Science in the Real World: - PETE



Instructor’s Notes: Hydraulic Fracturing and the Health of our Water

Developed in 2014 by Sharyl Majorski, Chemistry Instructor at Saginaw Chippewa Tribal College

Introduction: Over the course of this lab students examine local surface water samples that run through the local reservation. Michigan, particularly central and northern Michigan, is becoming increasingly active in the fracking industry, but pales in comparison to places like North Dakota. As the industry grows, what was missing in North Dakota is a baseline of water quality data. Without having a baseline of data, communities struggle to realize damages caused by spills and leaks that commonly occur. The goal of this experiment is to build a baseline of fresh water quality data within the Isabella Indian Reservation. By running a series of standard analytical tests using HACH and Vernier analytical instruments and equipment, the students will contribute to baseline data so that a basic level of water quality is realized.

Goals:

• To build a baseline of water quality data

• To have students participate in culturally relevant research projects

• To deliver a curriculum in a holistic and kinesthetic manner

• To have students think like a scientist while planning, acquiring, and analyzing data

Equipment Necessary:

HACH Education Test Kit, Water Ecology: Alkalinity, Hardness, Carbon Dioxide, and Chlorides

[HACH provides field ready water testing supplies for students to use. Each kit comes with pre-measured supplies to ensure easy field-testing. I have found these to be relatively accurate, however, would use advanced testing supplies if high precision is sought – these are great for first year students.]

Available from

Vernier LabQuest 2 (compatible with over 70 Vernier Sensor):

Temperature Probe

Conductivity Probe

pH Sensor

Turbidity Sensor

[Vernier LabQuest 2 is a standalone interface used to collect sensor data with its built-in graphing and analysis application. The large, high-resolution touch screen makes it easy and intuitive to collect, analyze, and share data from experiments. Its wireless connectivity encourages collaboration and personalized learning.]

Available from:

Background Information

I share with students my PowerPoint presentation. They are also given a hard copy of the presentation for their personal use. The background information is meant to be a start while students must go to the virtual library to extract additional background information on hydraulic fracturing and wastewater analysis.

In brief, hydraulic fracturing, commonly referred to as fracking, is best defined as a drilling process that utilizes highly-pressurized and chemically-treated water to break open deep layers of shale (a type of sedimentary rock) within the Earth’s crust in order to release a variety of natural gases. Concern regarding this process has slowly been spreading throughout the scientific community over the last decade. Many of these concerns revolve around the potential for chemically treated water to contaminate nearby water supplies both by leaking pipes and by spillage.

Though hydraulic fracturing has been used as a method of drilling for over fifty years, scientific testing to determine the environmental safety of the process is still in its infancy. This study includes a variety of chemical and ionic tests that can be used to various levels of components in water supplies (e.g., wells, rivers, lakes, etc.). The results of these tests will allow researchers a baseline of data should hydraulic fracturing have an impact on the environment over time. It important that data is collected over a significant period of time, as data from one instant of time is unlikely to accurately reflect the impact of hydraulic fracturing. One-time events, such as a flood, or a storm, or a sudden improper release of chemicals from an industrial company into the river will also impact the data. Additionally, all water supplies are not equal; some waters will naturally have a higher level of chloride, for instance, than others based on the geology of the area. What matters here is not an absolute value of concentrations, but a degree of change. This lab is meant to be an ongoing lab with classes contributing to the data pool each year. A water supply may have safe levels of an ion for a period of time, but an increase in the level indicates that something may be impacting the water supply. This study will provide the community information regarding the quality of their local water supply, with or without the presence of a hydraulic fracturing drill.

Determination of What Tests to Run:

[pic]

Figure 2. A depiction of the contents of the water used in the drilling process, known as “fracturing fluid”.

(Retrieved from . 1/24/14)

Tests were determined based on what was perceived to be “typical solutions” used in hydraulic fracturing as well as from various tests run from spill sites that occurred in North Dakota.

Tests include: pH, hardness (calcium and magnesium), sulfate, nitrates, conductivity (found to be very high at spill sites), Total alkalinity, carbon dioxide, and chlorides.

