Figure 2-2. Mixing Solutions

TM-10-6630-245-13P Water Quality Analysis Set Preventive Medicine NSN 6630-01-367-9402 (EIC) ZGF Manual
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TM 10-6630-245-13&P 2.6.1.5. Mixing. 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")(fig. 2-2). a. Mixing in a Square Sample Cell: Grasp the neck of the sample cell(l) with the thumb and index finger of one hand. Rest the 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. b. Mixing in a Graduated Cylinder or a Flask: Grip the cylinder(2) (or flask) firmly with the tips of three fingers. Hold the cylinder at a 45 degree angle and rotate the wrist several times as though stirring a pot. Reverse the direction of rotation. Repeat a few times. Figure 2-2. Mixing Solutions. 2.6.1.6. Using Graduated Cylinders. a. General. There are two identical 25 ml graduated cylinders in the WQAS-PM. They are used to measure water samples for tests. Only clean dry cylinders should be used for any test procedure. Before using a graduated cylinder, rinse it two or three times with a small quantity of the fluid to be measured. After use the cylinders should be cleaned thoroughly before returning them to the WQAS-PM. b. Reading the Cylinder. The wall of the cylinder is marked in millimeters. For accuracy, the level of the liquid in the cylinder should be determined by reading the meniscus at the top of the liquid level. c. Reading the Meniscus (fig. 2-3). The top surface of the water in a container or tube is not flat. Some of the water is pulled-up against the inside walls of the tube. This makes the surface concave. This curved water surface inside the tube is called the meniscus(l). For accurate measurements, the surface level must be read at the bottom of the meniscus. To do this hold the flask or cylinder so the water surface is at eye level. Hold it up against a uniform bright background. (A good technique is to hold a piece of white paper at a slight angle behind cylinder to help highlight the meniscus.) The meniscus will appear as a region at the top of the fluid with a thickness equal to the amount the water is pulled up the sides of the tube. Read the water level at the bottom of this region. Figure 2-3. Reading the Meniscus. 2-14

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