Purity of sodium carbonate needed for paper developer?

[Darryl Baird]

I have a large bucket of sodium carbonate (soda ash) from a chemical/pool supply company and would like to use it to mix some Ansco 130 paper developer. Does anyone have experience with using lower grade chemicals for paper developers?

thanks for any tips or advice

[D. Bryant]

I have a large bucket of sodium carbonate (soda ash) from a chemical/pool supply company and would like to use it to mix some Ansco 130 paper developer. Does anyone have experience with using lower grade chemicals for paper developers?

thanks for any tips or advice

That's what I use Darryl, it works fine.

I wish we had gotten together in Atlanta at the SPE. I looked for you but only saw you that one brief moment. Maybe next time.

Don

[Graybeard]

I have a large bucket of sodium carbonate (soda ash) from a chemical/pool supply company and would like to use it to mix some Ansco 130 paper developer. Does anyone have experience with using lower grade chemicals for paper developers?

thanks for any tips or advice

You'll want to note if your sodium carbonate is the monohydrate or the decahydrate; both types are sold commercially. The weight required in your developer formulation will differ depending on the form that you have.

I use Arm & Hammer "Super Washing Soda" (yellow box) that is the monohydrate.

[Darryl Baird]

Yes, me too. I had a couple of students in tow, one who was "pressing the flesh" with a couple of grad schools who's faculty were in attendance. I was in fulltime coaching mode. She got a great scholarship in the end (to Notre Dame), so my time was well spent. ;-}

Maybe San Fran?

I'm just finishing a new wet and alt-process darkroom, so I'll be asking for advice right and left. It's great to be 'wet' again.
db


That's what I use Darryl, it works fine.

I wish we had gotten together in Atlanta at the SPE. I looked for you but only saw you that one brief moment. Maybe next time.

Don

[Darryl Baird]

You'll want to note if your sodium carbonate is the monohydrate or the decahydrate; both types are sold commercially. The weight required in your developer formulation will differ depending on the form that you have.

I use Arm & Hammer "Super Washing Soda" (yellow box) that is the monohydrate.

Pretty sure its monohydrate. I have some anhydrous SC on hand and its a rock crystal form compared to a granular powder in the big bucket.

[Erik Larsen]

Pretty sure its monohydrate. I have some anhydrous SC on hand and its a rock crystal form compared to a granular powder in the big bucket.

How do you tell the difference between mono and anhydrous? I have 10lbs of soda ash that is used for making glazes in pottery applications. It has the consistency of very fine granuals, not as powdery, but not granular like salt or sugar. Do you know what type it is?

regards
erik

[mdm]

If you bake it in a warm oven, the decahydrate turns to mush and dries down to a fraction of its starting mass. Obviously it is full of water.

[Graybeard]

How do you tell the difference between mono and anhydrous? I have 10lbs of soda ash that is used for making glazes in pottery applications. It has the consistency of very fine granuals, not as powdery, but not granular like salt or sugar. Do you know what type it is?

regards
erik

The anhydrous material is less common than the decahydrate and the monohydrate.

The monohydrate, as sold by Arm & Hammer as "Super Washing Soda" is a granular, rather than powdery, material. There is the problem that physical consistency of a powder may tell you more about the processing history of that powder than about its chemical composition (e.g. grind granular material for a sufficient time and you'll wind up with a dusty powder).

I determined which hydrate I had by dissolving a measured weight of the powder in a known volume of water and then determining the resultant solution density with a hydrometer.

Arm & Hammer "Super Washing Soda" is a pretty low-cost purchase at a local supermarket (you may spend more in gasoline driving to the supermarket than the box of wahing soda will cost once you arrive there). It might be simpler to just use the Arm & hammer material in the short term while you are sorting out the composition of the bulk soda ash material that you have in hand.

[Brook Martin]

If you have enough of the soda ash you plan to use, try making up a few different batchs of developer, halving and doubling the amount of carbonate in each. Figure out which you like, and you have a brand new glycin based developer.

Simply making up a batch and seeing how it works will tell you alot.

[Sevo]

It is pretty easy to distinguish its hydrates by putting a bit into a test tube and heating it until water condenses on the cold upper of the test tube.

The monohydrate converts to anhydrous above 107°C, the decahydrate decomposes to monohydrate (with an intermediate unstable heptahydrate) above 35°C - if it already loses lots of crystallisation water while the test tube is warm rather than hot, it is the decahydrate, if it does not do so until it is boiling hot, it is the monohydrate, and if no water evaporates even if it is red hot or melts through the test tube, it is anhydrous.