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  1. #1
    gandolfi's Avatar
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    My cyanotype chemistry - a mystery occurs..



    help!!

    I don't get it!

    when making my chemistry, I always make the raw chemicals in teo seperate containers (100ml in each)

    When mising for use, I carefully use 1:1

    But when I am getting to the end of the chemistry, there's always more - much more left in one of the bottles!!

    and always in the ferriammoniumcitrate bottle...

    Magic/mystery? or?

    I can't explain it - can any of you?

  2. #2
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    Look at the amount/volume of Ferric Amm cirtrate you add compared to the Pot ferricyanide! It takes up a lot more space!
    Last edited by Vaughn; 04-05-2012 at 07:39 PM. Click to view previous post history.
    At least with LF landscape, a bad day of photography can still be a good day of exercise.

  3. #3

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    Emil, how do you measure the solutions? (a.) Drop count (by pipette) or (b.) proper ml (by syringe)? If the former - (a.) that is... - mind that different solutions' specific gravity and surface tension are also different, therefore the drop volumes are different - hence the different rate of consumption... If the latter, I can't think of anything other than the phenomenon may be caused due to different vapor pressures (highly affects evaporation speed / rate) of the solutions. (But, most probably that can be omitted if you aren't using very large containers / small amounts of solutions and I highly suspect it would cause a significant difference...)

    ???

    Regards,
    Loris.

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    Nah, I have to go with magic.

  5. #5
    gandolfi's Avatar
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    Quote Originally Posted by Vaughn View Post
    Look at the amount/volume of Ferric Amm cirtrate you add compared to the Pot ferricyanide! It takes up a lot more space!
    yes - but I first dilute the Pot ferricyanide in about 50ml water - and then when dissolved I add water to 100ml... so there's the same ml in both bottles.

  6. #6
    gandolfi's Avatar
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    Quote Originally Posted by Loris Medici View Post
    Emil, how do you measure the solutions? (a.) Drop count (by pipette) or (b.) proper ml (by syringe)? If the former - (a.) that is... - mind that different solutions' specific gravity and surface tension are also different, therefore the drop volumes are different - hence the different rate of consumption... If the latter, I can't think of anything other than the phenomenon may be caused due to different vapor pressures (highly affects evaporation speed / rate) of the solutions. (But, most probably that can be omitted if you aren't using very large containers / small amounts of solutions and I highly suspect it would cause a significant difference...)

    ???

    Regards,
    Loris.
    I use a small mesuring beaker/glass (I think it is the name).
    So I could just be unprecise, but why be that on the same chemistry every time.....

    I thank you for your ideas - it might make sense - I have to think that over..

    Question: Am I the only one experiencing this?

  7. #7

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    Emil,

    You can't be absolutely sure unless you're using identical syringes... (What about the beakers - Are you sure they're absolutely identical?) I completely switched to syringes myself, I don't measure with pipettes anymore. Beakers (to me) are fine for relatively large mixtures. (Few hundred ml and such...)

    About "Why always the same solution?": The (A) ammonium iron(III) citrate solution is quite different (in terms of specific gravity and surface tension) from the (B) potassium ferricyanide solution, and maybe this is causing you to always slightly err towards less for A, and more for B !??? At least that shows YOU are pretty consistent! Which is something good in my eyes...

    Regards,
    Loris.


    Quote Originally Posted by gandolfi View Post
    I use a small mesuring beaker/glass (I think it is the name).
    So I could just be unprecise, but why be that on the same chemistry every time.....
    ...

  8. #8
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    Are you measuring solutions in two separate beakers and pouring them together into a third or are you measuring 100 ml. of the first solution into a beaker then filling with the second solution up to 200 ml.?

    Try this experiment: Get some 90% isopropyl alcohol (from the drug store) and measure 50 ml. into a beaker or graduate. Next, using a second container, measure out 50 ml. of plain water. Pour them together. Note the volume of the combined solutions.

    You would expect the volume to be 100 ml. but it's not. It will be less.

    The reason is because the molecules of water and alcohol are different sized. The molecules of alcohol slip into the spaces between the water molecules. It's similar to what would happen if you poured a bucket full of sand into a bucket full of marbles. The total volume will be less because the sand is going between the marbles.

    The answer would be to measure two solutions separately and pour them together into a third container.
    Randy S.

    In girum imus nocte et consumimur igni.

    -----

    http://www.flickr.com/photos/randystankey/

  9. #9
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    You guys ever hear of density?

    Whenever you mix up a solution of ANYTHING, the density changes from 1.0 (water at 20 deg C roughly) to something else that may be lower or greater than 1.0. That is why in exact photographic work, we measure things by weight or use solutions made to a volumetric standard. In other words, you do not add 100 ml of water, you dilute to 100 ml with water, or you dilute to 100 g total with water, using whatever method applies.

    PE

  10. #10

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    Randy, bullseye! I just noticed the nuance: Emil writes about *THE* beaker, whereas I write about identical syringe*S*, identical beaker*S*... Knowing about the fact you describe, I never did it the other way around! (Combining different solutions by pouring them on top of each other, watching the intermediate/final volume, that is...) I always use the same number of measuring vessels as the the number of different solutions the job needs...

    Regards,
    Loris.

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