Sciencemadness Discussion Board

Boilling flask method

nelsonB - 29-4-2016 at 15:25

Hi
so we know the oil bath,
sandbath is a little more uncommon,

oil can go rancid after a while, sand might scratch the glassware,
what about bentonite clay bath ? AKA = Uncented cat litter.

Will it work ?

elementcollector1 - 29-4-2016 at 15:54

Larger particles are easier to clean off; smaller particles give more even heating. Personally, I find that regular sand works very well.

macckone - 29-4-2016 at 15:54

Too insulating. Lead shot is soft and conductive.

JJay - 29-4-2016 at 16:00

I've broken too many flasks in sand baths to recommend them. Maybe if you heat really slowly....

careysub - 29-4-2016 at 17:30

If you are concerned with scratching glass (silica sand Mohs hardness is 7) you might try calcium carbonate sand (Mohs harness 3), sold as "play sand" in hardware stores and for reptile cages in pet stores. Glass beads would fix the scratching problem also.

But a problem with any mineral type bath is that minerals are basically insulators which is the opposite of what you want for a bath. Sand baths probably work best for very small scale baths. Bentonite for kitty litter in particular is porous and thus an even better insulator than sand.

The thermal conductivity k (W/(m K)) for sand is 0.2 which is fair for an insulator but bloody awful for a conductor. Lead has a conductivity of 35, iron is 73, aluminum is 200 and pure copper is 386. Now a shot bath is going to be lower than these values (which are for solid metal) but still far higher than sand.

nelsonB - 29-4-2016 at 17:37

i tought lead bb covered with copper could be good.
but kind of expensive.

0750093_1.jpg - 5kB

careysub - 29-4-2016 at 18:06

Steel shot is probably cheaper and better than lead.

On eBay you can get pure copper filings for $10/lb (6 lb for $60) and copper pennies for $2.50-$4/lb. You could mix them together for a ~$6/lb bath perhaps. Copper pennies are an alloy that is 95% copper, and has a conductivity half that of pure copper, but still as good as aluminum.

Aluminum pellets are available on eBay as well for $5/lb (which due to their lower density makes a much bigger bath per lb).

I was going to also suggest dibutyl phthalate from Firefox-FX which is cheaper per qr than some expensive high smoke point cooking oils and is used by some up to its BP of 340 C, but then found that it's flash point is 180 C, so it does not look like such a good idea. Cooking oil may smoke or oxidize, but it does not flash ignite until very high temps. Soybean oil (based on smoke point) is probably the best cheap oil with a smoke point of 257 C (probably spurious precision) for ~$10/gallon. I'd use metal shot baths to go higher.

[Edited on 30-4-2016 by careysub]

OneEyedPyro - 29-4-2016 at 18:13

Cat litter is too fluffy and would likely conduct heat quite poorly.

Regular cooking oil may go rancid but there are plenty of liquids that could be used, ethylene glycol or most motor oils could be used to pretty high temps.

Artemus Gordon - 2-5-2016 at 12:29

Quote: Originally posted by careysub  
Copper pennies are an alloy that is 95% copper, and has a conductivity half that of pure copper, but still as good as aluminum.

American pennies have been made of zinc plated with copper since 1982. Zinc is a much poorer thermal conductor than either Cu or Al, so unless you can get some old pennies at a good price, this probably won't work too well.

OTOH, they are GREAT for making a Voltaic pile.



[Edited on 2-5-2016 by Artemus Gordon]

Orenousername - 2-5-2016 at 12:48

Quote: Originally posted by careysub  
If you are concerned with scratching glass (silica sand Mohs hardness is 7) you might try calcium carbonate sand (Mohs harness 3), sold as "play sand" in hardware stores and for reptile cages in pet stores. Glass beads would fix the scratching problem also.



Quikrete's msds for play sand I purchased and home depot states that the sand is ~99% silicon dioxide. However, when I tried cleaning it in hardware store h2so4 a large amount of bubbling occurred and a very fine percipitate formed with some of the rocks left behind on the bottom.. any ideas on what might cause this?

