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Thread: Out of Date sofnolime 797

  1. #31
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    Re: Out of Date sofnolime 797

    Quote Originally Posted by ScubaAl  View Original Post
    Below is from US Navy testing done in 1986. How relevant to this discussion I don't know.

    The results of unmanned performance testing revealed that
    subjecting absorbent material to freezing temperatures prior to use did
    not substantially effect canister duration times in four of the five
    brands tested. Of the five, only PROTOSORB showed marked performance
    degradation as a result of freezing. The relative ranking, from the
    longest to the shortest frozen canister duration time, revealed AGASORB
    as the best performer. Frozen DRAEGERSORB and PROTOSORB had similar
    duration times, followed by HP SODASORB and finally DIVEASORB which
    displayed the poorest performance.

    Thanks Al,

    very relevant to the "freeze out" part. Very interesting as well..
    Do you have a reference to this..
    Would be intersted to learn more about the testing parameters.
    Especially how long and at which temperatures they were freezing the lime..
    Unfortunately they have not tested good old sofno as it seems..
    And they may have tested the military grade limes, which are a bit more aggresive (more NaOH in it AFAIK, which shouldn't have impact on the freezing outcome)

    Does anybody know about the granules sizes and shapes of the limes mentioned?
    The only one I know is Draegersorb.

  2. #32
    RBW Member hawai is an unknown quantity at this point hawai's Avatar
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    Re: Out of Date sofnolime 797

    Hi Nitrogenius,

    Quote Originally Posted by Nitrogenius  View Original Post
    Otherwise you could just "moisten" the lime to have the necessary effect, but it does not work that way unfortunately..
    And what exactly makes you think this is the case?
    Second hand experience tells otherwise. Sorb deliberately blow dried over night with high flow oxygen. Then split and one part just sprinkled with water. After that brought into contact with Desflurane. Dry sorb produced copious amounts of CO as an indication that the sorb is too dry to work properly. The "re-wetted" sorb worked just fine. Unpublished backroom experiments performed out of sheer curiosity.

    OK, admitted the breakdown of volatile anaesthetics is not the same as the CO2 binding reaction, but both are crucially dependent on the moisture of the sorb being around 15%. So I would safely assume that "re-wetting" the sorb works.
    Although I would not be so bold as to give procedural advice or even amounts of fluid needed in making "dry" sorb work properly again.

    Cheers
    Hansjoerg

  3. #33
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    Re: Out of Date sofnolime 797

    Quote Originally Posted by hawai  View Original Post
    Hi Nitrogenius,



    And what exactly makes you think this is the case?
    Second hand experience tells otherwise. Sorb deliberately blow dried over night with high flow oxygen. Then split and one part just sprinkled with water. After that brought into contact with Desflurane. Dry sorb produced copious amounts of CO as an indication that the sorb is too dry to work properly. The "re-wetted" sorb worked just fine. Unpublished backroom experiments performed out of sheer curiosity.

    OK, admitted the breakdown of volatile anaesthetics is not the same as the CO2 binding reaction, but both are crucially dependent on the moisture of the sorb being around 15%. So I would safely assume that "re-wetting" the sorb works.
    Although I would not be so bold as to give procedural advice or even amounts of fluid needed in making "dry" sorb work properly again.

    Cheers
    Hansjoerg
    Nice work!

  4. #34
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    Re: Out of Date sofnolime 797

    Quote Originally Posted by ScubaAl  View Original Post
    Below is from US Navy testing done in 1986. How relevant to this discussion I don't know.

    The results of unmanned performance testing revealed that
    subjecting absorbent material to freezing temperatures prior to use did
    not substantially effect canister duration times in four of the five
    brands tested. Of the five, only PROTOSORB showed marked performance
    degradation as a result of freezing. The relative ranking, from the
    longest to the shortest frozen canister duration time, revealed AGASORB
    as the best performer. Frozen DRAEGERSORB and PROTOSORB had similar
    duration times, followed by HP SODASORB and finally DIVEASORB which
    displayed the poorest performance.
    Here is another extract, this time from the "Cobra Operation and Maintenance Manual" in respect of stored sorb....
    Attached Images

  5. #35
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    Re: Out of Date sofnolime 797

    Hi Hansjoerg

    Quote Originally Posted by hawai  View Original Post
    And what exactly makes you think this is the case?
    That I had explained before already.. There is a high risk that physically induced water to the lime immiately reacts with the Sodiumydroxide to Sodiumhydrogenecarbonate
    Thus you have the H2O chemically bound again and not available for the necessary 1st step reaction with the CO2 to carbonic acid and you have that "shitty caustic juice" in your scrubber..

