Decagon WP4-T - Preparing Salt Solution; Appendix A

WP
4
PotentiaMeter
Appendix A
67
Appendix A
Preparing Salt Solution
If you choose to mix a saturated salt solution for use
as a verification standard, we recommend that you
use the approved AOAC method. This method is as
follows:
1. Select a reagent-grade salt and place it in a test
container to a depth of about 4cm for more solu-
ble salts (higher water potential), to a depth of
about 1.5 cm for less soluble salts (low water
potential), and to an intermediate depth for
intermediate salts.
2. Add distilled water in increments of about 2mL,
stirring constantly.
3. Add water until the salt can absorb no more
water, as evidenced by the presence of free liq-
uid. Keep the amount of free liquid to the mini-
mum needed to keep the solution saturated with
water. If you intend on using this solution over a
long term period, make sure to seal the solution
well to prevent losses from evaporation.