Implications of subbing sodium bicarbonate for sodium carbonate in developers?

Trey

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I've recently been buying metol, hydroquinone etc. so we could save money on chemistry at my community darkroom. One of our members mentioned that he uses sodium bicarbonate in place of sodium carbonate in his Ansco 130 variant paper developer.

A quick Google search shows that we'd save a ton of money doing this, but I can't find any photo-related documentation on the implications.

Is this a good idea? How would you modify formulas to accommodate for the difference? IS there a difference in terms of how it works in the developer?
 

Anon Ymous

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Sodium bicarbonate is less alkaline, so I wouldn't expect it to give a pH level that is as high. You could make carbonate from bicarbonate by adding the right amount of Sodium hydroxide, but it is pointless. Apart from that, Sodium Carbonate is a cheap ingredient and shouldn't cost you much, nor make sense to try to substitute. I'd hazard a guess that you haven't found a reasonably cheap source of carbonate.

PS You can make carbonate from bicarbonate by heating it, but it a bit of a chore that you don't need to mess with.
 

trendland

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Caffenol is with sodium bicarbonate - but I like to drink Coffee - my films like REAL chems..!

with regards
 

Luckless

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A related question to go along with it: If Sodium Bicarbonate isn't as well suited, is it reliable/worth the effort to heat convert Sodium Bicarbonate to Sodium Carbonate, rather than just buying it ready made?

I've only been around the edges of lab chemistry, but I've gotten the impression that a good chunk of the cost of 'lab grade' Sodium Carbonate is in packaging and purity so that end users actually receive the carbonate form, rather than having some/most/all degrade into the bicarbonate form, rather than it actually being hard to make.
 

trendland

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Listen Tray : there are ALLWAYS alternates 1) you look at eBay for chemicals! 2) you look at chemical supliers 3) you look about washing soda :


with regards
 
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Trey

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Thanks guys. now that I've searched for "washing soda" I've found it for about half the price I was paying otherwise. Didn't come looking for further savings but here we are!

What would be the actual changes to the developer? Has anyone compared the differences?
 

koraks

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With sodium carbonate, the main issue is getting clarity of which hydrate you have. Photographic formulas tend to ask for monohydrate (although it's often not made explicit), while washing soda is generally decahydrate. As long as you know which hydrate is asked for, which one you've got and apply the correct conversion factor, you should generally be fine.
I always use washing soda (decahydrate) in my photographic chemistry and it has always worked fine.
 

KN4SMF

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I bake my own carbonate from bicarb. But then I have some good Ohaus scales to make sure the conversion is complete
 

BradS

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Anon Ymous said:
.... You could make carbonate from bicarbonate by adding the right amount of Sodium hydroxide, but it is pointless.
Click to expand...

No. This is incorrect. (EDIT No. actually, it is correct. Sorry for any confusion)

Anon Ymous said:
PS You can make carbonate from bicarbonate by heating it, but it a bit of a chore that you don't need to mess with.
Click to expand...

It is really no effort at all. buy a box of baking soda, dump the whole box into a glass baking dish, spread it out and bake it in the oven at 350 degrees F for an hour. Stir about every fifteen minutes or so...

The benefits of making it this way is that the resultant sodium carbonate is very pure....and , you KNOW that the resultant is Anhydrous. This can be verified by comparing the mass of the original bicarbonate to the mass of the resultant.
 
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Anon Ymous

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BradS said:
No. This is incorrect.
Click to expand...
How is this incorrect? It's a reaction between a base and a partially neutralised acid:
NaHCO3 + NaOH -> Na2CO3 + H20
Once in solution, the bicarbonate - hydroxide mixture is exactly equivalent to carbonate. But IMHO there's no point in doing so, because Sodium Carbonate is easily obtainable, cheap and you don't have to mess with any method of synthesis, including heating bicarbonate in the oven.
 

BradS

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Ah, yes. I see. You are correct. I hadn't thought about an aqueous solution...I learned something. Thank you.

(one day I'll learn to not spout off like I know everything!...at least not until after I've had my second cup of coffee).
 
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trendland

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Guess you are quite right - but perhaps this" incorrect" is mentioned in concern:
There is no need to make work in chem lab ! AS you self stated : because it isn't expensive !
with regards
 

removed account4

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Trey
If you can't get Super Washing Soda there is a conversion factor on one of the Caffenol Blogs. I don't know which one maybe Caffenol.com? ( or .org ). You probably won't have trouble finding Washing Soda though it usually costs a few dollars for a giant box.

trendland said:
Caffenol is with sodium bicarbonate - but I like to drink Coffee - my films like REAL chems..!

with regards
Click to expand...

Caffenol is typically made with Sodium Carbonate ( Washing Soda ) but there is a conversion scale if one can't get Sodium Carbonate and doesn't have an oven handy to purge the water from Sodium Carbonate, as I mentioned above it is on one of the caffenol blogs.
 

David Lyga

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Sodium carbonate, mono, is washing soda found in any large supermarket. It speeds up development time.

Sodium Bicarbonate (baking soda) slows down development time.

Sodium Bicarbonate can be turned into sodium carbonate, anhydrous, by heating it in a pan on a stove. It lets out little jets of steam and when that is done (after continuously stirring it) you have the carbonate. CAUTION: IT GETS HOTTER THAN BOILING WATER: BE FOREWARNED.- David Lyga
 

BAC1967

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I have converted Sodium Bicarbonate to Sodium Carbonate by cooking it in the oven but it is just as easy to buy washing soda at the grocery store. Even then I bake it in the oven to make sure it’s anhydrous. I spread it out about 1cm or less in a glass pan and bake it at 250F for at least an hour. After baking and letting it cool down I put it in air tight containers to keep it from absorbing moisture from the air. I’ve had it go bad over time because I stored it in the box it came in.
 

David Lyga

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The Sodium Carbonate, MONO that you buy in the store as washing soda is NOT anhydrous and it is BETTER to use that MONO form for washing soda. Don't bake it in the oven. It is much easier to pour in its original form. Just open the box and pour. Never had problems. - David Lyga
 

koraks

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The sodium carbonate I buy in the supermarket is usually decahydrate, not monohydrate. When buying soda intended for household purposes, verify which one it is and don't simply assume it.
 

darkroommike

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adelorenzo said:
I get mine at the local big box store in the pool chemicals section. It's less expensive and one of the few things I don't have to mail order.
Click to expand...

Be aware that swimming pool supplies have both sodium bicarbonate (aka sodium hydrogen carbonate) AND sodium carbonate on the shelf. Be sure to get sodium carbonate, soda ash.
 
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