Sodium Carbonate replacement

Discussion in 'B&W: Film, Paper, Chemistry' started by Bruce Osgood, Nov 19, 2011.

  1. Bruce Osgood

    Bruce Osgood Membership Council Council

    Messages:
    2,611
    Joined:
    Sep 9, 2002
    Location:
    Brooklyn, N.Y.
    Shooter:
    Multi Format
    I'm re-examining many of my long time assumptions:

    When using Arm & Hammer washing soda in place of Sodium carbonate is it used as a mono-hydrate or anhydrous?

    TIA,
     
  2. Wayne

    Wayne Subscriber

    Messages:
    2,116
    Joined:
    Jul 8, 2005
    Location:
    USA
    Shooter:
    Large Format
    anyhydrous
     
  3. Wayne

    Wayne Subscriber

    Messages:
    2,116
    Joined:
    Jul 8, 2005
    Location:
    USA
    Shooter:
    Large Format
    i think. :smile:
     
  4. Bruce Osgood

    Bruce Osgood Membership Council Council

    Messages:
    2,611
    Joined:
    Sep 9, 2002
    Location:
    Brooklyn, N.Y.
    Shooter:
    Multi Format

    OOP'S, you're in the same boat as I am....
     
  5. ntenny

    ntenny Member

    Messages:
    2,283
    Joined:
    Mar 5, 2008
    Location:
    San Diego, C
    Shooter:
    Multi Format
    Everything I've been able to find online indicates that the monohydrate is the most stable form---the others tend to change into it over time in normal storage conditions. You can get it in the anhydrous form (e.g., from the Formulary), but in a cardboard washing-soda box it would pick up water molecules from the air and turn into monohydrate even if it didn't start that way.

    Disclaimer: I'm repeating what I've read, so I'm only as sure as my trust in my sources (which, however, include some of the Actual Chemists here on APUG).

    -NT
     
  6. Ian C

    Ian C Member

    Messages:
    724
    Joined:
    Feb 8, 2009
    Shooter:
    Large Format
    This states that Arm & Hammer Washing Soda is 85% sodium carbonate, 15% water, so it’s probably not anhydrous.

    http://hpd.nlm.nih.gov/cgi-bin/household/brands?tbl=brands&id=3005022

    The monohydrate form has a mass of about 124g/mol, while the anhydrous form is about 106g/mol.

    (106g/mol)/(124g/mol) = 0.85, which is about the stated percentage of sodium carbonate in Arm & Hammer Washing Soda.

    Based on this, my estimate is that it’s the monohydrate form.

    Perhaps one of our experienced chemists will contribute an authoritative answer.
     
  7. jnanian

    jnanian Advertiser Advertiser

    Messages:
    19,971
    Joined:
    Jun 21, 2003
    Location:
    local
    Shooter:
    Multi Format
    i suppose you could force out some of the water
    by heating it up in your oven on a cookie sheet
    the same way you would "convert" baking soda into
    sodium carbonate.
     
  8. Gerald C Koch

    Gerald C Koch Member

    Messages:
    6,238
    Joined:
    Jul 12, 2010
    Location:
    Southern USA
    Shooter:
    Multi Format
    It is the monohydrate form and is essentially technical grade and contains a small amount of sodium chloride and a smaller amount of iron. It is good enough for paper developers but not for ascorbate developers where the iron may be a problem.

    A purer form can be obtained by heating Arm & Hammer Bicarbonate of Soda which is USP grade. I would recommend doing this for developers such as Xtol substitutes and for the Beutler formula.
     
    Last edited by a moderator: Nov 19, 2011