hydrated soda question

[grommi]

Hi Folks,

I need your help fpr my Caffenol blog. Washing soda is availble in different versions from anhydous (waterfree) soda to different kinds of hydrates like mono- or decahydrate or something in between.

Here I'm only able to get the waterfree one, not bad because 1 gramm soda is 1 gramm soda without useless water. But in many parts of the world only hydrates are available. I asked a friend in France to test his hydrate called "sode cristeaux".

He heated 30 gramms of his "crystal" soda in the oven to 140 °C. After about 15 minutes all water had evaporated and the weight was about 15 gramms and it turned to a white powder, the look of waterfree soda. So he lost 50 % of weight. That doesn't match to the monohydrate nor the decahydrate but is something in the middle. Above 107 °C the reaction starts, but it should be better to heat up to about 150 °C. Don't worry, it won't explode nor set free any dangerous gas, only water will evaporate. But be sure to heat up washing soda and nothing else, your poodle may be hurt. You can also fry it in a (clean) pan. Aluminium foil in the oven will be fine.

1 gramm waterfree equals 1.2 gramms monohydrate or 2.7 gramms decahydrate

So I ask you to tell me what your soda is like and how the weight changes if heated up long enough. F.e. the famous Arm & Hammer soda would be of big interest, but also all other brands you use.

So my soda is "Holste feine kalzinierte Soda", waterfree by definition. After heating up to 150 °C for 30 minutes it looses only 2 % of weight and that should be neglectible. I always store it in an airtight box.

I'm only asking for the weight- not the volume ;-) Thank you very much for sharing your experiance.

Best - Reinhold

 

[Роберт]

Sodiumcabonate Na2CO3 can be often replaced by household soda.
In Europe it's often decahydrate Soda which means 10. H2O. Na2CO3.

1 mol Na2CO3 = 106g
1 mol 10.H2O.Na2CO3 = 286g

Using decahydrate Soda you need: 286/106 * x g= x g Soda (Decahydrate)
Soda is cheap: €0,50 - €0,70 for a kilo (1000g). Approx. 5 Grvna.
Here in Ukraine and in Holland it's written on the package Soda Decahydrate, so you know what you have.

Best regards,

R.

 

[Роберт]

I forgot to tell you I am using Senzora Soda from Deventer the Netherlands. Decahydrate, also for my own Beutler A+B receipt. Very simple to make.
I will try your Caffenol version too

 

[Gerald C Koch]

If you wish to make anhyrous sodium carbonate you can heat sodium bicarbonate (baking soda) for 1 hour at 350 degrees F. The crystalline baking soda will change to a white fluffy powder. While heating stir the soda two or three times.

The monohydrate is the most stable of the three sodium carbonates since it will not absorb water nor easily lose iit.

 

[grommi]

Sorry, I know a lot about soda and I can buy waterfree for a few cents as much as I want. But I would like to know how much soda and water is really in the brands you use across the world. F.e. how much soda or water is really in Arm & Hammer washing soda. Did nobody try this out simply by drying?
Thank you - Reinhold

 

[brucemuir]

The 2 grocery stores I tried recently here in the US would not stock any Arm & Hammer Washing Soda.

Sorry I can't help at the moment.

 

[removed account4]

hi reinhold

i wish i could tell you the answer !
i haven't measured out baking and washing soda and to be honest i wouldn't know
how to measure the amount of water in washing soda ..
it comes in a cardboard box, and i am sure it slowly becomes hydrated as it sits on the shelf

john

 

[grommi]

i wouldn't know how to measure the amount of water in washing soda ..

If you have a scale/balance it's quite easy, John. Measure the weight of let's say 50 gramms. Put the soda in a pan or on alu-foil in the oven and heat it to about 150 °C. Wait about 30 minutes and measure the weight again. Do the same after another 15 or 30 minutes. When there is no more loss of weight, all the water has evaporated. The difference in weight is the water that was in the soda before.

So if anybody did this before or may want to do this, please reply with the brand name, how it is declared (f.e. crystal, monohydrate ...... if declared at all) and the weight before and after heating.

Imho anybody mixing developers with soda should do this because there are obviously big differences between brands and a reproducible recipe should declare the real amount of soda and not an undefined amount of useless water. When you finally know how much water your soda contains, it's easy to calculate the needed amount, and serious recipes are allways based on waterfree soda.

What applies to any other recipe, why shouldn't it apply to Caffenol developers? And even if you buy waterfree soda, it no fault to verify that it's really waterfree.

I asked a friend in France to do that with his "sode cristeaux". One could think it's the monohydrate, then it should loose 20 % of weight, but there was 50 % water in it. And if it's the decahydrate it should have lost almost 70 % of weight. Obviously it was none of both but something in between.

I try to make a trouble shooting guide for Caffenol, and the soda seems to be the biggest source for trouble. That's why I'm asking.

Thank you - Reinhold

 

[Роберт]

1 mol Na2CO3 = 106g
1 mol 10.H2O.Na2CO3 = 286g

Using decahydrate Soda you need: 286/106 * x g= x g Soda (Decahydrate)

Well the lab of the Senzora factory re-calculated for me and acknowledged as written on their package: Soda Decahydrate.

It worked for the standard Caffenol and Beutler formulae.

 

[grommi]

Thank you Robert. I guess we can trust the labs statement.

 

[hrst]

Okay, I'll show an example .

"Crystal soda" sold in Finland under the name "Kidesooda" in 1 kg packages ( http://kauppa.motonet.fi/images/app/4/big/422025.jpg );

45.76 g before drying
18.19 g after drying
= 0.40x ratio

Ratio of anhydr/decahydr molar masses = 0.37x

So this is very close to pure decahydrate.

Oh, it was this easy. There can be quite a big difference so it's good to check. The drying takes time, it took a few hours in 150 degC oven.

OTOH, the exact amount does not affect pH that much in most cases, it will affect the buffer capacity more than pH. For exact work, you should anyway measure the pH when making up the solution, so you can just throw in enough carbonate to get the right pH and come back with bicarbonate if you go over.

Many formulas use the monohydrate form and it's not a sign of recipe not being "serious". Monohydrate is more stable if you have to open the bottle often, because the anhydrous form takes up moisture from air more easily and ends up in an unknown hydration state.

 

[Kirk Keyes]

the exact amount does not affect pH that much in most cases, it will affect the buffer capacity more than pH.

That's a point that few people learn, and even fewer people grok.

 

[grommi]

....OTOH, the exact amount does not affect pH that much in most cases......

My Caffenol-C-L contains only 12 g/l soda (waterfree) but still a lot of acids and has a pH of 9.0 ("regular" Caffenol-C is about pH 10-10.5) and it's important to have the right amount of soda. Small differences will have a big impact on the pH and the resulting activity. It's designed for lower activity than usual and stand development. So it's essential to know which kind of soda you use and how many water it contains. And only very few people have a pH-meter. That's the main reason why I'm asking. I also don't meter the pH for every batch that I make. I weigh the agents with some accuracy and that's fine. Always. Because I know what and how much I put in.

BTW, I keep the waterfree soda in an airtight plastic box, it doesn't accumulate water at all. That's my experiance since about 1 year.

Thank you for posting additional data.

Best regards - Reinhold