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5. UV-Vis Spectroscopy5.1 IntroductionObjectiveReview basic analytical chemistry skills, including solution making, transferring and linear diluting. Understand the error involved and error propagation.Materials:Methylene Blue C16H18ClN3S, MW 319.85.Also called Swiss blue. One gram dissolves in about 1000 ml of water. Peak absorption at 369 nm5.2 Create Calibration Curve from standard solutionsProcedures:Weigh 500mg dye on electric balanceDissolving all the solid dye in beakerTransfer all the solution into a 500ml volumetric flaskFill up the volumetric flask to the tick markPrepare standard solutions of 500, 200, 100, 50 and 20 ppm from 1000 ppm stocksolutionTable 5-1 Preparation of standard solutionsPPMSTDStockDI waterTotal Volume200.29.810ml500.59.510ml1001910ml2002810ml5005510mlVortex vial to complete mixTransfer Standard solutions to cuvette26Measure the transmissivity at a peak measure three times and make a note of your results in your lab notebookCreate calibration curves from data.Table 5-2 Absorbance of standard solutionsPPMWavelengthAbsorbance12Average20501002005001 0.8 0.6 0.4 0.2 0UV/VIS0 50 100 150 200 250 300 350 400 450 500Concentration (ppm)Figure 5-1 Calibration curve from standard solutions5.3 Two steps of a serial dilution and measure the concentrations of unknown samplesPour about 11 ml unknown concentration of methylene blue solution from the bottle to your vialDilute the dye solution 10 fold by using pipettes : Pipette 1 ml above sample solution to your vialFill the solution to 10 mlTransfer Standard solutions to cuvetteMeasure absorbance of each27AbsorbanceFigure 5-2 Serial Dilution of unknown samples Table 5-3 Absorbance of unknown samplesInstrument UsePower on instrument (switch is on left side).Turn on monitor and double-click ‘Cary win UV’Instrument will run through a start-up check for about 1 minutes.In the toolbar frame, select the ‘Concentration’ icon.In dialog box, enter wavelength 369 nm.Serial DilutionAbsorbanceWavelength11/101/100Sample 1 Sample 2Sample 3a.b.Clicka. b.ClickClickClickChoose Abs (absorbance).Replicate is 2on ‘Standard’.unit : mg/Lnumber of standard and concentration of standard solutionon ‘Sample’ and enter sample number‘OK’on Zero icon after insert Blank cuvette into UV slot.Fill cuvette 3⁄4 with standard samples and cleaning cuvette surface with chem wipes.Place cuvette in the slot.Click ‘Start’Record Abs(absorbance)Drawing standard graphFill cuvette 3⁄4 with unknown samples and cleaning cuvette surface with chem wipes.Place cuvette in the slot.Click ‘Start’Record concentrations28Lab report requiremento Calculate solution concentration by ppm for all solutionso Discuss source of data errorso How do you improve your skill to get better accuracy and precision of solution makingo Describe the key steps of the experimento Attach all the original data and spectrum
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Environmental
Engineering
Laboratory Manual
Morgan State University School
Department of Civil Engineering
CEGR 338 Environmental Engineering Lab
2
Table of Contents
Background of Environmental Engineering ………………………………………………………………….. 4
Lab Safety Discussion………………………………………………………………………………………………… 5
General Guidelines ……………………………………………………………………………………………….. 5
Glassware and Experiment …………………………………………………………………………………… 6
Chemical Handling……………………………………………………………………………………………….. 6
Heating Procedures ………………………………………………………………………………………………. 7
Accidents and Injuries ………………………………………………………………………………………….. 7
Personal Safety …………………………………………………………………………………………………….. 7
1.
pH Measurement ……………………………………………………………………………………………….. 8
2.
Salinity (Hydrometric Method) ………………………………………………………………………….. 12
3.
Settleable Matter / Total Solids ………………………………………………………………………….. 18
4. Total Dissolved and Suspended Solids Dried at 103-105 C / Fixed and Volatile Solids
Ignited at 550 C …………………………………………………………………………………………………………… 21
5.
