Laboratory Activity Report—Blood
Forensics Student Manual 3 Copyright Information Forensics Lab Manual © 2015 eScience Labs, LLC. All rights reserved. This material may not be repro-duced, displayed, modified, or distributed, in whole or in part, without the express pri-or written permission of eScience Labs. Appropriate citations must accompany all ex-cerpts and/or quotations. For written permissions, please contact [email protected] Note: Educational institutions and customers who have purchased a complete lab kit may reproduce the manual as a print copy for academic use provided that all copies include the following statement: “© 2015 eScience Labs, LLC. All rights reserved”. This manual was typeset in 11 Arial and 12 Chalet-London 1960. Arial font provided by Microsoft Office Suite, 2010. Chalet-London 1960 font licensed from House Indus-tries, 2011. The experiments included within this lab manual are suitable for supervised or unsu-pervised learning environments. eScience Labs assumes full liability for the safety and techniques employed within this manual provided that all users adhere to the safety guidelines outlined in the mandatory eScience Labs Safety Video, Preface, and Appendix. All users must understand and agree to the eScience Labs safety guide-lines prior to beginning their lab experiments. eScience Labs does not condone use of the lab materials provided in its lab kits for any use outside of the curriculum express-ly outlined within the lab manual. 5 Acknowledgements Acknowledgements The Forensics Lab Manual is a collaborative development which we are delighted to provide to higher education curriculum. Key contributors, including Cindy Higgins (M.S., Educational Instructional Design and Technology) and Dr. Max Houck (Ph.D., Forensic Chemistry), have brought creativity, rigor, intelligence, and industry applica-bility to this lab kit. We have greatly enjoyed working with this team, and look forward to serving students around the world with our hands-on lab experiments. 7
Table of Contents
Forensics Lab Manual
Table of Contents Blood 9 Using Your Lab Kit Using Your Forensics Lab Kit To successfully use and get the most learning and enjoyment out of your Forensics lab kit here are some tips before you begin: Refer to your course’s syllabus for the due date and sequence of your lab as-signments. Your instructor may not assign all of the labs or may not assign them in the order they are presented in the lab manual, on the Student Portal, or your school’s Learning Management System (LMS). As soon as you receive your kit, compare the contents of your kit to the inven-tory insert that comes in your kit. If you are missing any items or any item was broken during delivery call eScience Labs at 1-888-375-5487 or email [email protected] immediately for a replacement. There are a few materials that you will need to complete your experiments that are not provided in your kits such as fresh produce or water. Review the Time and Materials section (after these tips) for a list of these items. The Time and Materials section also includes an estimate of the amount of time it will take a student to complete each lab to help you plan to set aside time to complete them. Some experiments may require a few days to a week for observation, so don’t wait until the last minute to begin experiments. Before performing an experiment, read through the procedure thoroughly so that you know what to expect when you begin to handle materials. Most importantly, have fun! 11 Time and Materials Time and Materials Required There may be a few additional materials required to complete your lab experiments which are not included in your eScience Labs kit. Please review the procedures and plan accordingly. Note that the times listed are approximations and may differ de-pending on the assignments required by your instructor and/or your previous subject knowledge. Evidence and Crime Scenes Time Required: 1 hour Additional Materials: Camera (camera phones are acceptable), Scissors, Blue or Black Ink Pen, Computer, Internet Access Fingerprinting Time Required: 1.5 hours Additional Materials: Camera (camera phones are acceptable), Right Hand Fingerprints, Left Hand Fingerprints, Paper Towel or Clean Towel, Soap and Water (for hand washing), Work Surface (See Step 1 in Experi-ment 1 Procedure), Glass Surface (window, bottle, etc.), Metal surface (chair, door knob, etc.), Skin Oil (from face) Blood Time Required: 1.5 hours Additional Materials: Camera (a camera phone is acceptable), Paper Tow-els, Pencil, Adjacent Floor and Wall, Flat Surface If you are allergic to nitrile, please contact eScience Labs at [email protected] and we will send you an alternative type of safety gloves. Some of your kit materials, such as rubber bands, may include latex. Always wear your nitrile safety gloves when working with these items! 12 Time and Materials Impression Evidence: Shoes, Tires, Tools Time Required: 1 hour Additional Materials: Camera (a camera phone is acceptable) 13 Safety Information Lab Safety Always follow the procedure in your laboratory manual and these general rules: Lab Preparation Please thoroughly read the experiment procedure before starting. If you have any doubt as to what you are supposed to be doing and how to do it safely, please STOP and then: Double-check the manual instructions. Check www.esciencelabs.com for updates and tips. Contact us for technical support by phone at 1-888-ESL-Kits (1-888-375-5487) or by email at [email protected]. Read and understand all labels on chemicals. If you have any questions or concerns, refer to the Material Safely Data Sheets (MSDS) available at www.esciencelabs.com. The MSDS lists the dangers, storage requirements, exposure treatment and disposal instructions for each