Barium Oxalate Synthesis Report

[Nitrato]

Sorry if Im wrong, but I've searched for the word "oxalate" and dont see any specific thread on its synthesis, that is very simple and many of you folks already know. So Im just starting this topic.

 

Barium oxalate (as well strontium equivalent) is nearly insoluble in water and is widely used in green coloured light devices and unlike other barium salts used in pyro, it is a reducing salt. BTW, Barium oxalate (ppted along with TiO2) is a precursor to make barium titanate dielectric, vastly used in many ceramic (disk or monolithic) capacitors and other high technologic stuff.

 

You can make barium oxalate using oxalic acid solution and barium chloride solution:

 

BaCl2 + (COOH)2 ---> BaC2O4 + HCl

 

At first you can say it wont work since this is a weak acid (oxalic) giving a strong acid (HCl), but thanks the very low solubility of barium oxalate it will work.

 

My first time making it, Ive used 60g BaCl2*2H2O, 30g oxalic acid and a total amount of 600mL hot tap water that resulted in ~40g barium oxalate (~70% yield after several washes):

 

http://i242.photobucket.com/albums/ff176/tnitrato/MADSCIENCE%20II/DSC05506.jpg

 

From the expent liquor I neutralized with Na2CO3 and got a lot of BaCO3 (that Ive used at time for chemical purposes, not pyro).

 

So seeing this, the reaction abovementioned is actually a equilibrium reaction:

BaCl2 + (COOH)2 <---> BaC2O4 + HCl

as the HCl concentration raise, the barium oxalate is prevented from further precipitating from solution.

Also, due to acid presence and low solubility of oxalate (in other words you cant recrystallize it), its difficult to properly neutralize the acid traces and this may be dangerous in pyro comps.

 

As alternative to increase the yield, eliminating equilibrium and having a non-acidic product you need to use oxalic acid as a soluble salt. Sodium oxalate is OK if you need the BaC2O4 for purposes other than pyro since its very difficult to remove Na; it will ruins your green comps.

 

So another soluble salt is what is needed. Potassium oxalate is perfect!

 

Relevant reactions:

 

2 KOH + (COOH)2*2H2O --H2O--> K2C2O4 + 4 H2O (I)

 

K2C2O4 + BaCl2*2H2O --H2O--> BaC2O4(s) + 2 KCl + 2 H2O (II)

 

Precursors:

 

KOH = potassium hydroxide (MW = 56.106g/mol), from chem lab (make sure its sodium free). More corrosive and deliquescent than NaOH. Try to avoid contact of the flakes/pellets with glass for long time, as it will be attacked.

 

(COOH)2*2H2O = oxalic acid dihydrate (MW = 126.065g/mol), technical grade from chem lab supplier.

 

BaCl2*2H2O = barium chloride dihydrate (MW = 244.263g/mol), technical grade from lab supplier or you can make your own by pottery grade BaCO3 and HCl. Gloves are needed in order to work with this nasty stuff. Have a bottle of epsom's salt (magnesium sulfate heptahydrate)laying around just for safety sake if you accidentally ingest some soluble barium.

 

BaC2O4 = barium oxalate (MW = 225,346g/mol), here the desired product. Use gloves always when working with this stuff. Although of low solubility (about 3mg/100mL H2O at room temperature), if you accidently ingest the HCl in your stomach you dissolve it creating oxalic acid and soluble barium, both are not good to you..Ingest enough epsom's salt and call the doctor if this happens.

 

So now, after all mumbo-jumbo, lets do the funny part!

 

I did weight 65g of oxalic acid dihydrate:

http://i242.photobucket.com/albums/ff176/tnitrato/Barium%20Oxalate/100_0429.jpg

 

and then put in 200mL of demineralized water on a beaker, not all dissolved. The dissolution of oxalic is endothermic as the beaker feel cool and starts condensing moisture on external walls.

 

57g of KOH was taken and slowly dissolved in 200mL of demineralized water in another container (made out of PP), this was made with care since caustic solution could boil if you are to hurried to dissolve it. The KOH solution was gradually added to oxalic solution very slowly stirring with glass rod, after all of it added, the beaker was too hot to touch but the solution didnt boiled.

http://i242.photobucket.com/albums/ff176/tnitrato/Barium%20Oxalate/100_0435.jpg

http://i242.photobucket.com/albums/ff176/tnitrato/Barium%20Oxalate/100_0430.jpg

 

Crystals of potassium oxalate forming at stirring rod surface:

http://i242.photobucket.com/albums/ff176/tnitrato/Barium%20Oxalate/100_0441.jpg

 

Meanwhile, 124g of BaCl2*2H2O were dissolved with two portions of demineralized water and filtered through a funnel and a large glass pot to remove some black insoluble material.

http://i242.photobucket.com/albums/ff176/tnitrato/Barium%20Oxalate/100_0427.jpg

http://i242.photobucket.com/albums/ff176/tnitrato/Barium%20Oxalate/100_0436.jpg

 

 

