TM 10-6630-245-13&P
WARNING
SPADNS REAGENT
POISON. Very strong acid. May cause burns. Harmful if swallowed. Do not
ingest or allow contact with skin or eyes. In case of contact, immediately flush
eyes and skin with water for 15 minutes. Remove contaminated clothing. In case
of ingestion, DO NOT induce vomiting. Give one or two glasses of water. Never
give anything by mouth to an unconscious person. In case of inhalation, remove
victim to fresh air. Give artificial respiration if necessary. Treat for ingestion if
symptoms appear. In all cases, call medic immediately.
NOTE
DO NOT wait longer than 3 minutes for color to develop.
(6)
Use the 5 ml pipet(4, fig. 1-1) and the piper filler(27) to measure 5 ml of SPADNS reagent(16). Add the
solution to the first spectrophotometer sample cell(7, fig. 2-5) containing the test sample. Swirl to mix.
Repeat to add 5 ml of SPADNS(16, fig. 1-1) to the second spectrophotometer sample cell. Wait one
minute for the color to fully develop.
(7)
Insert the "Fluoride (SPADNS Method)" meter scale card(2, fig. 2-5) into spectrophotometer. Place the
sample cell containing the fluoride standard solution into the cell holder well(5) in the spectrophotometer.
Adjust the wavelength dial(8) to 580 nm. Turn the LIGHT CONTROL knob(l0) so that the meter scale(14)
reads 1.0 mg/l. Remove the sample cell(7) from the spectrophotometer well(5).
(8)
Place the sample cell containing the water to be tested into the cell holder well(5) in the
spectrophotometer. Record the reading on the meter scale(14).
f.
Interpretation of Results:
NOTE
The recorded reading corresponds to the concentration of fluorides in mg/l.
(1)
Several other chemicals if present can affect the reading obtained. If desired the value read may be
adjusted for the presence of other chemicals if their presence and amounts are known. Table 2-3 shows
the errors in reading caused by the presence of several chemicals. For instance if the test sample is
known to contain chlorides in a concentration of 7250 mg/I, round the quantity off to the value shown in the
table (7000) and read the error of +0.1 mg/I. This means the spectrophotometer reading is +0.1 mg/l of
fluoride too high due to the presence of chlorides. Subtract 0.1 from the spectrophotometer reading to
compensate for chlorides.
Table 2-3. SPADNS Method Errors Due to Interference
Interference Substance
Concentration
Error
Alkalinity (as CaCO3)
5000 mg/1
-0.1 mg/l F
Aluminum
0.1 mg/1
-0.1 mg/l F
Chloride
7000 mg/1
+0.1 mg/l F
Iron, ferric
10 mg/1
-0.1 mg/l F
Sodium Hexametaphosphate
1.0 mg/1
+0.1 mg/l F
Phosphate, ortho
16 mg/1
+0.1 mg/l F
Sulfate
200 mg/1
+0.1 mg/l F
2-44
