Dissolved Oxygen Protocol
Materials
In the Field
300 ml BOD bottle
Cooler with Ice packs
Thermometer, C
Scissors
Chemical pouches (to immediately fix dissolved oxygen in the field)
#1 Manganous Sulfate Powder Pillow
#2 Alkaline Iodide Azide Powder Pillow
#3 Sulfamic Acid Powder Pillow
In the Lab
Chemical Solutions (for titration)
0.0125 N Sodium Thiosulfate (Na2S2O3) Titrant
Starch solution
Plastic pipette
Graduated cylinder, 100 ml
Erlenmeyer flask, 250 ml
50 ml Burette
Ring Stand and burette clamp
Vacuum Grease for ground glass stopcocks
Magnetic stirrer and stirring bar (optional)
Preparation
To make up Sodium Thiosulfate Titrant.
1. Make up 100 mls of 0.1N Na2S2O3 (F.W. 158.11) Stock solution by dissolving 1.58 grams in
a total of 100 mls CO2-free
distilled water (boil water for 15 minutes and let cool to room temperature).
2. Dilute 62.5 mls of 0.1N Na2S2O3 to 500 mls with CO2-free distilled water.
Make up a Starch Solution by adding 6 grams of soluble starch to a liter of distilled water. Boil
the solution a few
minutes, allow to settle overnight, and decant the supernatant. Use the supernatant. Add 1.25
grams Salicylic acid as a
preservative.
Procedure in the Field
1. Sample collection. Collect water sample using a clean 300 ml BOD bottle. Holding the BOD
bottle horizontal with the
opening facing downstream, carefully lower the bottle into the stream and allow the bottle to fill
slowly, avoiding
turbulence which could alter the oxygen determination. When the bottle is almost full, continue
to lower the bottle into
the water while rotating the bottle to a vertical position. When the water level reaches the top of
the bottle, remove the
bottle from the stream holding the BOD bottle vertically and close the bottle by dropping the
glass top into position.
2. Using scissors, open Powder Pillow #1 and carefully add to water sample. Be sure that all the
powder is introduced to
the water sample. Replace glass top and slowly invert BOD bottle a few times to disperse the
powder.
3. Open Powder pillow #2 and carefully add the Alkaline Iodide Azide to the BOD bottle.
Replace glass top and disperse
powder as before. A light brown flocculant should form. Set BOD bottle in a secure level place
and allow the flocculant
to settle undisturbed.
4. When flocculant has settled, leaving the top third of the BOD bottle clear, open and add
Powder Pillow #3, Sulfamic
Acid, to the water sample. Replace glass top and invert BOD bottle a few times to dissolve the
powder and flocculant.
The water sample should now appear a clear golden-brown. The sample is now ready to
transport to the lab using the
cooler.
Procedure in the Lab.
1. Fill 50 ml burette with the 0.1N Na2S2O3 Titrant and bring the level to zero (bottom of
meniscus to zero line).
2. Using a graduated cylinder, measure out 100 mls of water sample and transfer the sample to a
250-ml Erlenmeyer flask.
3. Place the flask under the burette tip and slowly titrate water sample with standard Sodium
Thiosulfate solution while
gently swirling the sample until the sample turns a light yellow.
4. Using a calibrated plastic pipet, add 1 ml of the starch solution to the water sample. The
sample should turn a dark
blue. If the sample turns black, you have added the starch solution too soon.
5. Continue to titrate the water sample until sample turns clear. Record the volume (mls) of
Titrant used to reach this
end point.
6. Calculate the mg of Dissolved Oxygen in your water sample by the following relationship.
1 ml of Titrant = 0.1 mg D.O.
mls of Titrant used x 0.1 mg D.O. x 1000 mls
= mg D.O./ L (liter)
100 mls (sample size)
MJI/ 2001-2002
Alkalinity and pH
Protocol
Alkalinity of water is a measure of the quantity and kinds of compounds present in the water that
together shift the pH
of the water to the alkaline side of neutrality. Three types of alkalinity are indicated: hydroxide
(OH-); carbonate
(CO3=), and bicarbonate (HCO3-). Carbonates and bicarbonates are common to most waters.
