1.9. EQUIPMENT DATA.
WEIGHTS AND DIMENSIONS
55 lbs (25 kg)
21.12 in. (53.65 cm)
20.12 in. (51.11 cm)
16.34 in. (41.50 cm)
BEST OPERATING TEMPERATURE
+68 °F to +77 °F (+20 °C to +25 °C)
POWER SPECIFICATIONS (Spectrophotometer)
115/220 volt ac or dc battery
400 to 700 nanometers (nm), accuracy ±2.5 nm
SECTION III. PRINCIPLES OF OPERATION
1.10. PURPOSE OF EQUIPMENT.
The Water Quality Test Set, Preventive Medicine (WQAS-PM) is used to test for the presence and amount of several
chemical substances in water. The substances that can be detected and measured with the WQAS-PM are listed in
paragraph 1.7. The WQAS-PM contains all the chemicals, labware, supporting items, and a spectrophotometer as
needed to perform the tests described in this manual.
1.10.1. Test Kits.
Substances are tested for by using either the Spectrophotometer or one of the five individually packaged test kits. Each
test kit contains chemicals and equipment necessary to perform its particular tests. The tests performed with the test kits
are of two general types (1) titration tests and (2) color matching tests.
1.10.2. Titration Tests.
Titration tests are used with the Acidity Test Kit, the Chloride Test Kit, and the Dissolved Oxygen Test Kit. Titration is
based on a chemical reaction that produces a change in color in the test sample if the substance being tested for is
present. Sometimes the test sample is first treated with a chemical reagent in order to make the desired color-producing
reaction occur in the next step. Then a reagent called the titrant is added to the test sample until color change occurs.
The amount of titrant needed to change the color is related directly to the amount of substance being tested for.
1.10.3. Color Matching Tests.
Color matching tests are used in the Iron Test Kit and the Zinc Test Kit. Color matching tests are based on adding a
specific fixed amount of a test reagent to a water sample. If the substance being tested for is present, a color change will
occur. The exact shade or color formed will depend on how much of the test substance was present in the water sample.
A color reference is provided and used to compare the color of the treated sample to standard reference colors.
1.10.4. Colorimetric Tests Using a Spectrophotometer.
Colorimetric tests in the WQAS-PM are similar to color matching tests. Specific fixed amounts of chemicals are added
to the water sample to produce a color change if the substance being tested for is present. However, in the colorimetric
test, the color intensity is measured using an optical instrument called a spectrophotometer. The intensity of the color is
related to the concentration of the substance being tested for.