[Amps] current threads about silver solder and resoldering

[Roger (K8RI)]

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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