chemical. Consult your physician if you are pregnant, allergic to chemicals, or have other medi-cal conditions that may require additional protective measures. Proper Lab Attire Remove all loose clothing (jackets, sweatshirts, etc.) and always wear closed-toe shoes. Long hair should be pulled back and secured. All jewelry (rings, watches, necklaces, earrings, bracelets, etc.) should be removed. Safety glasses should be worn at all times. In addition, wearing soft contact lenses while conducting experiments is discouraged, as they can absorb potentially harmful chemicals. When handling chemicals, always wear the protective glasses, gloves, and apron pro-vided in your safety kit. 14 Safety Information Performing Experiments Do not eat, drink, chew gum, apply cosmetics, or smoke while conducting an experi-ment. Work in a well ventilated area and monitor experiments at all times, unless instructed otherwise. When working with chemicals: Never return unused chemicals to their original container to avoid contamination. Never place chemicals in an unmarked container to avoid identification or proper disposal problems. Always put lids back onto chemicals immediately after use to avoid contamination or potential hydration problems. Never ingest chemicals. If this occurs, seek immediate help. Call 911 or “Poison Control” 1-800-222-1222 Never leave a heat source unattended. If there is a fire, evacuate the room immediately and dial 911. Lab Cleanup and Disposal If a spill occurs, consult the MSDS to determine how to clean it up. Never pick up broken glassware with your hands. Use a broom and a dustpan and discard in a safe area. Do not use any part of the lab kit as a container for food. Safely dispose of chemicals. If there are any special requirements for disposal, it will be noted in the lab manual. When finished, wash hands and lab equipment thoroughly with soap and water. Above all, use common sense. Read the manual carefully and pay close atten-tion to the safety concerns prior to starting an experiment. 15 Student Portal Student Portal Resources You can find supplemental resources including, videos, simulations, and tutorials on the eScience Labs Stu-dent Portal. The following list outlines available resources by lab: Evidence and Crime Scenes Evidence and Crime Scenes Concept Animation Evidence and Crime Scenes Lab Drill Virtual Microscope Fingerprinting Fingerprinting Concept Animation Fingerprinting Lab Drill Blood Blood Concept Animation Blood Lab Drill Impression Evidence: Shoes, Tires, Tools Impression Evidence: Shoes, Tires, Tools Concept Animation Impression Evidence: Shoes, Tires, Tools Lab Drill Access your Student Resources with these easy steps: If you purchased a kit directly from www.eScienceLabs.com, your user account already has access to the Student Resources for your course. To access these, please visit www.eScienceLabs.com, and click on the Stu-dent tab. Then, enter your username and password. On the following page, scroll down until you see the name of your lab kit or prod-uct SKU. This should be a hyperlink. Click this hyperlink. You will see a series of topics, each of which contain lab information or virtual as-sets. If you purchased a kit from somewhere else (e.g., your bookstore), you’ll need to set up a new user account. Begin by going to www.eScienceLabs.com, and clicking the Cre-ate Account button in the upper right-hand corner. After you are registered and logged in, click the HAVE A CODE button, located on the right side of the home page. Enter the access code located on the underside of your lab kit box lid and press Submit. Click on the Student tab from the home page. On the following page, scroll down until you see the name of your lab kit or product SKU. This should be a hyperlink. Click this hyperlink. You will see a series of topics, each of which contain lab in-formation or virtual assets. 49 Fingerprinting Blood Lab Blood 51 Fingerprinting Blood Introduction Blood, a t yp e o f b i o l o gi c al evi d en c e, c o n si s ts o f r ed b l o o d cells, white blood cells, and a liquid called plasma (Figure 1). Blood is fundamental to crime scene investigation because it is commonly found at crime scenes and can provide a wealth of information about a crime. Many aspects of the crime, includ-ing the height the blood source was located, how much blood was spilled, the angle of impact, and the force at which the blood was spattered, can be analyzed using blood. It can also aid in identification through blood typing and genetic (DNA) analysis. Blood To fully understand the power of blood in forensic diagnosis, one must understand the molecular compo-nents of blood cells. The adult human body contains approximately five liters of blood, accounting for nearly 8% of a person’s body weight. The majority of blood consists of plasma, an aqueous solution composed of over 90% water that contains proteins, mineral ions, blood cells, and cell fragments. Plasma contributes to approximately 55% of blood. Learning Objectives Explain the role of blood and bloodstain patterns in forensics science Analyze and identify bloodstain patterns by performing bloodstain analysis Figure 1: Red blood cells (bright red) and white blood cells (light pink with a dark nucle-us) are suspended in plasma. ? Did You Know... There are several different types of blood cells, although erythrocytes (red blood cells; or, RBCs) are by far the most predominant cell type. These cells are respon-sible for transporting oxygen from the lungs to tissues and cells throughout the body. They are able to do this highly specialized function because of a special iron-containing protein called hemoglobin. Hemoglobin possesses a special bind-ing site for oxygen, which can be released into tissues. Hemoglobin also gives blood its characteristic scarlet color; however, it emits a purple-blue hue when deoxygenated. This is why veins appear purple. Other types of blood cells are white blood cells, including macrophages, neutrophils, and basophils that per-form specialized functions during an immune response. 