Ozone Testing Using the Schoenbein Color Scale &
Particulate Sampling from High Traffic Locations
Adapted from:
(http://www.ucar.edu/learn/1_7_2_29t.htm) & (http://www.epa.gov/ttn/oarpg/naaqsfin/pmhealth.html)
LABORATORY OBJECTIVES/PURPOSES:
1)
The student will prepare Schoenbein ozone testing paper and a particulate sampling plate.
2)
The student will use the paper to test two of the EPA's creiteria air pollutants, ground level
ozone and suspended particulate matter.
INTRODUCTION:
Sampling Ozone
Christian Friedrich Schoenbein discovered ozone in 1839 during his tenure as a professor at the
University of Basel, Switzerland. He used the reactivity of ozone to measure its presence and
demonstrate that it is a naturally occurring component of the atmosphere. He developed a way to
measure ozone in the troposphere using a mixture of starch, potassium iodide, and water spread on
filter paper. The paper, called Schoenbein paper, changes color when ozone is present. Ozone
causes iodide to oxidize into iodine ( ).
This test is based on the oxidation capability of ozone. Ozone in the air will oxidize the potassium
iodide on the test paper to produce iodine. The iodine reacts with starch, staining the paper a
shade of purple. The intensity of the purple color depends on the amount of ozone present in the
air. The darker the color, the more ozone is present.
The reactions involved are:
2KI + O3 + H2O --> 2KOH + O2 + I2
I2 + starch --> blue color
Sampling Particulates
Particulate matter is the term used for a mixture of solid particles and liquid droplets found in the
air. Coarse particles (larger than 2.5 micrometers) come from a variety of sources including
windblown dust and grinding operations. Fine particles (less than 2.5 micrometers) often come
from fuel combustion, power plants, and diesel buses and trucks.
These fine particles are so small that several thousand of them could fit on the period at the end of
this sentence. They are of health concern because they easily reach the deepest recesses of the
lungs. Batteries of scientific studies have linked particulate matter, especially fine particles (alone
or in combination with other air pollutants), with a series of significant health problems, including
premature death, respiratory related hospital admissions and emergency room visits, aggravated
asthma, acute respiratory symptoms, including aggravated coughing and difficult or painful
breathing, chronic bronchitis, decreased lung function that can be experienced as shortness of
breath, and work and school absences.
It is quite easy to create sample plate for particulates. An viscous, organic solvent, such as
petroleum jelly, will act as a "sticky" surface to which particulates can adhere. Qualitative &
quantitative examination of the particulates can be made with the assistance of a dissecting
microscope.
APPARATUS/MATERIALS:
OZONE TESTING:
hot plate
250 ml beaker
100 ml distilled water
corn starch
glass stirring rod
Potassium iodide (Lugol's reagent)
filter paper
small paint brush
paper or rack for drying filter paper
distilled water in spray bottle
PARTICULATE SAMPLING:
1 glass microscope slide
petroleum jelly (Vaseline)
plastic Petri dish
PROCEDURE:
OZONE TESTING:
>>PREPARATION
1. Place 100 ml of distilled water in a 250 ml beaker and add approximately 5.0 g of corn
starch.
2. Heat and stir mixture until it gels (thickens) and becomes somewhat translucent.
3. Remove the beaker from the heat source and add 15 drops potassium iodide. Stir well.
Allow the solution to cool 5 minutes.
4. Lay a piece of filter paper on a glass plate or a piece of printer paper. Use a small paint
brush to evenly & uniformly coat both sides of the filter paper.
5. Schoenbein papers can be cut into smaller pieces if desired (3cm wide strips).
6. Use soap to wash hands and scrub under fingernails after working with potassium iodide!
Although it is nontoxic, it can cause mild skin irritation.
a. NOTE: for immediate testing, the paper is ready for use at this point.
b. If storing the Schoenbein paper for later use, follow these steps:
i. Dry the Schoenbein paper in a drying oven at a low temperature, or hang to
dry. When dry, place in an airtight Ziploc bag.
ii. Never expose Schoenbein paper to direct sunlight.
>>TESTING
7. Decide where testing will occur. Outdoor and indoor sites should be used, considering
places where ozone levels would be high.
8. If Schoenbein strips have been freshly made, they are ready for immediate testing. If strips
have been stored, moisten a strip of test paper with distilled water and hang it, out of direct
sunlight, at the test site. The strip must hang freely. Suspend the strips with tape,
thumbtacks, clothespins, etc.