Time Frame with Activities:

Week I: Discussion of project – PowerPoint presentation, Decisions on Site Location (Proximity and Accessibility are important), Discussion on logistics of experiment, Plan for testing (if weather is nice, we sample outside, if not, I bring back samples and we run the experiment inside). Sampling should be done at multiple sites and I generally look at Near, Middle, and Far for the cross section of the river. Discussion on how to set up a laboratory notebook for the experiment also needs to take place.

[Total time: 1.5 hours.]

Week II: [Note: Since weather was cold and freezing rain, I obtained samples and we worked inside lab – this is Michigan! When students can sample themselves, lab is so much better!]

Students work in partners and perform 3 tests for each sample (multiple trials increase accuracy). Notebook set-up is homework and students cannot participate until they demonstrate they put their time in to be ready.

[Total time: 2.5 hours]

Week III: Additional water tests could be run this week if students feel they are necessary. Otherwise this is Analysis of Data Week. We spend time graphing and analyzing the data that was generated. Graphs are computer generated with Excel. We also work on how to make a poster. [Prior to this we had a field trip to a local university to showcase what scientific posters should look like and discussed pros and cons of those showcased.

[Total time: 2.5 hours]

Water Quality Parameters:

Turbidity is a measurement of the cloudiness of the water. Increased turbidity can result from increased runoff, storm activity, and soil erosion. Water sources with a high level of turbidity can facilitate the growth and spread of viruses and bacteria. The suspended particles interfere with chlorine and UV sterilization processes when purifying water for drinking. Increases in turbidity can also have negative effects on a water environment by preventing sunlight from reaching lower depths and inhibiting plant growth. Many states have imposed a chronic turbidity standard of 10 FAU (Formazin Attenuation Units), where “chronic standard” refers to the highest amount of a toxicant which organisms can be exposed without experiencing chronic toxicity effects.

Sulfate-containing compounds are naturally found in water sources; however these levels must also remain in check in order to prevent any health concerns. Currently, the EPA has a secondary maximum contaminant level of 250 mg/L SO42- which is a non-enforceable level (EPA 2009). Sometimes, ingesting water that contains high levels of sulfates can lead to diarrhea and dehydration. This condition can be especially dangerous for infants and young children.

Alkalinity and pH can vary greatly depending on the constituents in the water. Water supplies that contain dissolved gases, minerals and chemicals often have a pH range of 5 to 9. Freshwater fish require an aquatic environment with a pH of between 5.5 and 8.5. Increased gases from the fracturing process may lead to a critical change in pH, which can alter not only the fish population’s ability to live, but also their ability to breed.

Knowing the pH of a water source may not provide enough information about the water quality. It is also important to know how well a system can handle the addition of acids and bases. This buffering capacity of the water is known as alkalinity, and it is a fresh water source’s last line of defense when it comes to a leak in the fracturing process. Consider the chemically treated water that is used to fracture the shale rock: if that water were to enter the surrounding fresh water supply, the change in pH could be substantial, depending on how well the water could handle acidic and basic additions. Acceptable alkalinity levels range from 20-250 mg/L CaCO3. Water systems with less than 10 mg/L CaCO3 are more susceptible to damage from acid and other pollutants. Alkalinity is typically the result of the dissolution of calcium carbonate from limestone bedrock that has eroded due to weathering. The released CO2 from the calcium carbonate undergoes several equilibrium reactions, ultimately forming bicarbonate, HCO3-, and carbonate, CO32-, ions.

Hardness is the measured amount of minerals dissolved in the water. The typical ions are calcium and magnesium, typically expressed as the concentration of calcium carbonate. The hardness of the water can be a good indicator of the water’s ability to handle metal contaminants such as copper and zinc. As a result, levels over 200mg/L CaCO3 are considered acceptable for a typical river in Michigan.

Chloride ions are a result of metallic salts (containing a metal and chloride) dissolving in the water. Chloride ions are found in nearly every naturally occurring water supply, usually as a result of chloride-containing rocks present nearby. Chloride ions are typically not harmful to people, and small amounts are essential for aquatic life. The EPA has recommended a concentration of no more than 250 mg/L Cl- in drinking water (EPA 2009).

