Re: vacuum pump

Tesla List wrote:

>         Have often wondered if a water aspirator of this type would be OK for
> the kind of evacuation being discussed here, but worried over the vapor
> pressure of the water vapor in the "vacuum" line.  Freeze trap would
> take care of that, I guess.  Wonder if you have any thoughts on the
> matter.

I don't think that some water vapor is a problem. The amount of water
is insignificant due to the low pressure. It is not trivial to make a 
vacuum pump that produces better vacuum than this. I have built another,
with a piston inside a PVC tube and valves made with steel balls sitting
over small greased "O" rings, one at the base and another in the piston,
in holes, and could at most reach the same pressure.

Antonio Carlos M. de Queiroz