Sciencemadness Discussion Board

Sodium Oxide

Panache - 9-4-2009 at 23:52

Wiki claims heating sodium carbonate over 1000C produces sodium oxide, analogous to the heating of Calcium carbonate to form calcium oxide. I find this difficult to believe given potassium carbonate certainly does not revert/decompose to the oxide when strongly heated. Is wiki FOS here?
If not, anyone got anything interesting to do with some, sounds like a fun chemical, would be super hygroscopic i imagine and probably a great co2 absorber.


What the hell, for shits and giggles i'll throw some bicarb in the kiln now.

garage chemist - 10-4-2009 at 00:53

Hollemann-Wiberg says Na2CO3 will not decompose at all, not even at the highest heat, just eventually evaporate. So I say that wikipedia is in the wrong. But of course you can argument with thermodynamic equilibrium and that decomposition will happen if the CO2 partial pressure if low enough, but it doesn't seem like it is practically possible here.

Sodium oxide can be prepared by burning sodium to sodium peroxide, and heating this with more sodium to reduce it to sodium oxide. This is described in Brauer.

Very strong heating of sodium nitrate will also definately cause it to eventually give sodium oxide. The problem is finding a suitable vessel to do this in.

Taoiseach - 10-4-2009 at 02:58

Sodium nitrite, NaNO2, is also said to decompose @320°C giving off NOx fumes. Theoretically this should leave only sodium oxide.

Sodium nitrate, NaNO3 however is quite difficult to decompose thermally. Only little NaNO2 is formed upon heating. So its probably more feasible to start with NaNO2. The key to success here is to exclude moisture and CO2, otherwise only NaOH and Na2CO3 is obtained. A quartz tube with a steady stream of some inert gas might work, but in my experience quartz tubes tend to crack in these kind of experiments. The melted solid adheres very tightly to the glass. Upon cooling it shrinks/expands and breaks the glass. I killed 2 or 3 pieces of expensive lab glass until I switched to empty food cans for these kind of experiments :(

Globey - 10-4-2009 at 11:24

The elegance of Panache's idea would be that this would be a completely OTC source of food grade NaOH (via heating strongly the bicarbonate), and then adding water.

I bet if someone built mini professional versions of liquid air, Downs Na cell, ammonia plant (all made of same/similar materials of their larger brothers'), people would pay a few grand each.

Imagine adding table salt, plugging in, flipping a switch, and coming back to sodium metal (& optionally, Cl2). Imagine hitting the switch, and getting a hundred ml of so of liquid air.

kclo4 - 10-4-2009 at 12:31

Desiccating, absorbing gases, or further oxidizing it to a peroxide/superoxide would be about the only interests I would think.

Quote:
he elegance of Panache's idea would be that this would be a completely OTC source of food grade NaOH (via heating strongly the bicarbonate), and then adding water.


or you could just buy the NaOH an isle over from the baking soda. If you cant get that then CaO and Na2CO3 would work as well to make NaOH. Making NaOH from NaO is just horrible IMO.

Globey - 10-4-2009 at 15:21

"A" completely OTC source, not the only. "Food grade", not Red Devil grade. Besides, didn't they stop selling Red Devil? Why horrible, just add water and you got pure NaOH solution, good 'nuff for making great Philly/NY NY pretzels. Sorry, I would see this as more elegant than the CaO method (if it actually worked, which it doesn't, apparently). The feedstock would be an already food grade ingredient. Garbage in, garbage out.

Sedit - 10-4-2009 at 15:27

Globey being able to reach 1000 degrees C is not exactly over the counter. Not to mention where even though I lack personal experiance many people have reported successful production using CaOH method.

chief - 10-4-2009 at 16:15

Na2CO3 begins to decompose at 800 [Celsius] ; the stuff foams then, gets out of the crucible and into the furnace, and easily ruins it if the ceramics is acidic ... .
Besides probably K2CO3 decomposes too ... ; the fact, that its found in the ash of very hot burning wood doesn't mean any temp-resistance, since the K2O may well have reacted with CO2 when already cooled to a temperature where K2CO3 is stable.

Globey - 10-4-2009 at 17:14

Sedit, generally it is acknowledged that OTC in these contexts referrers most likely to reagents (which may have controls), unless you are in Texas, and that would involve glassware as well sometimes (but not to the exclusion of chemicals.) But, for sake of argument, even if OTC is being used in a broader sense, a kiln can still be bought cash & carry, so it is OTC.

Sedit - 10-4-2009 at 17:52

Sure I guess.......:o

Globey - 10-4-2009 at 18:48

Heh, I'm not the one who picked it apart.;)

Sedit - 10-4-2009 at 18:52

F'it

Never mind

[Edited on 11-4-2009 by Sedit]

Panache - 11-4-2009 at 17:23

Quote: Originally posted by chief  
Na2CO3 begins to decompose at 800 [Celsius] ; the stuff foams then, gets out of the crucible and into the furnace, and easily ruins it if the ceramics is acidic ... .
Besides probably K2CO3 decomposes too ... ; the fact, that its found in the ash of very hot burning wood doesn't mean any temp-resistance, since the K2O may well have reacted with CO2 when already cooled to a temperature where K2CO3 is stable.


Thanks you could have told me that before i did this for shits and giggles.

I'm very fortunate to only have chewed out one fire brick i used as a platform so the crucibles were eye level with the lower viewing plug otherwise the bottom of the kiln would have been chewed out.

I have had this kiln for a couple of years but never use it, largely because i am so ignorant. I really must learn further before doing more work in it.

The crucibles all cracked to random pieces, they were those german porcelain evaporating dishes, why would this be, was my ramp rate at 50C/min set way too high? The steel crucible i had in there to see if it would survive was turned to some crazy reduced shell of itself. The slaked lime just turned darker, not into CaO, and one of the pieces of broken porcelain had managed to sit sidways and as such didn't spill all of its liquid. it had an clear green glass-like substance in it. I had the kiln set to go to 1040 and hold there for 15mins.

Sedit - 11-4-2009 at 17:32

If you need any small pointers Panache just PM me. Ill show you how to make cleaning of the kiln a breeze and some other small tidbits. Iv had mine for some time and took classes for stuff like this.

not_important - 11-4-2009 at 18:30

The alkali carbonates and oxides are pretty agressive towards stuff with much SiO2, Al2O3, TiO2, or even ZrO2/ZrSiO4 in them. SiO2 goes the the alkali silicate and so on, in effect converting the ceramic to a lower melting glass that generally has much different thermal expansion than the original ceramic.

Li is worse that Na and K, in particular Li2O seems to attack many ferrous allows that Na2O does little to.

That temperature profile was too fast and short to do a decent job decomposing CaCO3 without additional airflow.

JohnWW - 12-4-2009 at 00:52

Another problem would arise if the oxide product of such pyrolysis of an alkali metal salt is allowed to cool in the presence of air., even if it could be done in a suitably alkali-resistant vessel. The presence of moist air would quickly result in the formation of the hydroxides, and probably also peroxides and hydroperoxides and (in the case of K, Rb, Cs) superoxides, all of which are also very deliquescent, along with small amounts of the bicarbonates and carbonates if CO2 is present.

[Edited on 12-4-09 by JohnWW]

chief - 12-4-2009 at 01:23

_Stainless_ steel lasts for a while, even at 800 Celsius and with Na2CO3 melt in it. But better have this in another stainless steel vessel, because at the end it will get some holes too ...