Conductivity is the measure of the flow of current through a substance, such as a solution. Any such current is made possible by ions, which are formed when ionic compounds dissolve into their component cations and anions; for instance, NaCl will generate Na+ and Cl- ions when dissolved in solution. These ions then act as carriers for electricity. The concentration of ionic compounds will therefore influence a solution’s conductivity. Generally speaking, a solution can be considered non-conducting, where the solution allows no current to flow; weakly-conducting, where the solution allows some current to flow; and strongly-conducting, where the solution easily allows current to flow. This information can be obtained in this lab by using a battery-operated probe. Speaking in more concrete terms, numerical values of the conductivity can be obtained in this lab by using a conductivity meter. The standard unit of electrical conductance is Siemens, indicated by the capital letter S. For reference, laboratory deionized water will have a conductance of at least 1.0 μS/cm. Drinking water has conductivities ranging between 100 μS/cm and 1,000 μS/cm (1mS/cm). Wastewater has conductivities ranging between 85μS/cm to 9,000 μS/cm (9mS/cm). Seawater will have a conductance of 50,000 μS/cm or more. Surface or ground waters will have varying degrees of conductivity, depending on environmental factors, such as vegetation and rocks present at the source, but may be as low at 50 μS/cm. Fresh water streams should ideally have conductivity between 150 to 500 μS/cm to support diverse aquatic life particular to that environment.

Conductivity can be reported as an electrical property of the water, or it can be used to evaluate the amount of total dissolved solids (TDS) in the water by multiplying the conductivity in μS/cm by a predetermined factor to give the amount of solids dissolved in the water in mg/L of total dissolved solids. This factor varies to some degree depending on the dominant ion chemistry of the water. Here, we will assume this factor to be 0.67. TDS is related to conductivity due to the fact that as solids dissolve, some may form ions. These ions then act as carriers for electricity, reflected in the solution’s conductivity. However, TDS and conductivity are distinct measurements: TDS is a measurement of the amount of solids dissolved in a solution and is reported in units of mg/L of total dissolved solids, whereas conductivity is a measurement of current through a solution and is reported in μS/cm. Common ions present in water include: chloride, nitrate, sulfate, phosphate anions; and sodium, calcium, magnesium, iron, and aluminum cations. For the sake of comparison, mineral water that can be purchased contains 250mg/L or more total dissolved solids, but must still be below federally allowed maximum contaminant values; i.e., TDS levels around 300 are nothing to be concerned about, as this bottled mineral water is around this level.

Below is a table of data obtained from a certified laboratory on a surface water sample in an area where a spill from a fracturing drill was known to have occurred. These are example data only.

|Test |Result |

|Total Hardness |192 mg/L CaCO3 |

|Sulfate |364 mg/L |

|Chloride |1.9 mg/L |

|Total Dissolved Solids |886 mg/L |

|pH |7.88 |

|Total Alkalinity |746 mg/L CaCO3 |

|Conductivity |1,968 μS/cm |

Remember, each water source is different, and what is important for you to consider are whether the values you obtain on your water sample are abnormal. These numbers are just to give you an idea of how hydraulic fracturing may impact water quality.

Useful Links for More Information

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Experimental Overview

General

Over the course of two lab periods, you and your partner will run a series of tests to gather information about your water sample, which is from one of 4 sites along the Chippewa River. At the end of this lab, you will be asked to state whether or not you have found any evidence to suggest that the local hydraulic fracking drill spillage has contaminated the water supply. In other words, are there any irregularities in the water quality that could be linked to hydraulic fracturing? Remember that you are not being asked to evaluate or take a stance on the drilling process.

Below is a list of chemical tests that will provide you with useful data; however it is up to you and your partner to determine which tests would be the MOST useful since you have limited time and cannot run them all. Using the information provided in the introduction and your knowledge of chemistry, you should be able to explain the link between the tests you chose and their relevance in determining the presence of pollution due to fracking. Think about what the test measures, and consider how hydraulic fracturing may influence the numbers obtained from the test. Be specific: What about the hydraulic fracturing process would change, for instance, the levels of chloride in the water? Consider the components of the fracturing fluid (Figure 2) and how those components would influence the water quality factor you are measuring. Also consider the process itself: what physical effects is the process having on the earth that may influence these measurements as well?

