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  1. #21
    Mick Fagan's Avatar
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    Gainer, Interesting thing about the impurities I encountered, was that it was supposed to be 100% Borax. That is really was what I was trying to convey.

    I do take your point, about the different molecular weight of the reagent grade.

    The label on my current jar, tells me that it's weight is 381.43.

    Mick.

  2. #22
    gainer's Avatar
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    So it must be the decahydrate, as it should be if it says "Borax". Labels are strange things. Then, too, impurities can get into a product several places along the line. IMHO, borax is the thing we should worry about the least, as in most recipies + or - 10% won't make a noticable difference. The concentration of the sodium borate will affect the local rate of change of pH more than the equilibrium value. Old timers used to increase borax in D-76 to as much as 20 grams/l to boost the film speed.
    Gadget Gainer

  3. #23

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    Quote Originally Posted by gainer View Post
    Labels are strange things.
    Like ones that tell you something is 100%. Don't believe them. They are not looking hard enough to find the impurities.

    Mick's AR grade is certainly more believable - to get to AR grade it was most certainly purified more that Borax that was hauled by a 20 mule team, and even that extra purity could not get it to 100%.

    So, Pat, why are we supposed to beleive that your inexpensive grade of borax is actually 100%?

  4. #24

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    Quote Originally Posted by gainer View Post
    IMHO, borax is the thing we should worry about the least, as in most recipies + or - 10% won't make a noticable difference. The concentration of the sodium borate will affect the local rate of change of pH more than the equilibrium value.
    If we are only worried about pH, then you are right. If we are worried about buffer capacity, then you are less right. If we are worried about impurities that may affect our results or scratch our negs, then you are way less right.

  5. #25
    gainer's Avatar
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    Quote Originally Posted by Kirk Keyes View Post
    Like ones that tell you something is 100%. Don't believe them. They are not looking hard enough to find the impurities.

    Mick's AR grade is certainly more believable - to get to AR grade it was most certainly purified more that Borax that was hauled by a 20 mule team, and even that extra purity could not get it to 100%.

    So, Pat, why are we supposed to beleive that your inexpensive grade of borax is actually 100%?
    I never said you had to believe anything. I did not assume anything. The statement that something is probably this or that is not an assumption of fact, and I did not even estimate the probable eror of my statement. I did not even say I believed what the label said. I only reported it. My assertion that in most cases for which we use borax, accuracy is not critical is, I think, true or I would not have said it. If you have some evidence of harmful impurities in 20 Mule Team Borax, please tell us what they are. All I can say is I have used it photographically for over 60 years with no troubles. Anything that is good enough to deodorize baby diapers is good enough for my needs.

    If you are so concerned about the content of the 20 Mule Team Borax box, you could do us a great service by analyzing it to see if it comes up to the 99+ % of the analytical reagent, and what in fact makes up the difference, and also what makes up the difference between the analytical reagent and absolute purity.

    I am a great believer in the word ASS-U-ME. I learned it in my 30 years as an Aeronautical Research Engineer-Scientist.
    Gadget Gainer

  6. #26

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    It depends what the impurities are too. Once I was agonising over whether to buy 96% or 98.5% sodium sulphite. I asked the suppliers what the impurities were, and it was mostly sodium sulphate, which is not going to do anything noticeable in a developer or a fixer or a wash aid. The problem then was simple, since the price differential was significant.

    What sort of impurities would be bad news for a developer? Insoluble stuff will settle, if you have time. Metal ions? What else?

  7. #27
    Photo Engineer's Avatar
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    Halides, Calcium, Magnesium, Sulfides. Lots of things actually.

    Photograde chemicals are certified to have the right proportion or lack of these items. You don't want sodium bromide with sodium iodide in it for example, or you don't want carbonate with halide in it.

    The list is long.

    PE

  8. #28
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    I certainly would not use iodized table salt to make up the 50 grams or so of an ersatz Microdol X, but it would take much more than 1 0r 2% of NaCl in the 2 grams of borax in a liter of D-76 to have any measurable effect on that batch. In any case, you don't want salt in soap, as you know if you've been in the Navy or even on a troop ship. (far fetched, of course.) What surprised me most in this interchange about the evils of cheap borax was the 0.89% of impurities allowed in a batch of analytical grade sodium tetraborate decahydrate. What also surprised me was the fact that certain of our resident chemists would make a blanket statement about the unsuitability of household borax without identifying the actual impurities that make it unsuitable. The pentahydrate or the anhydrate could, in some uses, qualify as an impurity when the borax is used as a quantitative analytical reagent, but would have no effect that we could measure or even see. I know, better safe than sorry, but if 99.11% purity qualifies as analytical grade, you could be safe AND sorry without knowing why. Now, if the allowed impurities were known to be photographically inert, like quartz particles, we could tolerate, probably, 95% purity as long as the impurities settled out or dissolved. As you know, I have been using nearly saturated solutions of borax in some developers and have not seen any sign of sediment or colloidal suspension when I use 20 Mule Team Borax. If there are any harmful soluble impurities, they have not shown up in any photographic way.
    Gadget Gainer

  9. #29
    Photo Engineer's Avatar
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    Patrick;

    Sometimes it is not what the impurity is, or how much is present, but rather the amount of variability that is introduced by the variability in manufacturing a 'cheap' household product compared to a photo grade chemical.

    As an example, Detol contains bromide. Today, most papers are high in chloride and some are pure chloride (or nearly so). Any variability in bromide purity or any iodide salt in any of the chemicals causes a big swing in speed and contrast of chloride papers. Iodide in some salts in developers for films changes the edge effects because iodide is a 'buffer' for edge effects.

    So, some hidden or difficult to measure effects may vary and qualitative or eyeball tests will not show it. And, BTW, this becomes even more critical in color.

    PE

  10. #30
    gainer's Avatar
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    Quote Originally Posted by Photo Engineer View Post
    Patrick;

    Sometimes it is not what the impurity is, or how much is present, but rather the amount of variability that is introduced by the variability in manufacturing a 'cheap' household product compared to a photo grade chemical.

    As an example, Detol contains bromide. Today, most papers are high in chloride and some are pure chloride (or nearly so). Any variability in bromide purity or any iodide salt in any of the chemicals causes a big swing in speed and contrast of chloride papers. Iodide in some salts in developers for films changes the edge effects because iodide is a 'buffer' for edge effects.

    So, some hidden or difficult to measure effects may vary and qualitative or eyeball tests will not show it. And, BTW, this becomes even more critical in color.

    PE
    There is no disagreement there, as far as I am concerned. The disagreement on my part is that some household products may actually be required to be more pure than would be required for photographic use. The analytical reagent use of borax appears to require no more than 99.11% purity. Is that sufficient for medical use? Would we not want to know the nature of the impurities? But because we do not seem to know what the purity of 20 Mule Team Borax is, or what its impurities might be, we resort to something that is certified by some vendor as "Photographic quality" which, for all we know, may have come out of a barrel of 20 Mule Team Borax, and even if we knew it to be analytical reagent grade, we still don't know if it could have come out of the same barrel, simply because we do not know the purity of 20 Mule Team Borax that we get at the supermarket. Talk about assumptions!

    Is there some test we photographers could do in order to find out if indeed there is sufficient reason to avoid using the "cheap" stuff? BTW, I don't think cheapness has much to do with my choice. It is more a case of ready availability. If I run out of borax, I cannot run out and get the analytical grade, or the so-called photographic grade, but I can get what I have used for at least 60 of my 80 years within 10 miles of my rural home.
    Gadget Gainer

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