desalting DNA

[C.S. Wilding]

Hi,
I know there has been a bit about this already but...
I don't think 2X 70% etoh washes are satisfactoraly washing my DNA 
extractions and am looking for alternatives. Are there any kits that allow 
either dialysis in a convenient format (easy to get the small vols back 
from whatever dialysis is performed in), or some kind of column. Cost is 
an issue due to the high number of samples.
As for the washes, if you precipitate your DNA with 2 vols etoh you have 
67% etoh. Why then would washing with 70% remove any salt that had 
precipitated. I would have thought that something less concentrated is 
necessary, although I can see that this is not possible unless you want to 
redissolve the DNA.
Craig