UV-Vis Spectroscopy……………………………………………………………………………………….. 26
3
Background of Environmental Engineering
Environmental engineering developed from the historical branch of civil engineering
know as sanitary engineering involving drinking water and water treatment. The field was
defined in 1955 by Kilcawley, Pincus and Burden of Rensselaer Polytechnic Institute (RPI) as
“…that portion of the science of environmental control in which engineering is used to conserve
and develop the world’s resources for the general well-being of man as measured by such indices
as the absence of disease, comfort, convenience and productivity.” Environmental engineers
develop solutions to environmental problems utilizing the principles of biology and chemistry.
Environmental engineers are involved in water and air pollution, recycling, waste disposal, and
public health issues. They design municipal water supply and industrial wastewater treatment
systems. The U.S. Department of Labor, Bureau of Labor Statistics projects that jobs for
environmental engineers will grow by 25% from 2006 to 2016…
4
Lab Safety Discussion
Safety is the responsibility of every student. This includes personal safety and the safety of
your fellow students. REMEMBER TO THINK before you ACT… There are various safety
programs, which are adequate and assist in reducing accidents, however, the benefits obtained
from the use of common sense can outweigh the benefits from any safety rules. REMEMBER
ALWAYS: THINK before you ACT!!!
General Guidelines
1. All students should conduct themselves in a responsible manner at all times in the
laboratory environment.
2. All written and verbal instructions should be followed carefully. Ask instructor
immediately before proceeding with a part of procedure, if you did not understand
directions.
3. Do not work in laboratory without instructor present or proper instruction.
4. Do not touch any equipment, chemicals or experimental materials until properly
instructed to do so.
5. Be prepared for laboratory experiments by reading all procedures thoroughly before
commencing with the experiment.
6. Do not eat food, drink beverages, or chew gum during lab experimentation.
7. Perform only the experiments designated by the instructor. Unauthorized experiments are
prohibited.
8. Work areas should be clean and tidy at all times.
9. No horseplay, practical jokes, and pranks are dangerous and prohibited.
10. Cell phone operation should not be conducted during lab experimentation.
11. Know locations of the proceeding:
5
a. First aid kit
b. Eyewash station
c. Safety shower
d. Fire extinguisher
e. Fire alarm and exits
12. Wash hands after all spills and at the end of the lab.
13. Examine all equipment for any defect before using.
14. Do not leave experiments in process unattended.
15. ALL INSTRUCTIONS, ORAL OR WRITTEN, MUST BE FOLLOWED AT ALL
TIMES.
Glassware and Experiment
1.
2.
3.
4.
5.
6.
7.
8.
9.
Never assume glassware is clean; wash at the beginning and end of each lab session.
Examine all equipment for defects before using.
Do not pipette or siphon lab chemicals by mouth, use rubber bulb or pipette pump.
Carry glass tubing in vertical position to minimize the likelihood of breakage and injury.
Always protect your hands with proper material when inserting glass tubing into, or
removing it from, a rubber stopper.
Fill wash bottle with distilled water only and use as instructed.
Never use chipped or cracked glassware for lab experimentation purposes.
Do not immerse hot glassware into cold water, possibility of shattering.
Contact instructor if you do not understand the operation of a piece of equipment.
Chemical Handling
1.
2.
3.
4.
5.
6.
Notify instructor if hazardous material are observed.
Never mix chemicals together unless instructed to or experiment indicates.
Do not touch, taste, nor smell any chemicals, unless specifically instructed.
Check labels carefully before removing contents from container.
Never return unused chemicals to their original containers.
Acids should be handled with extreme caution and care.
 Always add acid to water, swirl or stir solution and notice heat produced,
especially sulfuric acid.
 Care should be observed when transferring acids from one section of the lab to
another.
7. Never remove chemicals or other materials from the laboratory environment.
8. Hold container away from body when transferring reagents from one container to
another.
6
Heating Procedures
1.
2.
3.
4.
Never leave heated burner unattended.
Never leave anything being heated unattended.
Always turn hot plate or burner off when finished.
Do not point the open end of a test tube being heated at self or anyone else in lab
environment.
