3/5     How do people calculate the surface area of porous rocks
        or other similar "holey" surfaces?
        \_ Heat exchange is proportional to surface area.  You can try putting
           the rock in water, and designing some simple experiments to figure
           out what the surface area must be.  (This will not give you an
           exact answer, but a better approximation than geometric methods, I
           think).  -- ilyas
        \_ exact or estimate?
                \_ either -op
                   \_ estimate: get a box, ball or other object of the same
                      general shape, measure & calculate.  i have no clue at
                      all how to do the exact surface area.  i guess if you
                      painted the object with a known thickness of another
                      substance but that sounds really iffy to me.
                      \_ estimates should at be accurate within an order of
                         magnitude.  your method provides no such guarantee and
                         is likely to be way, way off.
                         \_ shrug, no one else was even trying.  note below
                            that someone else says my 'coat it with a
                            substance' method is actually what chemists do.
                            so if my method is so poor, what is your method?
                            \_ I don't have a method.  I know that I don't know
                               the answer.
                               \_ ok then, someone else said my idea is what
                                  happens in the real world and you have no
                                  idea at all.  thanks for clarifying.
                                  \_ I was objecting to your /estimate/ about
                                     finding an object of the same general
                                     shape.  The /exact/ method with the paint
                                     is fine.  Yeesh.
        \_ this is a very common problem among chemical enginners who
           dealt with catalyst all the time. go ask them.  If it's a rock
           of irregular shape, then, people usually just estimate them.
           otherwise, there are fancy ways such as putting a chemical cloat
           on that thing, by finding out how much chemical you used, you get
           a good estimate of what is the surface area.
        \_ see Perry's Chemical Engineering Guide. in Chemistry Library
                \_ I'm nowhere near berkeley. can you summarize then?