pH Measurement Instructions (Hanna Meter)
- Remove protective cap from pH probe.
- Soak the pH probe (not ATC probe) in KCl solution for half an hour prior to the first use of the day.
- Rinse the square sample bottle 2 times with sample, add sample, cap and allow sample to come to room temperature (at least 20 oC).
- Rinse the pH and ATC probes with deionized (DI) water and then dry with paper towel.
- Rinse both probes with pH7 buffer solution from the pH7 buffer squeeze bottle.
- Turn the meter on and make sure the display shows the pH value. Press [RANGE] to change the display until it shows pH.
- Place both probes into the square pH7 buffer sample bottle and lightly stir.
- Press [CAL] to set the first calibration; the pH symbol will flash. When the calibration value is reached, the pH symbol will stop flashing, the hourglass symbol disappears and the CFM symbol will blink.
- On your Field Data sheet, record the pH 7 standard calibration and the temperature of the pH 7 buffer. To get the temperature, press the [RANGE] button. Press [RANGE] again after recording temperature to get back to pH measurement.
- Press [CFM] to store this value. Immediate continue to step 11.
- Rinse both probes with DI water, then pH 10 buffer solution from the pH10 buffer squeeze bottle and dry lightly with a paper towel.
- Put the probes in the square pH10 buffer bottle and stir; the pH symbol will flash. When the calibration value is reached, the pH symbol will stop flashing, the hourglass symbol disappears and the CFM symbol will blink.
- If the pH reading is between 9.85 and 10.15, you can proceed to the next step. If not, repeat steps 3-13. If after repeating, it still is not in range try replacing the buffer, re-rinse the probes and try steps 3-13 again.
- On your Field Data sheet, record the pH 10 standard calibration and the temperature of the pH 10 buffer. To get the temperature, press the [RANGE] button. Press [RANGE] again after recording temperature to get back to pH measurement.
- Press [CFM] to store this value.
- The pH calibration is now complete. The pH calibration should show 7/10 at the top of the display screen to reflect the calibration points.
- Rinse both probes with sample water.
- Place both probes in the sample bottle and gently stir for a couple of seconds. Wait for the meter to stabilize – when it has stabilized, the hourglass on the left side of the screen will disappear. After it stabilizes, gently stir the probes in the sample to destabilize this reading. The hourglass may appear again until the new reading has stabilized and then will disappear. Repeat stirring the probes until the hourglass does not reappear after stirring. Once this happens, record that final pH on the field datasheet and your alkalinity datasheet.
- If taking the pH of another sample, change the sample water in the pH bottle. Rinse probes with DI water and sample, place in new sample and repeat step 16 and 17.
- If you are done for the day, turn the pH meter off. Rinse both probes with DI water and pat dry. Recap the pH probe for storage, and store in the padded black case. Place the black case in the blue case with the square pH buffer bottles.
Hardness Titration Instructions
*Use the metal scoop and to add about 1/8 inch of EBT. Remember, more can be added if needed, but cannot be taken out of the sample. The sample should be purple (magenta), you should be able to just see through the solution. The key here is to produce a consistent purple. I
Answer questions 1 and 2 on the hardness datasheet.
This is a slower reaction than alkalinity, thus needs more time in between drops to react. This solution should stay blue, and if not add another drop of EDTA. The shade of “blue” will correlate to the purple. If your purple was dark, the blue will be dark blue. Likewise, if the purple was light, the blue will be light. The first blue you see is your endpoint.
Example: if the endpoint = 7.4 mL and the start = 0.0 mL, so the difference is 7.4 mL. Now multiply 7.4 mL x 20 to get 148 mg/L hardness as CaCO3.
Common mistakes
- Complete the top portion of the “Hardness Data Sheet”.
- Rinse the graduated cylinder and “H” Erlenmeyer flask (flask) once with deionized water and twice with sample water.
- Fill the graduated cylinder with 50 ml of sample, and then pour into the flask.
- Add 15 drops of ammonia buffer to flask and swirl.
- Place a small amount of the EBT indicator into the flask and swirl.* Place sheet of white paper under flask.
*Use the metal scoop and to add about 1/8 inch of EBT. Remember, more can be added if needed, but cannot be taken out of the sample. The sample should be purple (magenta), you should be able to just see through the solution. The key here is to produce a consistent purple. I
Answer questions 1 and 2 on the hardness datasheet.