5. Never peer into a container you are heating.
6. Do not place heated materials directly on lab desk surface. Please use insulating pad.
7. Do not place any substances directly into heater flame unless directed by instructor.
Accidents and Injuries
1. Report all accidents, no matter how minor, immediately to instructor.
2. If chemicals are spilled or splashed in eye(s) or skin flush immediately with water from
safety shower or eyewash station for at least 20 minutes.
3. If mercury thermometers or instruments with mercury are broken, the mercury must not
contact skin.
4. Skin burns: Immediately place affected area under cold running water for 5-10 minutes to
remove the heat or irritant.
5. Hair or clothing fire: To extinguish the flames use the safety shower.
6. If inhale chemical irritants –close containers, open widows or otherwise increase
ventilation.
7. Ingestion of chemicals-immediately report to Health Center.
8. Notify the appropriate authorities immediately in case of fire at 911.
9. If clothes catch fire drop to the floor and roll to smother the fire.
10. If fire is large and spreading, activate the fire alarm to alert building occupants.
11. Evacuate building in appropriate manner.
Personal Safety
1.
2.
3.
4.
Please wear proper eye protection—goggles at all times.
Wear appropriate lab coat or lab apron while in lab environment.
Do not wear contact lens during lab experiments.
Please wear shoes that do not have open spaces; sandals and open-toe shoes are not
acceptable.
5. Confine long hair, neckties, jewelry and loose clothing while in lab environment.
7
1. pH Measurement
1.1 Introduction
A very important measurement in many liquid chemical processes (industry, pharmaceutical,
manufacturing, food production, etc.) is that of pH: which represents the hydrogen ion
concentration in a liquid solution. The concentration of H¯¹ affects the solubility of inorganic
and organic species, the nature of complex metal cations and the rates of chemical reactions.
The concentration of the H¯¹ is frequently expressed as the pH of the solution rather than
hydrogen ion molarity. pH is defined by the equation below:
pH = log [H+¹]
(1.1)
In the equation above the logarithm is taken to the base. If [H¯¹] is 1 x 10¯4 moles per liter, the
pH of the solution is 4. If [H+¹] = 1 x 10¯² M, the pH is 2.
[H+¹] x [OH¯¹] = Kw = 1.0 x 10¯14 at 25ºC
(1.2)
The above equation shows the relation of pH in a basic solution. Since [H¯¹] equals [OH¯¹] in
pure water, in equation 2, [H+¹] must be 1 x 10¯ 7M. Therefore, the pH represented in distilled
water is 7. The solutions that exhibit [H¯¹] > [OH¯¹] are acidic and are denoted with a pH <7. A solution that is basic and a pH >7 applies when [H¯¹] < [OH¯¹] and a solution with a pH of 10 will have [H+¹] = 1 x 10-10 M and a [OH¯¹] = x 10-4M. Therefore, a solution with a high pH is called “caustic” and “acid”, if it exhibits a low pH. pH measurement can be determined experimentally in two ways. One is to use an indicator, a soluble dye whose color is sensitive to pH. Indicator colors change over a relatively short (about 2 – unit) pH range. When properly chosen, they give the approximate pH of solutions. Two common indicators are litmus, usually used on paper, and phenolphthalein, commonly used in acid-base titrations. Litmus changes from red to blue in the pH range 6 to 8. Phenolphthalein changes from colorless to red on the range 8 to 10. Any one indicator is useful for determining pH only in the region where it changes color. Indicators are available for measuring pH in any part of the scale. Universal indicator papers, which contain a mixture of several indicators and change color over a wide pH range, are also in common use. An electronic pH meter is used for more precise measurements of pH from the electrical potential between two electrodes in a solution. The potential varies with pH and activities an 8 analog or digital meter calibrated to read pH directly to the nearest 0.01 or 0.001 unit. A pH meter is used when reliable knowledge or control of pH is necessary. Solutions, which undergo only a small change in pH when small quantities of acid or base are added, are called buffers. A buffer solution can be prepared from approximately equal amounts of a weak acid and its salt with a strong base or from a weak base and its salt with a strong acid. Figure 1-1. pH meter(left) and typical pH Probe Design(right) The qualitative determine of the pH value of foodstuffs is probably the oldest analysis method in the world. All foodstuffs are tested with taste organs. Thereby some are noticed to be acidic and some to be alkaline. With modern pH electrodes these taste sensations can be measured in exact figures, i.e.: Cold beverages………………………………………pH – 2.8 Fruit vinegar…………………………………………pH – 3.2 Orange juice…………………………………………pH – 3.7 Beer………………………………………………….pH – 4.4 Coffee………………………………………………..pH – 5.0 Milk………………………………………………….pH – 6.6 Distilled water……………………………………….pH – 7.0 (neutral) Baking Soda ……………………..