    But interesting experiment you did though.. Most likely it is really depending how much water to apply exactly..
    You certaintly get caustic.. some H2O apparently was also reacting with CO2 in your moistioned probe.. and apparently still enough Sodiumhydroxide remained for the second step reaction of scrubbing..

    The other question is how dried out you really got your lime there..
    15%-18% as they mostly have is really not much and I am quite confident that it is in fact quite hard to get much out without as well "baking" it a bit with dry gas..
    You still might have had some 5-10% remaining in that sorb, not being enough for that not wetted probe, but then in this single constellation just being enough topped up for the wetted probe..

    All certaintly something I won't bet my life on ;)

    Cheers,
    Frank

  6. #36
    RBW Member hawai is an unknown quantity at this point hawai's Avatar
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    Re: Out of Date sofnolime 797

    Hi Frank,

    sorry for the belated answer...

    Quote Originally Posted by Nitrogenius  View Original Post
    That I had explained before already.. There is a high risk that physically induced water to the lime immiately reacts with the Sodiumydroxide to Sodiumhydrogenecarbonate
    Thus you have the H2O chemically bound again and not available for the necessary 1st step reaction with the CO2 to carbonic acid and you have that "shitty caustic juice" in your scrubber..

    But interesting experiment you did though.. Most likely it is really depending how much water to apply exactly..
    You certaintly get caustic.. some H2O apparently was also reacting with CO2 in your moistioned probe.. and apparently still enough Sodiumhydroxide remained for the second step reaction of scrubbing..

    The other question is how dried out you really got your lime there..
    15%-18% as they mostly have is really not much and I am quite confident that it is in fact quite hard to get much out without as well "baking" it a bit with dry gas..
    You still might have had some 5-10% remaining in that sorb, not being enough for that not wetted probe, but then in this single constellation just being enough topped up for the wetted probe..

    All certaintly something I won't bet my life on ;)

    Cheers,
    Frank
    Unfortunately it was no "my" experiment, I was just peripherally involved.
    The blow dried method was establisged by two guys who did a ,ot of work around breakdown of volatile anaesthetics on dry sorb. So they made sure that the sorb was bone dry. IFRC they even validated their method by measuring the water content of the blow dried sorb ( stuff in question was: Draegersorb 800(tm), Sodalime (tm), Amsorb(tm) and Sofnolime in the coarser size).

    The whole work was done with the focus on breakdown products and IIRC centred around sorbs that contained Potassiumhydroxide, which were responsible for a lot of ugly byproducts. After those disappeared from the market the research became somewhat obsolete.

    According to the guys there was a pretty linear correlation between moister content (or absence thereof) and reaction temperature. And believe me those test containers got really hot. So assume the water content was negligible. And, again IIRC they added the "missing" water to make up for a theoretical water content of 15% approx. (850g sorb + 150ml water).

    But I certainly do agree completely: sorb is cheap, life is not. So I wouldn't bet my life on those experiments either. Which was btw the conclusion as well: don't bother trying to get the sorb to work again, just use fresh one...

    Cheers
    Hansjoerg

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    RBW Member hawai is an unknown quantity at this point hawai's Avatar
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    Re: Out of Date sofnolime 797

    Quote Originally Posted by osiris  View Original Post
    Nice work!
    Thanks, but not mine. I was just the innocent bystander trying to find out how this research thing works. Haven't learned until today though...

    In case you're interested in that stuff (as far as it ever got published) you migth want to search for H. Wissing or U. Warnken, they were the core people in that group then.

    Cheers
    Hansjoerg

  8. #38
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    Re: Out of Date sofnolime 797

    This whole post makes very interesting reading and almost gave me a headache and I can understand the disputed opinions etc. thats why I just try to follow manufacturers guidelines.

    As I say still makes interesting reading, we all have our opinions.

  9. #39
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    Re: Out of Date sofnolime 797

    What is the time u normalt can have ā new can of sorb before it expires.
    I am brand new in the game just got my meg 2 days ago so I have never naught any products before.

  10. #40
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    Re: Out of Date sofnolime 797

    Quote Originally Posted by osiris  View Original Post
    Here is another extract, this time from the "Cobra Operation and Maintenance Manual" in respect of stored sorb....
    Interesting. What do they expect to happen to the sorb in 1 hour at 1ATA?

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