degrees!
were you using a gas burner/naked flame?

source: http://drum.lib.umd.edu/bitstream/1903/11333/2/Buda_Ortins_R...

Edit: What about ionic compounds? copper sulfate has a melting point of either 110 or 150 degrees, you could use that. Idk about copper poisoning though.

[Edited on 18-12-2012 by Oscilllator]

sargent1015 - 17-12-2012 at 21:24

Quote: Originally posted by Oscilllator

Your cooking oil auto ignited?! according to the below website the auto-ignition temp of vegetable oil is 424 degrees!
were you using a gas burner/naked flame?

Interesting, I have never had a problem with mine, other than the whole house smelling like I deep fried stuff

Broken Gears - 17-12-2012 at 22:16

How about alumina? I work with a fluidized bath that goes to 600 °C and it heats up in an hour. It will probably go slower if it is not air agitated. I got tons of aluminium oxide if you need some.

Ceran

Organikum - 17-12-2012 at 23:48

Used and partially broken glass-ceramic "Ceran" cooking units are virtually for free. The plate can be cut by any glazier or oneself (tools for cutting tiles work better then a standard glasscutter) and one gets 2 or 3 hotplates for almost free. Infrared hotplates which work up to pretty high temperatures. Putting a jacket around the flask with a cover on top (as with the hot-air-bath in Vogels and other reference literature) provides very good controlable heating. The infrared in addition gives rapid heating up. Temperature can be controlled easily and smooth by something like this. Well if you want to watch then youĺl have to cut the bottom of a big beaker and use this as sleeve or integrate a oven window - also cheap and easy. Otherwise a big old can or some aluminium sheet 0,5-0,8mm do it nicely, both can be worked with strong scissors.
Leave some small holes at the bottom and top, don't close it hermetically thats bad for the performance, air must be able to enter and leave to generate a chimney effect.

The drawback of the hot-air-bath was always the use of open flames, a burner to heat and even then it took time to get on temperature. The infrared eliminates both problems.

I have improvised such setups with strong aluminium foil made to a tent over electric and gas heaters and it works perfectly also in in higher temperatures (dry destillations for example). The bottomless beaker is of course the hit, alone by optics :cool:

But this may be not your cup of tea. Then add some oil to your sand this prevents ignition and nasty reactions with stupid waterdrops falling into the overheated oil. When the sand is just wetted and not swimming this is no isssue anymore. Heat-transfer is of course very much improved and about similar to a plain oil-bath, using a SS bowl so the mantel of sand/oil is thin, a centimeter about, is a good idea too, reduces the latency of mass by magnitudes. I know people who have buried heating wire directly in such a sand/oil mixture and used this for a kind of heating mantle with good success.

/ORG

woelen - 18-12-2012 at 00:01

I have good experiences with a concentrated solution of CaCl2 in water. This can go as high as 140 C. The only problem is that you have to refill the water every few minutes and that a lot of water vapor is released. You also get white powder of CaCl2 on your glassware and on the table where you are working, but this is easy to rinse away.

phlogiston - 18-12-2012 at 01:48

Woelen, is the salt sold for snow removal in the Netherlands mostly CaCl2? The bags I see in hardware stores are hardly ever labelled. I used to buy CaCl2 meant for dehumidifying closets etc, but 'strooizout' would be more economical.

woelen - 18-12-2012 at 02:50

No, "strooizout" is mainly NaCl, actually, it is quite pure NaCl. I have a 25 kg bag of this, and it dissolves in water completely clear and when electrolysed it does not produce any turbidity near the cathode (if it contained Ca-salts or Mg-salts it would, due to formation of insoluble carbonates with CO2 from the air). Usually "strooizout" is not suitable as table salt, because it is humid and not easy to sprinkle over food and the purity of the product is not guaranteed. The bag I have is good, but other bags of different brands or even bags of the same brand, purchased a few months from now may have lower purity.

chucknorris - 18-12-2012 at 10:35

The veg oil autoignition went actually pretty fast, I had the plate on for maybe 15-20 minutes, it smoked a bit for first, and then - it just went meter-high flames. Having fireproof gloves, I took the glassware quickly off and damped a plate on the bath pot to suffocate the flames. Never tried veg oils again. Im using a 2kW hotplate, 1kW bunsen, and a 6kW gas burner, and this happened with the first one.

The liquid copper sulfate and the aluminium oxide sounds rather interesting. Im mostly interested in liquids and powders because of the easy handling.

I was also using an air bath earlier, which I used the aluminium trangia ring, which fitted perfectly on top of the hotplate and carried 2L and 4L RBFlasks just like from factory, leaving about 1cm air between the plate and the flask bottom.

http://i3.squidoocdn.com/resize/squidoo_images/590/draft_len...

The second part from the right.

And a question:

If heated up to 500C, will copper sulfate release toxic or harmful fumes? The place I am using has a filter which I want to minimize the amount of vapors and fumes because it has to be replenished every soon it loses its filtering capacity. Thats why I do all the boiling in distillation setup.

[Edited on 18-12-2012 by chucknorris]

Oscilllator - 18-12-2012 at 12:32

Quote: Originally posted by chucknorris

The veg oil autoignition went actually pretty fast, I had the plate on for maybe 15-20 minutes, it smoked a bit for first, and then - it just went meter-high flames. Having fireproof gloves, I took the glassware quickly off and damped a plate on the bath pot to suffocate the flames. Never tried veg oils again. Im using a 2kW hotplate, 1kW bunsen, and a 6kW gas burner, and this happened with the first one.

The liquid copper sulfate and the aluminium oxide sounds rather interesting. Im mostly interested in liquids and powders because of the easy handling.

