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Chlorine - bromine - iodine, Chlorine – LaMotte DC1600 Colorimeter User Manual

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CHLORINE - BROMINE - IODINE

DPD METHOD

CODE 3643

QUANTITY

CONTENTS

CODE

2 x 100

*DPD #1 Instrument Grade Tablets

*6903-J

100

DPD #3 Instrument Grade Tablets

6197-J

15 mL

Glycine Solution

6811-E

1

Tablet Crusher

0175

*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.

NOTE: To distinguish bromine, free chlorine, total chlorine and combined chlorine, order Glycine Solution (Code

6811-E).

CHLORINE

All water for cities and communities must be disinfected; even waters that come from clean sources, protected watersheds,

reservoirs, and deep wells, are commonly disinfected to assure safety. Chlorine is the most commonly used disinfectant for

several reasons: it is effective against a wide range of microorganisms, its cost is low, and the methods of applying it have

been well developed. If chlorine is present in the water for a few minutes, disease producing bacteria will be destroyed. A

number of conditions affect the disinfecting action of chlorine. In municipal systems these can be controlled so that if

chlorine is detectable, it can be assumed that bacteria have been killed. The factors that influence the rate of disinfection

are temperature, pH, presence of other materials that react with chlorine, time, and the concentrations of the various

chlorine combinations that are formed in the water with ammonia and other substances that react with chlorine.
The fact that chlorine can be easily detected and measured makes chlorine a favorite water disinfectant of those concerned

with the public safety of water supplies. Chlorine concentrations in the range of 0.1 to 0.4 milligrams per liter are usually

maintained in municipal supplies.
Chlorine can be added in the form of chlorine gas, liquid sodium hypochlorite (bleach), granular calcium hypochlorite or

as organic chlorine compounds. Chlorine is not present in natural water supplies; if it is present it is the result of

chlorination of a water supply or of chlorinated compounds being discharged as waste from industrial operations. The

presence of chlorine in concentrations above 0.5 parts per million should be considered evidence of pollution from chlorine

treated effluents or from a process in which high concentrations of chlorine are used.

APPLICATION:

Drinking, surface, saline waters; swimming pool water; domestic and industrial wastes.

RANGE:

0.00 – 4.0 ppm Chlorine

METHOD:

In the absence of iodide, free available chlorine reacts instantly with DPD to produce a red

color. Subsequent addition of potassium iodide evokes a rapid color response from the

combined forms of chlorine (chloramines).

SAMPLE HANDLING

& PRESERVATION:

Chlorine in aqueous solutions is not stable, and the chlorine content of samples or solutions,

particularly weak solutions, will rapidly decrease. Exposure to sunlight or agitation will

accelerate the reduction of chlorine present in such solutions. For best results, start analysis

immediately after sampling. Samples to be analyzed for chlorine cannot be preserved or stored.

INTERFERENCE:

The only interfering substance likely to be encountered in water is oxidized manganese. The

extent of this interference can be determined by treating a sample with sodium arsenite to

destroy the chlorine present so that the degree of interference can be measured.
Iodine and bromine can give a positive interference, but these are not normally present unless

they have been added as disinfectants.

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