Water content of Arm & Hammer washing soda?

Discussion in 'B&W: Film, Paper, Chemistry' started by walbergb, Jun 25, 2012.

  1. walbergb

    walbergb Subscriber

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    Does anyone know what form Arm & Hammer's Washing Soda is (anhydrous, monohydrate, decahydrate, or something else)? I want to use it as a source of sodium carbonate, but I don't know its water content so I don't know how much to use. I can convert from one form to another, but I don't know what I'm starting with.
     
  2. F/1.4

    F/1.4 Member

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    I don't know, but usually when I use it to make Caffenol, I'm mixing with water anyway.
     
  3. Gerald C Koch

    Gerald C Koch Member

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    I believe that it is the monohydrate as this is the only form that is stable at ambient temperature and humidity. However it is only technical grade and does contain some iron as an impurity. I would not recommend its use for ascorbate developers. It is good enough for paper developers. There are two suppliers of photograde chemicals in the US that I am familiar with; www.techcheminc.com and www.chemistrystore.com. I don't know if they will ship to Canada. As a last resort you can prepare anydrous sodium carbonate from USP grade Arm & Hammera Baking Soda. Place the baking soda in a glass or stainless steel baking pan and heat it at 350 F for an hour. Heating it for longer will not hurt it but it should be a minimum of an hour. Stir it a couple of times while heating. The baking soda will change from fine crystals to a fluffy powder. Allow it to cool and store in a tightly sealed container as it will absorb moisture and convert to the monohydrate.

    The reaction is 2NaHCO3 ---> Na2CO3 + CO2 + H2O
     
    Last edited by a moderator: Jun 25, 2012
  4. Denverdad

    Denverdad Subscriber

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    We've had a couple discussions about that over on Flickr; for example, here. My measurements (outside of one outlyer) showed about 9% water by weight. I don't have a good sense of how stable it is however. For completeness, I should also mention that I live in a very dry climate.
     
  5. ezwriter

    ezwriter Member

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    Where did u find it? All i could find at stores was A&H laundry soap now.
     
  6. Alan Johnson

    Alan Johnson Subscriber

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    In the UK ,widely available Dri-Pak Soda Crystals are labelled as containing greater than 30% sodium carbonate decahydrate.I phoned them up and spoke to a technical guy from the factory who told me the crystals in fact contain 99% decahydrate.There is now some anomaly in the packing regulations that causes >30% to be written on the packs (sounds like the EU again).I have not actually done the heating test to confirm this.
     
  7. pdeeh

    pdeeh Member

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  8. Denverdad

    Denverdad Subscriber

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    Where are you ezwriter? Grocery stores would be my main target to check, at least here in the US. But it is really hit or miss, so you may have to look around. As an example, none of the grocery stores closest to where I live here in Colorado carried it, including the Safeway store that is within walking distance. But I finally found it at a large Safeway store in Boulder (about a 20 minute drive from home). It is funny how some carry it and others don't. Anyway, you might want to check out some of the smaller, non-chain groceries, or perhaps in locations that tend to cater to the environmentally conscious, or perhaps in older, more traditional neighborhoods.
     
  9. Bruce Osgood

    Bruce Osgood Membership Council Council

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    Do not confuse A&H Baking Soda and Washing Soda.

    I use A&H Washing Soda, bought at the local market, as a one to one replacement to Sodium Carbonate mono hydrate in photo chemistry. I've not experienced a problem I would identify with Sodium Carbonates' miss use.
     
  10. Peltigera

    Peltigera Member

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    In the USA, sodium carbonate is usually mono-hydrate. In the UK, it is usually deca-hydrate when packed. But neither is stable with time. In a warm, dry atmosphere, the deca-hydrate will lose moisture to become mon-hydrate. In damp conditions, the mono-hydrate is likely to pick up some water.

    If it is clearly crystalline, it will mostly be deca-hydrate. If clearly a powder, mostly mono-hydrate.
     
  11. Peltigera

    Peltigera Member

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    It matters as the water content determines the weight to be used.
     
  12. hrst

    hrst Member

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    It is probably something between mono and decahydrate.

    The only way to REALLY know is to test. There was a thread here in APUG where people reported their test results (or at least I did):
    http://www.apug.org/forums/forum37/87576-hydrated-soda-question.html

    Once you figure it out, maybe you can assume that the different batches with the same label are close enough. Luckily, the amount of carbonate in a developer, for example, does not affect pH that much; it's more about buffering capacity.
     
  13. ezwriter

    ezwriter Member

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    i'm in So Cal, CA area and none of grocery stores carry it. Finally found TSP i think at a home depot.
     
  14. Prof_Pixel

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    I found a couple of MSDS sheets on the web that said A&H Washing Soda is approximately 85% sodium carbonate and 15% water so it sounds like it is the monohydrate
     
  15. bdial

    bdial Subscriber

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    TSP is not the same stuff.

    As for the washing soda, it seems to have disappeared in the grocery stores here too, but my wife just got some from the local hardware store.
     
  16. jnanian

    jnanian Advertiser Advertiser

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    tsp is tri sodium phosphate

    you can convert baking soda to washing soda if you run into a problem
    just put it on a cookie sheet and then in an oven low heat for a few hours
    the heat will force the moisture out and convert it to sodium carbonate.
     
    Last edited by a moderator: Jun 26, 2012
  17. Prof_Pixel

    Prof_Pixel Member

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    I believe you mean baking soda and not baking power. Baking power contains both an alkaline component (typically sodium bicarbonate, also known as baking soda), one or more acid salts(like Tartaric Acid), and an inert starch (cornstarch in most cases, though potato starch may also be used).


    Baking soda is just sodium bicarbonate without all the extras.
     
  18. Gerald C Koch

    Gerald C Koch Member

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    This is surprising considering the cost of shipping. It is rather inefficient to ship the decahydrate as you are paying to ship a lot of water.
     
  19. desertrat

    desertrat Subscriber

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    Most hardware stores and most Walmarts have swimming pool chemicals. A common pool chemical known as PH Plus is sodium carbonate, same as the hard-to-get washing soda. It may be the mono-hydrate. I use it to make my developers that use sodium carbonate.
     
  20. kiku

    kiku Subscriber

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    Try a wine and beer making supply shop. They will have it as "washing soda" or maybe sodium carbonate. Howard Tanger
     
  21. Gerald C Koch

    Gerald C Koch Member

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    The last time I remember seeing the decahydrate was in the 1940's. It consisted of large (3/4 to 1 inch) lumps which looked like ice. Soon after the box was opened the lumps began to take on a white powery coating of the monohydrate. Left exposed to the air the lumps eventually dried out to a white powder.
     
  22. hrst

    hrst Member

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    You describe perfectly the product I buy here! It really looks like a mixture of mostly ice and a bit of powdery snow. As I showed in the thread I referred to, it is almost pure decahydrate.

    The ratio between "ice" and "snow" seems to vary between batches.

    Of course it does not make real sense to ship water, but it makes a LOT of "business sense" to sell water. Think about liquid detergent business... Or, think about liquid photochemistry business!