I was also using an air bath earlier, which I used the aluminium trangia ring, which fitted perfectly on top of the hotplate and carried 2L and 4L RBFlasks just like from factory, leaving about 1cm air between the plate and the flask bottom.

http://i3.squidoocdn.com/resize/squidoo_images/590/draft_len...

The second part from the right.

And a question:

If heated up to 500C, will copper sulfate release toxic or harmful fumes? The place I am using has a filter which I want to minimize the amount of vapors and fumes because it has to be replenished every soon it loses its filtering capacity. Thats why I do all the boiling in distillation setup.

[Edited on 18-12-2012 by chucknorris]

I only used copper sulfate as an example, I am sure there are many other ionic compounds that melt at relatively low temperatures and have no chance of giving off toxic fumes.
However I imagine copper sulfate would decompose in a similar way to iron sulfate, to release sulfur oxides and leaving behind copper oxide.
Apparently the decahydrate of sodium sulfate has a melting point of 32 degrees

chucknorris - 18-12-2012 at 15:26

How about steel grains? I found a bag of 0.2-0.4mm sized stuff. I also found 0.5-1mm sized, which one is better, the smaller or larger ones?

Just out of interest, how about a mercury bath?

smaerd - 18-12-2012 at 15:56

There is a thread on this forum about a product called I think "Lab-armor".

http://www.sciencemadness.org/talk/viewthread.php?tid=19580

Using mercury is not a good idea. Imagine a spill? Not to mention it is volatile(goes into the air) and inherently toxic.

Magpie - 18-12-2012 at 16:11

I use silicone oil (DOT5 brakefluid) up to about 288°C. When I had to go higher I used a Bi/Sn eutectic mixture.

chucknorris - 18-12-2012 at 17:18

I used DOT5.1 fluid, but it started smoking heavily at just only 120C. IDK if its shitty or something, but dont wanna use it again.

Magpie - 18-12-2012 at 18:56

Quote: Originally posted by chucknorris

I used DOT5.1 fluid, but it started smoking heavily at just only 120C. IDK if its shitty or something, but dont wanna use it again.

DOT5.1 is not a silicone oil. See: http://en.wikipedia.org/wiki/DOT_5.1

Silicone Brake Fluid

cal - 19-12-2012 at 10:37

I use the silicone brake fluid from auto zone, no smoke and has a boiling point as follows: DOT 5 260 °C (500 °F)
DOT 5.1 270 °C (518 °F) . This works well with a foil or heat blanket wrap around the flask.

smaerd - 19-12-2012 at 11:17

Has anyone used glycerine as a heating bath liquid? It's pretty cheap, available to amateurs and has a high boiling point(290*C). It's also environmentally benign for the most part.

watson.fawkes - 19-12-2012 at 12:16

Quote: Originally posted by chucknorris

Just out of interest, how about a mercury bath?

The vapor pressure of Hg is pretty high even at room temperature. An open pool of Hg will saturate its vapor in a closed room within a few days (or less, I forget). A hot pool of Hg will do so even faster.

Even putting inside a fume hood isn't a cure all. Hg vapor does condense, after all, and the first place it will condense is in the output duct of the fume hood. When the fan's not on, Hg vapor diffuses right back down through the fume hood into the laboratory. This isn't nearly as rapid, of course, but using a hood does is to create a slower hazard; it won't eliminate it.

feacetech - 20-12-2012 at 13:54

I use to use parafin oil for bleaching tallow at 105C the bath would smell, go brown and fill with a sludge over time

I use to use glycerol in my drying ovens for my thermo meters at 100C it would brown and thicken over time, acrolein formation migth be a problem.

Pyro - 20-12-2012 at 15:54

how can you guys put up with oil baths? they are horrible. get oil everywhere. why not just regulate the heat on your hotplate?

kristofvagyok - 20-12-2012 at 16:13

Quote: Originally posted by Pyro

how can you guys put up with oil baths? they are horrible. get oil everywhere. why not just regulate the heat on your hotplate?

Oil bath is a good thing if you do not spill the oil everywhere. Just be careful and always have some paper nearby to get off the oil from the bottom of the breaker.

The problem with the direct hotplate heating is that how would I heat to boiling point 2 liter of pyridine without a bath?

Pyro - 20-12-2012 at 16:24

you get a hotplate with temp. regulator. I got one and it cost a little less than a normal one.
just put the supplied thermometer on the plate, and set it to whatever temp. you want, then it will heat until the thermometer reaches that temp. and will hold it there. the only problem is that if you don't put the thermometer on the hotplate it thinks it is room temp. and will keep heating

I prefer this method, no oil everywhere, no fuss, no smoke

kristofvagyok - 20-12-2012 at 16:34

Quote: Originally posted by Pyro

you get a hotplate with temp. regulator. I got one and it cost a little less than a normal one.
just put the supplied thermometer on the plate, and set it to whatever temp. you want

If you are working in a round bottomed flask (what is the only what could be heated as we know....), then just a tiny surface of your flask will contact with the hotplate and the rest, 99% will contact with air what will simply go away and won't heat up your flask.
Oil is good, because it heats up easily and your flask surface is easily contacted with it.

Pyro - 20-12-2012 at 16:56

true. I don't have that problem as I use ground glass erlenmeyers

kristofvagyok - 20-12-2012 at 17:18

Quote: Originally posted by Pyro

true. I don't have that problem as I use ground glass erlenmeyers

The first time when it will break you will be really surprised. Always use round bottomed flasks and not Erlenmeyers.

Pyro - 20-12-2012 at 17:34

why? whats the deal with them?

elementcollector1 - 20-12-2012 at 19:48

I've used Erlenmeyers for heating and boiling liquids multiple times, never had a problem.

Pyro - 20-12-2012 at 20:05

thats what i mean. Its baisically just an erlenmeyer but with a ground glass top
like this one