- Self-zero the EDTA buret. Record the stating point on line 4. Be sure air bubbles are not in the nozzle of the buret by releasing a few drops and self-zeroing the buret again. Also remove any crust that may be on the tip of the buret.
- Place flask under EDTA buret and add EDTA drop-by-drop. Swirl the flask after each drop. Be sure to give yourself plenty of time between drops to swirl the flask sufficiently. Keep adding a drop at a time until the next drop turns the solution from purple to a blue.
This is a slower reaction than alkalinity, thus needs more time in between drops to react. This solution should stay blue, and if not add another drop of EDTA. The shade of “blue” will correlate to the purple. If your purple was dark, the blue will be dark blue. Likewise, if the purple was light, the blue will be light. The first blue you see is your endpoint.
- Read the buret carefully and record the end point on line 4. Subtract the starting point from the endpoint (The starting point should have been “0”), and record the milliliters of EDTA used on line 4.
- Multiply the milliliters of EDTA used by 20. This is the total hardness in mg/L of CaCO3. Record the hardness result value in line 5.
Example: if the endpoint = 7.4 mL and the start = 0.0 mL, so the difference is 7.4 mL. Now multiply 7.4 mL x 20 to get 148 mg/L hardness as CaCO3.
- Dispose the solution in the flask into a waste bucket or the sink. Rinse out Erlenmeyer flask with deionized water and store UPSIDE DOWN.
- Sign and date data sheet and copy results onto the Field Data sheet.
Common mistakes
- Misreading the buret—check twice, get a second opinion.
- Purple is too deep or dark making endpoint hard to see and reaction not accurate.
- Participant does not allow enough time between drops for reaction to occur.
- Participant forgets to use ammonia buffer, color changes will never occur.
- Final multiplication is wrong.
Alkalinity Titration Instructions
Part I – Phenolphthalein Alkalinity
If your answer is NO and the sample did not turn pink, but instead turned a cloudy white or remained clear, record phenolphthalein alkalinity as 0.0 mg/L on line 5 and note this in the field data sheet comment section. It may mean the pH sample was too cold when pH was read, thus the pH reading is off slightly. Go on to Part II – Total Alkalinity.
4. Self zero the pipet with H2SO4, (sulfuric acid). Be sure NO air bubbles are in the stem of the flask by releasing a few drops and self zero the pipet again. Also make sure the tip of the pipet is not crusted with H2SO4.
5. Place the flask under the pipet and add H2SO4 drop by drop. Swirl the flask after each drop. Do this until the next drop turns the solution clear. This is your endpoint for phenolphthalein alkalinity.
Read the pipet carefully. Record the reading on the data sheet on line 4.
7. Subtract starting point from endpoint. Multiply that difference by 40 (see line 5). This is the phenolphthalein alkalinity in mg/L of CaCO3. Record phenolphthalein alkalinity value on line 5.
For example: endpoint = 0.2 ml, start = 0.0 ml, 0.2 ml x 40 = 8.0 mg/L phenolphthalein alkalinity as CaCO3.
You are NOT through; continue to Part II for BGMR alkalinity. DO NOT REZERO YOUR BURET. CONTINUE ON TO PART II.
Part II – Total Alkalinity
8. Place 6 drops of BGMR indicator into the same “A” Erlenmeyer flask used above and swirl (color should be a turquoise). Answer the question on line 7.
a. If your phenolphthalein alkalinity was less than or equal to zero (< 0), automatically zero your buret with the bulb.
b. If your phenolphthalein alkalinity was greater than zero (> 0), DO NOT zero the buret.
9. Place the flask under the pipet and add H2SO4 drop by drop. Swirl the flask after each drop. This reaction is relatively fast. The solution may turn pink, but return to blue. The color change proceeds from turquoise to blue-gray to a clear gray, then a pink-gray and finally a pink-peachy-pink. The color changes from blue-gray to pink-peachy-pink are usually a drop a part. Your endpoint is the pink-gray color not the pink-peachy-pink. Stop when you are at your endpoint (change should be gradual if you go drop by drop).
Past the pink-gray endpoint, the solution will stay a pink-peachy-pink, regardless of any additional H2SO4 you add. Learn your river’s color transition. A viable technique is to titrate through the endpoint color if you read the buret after every drop. Thus, you have a reading for every color change and can choose the best endpoint.
