Calculate the concentration for stock solutions of NaCl and NaI (both 50.00 mL) such that when you add small amounts of them (i.e. between 5 and 300 L per increment) to a cuvette containing 2.5 mL of sample, the following salt concentrations can be achieved: 0.003 M, 0.006 M, 0.01 M and 0.03 M in the cuvette. Start with an addition between 5 and 25 L to achieve the lowest concentration. A simple method to determine the incremental addition needed to achieve the next concentration is to:

1. calculate the total volume of salt stock needed to reach the desired salt concentration from the 2.5 mL sample
2. subtract the volume of salt stock previously added.

Double-check that the final volume in the cuvette is less than 3.0 mL.