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  1. #11

    Join Date
    Nov 2002
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    As you probably know, many salts are available in forms which differ in how much water is bound up in the crystalline structure. So you can get "anyhdrous" (no water) and various levels of "hydrate", the levels depending on the salt. e.g. sodium carbonate monohydrate, sodium carbonate decahydrate.

    In the case of sodium metaborate, there has been some unfortunate nomenclature which has been confusing. Lots of people don't know which version they have. Some vendors don't know what version they're selling (Vanbar in Melbourne, Australia where I got mine).

    These people make it (www.borax.com) and even they have made a mistake in one of the product sheets. See if you can find it.

    http://www.borax.com/docs/product_pd...l.pdf?sfvrsn=1

    http://www.borax.com/docs/product_pd...l.pdf?sfvrsn=1

    Some old photographic formulas don't specify which version was used.

    The maximum solubility depends on which level of water of crystallization. Maybe you have the one with less water of crystallization and you already have a saturated solution. I suggest that you use that, on the assumption that it's very close to what was intended. BUT, be very careful that any particles undissolved don't get into the working solution, for obvious reasons.

    Part B of PMK was always hard to dissolve completely.

  2. #12

    Join Date
    Sep 2002
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    Oregon and Austria
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    Quote Originally Posted by KennethGoodman View Post
    Hello
    I am new to this forum but would like some help with a problem

    Am in the process of making some PMK (Pyr-Metol-Kodalk) developer.

    Am having trouble dissolving the sodium metaborate in the water. The quantities are:

    600g metaborate
    2l distilled water
    at about 25 degrees Celsius

    Anybody out there who can help??

    Ken Rhodes
    Distilled water should do the trick. Make sure it's not just drinking water or the like. Make sure your metaborate is good quality (inferior grades may have impurities that won't dissolve). I've had trouble dissolving the metaborate in tap water, you really need distilled. You are making a saturated solution, so heat may also help. Start with a bit warmer water.

    If the problem persists, just double the amount of water you dissolve the metaborate in and then double the amount of part B you use when mixing the developer for use. The bit of extra water will make very little difference; if you are a stickler, compensate for the extra by mixing part A in appropriately less water.

    Best,

    Doremus

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