Hach DR/850, Procedures Manual, Page: 174 / 460

174
d) Turn the heat control to setting 10, with the thermometer
in place. The yellow pilot lamp shows when the heater is
on.
e) When the temperature reaches 180 °C (about one hour),
turn the still off.
f) Dilute the collected distillate to 100 mL, if necessary.
Analyze the distillate by the above method.
Summary of Method
The SPADNS Method for fluoride determination involves the
reaction of fluoride with a red zirconium-dye solution. The
fluoride combines with part of the zirconium to form a colorless
complex, thus bleaching the red color in an amount proportional
to the fluoride concentration. Seawater and wastewater samples
require distillation. See Optional Apparatus for Distillation
Apparatus listing.
Pollution Prevention and Waste Management
SPADNS Reagent contains sodium arsenite. Final solutions will
contain sodium arsenite (D004) in sufficient concentration to be
regulated as hazardous waste for Federal RCRA. See
Section 3
for more information on disposal of these materials.
REQUIRED REAGENTS (Using Solution)
Quantity Required
Description Per Test Unit Cat. No.
SPADNS Reagent for Fluoride ................................. 4 mL.................. 500 mL............. 444-49
Water, deionized........................................................ 10 mL ......................... 4 L.............. 272-56
REQUIRED APPARATUS (Using Solution)
Pipet Filler safety bulb.................................................. 1........................... each.......... 14651-00
Pipet, volumetric, Class A, 10.00 mL........................... 1........................... each.......... 14515-38
Pipet, volumetric, Class A, 2.00 mL............................. 1........................... each.......... 14515-36
Sample Cell, 10-20-25 mL w/ cap ................................ 2......................... 6/pkg.......... 24019-06
Thermometer, –20 to 110°C, non-mercury ................... 1........................... each.......... 26357-02
REQUIRED REAGENTS (Using AccuVac Ampuls)
SPADNS Fluoride Reagent AccuVac Ampuls........ 2 ampuls................. 25/pkg.......... 25060-25
Water, deionized........................................................ varies ......................... 4 L.............. 272-56
FLUORIDE,
continued