When all of the barium chloride solution has been filtered, it was heated to about 80-90°C:

http://i242.photobucket.com/albums/ff176/tnitrato/Barium%20Oxalate/100_0439.jpg

 

Then the still hot potassium oxalate solution was added with stirring to it (video):

http://s242.photobucket.com/albums/ff176/tnitrato/Barium%20Oxalate/?action=view&current=100_0442.mp4

 

A voluminous precipitate of barium oxalate was the result:

http://i242.photobucket.com/albums/ff176/tnitrato/Barium%20Oxalate/100_0443.jpg

 

Then it was filtered through funnel with two coffe filter paper and washed in filter first with 4 portions of 300mL hot tap water, then after with 7 portions of 100mL hot demineralized water.

http://i242.photobucket.com/albums/ff176/tnitrato/Barium%20Oxalate/100_0444.jpg

 

A newspaper was put above the filter to avoid dust falling in it while filtering

http://i242.photobucket.com/albums/ff176/tnitrato/Barium%20Oxalate/100_0445.jpg

 

After all washing cycles, the filter paper with moist BaC2O4 was carefully grabbed (gloves) and very slowly and carefully squeezed to remove excess water.

 

I then open the filter paper and spread the mass on two folded white A4 paper.

http://i242.photobucket.com/albums/ff176/tnitrato/Barium%20Oxalate/100_0462.jpg

 

My resistance hotplate pictured above, that I've used for many years, finally corroded (at electrical connection), just in this synthesis, so instead of throwing it in the trash bin, I've modified it a bit to funcion as drying plate. Resistance spring-wire was cut in half (about 19 ohms) and then stretched to fill again all the ceramic paths. A broken AC-DC converter was just with transformer (capacitor exploded) that gave abou 16,5 VAC and this was wired to the resistance wire, it heats the things above it to about 60-70°C. The still moist BaC2O4 was transferred to a plasticware container and put above this drying device, larger lumps were broken with a pestle and minor ones with the original glass rod to speed up drying process.

http://i242.photobucket.com/albums/ff176/tnitrato/Barium%20Oxalate/100_0451.jpg

http://i242.photobucket.com/albums/ff176/tnitrato/Barium%20Oxalate/100_0464.jpg

 

I didnt used the kitchen oven to avoid contamination/poisoning (and of course to avoid troubles with my mom); it would be faster to dry though.

 

After several hours on the drying plate, the salt was then weight: 112,1g ( This represents 97% yield but minding about 5% max moisture would represents about 93% yield based on barium chloride), put in a glass container and labelled:

http://i242.photobucket.com/albums/ff176/tnitrato/Barium%20Oxalate/100_0468.jpg (I put in the label 10% max of mositure but after a while I was under impression this couldnt be true.. It should be 5% max)

 

All the spent/washing solutions were put together and treated with sodium carbonate solution (ammonium bicarbonate or potassium carbonate would be better) and was then filtered and dried resulting in 3,2g BaCO3. Based on barium chloride and counting with barium recover, the yields of BaC2O4 increases to about 96% overal yield)

Sodium carbonate and spent solutions before mixing:

http://i242.photobucket.com/albums/ff176/tnitrato/Barium%20Oxalate/100_0458.jpg

After mixing:

http://i242.photobucket.com/albums/ff176/tnitrato/Barium%20Oxalate/100_0459.jpg

BaCO3 on the bottom:

http://i242.photobucket.com/albums/ff176/tnitrato/Barium%20Oxalate/100_0460.jpg

 

I still didnt test this oxalate and I think it may need a further drying step, but most of the job was done.

Please criticize and comment.

Thanks.

Edited January 31, 2012 by Nitrato

[kleberrios]

Very good tutorial, it should be fixed on site because it shows hard work and perseverance. I need urgent because this material is a material very difficult to achieve. Glad you're here in Brazil. Titanium and Magali and I have many other products to make the switch kkkk. See what you need and I will send. Congratulations.

[brimstoned]

I used a similar process to produce copper oxalate.

Mixed a solution of ammonia with the oxalic acid solution, then mixed the resulting ammonium oxalate soution

with a copper sulfate solution: the resulting sky-blue "mud" took a looong time to filter and wash.

[Swede]

I missed this since I returned to APC. Really nice write-up! I like the fact that you emphasized safety and also label your chems with appropriate danger signs.

 

Barium scares me a bit, but it's an important pyro element. It's funny, I also have epsom salts on hand, with the thought... "You never know. Bad things sometimes happen." Barium sulfate is SO insoluble, you could drink a gallon milk shake of it and you'd have zero ill effects. They use it in hospitals for imaging the digestive system. I also use it to ppt lead from solutions of the Pb acetate or nitrate. Lead sulfate is still poisonous, but less liable to get ingested or absorbed through the skin than the aqueous Pb salts.

 

We need more write-ups like this. Again, nice job.

 

Oh yes, anyone interested in basic chemistry processes that require filtering, a buchner funnel with a vacuum pump or aspirator is a HUGE bonus for your lab. There's nothing wrong with coffee filters, and I use them all the time too, but for fine precipitates, vacuum is the way to go.