The presence of hydroxides can
usually be attributed to contamination or water treatment.
Total alkalinities in nature range for 20 to 200 mg/L.
Materials
In the Field
250 ml glass or nalgene bottle with cap
Cooler with ice packs
In the Lab
Chemical Solutions (for titration)
0.005N Sulfuric Acid Standard Solution (H2SO4)
CO2-free distilled water
mL glass pipet equipped with pipet bulb
500 ml Storage bottle
Graduated cylinder, 100 ml
Erlenmeyer flask, 250 ml
100 ml or 150 ml beaker
50 ml Burette
Ring Stand and burette clamp
Vacuum Grease for ground glass stopcocks
Squirt bottle with distilled water
Vernier pH probe, connectors, and CBL Unit with batteries
TI-83 (Plus) Calculator programed with Vernier Biochem program
Magnetic stirrer and stirring bar (optional)
Preparation
To make up 0.005N Sulfuric Acid Titrant
1. Make up a 0.1 N H2SO4 Stock solution by adding 3 mls of concentrated Sulfuric Acid to 1
liter of CO2-free distilled
water using a mL glass pipet equipped with pipet bulb. DO NOT MOUTH PIPET THE ACID.
ALWAYS ADD ACID TO WATER AND NOT
WATER TO ACID.
2. Dilute by adding 5 mls of 0.1 N H2SO4 Stock solution to 95 mls of CO2-free distilled water.
Store in air tight bottle.
Standardization of pH probe
1. Connect pH probe to CBL channel one.
2. Connect CBL to TI-83 calculator via connectors.
3. Turn on both CBL and calculator. Choose program on calculator. Press enter until you obtain
main menu. Enter # of
probes = 1; Select pH probe; Channel # 1; Standard Curve, Manual entry. Enter intercept =
13.00 and slope = -3.884
(This intercept and slope represents the average intercept and slope obtained by multiple
Standard Curve determinations
using standard pH buffers, pH 4 and pH 10). pH probe is now ready for determinations. Be sure
pH probe is always in
liquid. If pH probe is allowed to remain dry, the electrode will be damaged.
Procedure in the Field
1. Collect water sample using a clean 250 ml or larger glass or nalgene bottle. Carefully fill the
bottle avoiding
turbulence which can increase aeration of the sample and cap bottle. Place sample in cooler for
transport to lab.
Analysis needs to be done within a few hours of collection.
Procedure in the Lab.
1. Fill 50 ml burette with the 0.005N Sulfuric Acid Titrant and bring the level to zero (bottom of
meniscus to zero line).
2. Using a graduated cylinder, measure out 100 mls of water sample and transfer the sample to a
250-ml Erlenmeyer flask.
3. Place the flask under the burette tip. Place the pH electrode (probe) in the sample. Record
initial pH.
4. Slowly titrate water sample with the standard Sulfuric Acid solution while gently swirling the
sample until a stable
reading of pH 4.5 is obtained. Record the volume of titrant used to reach this end point. If the
volume of titrant used
is less than 2.5 mls, repeat titration with a more dilute titrant. (For a 0.001N Sulfuric Acid
Titrant solution, add 1
ml of 0.1 N H2SO4 Stock solution to 99 mls of CO2-free distilled water.)
5. Calculate total alkalinity as mg CaCO3 per liter as follows:
total alkalinity as mg CaCO3 = mls of Titrant used x Normality of Titrant * x 50,000
mls of sample
total alkalinity as mg CaCO3 = mls of Titrant used x 0.005* x 50,000
100
* If a more or less dilute Sulfuric Acid Titrant is used be sure to enter the Normality of the
Titrant used correctly to
reflect the change.
MJI/ 2001-2002