Preparing Salt Solution; Appendix A - Decagon Devices AquaLab 4TE Operator's Manual

AquaLab

Appendix A

Appendix A

Preparing Salt Solution

If you choose to mix a saturated salt solution for use as a verifi cation
standard, we recommend that you use the approved AOAC method.
Th is 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 soluble salts (lower a ), to a depth of
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about 1.5 cm for less soluble salts (high a ), and to an intermediate
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depth for intermediate salts.
2. Add distilled water in increments of about 2mL, stirring con-
stantly.
3. Add water until the salt can absorb no more water, evidenced
by the presence of free liquid. Keep the amount of free liquid to
the minimum needed to keep the solution saturated with water. If
you plan on using this solution over a long term period, seal the
solution well to prevent losses from evaporation. Below is a table of
saturated salt solutions and their respective water activities at vari-
ous temperatures. Please note that these values are based on averaged
published data, and the standard errors shown refl ect Greenspan's
standard error for each salt solution, not the AquaLab's accuracy in
measuring the salt. AquaLab measures all samples with an accuracy
of ±0.003 a .
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