LaMotte COD Plus Colorimeter 1922-EX2 - Manual (Page 120)

SULFIDE - LOW RANGE
METHYLENE BLUE METHOD • CODE 3654-01-SC
QUANTITY CONTENTS CODE
2 X 30 mL *Sulfide Reagent A
*V-4458-G
15 mL *Sulfide Reagent B
*V-4459-E
2 x 60 mL Sulfide Reagent C
4460-H
2 Pipets, 1.0 mL, plastic
0354
*WARNING: Reagents marked with a * are considered hazardous substances. Material
Safety Data Sheets (MSDS) are supplied for these reagents. For your safety, read label
and accompanying MSDS before using.
Sulfide occurs in many well water supplies and sometimes is formed in lakes or
surface waters. In distribution systems, it may be formed as a result of bacterial
action on organic matter under anaerobic conditions. It may also be found in
waters receiving sewage or industrial wastes. Lake muds rich in sulfates produce
hydrogen sulfide during periods of very low oxygen levels that result from
stagnation. Concentrations of a few hundredths of a part per million (or
milligram per liter) cause a noticeable odor. At low concentrations, this odor is
described as “musty”; at high concentration, as “rotten eggs.” Removal of
sulfide odor is accomplished by aeration or chlorination. Hydrogen sulfide, a
toxic substance, acts as a respiratory depressant in both humans and fish.
APPLICATION:
Drinking, surface and saline waters; domestic and industrial
wastes.
RANGE: 0.00 – 1.50 ppm Sulfide
METHOD: Under suitable conditions the sulfide ion reacts with
p-aminodimethylaniline and ferric chloride to produce
methylene blue in proportion to the sulfide concentration.
Ammonium phosphate is added to remove the color due to
the ferric iron.
SAMPLE
HANDLING &
PRESERVATION: Samples must be taken with a minimum of aeration since
sulfide is volatilized by aeration and any oxygen which is
taken up will destroy sulfides by chemical action. Samples
that are used for total sulfide concentrations may be
preserved by adding 2M zinc acetate solution at a dosage of
2 mL per liter of sample. This precipitates sulfide as inert
zinc sulfide. Determination of dissolved sulfides in samples
not preserved with zinc acetate must be started within 3
minutes of sampling.
INTERFERENCES: Strong reducing agents such as sulfite, thiosulfate, and
hydrosulfite prevent the formation of the color or diminish
its intensity. High concentrations of sulfide will inhibit the
reaction, but dilution of the sample prior to analysis
eliminates this problem.
COD PLUS TEST PROCEDURES 6/02 SULFIDE - LOW RANGE 1/2