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  1. #31

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    Quote Originally Posted by Kirk Keyes View Post
    By the way, I walked into a walk-in refridgerator at work a couple Mondays ago that someone had put several pounds of dry ice into on the previous Friday. The the room was full of "air" but it had about 17% oxygen instead of the 21% my body was expecting. I noticed the taste of the air was odd, and about a minute later, I was feeling a little tight in the chest. I found what I was looking for and left the room, and felt like I was going to pass out about 30 second later. Pretty odd sensation. Good think there was still some oxygen left... At least I now know what being at the top of Everest is like now!
    Sounds like a really dangerous situation. The labs I've worked in have always kept dry-ice in its own ice-chest in a well-ventilated area, or even outside.

    Your symptoms were likely only partly due to oxygen deprivation -- I am more inclined to blame mild CO2 poisoning. Suffocation by CO2 can happen even in the presence of lots of oxygen (acidification of the blood, etc.)

    Dry-ice is definitely a substance to be respected -- I always try to remind my self that 44 g of the stuff "wants to be" 22-odd litres of suffocating gas. (PV=nRT and all that)

  2. #32

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    Thank you, Bozwart!

    Quote Originally Posted by bowzart View Post
    A good way to do that is to see if it will clear a small clipping of film. The leader that is cut off the 35mm roll when loading the tank is perfect for this; doesn't matter if it has been exposed. The test? Does it clear, or doesn't it?
    I wanted to thank you for this tip. Since I went shooting today I had all of my chemicals out and I had a chance to try it. A small clip from film was submerged into the fixer and it cleared in few minutes. I am assuming by "clear" I am supposed to check if all of the emulsion materials gone and all that is left is the base film material. It was.

  3. #33

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    Quote Originally Posted by Jordan View Post
    Sounds like a really dangerous situation. The labs I've worked in have always kept dry-ice in its own ice-chest in a well-ventilated area, or even outside.

    Your symptoms were likely only partly due to oxygen deprivation -- I am more inclined to blame mild CO2 poisoning. Suffocation by CO2 can happen even in the presence of lots of oxygen (acidification of the blood, etc.)

    Dry-ice is definitely a substance to be respected -- I always try to remind my self that 44 g of the stuff "wants to be" 22-odd litres of suffocating gas. (PV=nRT and all that)
    Yeah, it sure was a dangerous situation, looking back on it. They did put oxygen sensors in the walkins and one ready 21% and the one I went into read 17%. So now there are alarms for low oxygen content. And we trained the field people that use the dry ice to chill samples in coolers about removing the dry ice before putting their coolers in to the walkins. My understanding was there was about 5 lbs of dry ice that was put in there. So it certainly was a combination of low oxygen and high CO2 concentration.
    Kirk

    For up from the ashes, up from the ashes, grow the roses of success!

  4. #34
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    Quote Originally Posted by tkamiya View Post
    I wanted to thank you for this tip. Since I went shooting today I had all of my chemicals out and I had a chance to try it. A small clip from film was submerged into the fixer and it cleared in few minutes. I am assuming by "clear" I am supposed to check if all of the emulsion materials gone and all that is left is the base film material. It was.
    This is often a very useful "dumb test". Another one is the "Is this developer?" test. Put some exposed film, a clip as in the other one is good. Does it turn black? It doesn't tell you much about the specific qualities of the chemical, but at least you have a starting point.

    I once had an assistant who somehow got the idea that fixer should be mixed from concentrate in the same proportion that photo flow 200 is mixed. 1 part to 200 parts water. The fixer test showed that there was a very slight clearing over a rather long period of immersion. Replacing the fixer several times, over a longer period of time, eventually showed what might be happening; at least I knew what questions to ask. She was from Moldova and couldn't speak much English, and I could speak less of her language.

    We got it straightened out, but not before some real disasters occurred. The oft-practiced dumping of mystery chemical problems down the drain wouldn't have worked in that situation. My suspicion was that the same thing would only keep happening. Students were losing their work right at the end of the term.

    Glad you found it useful!

  5. #35

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    Fixer Testing

    Quote Originally Posted by bowzart View Post
    A good way to do that is to see if it will clear a small
    clipping of film. The leader that is cut off the 35mm roll
    when loading the tank is perfect for this; doesn't matter
    if it has been exposed. ... Does it clear, or doesn't it?
    If the portion of film being tested has been exposed
    the silver with in the emulsion may have printed out.
    That is the silver has become elemental due to it's
    reduction by exposure to light. IIRC I've a few
    black leaders packed away.

    It is important to note the time needed to clear using
    a FRESH fix. Twice that time is the standard minimum
    fix time for a FRESH fix. With USED fixer if the time to
    clear exceeds twice the fresh fix time to clear then the
    fix should be replaced with fresh. The time to fix in all
    cases is twice the time to clear.

    Of course if you use your fixer one-shot, as I do,
    then testing the fixer as it ages for it's clear
    time is not needed. Dan

  6. #36
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    A little hypercapnea and hypoxia and you could make the scientific journals:
    http://linkinghub.elsevier.com/retri...35675705001075

  7. #37

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    Mix your chems in the large bottles you currently have, then decant the chems into smaller bottles like empty plastic water bottles. Fill them all the way to the top (no air space). Filled like this and stored in a cool place, your chems should last for up to a year. Make sure you label the bottles well. Wouldn't want anybody drinking the stuff.
    Rick Jason.
    "I'm still developing"

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