10. Read the pipet carefully. Record the reading on the data sheet on line 8. Starting point should have been “0". Since you DID NOT rezero the buret, your total alkalinity should be calculated using “0” with or without phenolphthalein alkalinity.
11. Subtract starting point from endpoint. Multiply that difference by 20. This is the Total Alkalinity in mg/L of CaCO3. Record total alkalinity value on line 8.
For example: endpoint = 2.5 ml, start = 0.0 ml, 2.5 ml x 20 = 50 mg/L Total Alkalinity as CaCO3.
12. Dispose the solution in the flask into a waste bucket or sink. Rinse out Erlenmeyer flask with deionized water and store UPSIDE DOWN.
Common problems
did not add one drop at a time.
Part I – Phenolphthalein Alkalinity
- Complete top portion of the Alkalinity Datasheet.
- Rinse the graduated cylinder and the “A” labeled Erlenmeyer flask (flask) once with deionized water and twice with sample water.
- Fill graduated cylinder with 50 mls of sample. Pour into the “A” Erlenmeyer flask. Record amount of sample used on line 1.
- If known, record your pH value on line 2. Answer the question: Is pH greater than 8.3? Based on the pH value, what color do you predict your sample will be?
- Add 15 drops of phenolphthalein indicator to Erlenmeyer flask. Answer question on line 3: Did the solution turn a faint pink? If answer is YES, go on to step 6.
If your answer is NO and the sample did not turn pink, but instead turned a cloudy white or remained clear, record phenolphthalein alkalinity as 0.0 mg/L on line 5 and note this in the field data sheet comment section. It may mean the pH sample was too cold when pH was read, thus the pH reading is off slightly. Go on to Part II – Total Alkalinity.
4. Self zero the pipet with H2SO4, (sulfuric acid). Be sure NO air bubbles are in the stem of the flask by releasing a few drops and self zero the pipet again. Also make sure the tip of the pipet is not crusted with H2SO4.
5. Place the flask under the pipet and add H2SO4 drop by drop. Swirl the flask after each drop. Do this until the next drop turns the solution clear. This is your endpoint for phenolphthalein alkalinity.
Read the pipet carefully. Record the reading on the data sheet on line 4.
7. Subtract starting point from endpoint. Multiply that difference by 40 (see line 5). This is the phenolphthalein alkalinity in mg/L of CaCO3. Record phenolphthalein alkalinity value on line 5.
For example: endpoint = 0.2 ml, start = 0.0 ml, 0.2 ml x 40 = 8.0 mg/L phenolphthalein alkalinity as CaCO3.
You are NOT through; continue to Part II for BGMR alkalinity. DO NOT REZERO YOUR BURET. CONTINUE ON TO PART II.
Part II – Total Alkalinity
8. Place 6 drops of BGMR indicator into the same “A” Erlenmeyer flask used above and swirl (color should be a turquoise). Answer the question on line 7.
a. If your phenolphthalein alkalinity was less than or equal to zero (< 0), automatically zero your buret with the bulb.
b. If your phenolphthalein alkalinity was greater than zero (> 0), DO NOT zero the buret.
9. Place the flask under the pipet and add H2SO4 drop by drop. Swirl the flask after each drop. This reaction is relatively fast. The solution may turn pink, but return to blue. The color change proceeds from turquoise to blue-gray to a clear gray, then a pink-gray and finally a pink-peachy-pink. The color changes from blue-gray to pink-peachy-pink are usually a drop a part. Your endpoint is the pink-gray color not the pink-peachy-pink. Stop when you are at your endpoint (change should be gradual if you go drop by drop).
Past the pink-gray endpoint, the solution will stay a pink-peachy-pink, regardless of any additional H2SO4 you add. Learn your river’s color transition. A viable technique is to titrate through the endpoint color if you read the buret after every drop. Thus, you have a reading for every color change and can choose the best endpoint.
10. Read the pipet carefully. Record the reading on the data sheet on line 8. Starting point should have been “0". Since you DID NOT rezero the buret, your total alkalinity should be calculated using “0” with or without phenolphthalein alkalinity.
11. Subtract starting point from endpoint. Multiply that difference by 20. This is the Total Alkalinity in mg/L of CaCO3. Record total alkalinity value on line 8.