………………….pH – 8.3 9 1.2 Calibration of pH probe 1. Calibrate the pH probes with the given buffer solution of 4, 7 and 10 followed the calibration procedures given a separate sheet. 1.3 pH reading from buffer solutions Procedure 1. Remove probe from the aqueous solution and carefully rinse the probe with distilled water 2. Gently wipe probe with designated wipes 3. Carefully place probe into designated buffer solution for calibration 4. Allow probe to stabilize and record the temperature and pH of the solution 5. Remove probe and carefully rinse with distilled waster 6. Place probe back into its aqueous solution base 7. Follow steps 2 thru 6 for the other buffers (4,7, or 10) Table 1-1 pH of buffer solution Solution Beaker 1, Buffer 4 Beaker 2, Buffer 7 Beaker 3, Buffer 10 Temperature (oC) Measured pH 1.4 pH measurement of unknown samples Procedure 1. 2. 3. 4. 5. Rinse the pH probe with distilled water and place it into the test sample Take 3 separate measurements of the pH of this sample of solution Record the data into the data sheet provided Repeat steps 1 thru 3 for the other samples provided Record data in provided data sheet 10 Table 1-2 pH of unknown samples Solution Temperature(oC) Sample 1 Sample 2 Sample 3 Sample 4 Sample 5 Measured pH 1.5 Lab Report 1. Identify the unknown samples based on your pH measurements and show chemical formula for each sample. 2. Discuss temperature effect on pH, 3. Calculate the concentration of HCL, one of unknown samples. 11 2. Salinity (Hydrometric Method) 2.1 Introduction Salinity is determined by measuring specific gravity with a hydrometer, correcting for temperature, and converting specific gravity to salinity at 15° C by means of density salinity tables. Salinity is usually expressed in parts per thousand (ppt). When measuring how much salt is in water or more accurately, when measuring salinity, it is reported in parts per thousand (ppt or ‰). The salinity of ocean water is about 35 ppt. Seawater has about 35 parts of salt per 1000 parts of water. In other words, if you had 1,000 grams of water and dry up all the water, you would be left with 35 grams of salt. This means the ocean is about 3.5% salts. Salinity is not the same in all bodies of water. Most rivers, ponds, and streams have almost no salts with salinity ranging from 0-5 ppt. This range of measurement is considered fresh water. In an estuary (bay), the flow of fresh water from streams and rivers mixes with salty ocean water. That mixture is called brackish water, with a range of salinity from .05 to 30 ppt. In the Red Sea, the water is considered brine, with salinity up to 50 ppt. This is the saltiest lake in the world---even saltier than the ocean! Drinking water is less than 0.5 ppt. The density of seawater is a function of both water temperature and salinity, thus if we measure both the temperature and the density of a water sample we should be able to determine its salinity. To determine density we could take an exact volume of water and weigh it, then divide the mass by the volume. Unfortunately, it is difficult to determine both mass and volume to the precision we desire with the laboratory equipment we have available to us. 12 Instead of measuring mass and volume directly, we return to Archimedes’ principle: “a floating body will displace a volume of water equal to its own mass.” If we use a fixed mass that is less dense than the water sample, such as a hollow glass ball, it will sink down into the water until it displaces its mass. The greater the density of the water the higher the sphere will float. Hydrometers are devices designed to measure fluid density. The hydrometer’s mass is precisely fixed and it is concentrated at the bottom of the tube (like a buoy) so that the hydrometer will always float upright. The narrow stem is precisely graduated so that as the device sinks and displaces its own mass, the level to which it sinks is equal to the seawater density. As density of the seawater increases, the volume of the displaced seawater decreases (the hydrometer sinks less in the higher density fluid). Table 2-1 List of bodies of water by salinity Name A Salty Lake (like the Red Sea) The Ocean Mouth of estuary by a river Entrance of estuary by the ocean Tidal fresh river Freshman Stream or River Salinity 36 – 50 ppt 30 – 35 ppt 1 – 15 ppt 15 – 30 ppt .05 – 14 ppt < 1 ppt Types of water based on amount of dissolved salts in parts per thousand (ppt): Fresh water <0.5 ppt , Brackish water 0.5 – 30 ppt, Saline water 30 – 50 ppt, Brine >50 ppt
2.1 Determination of Salinity by Evaporation
As we have defined salinity as the total mass of dissolved salts (measured in grams) in one
kilogram of seawater, the most straightforward way to measure salinity is to measure exactly one
kilogram of seawater, evaporate the water, and weight the salt that precipitates out. Evaporating
a full kilogram of water would take more time than we have today however, so we will shorten
the process by evaporating a small fraction of a kilogram.