Mabus - 2-5-2016 at 13:59

What about dry table salt (NaCl)? It has high thermal conductivity, and that could be an advantage.
I used it once and it went fine. The only disadvantage I can think of is that it might corrode steel.

careysub - 2-5-2016 at 14:07

Quote: Originally posted by Artemus Gordon  

American pennies have been made of zinc plated with copper since 1982. Zinc is a much poorer thermal conductor than either Cu or Al, so unless you can get some old pennies at a good price...


Check out eBay as I recommended, you can get multi-pound lots of sorted COPPER pennies for the prices quoted.

careysub - 2-5-2016 at 14:10

Quote: Originally posted by Orenousername  
Quote: Originally posted by careysub  
If you are concerned with scratching glass (silica sand Mohs hardness is 7) you might try calcium carbonate sand (Mohs harness 3), sold as "play sand" in hardware stores and for reptile cages in pet stores. Glass beads would fix the scratching problem also.



Quikrete's msds for play sand I purchased and home depot states that the sand is ~99% silicon dioxide. However, when I tried cleaning it in hardware store h2so4 a large amount of bubbling occurred and a very fine percipitate formed with some of the rocks left behind on the bottom.. any ideas on what might cause this?


The bubbling would probably carbonates mixed in.

To get calcium carbonate sand, you do need to check that that is what they are selling. "Play sand" can be silica sand also or (it would seem from your sample) a mix of the two.

Orenousername - 2-5-2016 at 16:49

Quote: Originally posted by careysub  
Quote: Originally posted by Orenousername  
Quote: Originally posted by careysub  
If you are concerned with scratching glass (silica sand Mohs hardness is 7) you might try calcium carbonate sand (Mohs harness 3), sold as "play sand" in hardware stores and for reptile cages in pet stores. Glass beads would fix the scratching problem also.



Quikrete's msds for play sand I purchased and home depot states that the sand is ~99% silicon dioxide. However, when I tried cleaning it in hardware store h2so4 a large amount of bubbling occurred and a very fine percipitate formed with some of the rocks left behind on the bottom.. any ideas on what might cause this?


The bubbling would probably carbonates mixed in.

To get calcium carbonate sand, you do need to check that that is what they are selling. "Play sand" can be silica sand also or (it would seem from your sample) a mix of the two.


If that's the case then most of it was calcium carbonate because most of it reacted with the h2so4. I'll check later to see if the percipitate is caso4. I doubt the msds for a company as large as quikrete would be that unreliable though..

Texium - 3-5-2016 at 05:33

Play sand here is mostly silica, with small amounts of calcium carbonate and iron oxide. I once cleaned some with hydrochloric acid and analyzed it in a rather primitive way.

careysub - 3-5-2016 at 06:53

The contents of hefty bags of "play sand" no doubt varies with location, since it is a low value bulk product it is sourced locally. When I bought play sand in So Cal several years ago, it was calcium.

If want calcium carbonate sand you may have more reliable luck at the pet store with sand for reptile cages and fish tanks- it will be labeled calcium (or aragonite for fish) if it is. Both silica and calcium sands are used for reptiles and fish, but many reptile owners prefer calcium and some aquarium set-ups require it so I would expect it to be stocked in any pet store.

alking - 3-5-2016 at 18:27

Not all oils go appreciably rancid, you can use mineral oil or even motor oil would even be good, I always use mineral though. The bigger pain is dealing with hot oil, it's certainly easier to spill and burn yourself, as well as having to always clean the mess off of your flasks.

RogueRose - 3-5-2016 at 22:17

I'll second the mineral oil for a liquid as well as CaCO3 or possibly CaSO4 (plaster of paris anhydrous). Both are very fine powders which seem to handle heat very well.

MrHomeScientist - 4-5-2016 at 12:42

Also something to note is that insulating baths can damage your hot plate. I recently used a sand bath with the hot plate at max, and it hardly heated the flask at all and I ended up with lots of tiny cracks in the hot plate surface. I've heard of aluminum hot plate surfaces melting under those conditions too. I might try the copper plated BB bath, and I also considered making my own "lab armor" beads by pouring molten Al into a bucket of water.