Note that the percentages listed in Figure 2 refer to the amounts present in the hydraulic fracturing fluid. These percentages are not reflective of the levels that may be measured in a local water supply, as any contamination from the hydraulic fracturing fluid will be diluted in the water supply, and the water supply itself has its own chemical makeup

Remember that, as in the work of a professional, you do not have unlimited time and chemical resources; use what you have wisely! The tests are listed in order of the amount of time it takes to complete them, so keep this in mind when making your choices. Plan to complete three to four tests each week. You are not expected to complete all of these tests, but a total of at least six tests should be done to gather sufficient data.

pH (~1 minute)*

TDS (~1 minute)*

Conductivity (by category) (~2 minutes)

Turbidity (~2 minutes)

Alkalinity (~10 minutes)

Sulfates (~10 minutes)

Chloride (~12 minutes)

Hardness (~14 minutes)

*There may be some additional time required to wait for the availability of the instrument used for these tests.

Understanding the Data

You will be assigned one of several sampling locations on which to collect data. You will also need to collect data from the standard water solutions provided for you. Standards are materials of known properties (concentration, density, mass, etc) that are used as a reference to assess accuracy and/or reliability of a method. For instance, a standard weight of 100.00 g should give a mass of 100.00 g +/- 0.01 g when placed on a balance. If the balance reads 99.12 g, it can be inferred that the balance is not correctly calibrated, and that all readings from the balance are skewed lower than the actual values (until, of course, the balance is properly calibrated).

You will need to perform the same tests that you run on your sample on the corresponding standard water solution of known property provided to help you assess the accuracy of your testing methods. Keep this in mind as well when planning your tests, as the more samples you need to run, the more time and chemical resources you are using. You should plan to run multiple trials of both your sample and the standard for each test. Use the standard water solutions just as you would a sample: Perform the exact same steps on the standard water solution that are done on samples.

Not all of the tests have corresponding standards with which to check the reliability of the method. There are standards available for the sulfate, chloride, alkalinity, and hardness tests. There are not standards for turbidity, pH, conductivity, or total dissolved solids, as these are measured with an instrument that has already been calibrated. However, in the absence of a standard, judgments about the reliability of the method may be made based on the precision of the collected data. (Remember that precision reflects the reproducibility of the data.) For instance, a data set that contains numbers that vary significantly from each other reflects a low degree of reproducibility. This low reproducibility decreases the confidence in the accuracy of the data, as the lack of precision may obscure the obtained average. A data set that contains numbers which varies only minimally, however, shows a high degree of reproducibility, and increases the confidence in the accuracy of the data. (It should be noted, though, that it is possible to have a precise data set that is inaccurate, and it is possible to have a less-than-precise data set that is still accurate. However, the precision can influence the confidence about the accuracy of the data.)

This is where assessment of the limitations of an experimental method comes in. Assessing the limitations of an experimental method can help a researcher understand where error may be creeping in and steps can be taken to minimize this error. You will be asked, as part of your data analysis, to note at least two limitations present in the experimental methods used. Note that limitations of an experimental method are not procedural errors (e.g., dirty glassware, fingerprints on cuvettes, misuse of balance, etc.). Procedural errors are signs of poor lab technique and are not limitations on the method used.

Identifying limitations of an experimental method involves considering what the method is measuring, how the method is measuring it, and what may be preventing an accurate measurement. Consider a titration, for example. Titrations depend on volume data to obtain an accurate determination of concentration. Therefore, the accuracy of the determined concentration is limited by the accuracy of what is used to collect the volume data; e.g., a buret is more accurate than a graduated cylinder, and a graduated cylinder is more accurate than an unlabeled tube. If an unlabeled tube was used to measure volume, the use of this unlabeled tube is then a limitation of the experimental method. Consider, also, a titration is dependent on identifying the endpoint. Limitations may be present here, as well. Consider what may be obscuring a reliable determination of the endpoint (color ambiguity? choice of colored glassware or colorless glassware? lack of indicator specificity? etc.)

