Mixing Water Samples

TM-5-6630-215-12 Alarm-Monitor Group (AMG) OA-9431/F88-9(V) CAGEC 97403 Manual
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WARNING TM 5-6630-215-12 (a) Mixing Water Samples. The following two methods may be helpful in tests where it is necessary to mix the water sample with chemicals (usually indicated by the instructions, “Swirl to mix”). 1. When mixing is done in a square sample cell, the swirling motion is attained by a simple twisting motion as shown in figure 2-1. This is done by grasping 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 on the other hand. Rotate the cell quickly, first one way and then the other, to mix the samples. 2. A swirling motion is also recommended when the mixing takes place in a graduated cylinder or a titration flask. In this case, however, grip the cylinder (or flask) firmly with the tips of three fingers (fig. 2-1). Hold the cylinder at a 45 degree angle and twist the wrist. This motion will move the cylinder in an approxi- mately 12-inch circle, thereby giving liquids an intense rotation which accomplished complete mixing in a few turns. (b) Reading the Meniscus. When small sample quantities are used, the accuracy of the measurements is very important. Figure 2-2 illustrates the proper way of reading the sample level or the meniscus formed when the liquid wets the cylinder or pipet walls. Never pipet chemical solutions or unknown water samples by mouth. Figure 2-1. Swirling Techniques 2-4

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