CHLORIDE

Chloride is a material that is both a natural component of water in northeast Ohio and also a very common industrial material. It enters rivers from industrial processes, domestic sewage, and surface runoff. The most common chloride in widespread use is simple salt, which is also used for snow control in the winter. Chloride is often termed a conservative pollutant. That is, it does not react as readily as many other materials in the water; nor does it settle out as readily. As a result, it is often a very good indicator of the aggregate amount of anthropogenic materials dumped into the river from all sources.

INSTRUCTIONS FOR USING TEST KIT:

*YOU SHOULD BE AWARE that some Hach chloride kits are different from others. Compare the instructions here with those on the gray sheet that accompanies the kit. You should follow the instructions on the gray sheet! Teachers should also have an idea as to whether their station of the river is "high range" or "low range." If you don't know, try the high-range test first. If your measured chloride content is less than 100 ppm, run the low-range test and use that number.

HIGH RANGE:

1. Fill the plastic measuring tube level full with the water that is to be tested. Pour it into the mixing bottle.

2. Add the contents of one Hach Chloride 2 Indicator Powder Pillow. Swirl to mix, holding the mixing bottle upright.

3. Add the silver nitrate titrant drip by drop to the water in the mixing bottle. Hold the dropper in a vertical position and swirl the bottle to mix after each drop is added. Count each drop as it is added, until the water changes from yellow to red-brown in color. Note that the sample will go from a transparent yellow to an opaque yellow. This is NOT the change you are looking for. As soon as the color changes from yellow to a SLIGHT ORANGE-BROWN, the titration has ended.

4. To express the chloride content of the water in mg/l, multiply the number of drops that were added by 20.

LOW RANGE:

1. Fill the mixing bottle to the 23-ml mark with river water.

2. Step 2 is the same as in the high-range test, above: Add the contents of one Hach Chloride 2 Indicator Powder Pillow. Swirl to mix, holding the mixing bottle upright.

3. Step 3 is the same as in the high-range test, above: Add the silver nitrate titrant drip by drop to the water in the mixing bottle. Hold the dropper in a vertical position and swirl the bottle to mix after each drop is added. Count each drop as it is added, until the water changes from yellow to red-brown in color. Note that the sample will go from a transparent yellow to an opaque yellow. This is NOT the change you are looking for. As soon as the color changes from yellow to a SLIGHT ORANGE-BROWN, the titration has ended.

4. To express the chloride content of the water in mg/l, multiply the number of drops that were added by 5.

QUESTIONS TO THINK ABOUT

Is your chloride level above about 500 ppm? If so, it is unusual for this area.

WHY YOU HAVE TOO MUCH

• Is the area industrial? If so, do any of the industries use salt or some other chloride as part of their processes?
• Is there chloride in the rocks of the area?
• Has the highway department used salt for snow removal in the recent past?
• Are there oil wells in the area, so that brine may have been dumped illegally into the river?
• Might salt or some other chloride get washed into the sewer system?
• Do any other rural or urban land uses lead to chloride being washed into the river?

WHAT HAPPENS IF YOU HAVE TOO MUCH CHLORIDE IN THE WATER?

• To the river, to the plants and animals living there, or to the river's state of nutrition?
• To the lake, as the body of water that receives all of the river water?
• To people in and around the watershed?

LOOK AT HOW THE CHLORIDE CONCENTRATION CHANGES FROM ONE END OF THE RIVER TO THE OTHER.

• How does the downstream profile of other constituents of the water compare to that of chloride?
• Why is that?

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