Hydrate forms of sodium carbonate

gainer said:

The stuff I get claims it to be "inert ingredients". I can't think of very many ingredients that would be inert in a swimming pool and active in a developer that aren't already in most tap water.

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Uh... how about sand?

I considered sand, Kirk. Look again. Sand falls to the bottom and will show even in distilled water. Besides, I have seen tap water with sand in it.

I have seen no sign of iron in pHPlus. I'm fortunate that my well is not full of sulfur and iron. All my neighbors have it. Or maybe the black stuff that comes up is something else. Some say it's worth money.

I won't say anyone should not use USP carbonate. By all means, someone doing commercial work will use the most reliable source and the customer will pay for it. I do say that it may not be the wisest thing to believe that what you get at P. F. is uniformly any better than pHPlus. When you look at labels and see that one is for swimming pools and the other for darkrooms, is that a guarantee that the two are not the same? The only ones I have heard from here who have run tests have found that it is not any such guarantee. If you really are that afraid, you must test each new batch and take nobody's word for it.

What I used to get as A&H Washing Soda years ago was the stuff we used also for flushing auto radiators and such tasks. I can't get the current stuff here in rural West Virginia.

gainer said:

The stuff I get claims it to be "inert ingredients". I can't think of very many ingredients that would be inert in a swimming pool and active in a developer that aren't already in most tap water. It could be simply water. The carbonate as they package it may be very close to anhydrous. It could be sand, but 2% sand would surely show in the mixing. The only sediment I have seen is from the reaction with calcium and magnesium in my well water. It is not there when I use distilled or rain water or some EDTA.

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This is exactly how the A&H washing soda behaves with my well water, turns cloudy, and like yours the developer is clear when using distilled water.

Mike D

I use Arm and Hammer Washing Soda as part B of Pyrocat and it is cloudy at first but now in the bottle it looks ok. I use the 2+10+100 dilution


lee\c

Gerald Koch said:

Years ago when I used A&H Washing Soda for print developer it threw down a considerable amount of tan sediment. I tested this and it consisted, in part, of hydrated ferric oxide. I was put off by the amount of iron in the product and stopped using it. Iron is not the best thing to have as a contaminate in developers. I now buy my carbonate from The Chemistry Store or make it from USP baking soda.

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I routinely use Arm & Hammer in Caffenol and derivatives. I mix the soda first, because I can see when it's fully dissolved. It does produce some microbubbles, which surface and clear after a bit; that's expected, because of the flocular nature of the granulation as packaged. Otherwise, the solution produced (in distilled water, which is all I use for mixing, diluting, and film washing) is perfectly clear with no sediment.

If you got rust sediment, it was probably from water -- either yours, or that at the processing plant where the soda was produced for packaging (they surely don't use distilled water in processing those quantities). I wonder if the test you used could tell the difference between ferric oxide and ferric carbonate...