Below is an example of how you might organize your data for a test with a standard:

Table 1. Chloride Test--Sample

|Trial |Drops to endpoint |[Cl-] mg/L |

|1 |3 (dark orange) |60 |

|2 |2 (dark orange) |40 |

|3 |2 (dark orange) |40 |

|Average | |47 |

Table 2. Chloride Test—Standard (True Value=80mg/L Cl-)

|Trial |Drops to endpoint |[Cl-] mg/L |

|1 |4 (dark orange) |80 |

|2 |3 (dark orange) |60 |

|3 |4 (dark orange) |80 |

|Average | |73 |

Notice that the sample and standard values are very different from each other. That is to be expected--they are different samples. However, the average measured value for the standard is in good agreement with the true value of the standard. This then, in turn, imparts a degree of confidence that the average measured value for the sample is accurate.

LAB PERIOD 1

After choosing your tests as described above, conduct your chosen tests for the first week on your sample and the standard. Be sure to record all steps and observations, including data, in your laboratory notebook.

Conclusion

Address the following questions in your conclusion.

1. What is known about the chemistry of the water sample? Explain how the tests you ran are connected to hydraulic fracturing.

2. Take a look at the values obtained for the standards in comparison to the true value of the standards. How accurate are the experimental values? What are some limitations of the experiment that may affect the accuracy of the data? Give at least two limitations. Remember that experimental limitations are different from procedural errors; poor lab technique (dirty glassware, etc.) is not an experimental limitation.

3. Given this information, what level of confidence can the data support (low, high)? Explain your reasoning.

LAB PERIOD 2

Conduct your chosen tests for the second week on your sample and the standard. Make sure to consider your reflections from last week when choosing tests this week. You should still plan to do about 3 tests this week. Be sure to record all steps and observations, including data, in your laboratory notebook.

Conclusion

Address the following questions in your conclusion.

1. What is known about the chemistry of the water sample that wasn’t known before? Explain how the tests you ran are connected to hydraulic fracturing.

2. Take a look at the values obtained for the standards in comparison to the true value of the standards. How accurate are the experimental values? What are some limitations of the experiment that may affect the accuracy of the data? Give at least two limitations. Remember that experimental limitations are different from procedural errors; poor lab technique (dirty glassware, etc.) is not an experimental limitation.

3. Based on the results of both lab sections, have you found any evidence to suggest that the local hydraulic fracking drill has contaminated the water supply? Or, phrased differently, Are there any irregularities in the water quality that may be linked to hydraulic fracturing? Explain. Reference specific tests and their results that led you to your conclusion.

4. Given the limitations you identified in both labs, what would you change about the experiments, if you could? What might give you better information?

TEST INSTRUCTIONS

Safety:

Wear your splash goggles throughout experiment.

Follow specific test instructions for waste disposal.

General/Logistics

• Each partnership should perform each test on the assigned sample and on the standard.

• It is a little easier to open the foil packets by tearing rather than by cutting.

• Pay attention to all washing and disposal instructions.

• Obtain a 100mL portion of water in a beaker. Be sure to shake the container before obtaining your sample to make sure it is representative.

• Be sure to include a temperature reading of your water for reference.

Colorimeter Usage Tips

1. Shake your sample bottle before pouring into sample cell.

2. Be sure to use the appropriate blank as directed by the test instructions.

3. Clean sample cells by rinsing twice with deionized water.

4. When using a new or freshly cleaned sample cell, rinse out the sample cell with the sample water to be tested.

5. When inserting the sample cell into the colorimeter, place it so that the diamond mark on the cell faces the keypad.

6. Wipe off any fingerprints or marks on the sample cell with a KimWipe before placing in the colorimeter.

TURBIDITY

1. Enter stored program number for turbidity.

a. Press PRGM. The display will show PRGM ?

b. Press 95 ENTER. The display will show ‘FAU’ and ‘ZERO’ icons.

2. Fill sample cell with 10mL of deionized water. This is your blank for this test. Wipe surface of the sample cell with a soft cloth.

3. Place blank into the cell holder. Tightly cover sample cell with instrument cap.

4. Press ZERO. The cursor will move to the right, then display will show ‘0 FAU’.

5. Fill second sample cell with 10mL of your sample. Shake well to suspend particles.

6. Wipe surface of the sample cell with a soft cloth.

7. Place sample cell into the cell holder. Tightly cover the sample cell with the instrument cap.

8. Press READ. The cursor will move to the right. The result in Formazin Attenuation Units (FAU) will be displayed. Record.

