"Phil" wrote in message
oups.com...
Freezing point depression is directly proportional to the concentration
of the solution, and is about 6 Deg C for a 10% solution of salt in
water (ie the soln will freeze at -6 C at 1 atm)...

The freezing point is not linearly proportional to the concentration of salt.

See

http://www.madsci.org/posts/archives...8209.Es.r.html

http://antoine.frostburg.edu/chem/se...elts-ice.shtml



--

Michael Chare