For example: endpoint = 2.5 ml, start = 0.0 ml, 2.5 ml x 20 = 50 mg/L Total Alkalinity as CaCO3.
12. Dispose the solution in the flask into a waste bucket or sink. Rinse out Erlenmeyer flask with deionized water and store UPSIDE DOWN.
Common problems
- Misreading the buret—check twice, or get a second opinion.
- Passing the endpoint because you:
did not add one drop at a time.
- Titrating only for phenolphthalein alkalinity and forgetting to titrate BGMR alkalinity.
- Final multiplication is wrong.
Dissolved Oxygen Titration Instructions
SafetyThe Winkler titration test uses a number of potentially hazardous chemicals. Do not let chemicals come into contact with eyes, skin, or clothes - wear safety glasses and rubber gloves.
When testing, place the liquid waste bottle, paper towels and a squirt bottle of deionized water nearby.
Standard Winkler Titration Method Dissolved Oxygen
In the Field
The floc will dissolve and leave a golden/yellow color if oxygen is present. The sample is now ’fixed”.
In the Lab
Compare color to the remaining sample in the BOD bottle. If solution in Erlenmeyer flask is more gold than yellow, add more Sodium Thiosulfate.
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SafetyThe Winkler titration test uses a number of potentially hazardous chemicals. Do not let chemicals come into contact with eyes, skin, or clothes - wear safety glasses and rubber gloves.
When testing, place the liquid waste bottle, paper towels and a squirt bottle of deionized water nearby.
- Alkaline potassium iodide azide is a strong base and can cause severe burns.
- The azide is very poisonous.
- Sulfamic acid can cause eye burns and can cause skin and respiratory tract irritation
- Manganous sulfate can irritate eyes and skin.
Standard Winkler Titration Method Dissolved Oxygen
In the Field
- Record the temperature of the river on line 1 of datasheet.
- Rinse 300 mL, BOD in sample water.
- Collect a water sample the BOD bottle. Overflow the bottle for one to two minutes to remove any trapped air bubbles.
- Add 1 ml Manganese Sulfate Solution and 1 ml Alkaline Iodide-Azide Reagent (wearing gloves and goggles).
- Immediately insert the stopper so that no air is trapped in the bottle. Invert several times to mix.
- A flocculent precipitate will form. It will be orange-brown if oxygen is present or white/pale yellow if oxygen is absent.
- Wait until the floc in the solution has settled at least half way down the bottle.
- Remove the stopper and add the contents of one Sulfamic Acid Powder Pillow.
- Replace the stopper without trapping air in the bottle and invert several times to mix prepared sample.
The floc will dissolve and leave a golden/yellow color if oxygen is present. The sample is now ’fixed”.
In the Lab
- Rinse the 500 mL Erlenmeyer flask and graduated cylinder with deionized water.
- Measure 200 mL of the prepared sample using a graduated cylinder and pour into the 500 mL Erlenmeyer flask.
- Rinse and fill the 25 mL buret with 0.025 N Sodium Thiosulfate (Na2S2O3), by filling the buret to the 5 mL mark. Let 3 mL out to the 8 mL mark. If you go past 8 mL, fill back to 8 mL with more Na2S2O3.
- Record starting point on line 2 of Winkler Dissolved Oxygen datasheet.
- Titrate with Na2S2O3 to the prepared sample drop-by-drop, swirling the flask until the sample turns a pale, straw yellow color.
Compare color to the remaining sample in the BOD bottle. If solution in Erlenmeyer flask is more gold than yellow, add more Sodium Thiosulfate.
- Add 5 - 20 drops of Starch Indicator Solution, enough drops to make a dark blue or green.
- Continue to titrate with Sodium Thiosulfate from the dark blue to colorless or clear endpoint.
- Record end point on line 3 of Winkler Method Dissolved Oxygen datasheet.
- Calculate by subtracting starting point from end point, and record mL dissolved oxygen on line 4 of Winkler Dissolved Oxygen datasheet.
- 1 mL titrant used equals 1 mg/L dissolved oxygen.
- Calculate the percent saturation of dissolved oxygen, using the chart on the datasheet.
- Find your water temperature on the top scale and dissolved oxygen value on the bottom scale.
- Draw a straight line between the water temperature and dissolved oxygen measurement (oxygen mg/liter).
- Read the saturation percentage at the intercept on the sloping scale.
- Record the percent saturation on the percent saturation line.
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