9. Pour waste into the appropriate waste container. Rinse the sample cells thoroughly with deionized water.

SULFATE

The SulfaVer 4 Reagent Powder contains barium. The barium reacts with sulfate ions in the water to form barium sulfate, which is a solid. The amount of solid formed will be detected by the instrument, and the instrument will convert this to mg/L of sulfate ions for you.

1. Enter the stored program number for sulfate.

a. Press PRGM. The display will show PRGM ?

b. Press 91 ENTER. The display will show ‘mg/L, SO4’ and ‘ZERO’ icons.

2. Fill a clean sample cell with 10mL of your water sample.

3. Add the contents of one SulfaVer4 Sulfate Reagent Powder Pillow to the sample cell. Cap the cell and invert several times to mix.

4. Press TIMER ENTER. A 5-minute reaction period will begin. Let the sample cell stand undisturbed.

5. While you are waiting, fill a second sample cell with 10mL of your water sample. This will be your blank for this test. Wipe the cell with a soft cloth.

6. When the timer beeps, place the blank into the cell holder. Tightly cover the sample cell with the instrument cap.

7. Press ZERO. The cursor will move the right, and then the display will show 0 mg/L SO4. Remove the sample cell.

8. Place the prepared sample (the one you added the powder pillow to) into the sample holder. Tightly cover the sample cell with the instrument cap.

9. Press READ. The cursor will move to the right, and then the result in mg/L sulfate will be displayed. Record.

10. Pour waste into the appropriate waste container. Rinse the sample cells thoroughly with deionized water.

pH

There will be a station in the lab with a pH probe set up for you to use with the supervision of the instructor. Bring a single 50mL beaker containing your sample. (Replicates will be run from a single beaker.) The beaker should contain enough liquid to give a depth of at least 2-3 inches. Remember to bring your lab notebook and a pen to record your data while you are at the station.

*Note that if you are also testing for Total Dissolved Solids (below), you can use the same beaker of sample.

TOTAL DISSOLVED SOLIDS (TDS)

There will be a station in the lab with a conductivity probe set up for you to use with the supervision of the instructor. Bring a single 50mL beaker containing your sample. (Replicates will be run from a single beaker.) The beakers should contain enough liquid to give a depth of at least 2-3 inches. Remember to bring your lab notebook and a pen to record your data while you are at the station. To obtain results in mg/L of total dissolved solids, multiply your conductivity by 0.67.

*Note that if you are also testing the pH (above), you can use the same beaker of sample.

HARDNESS

The UniVer 3 powder contains the indicator calmagite, which combines with the Ca+2 and Mg+2 in water to form a pink color. The EDTA solution binds with the free calcium and magnesium ions in the sample, and pulls the calcium and magnesium bound to the calmagite indicator to change the sample to a blue color. This blue may be a deep periwinkle/cornflower blue/royal blue kind of color; it should have no red/pink hue. This color should persist for several seconds, and not immediately return to pink. See the color pictures provided in lab for reference.

1. Measure 5.80mL of water to be tested using a 10mL-graduated cylinder.

2. Pour water into the mixing bottle.

3. Add the contents of one UniVer 3 Hardness Reagent Powder Pillow to the mixing bottle. Swirl to mix.

4. Add EDTA Titrant one drop at a time to the mixing bottle while gently swirling to mix. When the solution has reached the blue color, record the number of drops added.

5. Multiply the number of drops of EDTA Titrant used by 20. This is the hardness recorded as mg/L of CaCO3. Record.

6. Pour the wastewater down the sink with a large quantity of water. Rinse your sample cell thoroughly with deionized water.

ALKALINITY

This reaction utilizes the pH changes that occur in an acid-base reaction. In this reaction, the sulfuric acid titrant reacts with any hydroxides and carbonates in the water sample. The sample is titrated with sulfuric acid to a colorimetric endpoint corresponding to a specific pH. The color change of phenolphthalein indicator indicates the total hydroxide and one half the carbonate present. Next, a bromocresol-green/methyl red indicator is added, where the solution turns to a green color. Sulfuric acid is added until this solution reaches a pink color, and indicates how much carbonate remained in the solution.

