pH changes w increasing saline conc.

This is a part of a commonly used IV solutions table:

[TABLE=align: center]

[TR]

[TD]Name of Solution

[/TD]

[TD]Type of Solution

[/TD]

[TD]Ingredients in

1-Liter

[/TD]

[/TR]

[TR]

[TD]0.45% Sodium Chloride

Shorthand Notation:

½NS

[/TD]

[TD]Hypotonic

pH 5.6

[/TD]

[TD]77 mEq Sodium

77 mEq Chloride

[/TD]

[/TR]

[TR]

[TD]0.9% Sodium Chloride

Shorthand Notation:

NS

[/TD]

[TD]Isotonic

pH 5.7

[/TD]

[TD]154 mEq Sodium

154 mEq Chloride

[/TD]

[/TR]

[TR]

[TD]3% Sodium Chloride

[/TD]

[TD]Hypertonic

pH 5.0

[/TD]

[TD]513 mEq Sodium

513 mEq Chloride

[/TD]

[/TR]

[TR]

[TD]5% Sodium Chloride

[/TD]

[TD]Hypertonic

pH 5.8

[/TD]

[TD]855 mEq Sodium

855 mEq Chloride

[/TD]

[/TR]

[/TABLE]

Why does the pH go "up, down, up" as NaCl conc. increases?