Procedure
1. Label three 250 mL beakers for the three samples. Fill each beaker to about 200 mL,
while making certain that you have the correct sample in each labeled beaker.
13
2. Label three evaporating dishes (with the same labels as the sample beakers) and weigh
each to the nearest 0.01 gram. Record the masses of the dishes, M1.
3. Using a pipette, transfer about 10 mL of each of the three salt solutions to the
corresponding labeled evaporating dishes. Weigh each evaporating dish with the water to
the nearest 0.01 gram and record the masses, M2. Determine the mass of the water
samples by subtracting the weight of the dish only, and record the masses, Mw=M2-M1.
4. Carefully bring the evaporating dishes to oven at the rear of the room and carefully place
them in the drying oven. Leave them in the oven until dry – this will take the majority of
the lab period.
5. Once the samples are dry allow them to cool for a few minutes, then weigh each
evaporating dish and record the results on the data sheet (dish + salt), M3. Subtract the
masses of the dishes to determine the mass of each of the salt samples and record the
results, Ms=M3-M1.
6. Determine the salinity of each sample using equation 1 (below).
𝒘𝒆𝒊𝒈𝒉𝒕 𝒐𝒇 𝒔𝒂𝒍𝒕
Salinity = 𝒘𝒆𝒊𝒈𝒉𝒕 𝒐𝒇 𝒘𝒂𝒕𝒆𝒓 x 1000 ‰
(2.1)
Table 2-2 Salinity by evaporation
Sample 1
Weight of evaporating dish, M1 (g)
Weight of evaporating dish and water, M2 (g)
Mass of water, Mw=M2-M1 (g)
Weight of evaporating dish and salt, M3 (g)
Mass of salt, Ms=M3-M1 (g)
𝑀
Salinity = 𝑀 𝑠 × 1000 ‰
𝑤
2.2 Determination of salinity using the hydrometer
Equipment:
1. Hydrometer jar – Use a 1000 mL graduated cylinder
2. Thermometer – graduated in 0.2 C divisions
3. Samples – Use set of 3 unknown samples of various grams of NaCl
The National Bureau of Standards for specific gravity of NaCl solutions should calibrate
hydrometers at 15 / 4 C.
14
Procedure:
1. Fill the hydrometer jar (1000 mL graduated cylinder) with sample.
2. Hang the thermometer into the cylinder while the jar is sitting in the vertical position.
Make certain the thermometer is totally immersed and you can read it through the side of
the cylinder.
3. Carefully remove the hydrometer from its enclosure and insert it into the cylinder, until it
begins to float then give it a slight twist to remove bubbles.
**Caution: Make sure that the hydrometer does not hit the bottom hard (it may break). Also,
take care that drops of water do not splash onto the hydrometer stem above the water level.
4. Read and record the temperature of sample to the nearest 0.5 C.
5. Read and record the specific gravity from the scale on the hydrometer stem to the nearest
0.001 (estimate three decimal place).
6. Repeat procedure 3 time …
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