1. Measure 5.80mL of water to be tested using a 10mL-graduated cylinder.

2. Pour water into the mixing bottle.

3. Add one drop of phenolphthalein indicator solution to the mixing bottle.

4. If water remains colorless upon addition of the phenolphthalein indicator solution, the phenolphthalein alkalinity is zero. In this case, proceed to Step 6.

5. If water becomes pink upon addition of the phenolphthalein indicator solution, add the Sulfuric Acid Standard Solution one drop at a time to the mixing bottle. Hold the dropper vertically above the bottle while dispensing drops. Swirl to mix after each drop is added, and count. Continue to add drops until the solution becomes colorless.

6. The phenolphthalein alkalinity of the water in grains per gallon as calcium carbonate is equal to the number of drops of Sulfuric Acid Standard Solution need to bring about the color change in Step 4.

7. Add the contents of one Bromocresol Green-Methyl Red Indicator Powder Pillow to the mixing bottle.

8. Add Sulfuric Acid Standard Solution one drop at a time to the mixing bottle. Swirl to mix after the addition of each drop. Count each drop as it is added, and continue to add drops until the color first changes from green to pink (it may be more red than pink). Add the number of drops needed to bring about this color change to the number of drops needed to bring about color change in Step 4.

9. The total alkalinity in grains per gallon as calcium carbonate is equal to the TOTAL number of drops of Sulfuric Acid Standard Solution needed in Steps 4 and 7. To express results as mg/L CaCO3, multiply the grains per gallon by 17.1. Record.

10. Pour waste into the appropriate waste container. Rinse the mixing bottle thoroughly with deionized water.

CHLORIDE

This method uses a reaction between silver nitrate, chloride ions, and potassium chromate to determine the amount of chloride in solution. The potassium chromate is contained in the Chloride 2 Indicator Powder Pillow that you will add to the water. In the beginning of the reaction, the silver nitrate (the titrant from the dropper bottle) reacts with the chloride ions in the water to form a precipitate that is evidenced by the solution turning cloudy. Once all of the chloride ions in the water have been consumed by the silver nitrate, the silver nitrate then reacts with the potassium chromate to form silver chromate, which is orange in color. (The silver nitrate prefers to react with chloride ions, so it will react with them when the ions are available. When chloride ions are not available, the silver nitrate will settle for reacting with potassium chromate.) The change in color from the yellow of the original solution to the orange of the silver chromate solution therefore indicates when all the chloride has been consumed, and indicates the endpoint.

1. Measure 5.80mL of water to be tested using a 10mL-graduated cylinder.

2. Pour water into the mixing-bottle.

3. Add the contents of one Chloride 2 Indicator Powder Pillow to the water. Swirl to mix.

4. Add Silver Nitrate Titrant one drop at a time to the mixing bottle. Hold dropper in a vertical position and swirl to mix after each drop is added. Count each drop as it is added until the solution changes from yellow to orange. If the solution turns red-orange, you have gone too far and will need to start over. See the color pictures provided in lab for reference.

5. To obtain the chloride ion content in mg/L Cl-, multiply the number of drops that were added by 20. Record.

CONDUCTIVITY

To determine if your solution is non-conducting, weakly conducting, or strongly conducting, use the battery probes available on the side counters. Turn on the switch. Check the tester by squeezing the two copper wires together. Both the green and red LED lights should glow brightly. If not, check the battery connection or ask your instructor for a new battery. Separate the copper wires. Rinse the electrodes with distilled water. Make sure the electrodes are not bent such that they touch each other. Insert the electrodes into a beaker of your water sample, making sure the liquid comes into contact with the electrodes. (This beaker can be the same beaker used for pH or TDS, or can be tested directly from the portion of water you collected for your pair..) Look at the red/green light combination and compare with the table below. Record your observations and identification. Rinse the electrodes with distilled water and dry them and turn it off when you are done with the tester.

|Conductivity Rating |Red Light |Green Light |

|Strong Conductor |Very bright to bright |Bright to dim |

|Weak Conductor |Medium bright |Dim to off |

|Non-conductor |Dim to off |Dim to off |

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