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Mixing Water Samples
The following two methods may be helpful in tests that require mixing
sample with chemicals (usually indicated by "swirl to mix" instructions).
1. A swirling motion is recommended when mixing sample in a
graduated cylinder or a titration flask. In this case, grip the cylinder (or
flask) firmly with the tips of three fingers; see Figure 12. Hold the
cylinder at a 45-degree angle and twist the wrist. This motion will move
the cylinder in an approximately 12-inch circle, giving the liquids an
intense rotation to accomplish complete mixing in a few turns.
This swirling procedure is the most gentle and offers the least
interference from the atmosphere when testing for carbon dioxide and
other gases. Both methods are simple but take a bit of practice in order
to obtain the best results.
2. When mixing sample in a square sample cell, the swirling motion is
attained by a simple twisting motion; see Figure 13. Grasp the neck of the
cell with the thumb and index finger of one hand while resting the concave
bottom of the cell on the tip of the index finger of other hand. Rotate the
cell quickly, first one way and then the other, to mix the sample.
Figure 12 Swirling Graduated Cylinder
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