Sodium Carbonate Anhydrous

Hello,

I am about to make some Cafennol Developer and already have ascorbic acid and Kbr.

I found a Sodium Carbonate provider to which i asked if the product is anhydrous. He replied saying the data sheet only states that hymidity is 0.150 max

Can this be considered anhydrous since it´s less than 1 gram?

I already know if heated sod. Bicarbonate becomes sod. Carbonate, but I just don´t want to do that.

Thanks in advance

romeo

If you have Arm & Hammer Washing Soda available, you can use it in your Cafennol developer. It is anhydrous right out of the box. Excellent results with it per most Caffenol "receipes" and I use it gram for gram in my current Obsidian Aqua pyro staining developer. Aloha, Bill

No, it´s not sold here! Thank you!

romeo

Some sort of "baking soda" is sold where you are. It doesn't have to be Arm & Hammer.

Not quite the same -- Difference Between Baking Soda and Washing Soda - DifferenceBetween.com

Not quite the same -- Difference Between Baking Soda and Washing Soda - DifferenceBetween.com

Right . . . The point is that it doesn't have to be Arm & Hammer . . .

If you heat up hydrated carbonates (or hydrated most chemicals) you drive out the water.

Eventually you also drive out the carbonate.

Arm & Hammer is a popular brand for both in the US.

Sodium carbonate - Wikipedia

sounds like monohydrate is the usual form.

If you buy it from a chemical supplier, reagent in glass bottles, you might get the anhydrous form,

but it will start to collect water out of the air as soon as you open it.

In a cardboard box, usual for washing soda, I don't think it will stay anhydrous for long.

From: Solvay process - Wikipedia

the bicarbonate (hydrogen carbonate in chemical literature) goes to anhydrous carbonate

at 160 to 230C. I suspect it is then hydrated to monohydrate before packaging and sale.

Anhydrous chemicals are often a fine powder, where the hydrated form is more coarse, the

water holding the crystal together.

Anhydrous is 106g/mole, monohydrate 124g/mole, so you can adjust the weights if needed.

If you heat up hydrated carbonates (or hydrated most chemicals) you drive out the water.

 

Eventually you also drive out the carbonate.

 

Arm & Hammer is a popular brand for both in the US.

 

Sodium carbonate - Wikipedia

 

sounds like monohydrate is the usual form.

 

If you buy it from a chemical supplier, reagent in glass bottles, you might get the anhydrous form,

but it will start to collect water out of the air as soon as you open it.

 

In a cardboard box, usual for washing soda, I don't think it will stay anhydrous for long.

 

From: Solvay process - Wikipedia

 

the bicarbonate (hydrogen carbonate in chemical literature) goes to anhydrous carbonate

at 160 to 230C. I suspect it is then hydrated to monohydrate before packaging and sale.

 

Anhydrous chemicals are often a fine powder, where the hydrated form is more coarse, the

water holding the crystal together.

 

Anhydrous is 106g/mole, monohydrate 124g/mole, so you can adjust the weights if needed.

Well, I live in a very humid port city, so in the end this takes me back to the beginning. I think i will just switch to Borax instead of the carbonate, or eventually buying any carbonate and adjusting the involved quantity.

Thanks for the answer.

romeo

Jeez, it's Caffenol. Not a highly-tuned fine-grain formulation needing weighing accuracy to the milligram.

Just throw in a slack handful of whatever washing soda you can get hold of. Or use bicarb and a pinch of caustic soda (drain cleaner). Not literally a pinch though, because it'll take the skin off your fingers!

Caffenol isn't really a 'formula' - just a sloppy recipe. The makers of instant coffee don't regulate or list the caffeic acid content, which is the active ingredient.

You can usually tell anhydrous or monohydrate sodium carbonate from the decahydrate by its appearance. The decahydrate appears obviously crystalline, while the 'anhydrous' version is a fine white powder.

Re: the bicarbonate and caustic soda. You need a molar equivalent mix to give sodium carbonate in solution. I'll work out the weight ratio if necessary.

bicarbonate isn't so soluble in water.

The process for making sodium carbonate creates the bicarbonate, precipitates it out, then converts it to carbonate.

If you heat sodium carbonate enough, you drive off the CO2, and get sodium oxide.

Then you can hydrate it back to sodium hydroxide.

I think borax is a fine alkaline buffer, too.

Mixing caustic soda (sodium hydroxide) and bicarbonate should give carbonate, too.

There might be enough else to buffer it with just sodium hydroxide, which I suspect is easier to find

than sodium carbonate. Usually in the drain cleaner section of the store.

4g caustic soda pellets + 8.4g sodium bicarbonate = 10.6g sodium carbonate (in solution).

A slight excess of bicarbonate will have a buffering effect and tend to stabilise the pH value of the solution. So if you mix 4g NaOH with 8.5g of NaHCO3, and substitute that for every 10g of anhydrous Na2CO3 in the 'formula', you'll be close enough.

...

If you heat sodium carbonate enough, you drive off the CO2, and get sodium oxide.

Then you can hydrate it back to sodium hydroxide.

 

...

It does better than I thought:

http://www.inchem.org/documents/sids/sids/naco.pdf

it begins to decompose (to Na2O and CO2) at 400C, melts at 851C, but has no boiling

point as it is completely decomposed by then. Given that it has started decomposing

at 400C, the melt must be some intermediate mixture.

