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    Re: Refilling a compass
    From: Bob Peterson
    Date: 2004 Jun 23, 16:11 -0500

    I bow in deference to Henry.  He is correct.  It turns out that glycerin
    does mix in water and his older references must, indeed, refer to
    glycerin instead of alcohol.  From "Materials Handbook," 13th ed., Brady
    & Clauser:
        Glycerin.  A colorless, syrupy liquid with a sweet, burning taste
    (not me!), soluble in water and in ethyl alcohol.  It is
        the simplest  _trihydroxy alcohol_, with the composition C3H5(OH)3.
    It has a specific gravity of 1.26, a boiling point
        at 290degreeC, an freezing point at 20degreeC.  It is also called
    glycerol, and was used as a lotion under the name
        of _sweet oil_  for more than a century after its discovery in
    1783.    ....skipping....  In water solutions the freezing point
        is lowered, reaching -60degreeF (-51degreeC), the lowest point, at
    37% of water, and it is thus valuable as an antifreeze.
    Indeed, this stuff looks like it would work.  Still, I'm sticking with
    the grain alcohol/water mixture.  The proportion I use and given by
    Henry of 45alcohol/55water from "A Practical Manual of the Compass"
    (p104) is echoed also in HO226 (p29);  "Navigation and Compass
    Deviations," Muir, 1918 (p46); and "The Ship's Compass," Grant &
    Klinkert, 1952 (p82).  More complete details are given in "Magnetic
    Compasses and Magnetometers," Hine, 1968 (appendix 1).  They all want a
    specific gravity of 0.93.
    Still, none of this applies if you have a compass post WWII.  Everything
    today is  petroleum distillates and not alcohol.  You can't mix the two.
    So, Henry, drinks are on me.  Vodka and water?
    -- Bob Peterson
    Henry C. Halboth wrote:
    >Your dissertation on glycerin is a bit difficult to understand, since you
    >allow that alcohol may be used in the magnetic wet compass. By definition
    >glycerine is a trihydric alcohol, commonly referred to as glycerol and
    >glycerine; further, as most modern compass manufacturers allude to
    >"special" fluids being utilized in there compasses it would appear
    >necessary to perform an analysis to be sure as to what constituents were
    >actually included therein.
    >I have no problem historically with allowing alcohol and water as the
    >basic constituents of compass fluid or that petroleum distillates are now
    >also used, but would respectfully invite your attention to glycerin and
    >alcohol being alternately referred to in texts that apparently predate
    >the experience of both your good self and that of your experts. Please
    >refer to for starters only Knights Modern Seamanship, 10th edition, and
    >Reisenberg's Standard Seamanship for the Merchant Service, 2nd edition,
    >in both of which glycerin and water, and alcohol and water are referred
    >to as floatation fluids for the magnetic compass card.
    >For the benefit of those who have otherwise asked, I would quote from A
    >Practical Manual of the Compass, US Naval Institute, 1921 edition, to the
    >effect that "The bowl is entirely filled with liquid, 45% alcohol, and
    >55% distilled water." My notes of some 60-years ago give the same
    >proportions except that they employ the then alternately employed term
    >glycerin instead of alcohol. Regardless,  I would not employ any home
    >brew fluid to make up a deficiency in a modern compass without completely
    >evacuating and thoroughly cleaning the bowl - or at least consulting the
    >By the way Vodka and water seems to remain an uncontested alternative.
    Robert S. Peterson
    31 N Alfred, Elgin IL  60123  USA
    Compass Adjusting & Repair for Lake Michigan Navigators Since 1985
    Physics @ Bartlett HS
    e-mail: rspeterson(at)wowway.com

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