Got this from page 11-94, subsection on salt brines in the 7th edition. Here is a cut and paste from that subsection.
Brine of concentration x (water concentration is 1-x) will not
solidify at 0°C (freezing temperature for water, point A). When the
temperature drops to B, the first crystal of ice is formed. As the temperature
decreases to C, ice crystals continue to form and their mixture
with the brine solution forms the slush. At the point C there will
be part ice in the mixture l2/(l1 + l2), and liquid (brine) l1/(l1 + l2).
At point D there is mixture of m1 parts eutectic brine solution D1
[concentration m1/(m1 + m2)], and m2 parts of ice [concentration
m2/(m1 + m2)]. Cooling the mixture below D solidifies the entire solution
at the eutectic temperature. Eutectic temperature is the lowest
temperature that can be reached with no solidification.
It is obvious that further strengthening of brine has no effect, and
can cause a different reaction—salt sometimes freezes out in the
installations where concentration is too high.
Sodium chloride, an ordinary salt (NaCl), is the least expensive per
volume of any brine available. It can be used in contact with food and
in open systems because of its low toxicity. Heat transfer coefficients
are relatively high. However, its drawbacks are it has a relatively high
freezing point and is highly corrosive (requires inhibitors thus must be
checked on a regular schedule).
Calcium chloride (CaCl2) is similar to NaCl. It is the second lowestcost
brine, with a somewhat lower freezing point (used for temperatures
as low as -37°C). Highly corrosive and not appropriate for direct
contact with food. Heat transfer coefficients are rapidly reduced at
temperatures below -20°C. The presence of magnesium salts in
either sodium or calcium chloride is undesirable because they tend to
form sludge. Air and carbon dioxide are contaminants and excessive
aeration of the brine should be prevented by use of close systems.
Oxygen, required for corrosion, normally comes from the atmosphere
and dissolves in the brine solution. Dilute brines dissolve oxygen more
readily and are generally more corrosive than concentrated brines. It
is believed that even a closed brine system will not prevent the infiltration
of oxygen.