But why would you burn sodium carbonate to decomposition if it's the stuff you want?

Since no domestic oven heats to 400C, it's all a bit academic. However a domestic oven could be used to drive off the water-of-crystallisation and turn decahydrate into the mono or anhydrous salt.

But why would you burn sodium carbonate to decomposition if it's the stuff you want?

 

Since no domestic oven heats to 400C, it's all a bit academic. However a domestic oven could be used to drive off the water-of-crystallisation and turn decahydrate into the mono or anhydrous salt.

Soda ash is routinely heated to much higher temperatures in e.g. glass manufacture (1500ºC) Also https://www.researchgate.net/post/Thermal_decomposition_of_Sodium_Carbonate

The domestic oven can also be used for converting sodium bicarbonate (baking soda) to sodium carbonate

The domestic oven can also be used for converting sodium bicarbonate (baking soda) to sodium carbonate

- Quicker and more energy efficient to just add some caustic soda in the weight proportions I posted above.

Carbonate is for buffering, but some of the other chemicals will buffer, too.

I was indicating the manufacturing process, not necessarily the way to make

it at home.

Mixing sodium hydroxide and sodium bicarbonate might be the easiest way

to make it at home, using easily (grocery store) available chemicals,

if you don't find washing soda.

4g caustic soda pellets + 8.4g sodium bicarbonate = 10.6g sodium carbonate (in solution).

 

A slight excess of bicarbonate will have a buffering effect and tend to stabilise the pH value of the solution. So if you mix 4g NaOH with 8.5g of NaHCO3, and substitute that for every 10g of anhydrous Na2CO3 in the 'formula', you'll be close enough.

I don't want to put your statement in doubt but, are you sure of this equation? Has this proved to be exact? As someone has referred (which BTW is completly right) anydrhous carbonate stops being anyhidrous for too long when box/package has been opened and exposed to ir since moisture reconverts it to bi-carbonate in some time, this makes difficult to be accurate when measuring chemicals which might eventually lead you to a undesired outcome.

romeo

I don't want to put your statement in doubt but, are you sure of this equation? Has this proved to be exact? As someone has referred (which BTW is completly right) anydrhous carbonate stops being anyhidrous for too long when box/package has been opened and exposed to ir since moisture reconverts it to bi-carbonate in some time, this makes difficult to be accurate when measuring chemicals which might eventually lead you to a undesired outcome.

romeo

- It's only a developer.

Not a cancer cure, or anything else important!

Nobody, in the history of photography, has ever bothered about niceties like carbonation of their alkali accelerator, weighing to an accuracy of a milligram or using analytical grade chemicals.

So yes, I'm sure the quantities I've given will be close enough for a Caffenol recipe.

I am not sure if NaOH or NaHCO3 are normally hydrated, but the usual way is to

adjust until the pH is right.

Carbonate buffers through the equilibrium between carbonate, bicarbonate,

and unionized carbonic acid.

One of the not so obvious things about ocean chemistry is that more CO2

in the ocean means less carbonate and bicarbonate for shellfish to make shells from.

(Also, that the ocean is a big buffer for atmospheric CO2, such that the increase in

the atmosphere is much lower than it would be without the ocean.)

Sodium hydroxide is both hygroscopic and subject to aerial carbonation. It needs to be stored in an airtight container otherwise it'll absorb atmospheric carbon dioxide and moisture. The CO2 will form a thin layer of sodium carbonate on the surface of the pellets and release water.

2NaOH + CO2 > Na2CO3 + H2O

None of this matters unless the pellets are exposed enough to turn into a watery sludge. With CO2 at only 0.04% by volume of the atmosphere, you'd need a lot of air exposure for the carbonate coating to become significant. Plus sodium carbonate is the end product wanted in any case.

Do not worry about it!

Photo-chemistry is relatively crude and imprecise. A pinch of this and a slack-handful of that is generally close enough.

If you look at most photographic formulae, the quantities are usually rounded to the nearest gram or tens of grams. Do you think that those nice round figures have been carefully calculated using molar masses? Or has someone just randomly decided that 20 grams of sodium carbonate (or whatever) is about right?

None of this matters unless the pellets are exposed enough to turn into a watery sludge.

Around here, in more humid parts of the year this can happen if a container is left open overnight. Pellets spilled on a benchtop will start "sweating" within a few minutes of being dropped.

Of course, taking the perfectly reasonable precaution of PUTTING THE LID ON IT takes care of this.

Hello,

I am about to make some Cafennol Developer and already have ascorbic acid and Kbr.

I found a Sodium Carbonate provider to which i asked if the product is anhydrous. He replied saying the data sheet only states that hymidity is 0.150 max

Can this be considered anhydrous since it´s less than 1 gram?

I already know if heated sod. Bicarbonate becomes sod. Carbonate, but I just don´t want to do that.

 

Thanks in advance

 

romeo

The washing soda sold in supermarkets can either be sodium carbonate decahydrate or sodium carbonate monohydrate. The Arm and Hammer "Super Washing Soda" is the monohydrate.

Both the monohydrate or the decahydrate will work perfectly well in a developer provided you adjust the quantity used for the water content. It is pointless to go to trouble to obtain anhydrous sodium carbonate then add it to water.