making sodium carbonate (anhydrous) at home?

[Gerald C Koch]

The reaction is 2NaHCO3 --> Na2CO3 + H2O + CO2

From the balanced equation and the molecular weights 2 x 84 g of bicarbonate should yield 106 g of carbonate or a yield of 63.1%. If your yield is greater than this then the conversion was not complete. Looks like you need to bake a bit more. Did you stir the bicarbonate a few times during the baking. Using a shallow baking pan also helps.

 

[Gerald C Koch]

You can also get sodium carbonate monohydrate from a pool supply store. One of the brands is called pH Plus. It is used to adjust the pool pH.

 

[Tom1956]

Thank you. No, I did not stir it. Baking dish was shallow to where I was afraid I'd spill some if I stirred. I'm just going to put it in a cookpot and turn the burner up and finish it. Sure wish my Elon would hurry up and get here. Can't wait to mix up my Beutler's. I just know it's the answer I've been researching for. I'm going to have this Xray film looking like the prettiest continuous-tone film you ever saw.

 

[Gerald C Koch]

Be sure to use a glass, stainless steel or enamel ware pot and not aluminum. The carbonate will attack the aluminum.

 

[Photo Engineer]

You can overdo the reaction and give off CO2 forming Na OH, which is why it is best to buy the Carbonate and Bicarbonate.

PE

 

[Tom1956]

Thanks men. Where I live there's no carbonate I could afford or justify the gasoline to go after. And can't just buy whatever I have a notion to, due to shipping charges. Somewhere the spending must end, and I have to just make do. Somewhere in this thread you guys had discussed everything I need to know 7 years ago. I just need to figure the percentages-by-weight of the before and after, and hope for the best.

BTW PE. Thank you. I guess you meant I could actually carry this too far and make lye out of it if I'm not careful.

 

[Tom1956]

Now we're down to 145 grams Na2CO3 from the original 230g of NaHCO3. Darn, it's been 40 years. I had forgotten all about Avagadro's number. It would take me 2 days of refresher study to work out this equation. Otherwise I guess I have to rely on the instincts of a cook rather than a chemist. And I sure ain't no cook. But still, you seem to get a feel for when it's done as you stir the pot. If I haven't driven off the water and CO2 by now, certainly it would still be good enough to make a bottle of developer out of. I don't think there's much more to be gained by throwing it on the stove again. I'll go back and study Avagadro's number another day.

Edit: A little touch of the fingertip of this stuff on your tongue is sharp and bitter as it can be.

 

[Gerald C Koch]

As a practical consideration you cannot heat sodium carbonate in an oven to a high enough temperature to have it decompose to sodium oxide and carbon dioxide. In order for decomposition to occur the carbonate must he heated enough for it to melt (854oC, 1569oF). So don't worry about "over cooking" things.

 

[Photo Engineer]

Thanks Jerry, I had forgotten that temp. I stand corrected.

PE

 

[Tom1956]

Thanks guys. I guess I've got this right. There could be a hair of bicarbonate still left in it I suppose. But I've seen developer formulas before somewhere with bicarb in them. It tastes very bitter, it is fine and sandy, and the leftover powder on my fingers feels slimy and "basey" when I rinse them off. I'm going to go with it.

 

[Gerald C Koch]

Sounds good. The resulting product is a light fluffy powder. Be sure to store the carbonate in an air-tight jar as it will absorb moisture and convert to the monohydrate. If this happens it will throw off any formula a bit. One of the advantages in doing this is that you are starting with USP grade sodium bicarbonate so the resulting carbonate is very pure, perfect for photo uses.

 

[john_s]

....One of the advantages in doing this is that you are starting with USP grade sodium bicarbonate so the resulting carbonate is very pure, perfect for photo uses.

This is much better than using pool chemicals which don't have to be pure. Purity costs money. I bought another water treatment chemical (aluminium sulphate) to clarify my swimming pool that has to be filled with creek water and the label said something like "up to 23% impurities" and including something like 5% insoluble impurities. Yuck! Just as well I don't need it for photography!