9. Use soap to wash hands and scrub under fingernails after working with potassium iodide!
10. Expose strips for at least 8 hours, during the daytime. Overnight is ok, as long as the
humidity is not too high or rain is present.
11. Remove the strip and Remove the strip and observe and record color immediately, then
place it in an airtight Ziploc bag out of direct sunlight until the official results are recorded.
>>RECORDING RESULTS
12. Moisten the strip with distilled water, then compare the color of the strip with the
Schoenbein Color Scale. And determine the Schoenbein Number. If the color of the paper is
not uniform, use the color in the area with the most conspicuous color change.
13. Use soap to wash hands and scrub under fingernails after working with potassium iodide!
14. Use internet weather sites or a psychrometer to determine the relative humidity at the test
site and round it to the nearest 10%. If you use the internet, use a site that will allow you
to get data by zip code (try www.weather.com or www.wunderground.com).
15. Use the Relative Humidity & the Schoenbein Number Chart as follows:
a. Along the bottom of the chart, find the point that corresponds to the Schoenbein
Number.
b. Draw a line upward from the Schoenbein Number until it intersects the curve that
represents the correct relative humidity.
c. Draw a line from this intersection to the left side of the chart. Note your ozone
concentration.
16. Collect CLASS DATA for this phase of the lab.
PROCEDURE:
PARTICULATE SAMPLING:
>>PREPARATION
1. Use a paper towel to carefully wash and clean a Petri dish.
2. Cut out a 10X10 square of graph paper and secure it to the bottom outside of the Petri dish
with tape.
3. Using your finger, coat the bottom inside of the Petri dish in a thin layer of petroleum jelly.
>>TESTING
4. Cover the Petri dish and take it to a location on campus (either indoor or outdoor) where you
anticipate there may be issues with particulate matter in the air. Each pair of students
should go to one indoor and one outdoor location in order to properly compare data.
5. Remove the lid to allow the petroleum jelly to collect particulate matter. If outdoors, try to
elevate your glass slide so that it is NOT at risk of being stepped on or having debris kicked
onto it.)
6. After 24 hours, collect your Petri dish, keeping it covered during transport back to the class.
>>RECORDING RESULTS
1. Set your Petri dish on a dissecting microscope and observe the slide. Use the chart below to
determine types of particulates. Not all particulates are listed below.
2. What do you see? What are the types of particles on the slide? How MANY different
particles do you see? Record all data/observations.
3. Collect PARTNER DATA only for this phase of the lab.
OZONE & PARTICULATE MATTER LAB
Table 1: Ozone Data (CLASS DATA)
Monitoring Location
Monitoring Strip
Color
1
NAME ___________________________________
Schoenbein Number
Relative
Humidity (%)
Ozone Concentration
(ppb)
2
3
4
5
6
7
8
9
10
11
Table 2: Particulate Matter Data (PARTNER DATA)
Indoor Location Description:
Approximate # particles in 10X10 square:
Description of Particle Type(s)
Radius Size(s)
Possible Source(s)
Anthropogenic or Natural
Outdoor Location Description:
Description of Particle Type(s)
Radius Size(s)
Approximate # particles in 10X10 square:
Possible Source(s)
Anthropogenic or Natural
OZONE & PARTICULATE MATTER LAB
NAME ___________________________________
1. Ozone: Compare the ozone concentrations at the various test sites. Were there differences between
sites? If so, can these differences be correlated to differences between the measurement locations?
Discuss thoroughly.
2. Ozone: Give the chemical reaction that produces tropospheric ozone. Then, explain how this relates to
the levels of ozone our class recorded outdoors. Discuss at least two different sites thoroughly.
3. Ozone: Consider the time of year in which we conducted this lab. Is this an appropriate time to conduct
this lab? Why/Why not? Is there a better time to do this lab?
4. Ozone: Describe two ways that tropospheric ozone can affect living organisms.
5. Particulates: What was the most frequently found type of indoor particulate? Outdoor particulate?
Where do you think they came from?
Indoor Particulate:
Source:
Outdoor Particulate:
Source:
6. Particulates: How could you reduce the amount of particulate matter found indoors?
7. Particulates: The government has mandated that devices must be installed on smokestacks that reduce
the amount of particulate matter released. Describe (in detail) one mechanism that can reduce and
control the amount of particulates released into the atmosphere.
8. Ozone & Particulates: Name at least 2 possible sources of error in each experiment.
OZONE EXPERIMENT ERRORS
PARTICULATES EXPERIMENT ERRORS