Prometheus wrote:
In article , litle ole me
writes

except that there is NO LEAD CONTENT IN THE FLUX FUMES.
Lead does not vaporize until much higher temperature than soldering
temperatures...

There will be lead in the fumes; molecules regularly detach themselves
and float off into the air from liquids (and can also do so for some
solids under certain conditions) at well below the vaporization
temperature, perhaps you have not noticed that water at room temperature
will evaporate, remember: molten is a liquid. This is why mercury spills
are such a problem, and why several years ago laboratories (schools
etc.) had to incur expense having floors lifted and mercury removed by
special vacuum cleaners, and using mercury vapour detectors to variety
'safe' levels. A few weeks ago I had to clean a spill caused by a broken
thermometer from a cupboard.
so, what protection should we use when soldering? how much lead would
have been ingested?

Having worked in a production and engineering environment for many
years, I would think that were there any risk of lead in solder fumes,
there would be HUGE guidelines from the EPA. but, there are none. we had
fans and filters to control the flux fumes, which were quite pungent.)

in your logic above, chemicals that are far fro similar are being
equated and their properties simplified. water and mercury are liquid at
room temp.
mercury, like lead does not evaporate at soldering temperatures.

(for ref: vapor pressure of water at 100C is 760 MM, or 100X the
below. try putting 37 C or even 200C in the math below, and I think the
answer will be that the vap press is minute and unmeasurable.)

_____
http://prola.aps.org/abstract/PR/v26/i6/p851_1
Vapor pressure of lead, 1118° to 1235°C was found to vary from 5.70 mm
to 19.70 mm in good agreement with the equation
log10p(mm)=-10372/T-log10T-11.35, which also fits the best results of
Egerton at lower temperatures. The heat of vaporization of lead at its
melting point is calculated to be 46,300 cal. The chemical constant
comes out -1.40 which is close to the value -1.59 computed from the
quantum theory of monatomic gases.
____

no one I know solders at 1118 degrees c or higher?

water has a vapor pressure FAR lower than lead. please realize that the
vapor pressure of lead and the vapor pressure of water are NOT close in
value.


by the above logic, my desk is evaporating. I know ice can evaporate.
how do can the the number of formica molecules floating out of the
kitchen counter be calculated or measured?

here is a bit from wikipedia.

Vapor pressure is the pressure of a vapor in equilibrium with its
non-vapor phases. Most often the term is used to describe a liquid's
tendency to evaporate. It is the tendency of molecules and atoms to
escape from a liquid or a solid. At any given temperature, for a
particular substance, there is a pressure at which the vapor of that
substance is in equilibrium with its liquid or solid forms. This is the
equilibrium vapor pressure or saturation vapor pressure of that
substance at that temperature. The term vapor pressure is often
understood to mean the saturation vapor pressure. A substance with a
high vapor pressure at normal temperatures is often referred to as
volatile. The higher the vapor pressure of a material at a given
temperature, the lower the boiling point.



the end.