LaMotte DC1600 Colorimeter - Manual (Page 83)

SULFIDE
METHYLENE BLUE METHOD CODE 3654
QUANTITY CONTENTS CODE
60 mL *Sulfide Reagent A *V-4458-H
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. For example, solutions used in the treatment of wood pulp in paper manufacturing
may contain large amounts of sulfite, which is reduced to sulfide. Lake muds rich in sulfates produce hydrogen sulfide during
periods of very low oxygen levels that result from summer 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 it is described as “rotten eggs.” Removal of sulfide odor is accomplished by aeration or chlorination.
Hydrogen sulfide is a toxic substance that acts as a respiratory depressant in both humans and fish.
APPLICATION: Drinking, surface and saline waters; domestic and industrial wastes.
RANGE: 0.0 – 3.0 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 and sample 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.
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