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  1. #1
    Murray Kelly's Avatar
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    Percentages and mgm/ml

    I have read a lot of threads here that describe amounts of a chemical required to make a working solution (or stock) using a concentrate that often requires mental gymnastics to work out how much of your concentrate are needed to make up a 'brew'.

    A trick I learned over 40 y ago in my line of business (anesthesiology) was a quck way to work out how much of the agent, in our case an amount of say Phenidone, you would add of a percentage solution you have to deliver the milligrams you want in the mix.

    The 'rule de thumb' is you mentally multiply the percentage by ten and call it mg/ml. E.G. a 1% (1 gram in 100ml of glycol) has (1 x 10) mgm / ml of phenidone. 10mgm.

    A 10% solution has 10 x 10 = 100 mgm/ml of the agent.

    A 2.5% solution has 2.5 x 10 = 25 mgm/ml of phenidone.

    And so it goes.

    If this is a puzzle to you, forget I said it!

    It can speed up ad hoc mixing of developers etc. if you remember the multiply by ten 'rule'

    Hope this is of some help to hombrewers.

    Murray
    Brisbane, Oz.

  2. #2
    MikeSeb's Avatar
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    Greetings to a fellow gas-passer, Murray. Now if you can only help me figure out how to do those copper-kettle gas-flow calculations.... Learned it for board exams (sorta--hoped to bluff through without having to answer a question) and forgot it the next day.

    I like to say that my brain does active transport--it pushes knowledge out from my skull against a concentration gradient!
    Michael Sebastian
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  3. #3
    Ian Grant's Avatar
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    Mike, don't worry Murray's going to translate everything about percentages first into US ounces, lbs, gallons etc, then he'll have time for your calculations.

    Ian

  4. #4
    Murray Kelly's Avatar
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    It often seems like the brain is like a sponge. Once it's full, you have to squeeze a bit out to get something more in! :-(

    I never had to use a copper kettle (thank the Good Lord) - any vaporisers were calibrated in % and of recent years that holds good for really low gas flows. I am a < 1l /min man myself. Without the gas analyser I'd be back in the 70's and flying by the seat of my pants. It worked, tho. Ever used a vaporiser in circuit? My record was 8ml/h of halo/hr. Important if you were paying for the stuff yourself.

    No, I just thought the info I gave was useful insofaras it saves a lot of mental agony trying to equate just how much of the stock (%) I need to use to get the desired amount of agent into a formula I read on the 'net.

    Murray (dope peddler)
    Brisbane, Oz

  5. #5
    Murray Kelly's Avatar
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    Ian, Percentages are percentages. :-)

    Did you know that the USofA went metric in 1975? Not the citizens but the official bodies? My Camaro is all metric. Another Ripley. Believe it or not.

    Murray
    Brisbane, Oz

  6. #6
    MurrayMinchin's Avatar
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    Hi Murray!

    Murray
    _________________________________________
    Note to self: Turn your negatives into positives.

  7. #7
    Murray Kelly's Avatar
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    Wot!? Another Murray? I often wonder where my poor old Mum ever got that name from in 1936? She was a Geordie, so the border wasn't too far away.

    Murray
    Brisbane, Oz

  8. #8
    MurrayMinchin's Avatar
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    You, me, and Murray@uptowngallery makes three

    My dads name is Bill (William) and his second name is Humphrey. Since he had already nabbed William that left me with Humphrey...until I got my moms maiden name, for which I'm eternally grateful!!!!!

    Murray
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    Note to self: Turn your negatives into positives.

  9. #9
    Murray@uptowngallery's Avatar
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    I didn't run into any other Murray's until I was about 30..and I really can't remember if I ever met them in person...just on the phone, then in later years on the Web.

    At least 2 were Canadian...

    I had a class in 1976 where they taught us SI units. I learned the exotic style of eliminating radix characters (period vs. comma) for large numbers and using blank spaces. I wonder if I was the only person to learn that because it freaks some people out.

    Not needed for developer luckily.

    Hey, Murray, at first I thought you were implying phenidone was used in your line of work, then I read it again.

    I certainly prefer metric for camera work, weighing chemicals and any small measurements for which the alternative is using a measuring tape with fractions to be misread.

    Murray
    Murray

  10. #10
    Murray@uptowngallery's Avatar
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    My mother had a cousin Mortimer...I'm glad I didn't end up Mortimer@uptowngallery. I'd have had to change my name to something more popular like Cornelius, Rufus or maybe just Spot. Works well for dogs.
    Murray

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