Useful 10% solutions

Discussion in 'Darkroom Developing and Printing' started by nobodyman, Mar 29, 2006.

  1. nobodyman

    nobodyman Guest

    "Hydroquinone: To increase the print contrast add 100ml per liter of
    working developer."

    How does one make a 10% solution of this photo chemical?

    the quote comes from,
    nobodyman, Mar 29, 2006
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  2. nobodyman

    Mike King Guest

    A 10% solution of anything (anything soluble anyway) starts with 10 grams of
    weighed material in 100ml water (which weighs 100 grams) the ration is 1
    part to 10 parts water.
    Mike King, Mar 29, 2006
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  3. nobodyman

    Wayne Guest

    Unless you are going to use it immediately you will probably want some
    sodium sulfite in this 10% solution too. Its best to start with less
    than 1000 ml water and add water to make 1000 after dissolving both the
    sulfite and HQ. Otherwise you may end up with slightly more than 1000
    ml, and hence a slightly weaker solution. It probably wont make much of
    a practical difference in this case but its a good practice to get
    into. I'll let someone else suggest how much sulfite you will need.
    Wayne, Mar 29, 2006
  4. Isn't it 10g of weighed material dissolved in enough water to make a total
    of 100ml of solution?


    Dana H. Myers, Mar 29, 2006
  5. nobodyman

    Lloyd Erlick Guest

    March 29, 2006, from Lloyd Erlick,

    Yes, it is.

    Lloyd Erlick, Mar 29, 2006
  6. nobodyman

    dan.c.quinn Guest

    A solution is a solvent plus solute. At least in the
    darkroom % solutions are used. A 10% solution will
    have as 1/10 it's volume some solute. Usually the
    portion of solute is in grams. Dan
    dan.c.quinn, Mar 30, 2006
  7. Though if it is two liquids the concentration can
    be by volume - Misters Walker and Daniel are 40%
    alcohol by volume.
    Nicholas O. Lindan, Mar 30, 2006
  8. I know what the volume of 10 grams of water is.
    What's the volume of 10g of NaOH?

    I think you're mixing up two different conventions.

    Dana H. Myers, Mar 30, 2006
  9. nobodyman

    dan.c.quinn Guest

    A 10ml solution of 10% NaOH will have 1 gram
    of the solute; 10% of the solutions volume. As I said
    the solute's amount is usually in grams. Dan
    dan.c.quinn, Mar 30, 2006
  10. Not 10% of the unit's volume ... usually the
    volume of the solution is less than the volume
    of the sum of the individual components.

    A 10% by weight solution is a bit confusing ...
    better to call it a .1g/ml or 100g/l solution.

    Mixing mass and volume is a no-no, though for
    water the two are functionally the same: 1g = 1ml.
    After the solution is made up, however, the density
    is normally greater than 1g/ml and the equivelance
    is no longer.

    Example, 10% mass(weight)/vol solution of salt water:

    100 g salt \
    = 1000ml salt water with a density
    990 ml H20 / of 1090 g/l

    (I can't remember the actual numbers for salt water
    and I can't find the CRC)

    To make a 10% w/v solution you put in 100 gm of stuff and
    add _however much water it takes_ to make 1 liter. The
    amount of water required varies with what the stuff is.

    Imagine a 10% w/v solution of Styrofoam balls: all Styrofoam
    and just about no water.
    Nicholas O. Lindan, Mar 30, 2006
  11. What's the volume of 1 gram of NaOH? Do you think
    it is 1 ml? I don't think it is. You're mixing weight
    and volume interchangeably here, which you can do with
    water but not the solute.

    Dana H. Myers, Mar 30, 2006
  12. nobodyman

    Lew Guest

    Try this 'mind' experiment. Into a beaker, place 10gms of salt. Now add
    enough water to dissolve the salt and bring the final volume up to 100ml.
    This is a 10% solution. The total weight of the salt in the 100ml of
    solution is still 10gms. Now pour off 10ml of the solution. How much salt
    will be in the 10ml? Well, since 10ml is 1/10th of the original solution,
    it'll contain 1/10th of the total amount that was added originally. 1/10th
    of the original 10gms is 1gm. We never need to know the volume of the salt.
    Lew, Mar 30, 2006
  13. nobodyman

    dan.c.quinn Guest

    We are not interested in the volume of that 1 gram of
    NaOH. We are only interested in the NaOH being 10%
    of the solutions volume expressed in grams.
    Do the math. If you need 1 liter of solution of 12.5 %
    concentration dissolve 125 grams of the solute in some
    of the solvent then bring the solution volume to 1 liter.
    12.5 % of 1000 is 125; grams in this case. It could
    be some volume of gas or weight or volume
    of fluid for that matter.
    It's a darkroom way of compounding chemistry. Likely
    the same method is used more universally. My chemists'
    book speaks of molal, molar, normal, and some amount
    of solute in specific amouts of solvent. Dan
    dan.c.quinn, Mar 31, 2006
  14. All the methods but the useful and easy one: grams/litre
    Nicholas O. Lindan, Mar 31, 2006
  15. I *get* it.

    Dana H. Myers, Mar 31, 2006
  16. But it isn't 10% of the solution's *volume* unless the solute
    has the same density as water. Do the math.

    Dana H. Myers, Mar 31, 2006
  17. It isn't 10% of the solution's volume unless the solute is water.

    Solids dissolved in liquids don't take up the same space - the
    dissolved solid occupies the 'voids' [there must be a better word]
    between the water molecules.

    .... anybody up for discussing Angels dancing on pinheads?
    Nicholas O. Lindan, Mar 31, 2006
  18. Somehow I want to spread my hands in a broad sweeping motion
    and declare "billions and billions of starstuff".

    Dana H. Myers, Mar 31, 2006
  19. nobodyman

    Wayne Guest

    Since the others seem to be occupied, I will recommend adding roughly
    30 grams of sodium sulfite to preserve your 10% solution. Jackspsc
    recommends adding some sodium bisulfite too, which may be helpful but
    it is probably optional if you dont happen to have any laying around.

    Chemical Amount Units
    Water (125°F/52°C) 750 ml
    Sodium sulfite 25 g
    Sodium bisulfite* 5 g
    Hydroquinone 10 g
    Water to make 1000 ml

    * The sodium bisulfite is not in the original formula. Maxim Muir
    recommends it to buffer the hydroquinone solution.
    Wayne, Mar 31, 2006
  20. That is only 1/10 %.
    If you want a long lived solution of hydroquinone without preservative,
    use Propylene glycol instead of water as the solvent. Hydroquinone,
    pyrogallol, paraminophenol base (not the hydrochloride), and
    pyrocatechol are all soluble enough in glycol to make a 10% solution
    which will then dissolve in water. By 10% I mean 100 grams dissolved in
    enough glycol to make 1 liter.
    PATRICK GAINER, Mar 31, 2006
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