On 9/1/2012 3:20 PM, Roger (K8RI) wrote:
On 9/1/2012 2:26 PM, Manfred Mornhinweg wrote:
Bill,
Most things are labeled the largest component to the smallest by weight,
Yes, for example the list of chemicals in food is like that. But solder
normally isn't. I think there is an ISO standard defining solder alloys,
and it requires tin contents to be specified first. I would have to
search for it to provide any evidence, though.
Such as eutectic alloy of 63% tin, 37% lead.
Oddly enough with that ratio by weight the number of atoms of each is
equal.
One atom of lead to one of tin.
I strongly disagree. Tin has much lower atomic weight than lead. If
there is far more tin, by weight, than lead, then the ratio of atoms of
tin to atoms of lead is even larger. According to my calculation, 63/37
solder has slightly more than 3 atoms of tin for each atom of lead.
Lead = 207.2
Tin 118.7
Figuring gram molecular weights
63% of 118.7 = 74.781grams/molecules
37% of 207.2 = 76.664grams/molecules
Oops...Slight correction... The numbers (Atomic Weight) are the
molecular weight or "Gram Molecular weight, or mole. A mole of any
element has the same number of atoms. It's called Avogadro's number, or
constant which is ~6.022 X 10^23 atoms.
IE IIRC and according to my old physics book, *both* 207.2 grams of
Lead and 118.7 grams of tin have the same number of atoms, or 6.022 X
10^23 atoms. So although the 63% and 37% have close to the same weight,
they do not have the same number of atoms.
And that extends my knowledge of chemistry well past what I can remember
from college oh so many years ago. IE: I had to look it up.
I sometimes have to remind our PHD Chemist neighbor whose back yard
abuts our back yard that he is talking to a guy who just survived
college chemistry 111 and 112.
Now, how long before I have to correct the correction?
73
Roger (K8RI)
They are close but not exact or they just round off to the nearest % for
simplicity.
I would think to be eutectic they would be the same, but due to
measuring tolerances this is pretty close.
73
Roger (K8RI)
Manfred
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