52 Fingerprinting Blood Testing for Blood The presence of blood at a crime scene often indicates a physical struggle, which provides clues about the criminal event. However, the first step to using blood in forensic analysis is to determine if an unknown sam-ple is actually blood. The following tests can be performed to determine the presence of blood in an unknown substance and if a blood sample is from a human or other animal: Kastle-Meyer blood test: Used i n p r el im i n ar y c ri m e s c en e i n ves t i g ati o n s d u e t o t h e si m pli ci t y an d low cost of the test. Phenolphthalein (a chemical indicator), followed by a drop of hydrogen peroxide, are added to the unknown sample. If blood is present, the iron in hemoglobin (a blood protein) will oxidize phenolphthalein and turn it a vivid pink color. Luminol test: A p o t en t ial bl o o d s t ai n i s s pr ayed w it h l um i n ol r eagen t. If t h e u n k n ow n s am p l e p r o -duces a light blue glow after contact, the sample is likely blood. This method is accurate, but not always practical, because the glow is very faint and requires a dark environment to clearly view the results. Bluestar test: Sim il ar to t h e l um i n ol t es t, b ut p r o d u c es c l ear er r es ul ts t h at d o n o t r eq u ir e a d ar k environment. A precipitin test: Af t er a s am pl e i s c o nf ir m ed t o b e bl o o d , t hi s t es t d et er mi n es t h e pr es en c e o f h u -man blood versus another animals’ blood. Bloodstain Analysis The patterns of bloodstains found at the crime scene can be telling as to what occurred during a crime. Like all other matter, blood follows the laws of physics as it is projected and hits a surface. It may provide infor-mation about the type of weapon, the time since the crime occurred, the injuries involved, or even the hand-edness of the criminal. Angle of Impact Depending on the angle at which blood spatter hits a wall, the bloodstain will have certain characteris-tics. For example, a drop of blood that hits a surface head-on at a 90º angle will have a fairly circular shape. As the angle of impact becomes smaller, a blood stain usually takes on a more elongated, el-liptical shape. This makes sense because, the more horizontal the path taken by the spatter, the more horizontal motion it will have when it hits a surface. Paul Theodor Uhlenhuth (1870-1957), a German bacteriologist, experimented with blood serum. When he injected a chickens’ blood into a rabbit, and then mixed the serum from the rabbit blood with an egg white, the egg proteins separated from the mix. The act of separation led to his 1901 discovery distinguishing animal blood from human blood and was termed the species precipitin test. Until that time, animal blood and human blood could not be distinguished. Image Source: © U.S. National Library of Medicine, History of Medicine Division, http://ihm.nlm.nih.gov/luna/servlet/view/search?q=B025272 Figures in Forensics 53 Fingerprinting Blood Origin and Direction of Travel The direction from which blood spatter came may also be determined by analysis of bloodstain patterns. If blood spatter hits a surface from left to right, typically the right side (or the direction in which the drop traveled) comes to a point and the left side of the stain is rounded (Figure 2). If mul-tiple spatters from the same origin occur, their direction of travel can be traced to where they intercept to determine where in the crime scene the origin was. This can be useful to determine if a body has been moved. Parent Drop The original source from which the rest of the spatter was created is re-ferred to as the parent drop. It is usually characterized by a larger blood-stain with smaller spatter emanating from it. Satellite Spatter Smaller drops of blood that originate from a parent drop and rest in a posi-tion that surrounds the parent drop. They may take on a circular shape or, with enough velocity, take on an elongated shape. Satellite bloodstains typically have a more pointed end oriented opposite the direction of travel (Figure 3). Spine Spines are pointed or curved lines that extend out from the parent drop. Figure 2: Direction of trav-el from left to right. Figure 3: A parent drop on the left and a satellite drop on the right. Note how the satellite drop has it pointed end in the opposite direc-tion that the blood was traveling. 54 Fingerprinting Blood Experiment 1: Bloodstain Analysis Height and Volume While blood samples are often used to develop evidence of who was involved in a crime, the bloodstain itself is also useful to learn about what happened during a crime. In this experiment, you will simulate bloodstains and learn to distinguish between the effect of height and volume on the resulting patterns. LAB SAFETY: Th e s i m u l at ed b l o o d s am pl e m ay c au s e s t ai n s t o c l o t h o r ot h er m at er ial s . Sm all amounts of simulated blood will get on the walls and floor where the experiment is performed. Complete this experiment in an area where blood splatters will not cause concern or protect the wall and floor with paper towels or other absorbent material. Procedure Part 1: Single Drop from Different Distances 1. Put on a pair of disposable gloves and safety glasses. 2. Use a ruler and permanent marker to divide one piece of cardstock into six areas of approximately equal size. Label the center of the cardstock “Part 1: Single Drop from Differ-ent Distances.” 3. Use the permanent marker to label one edge of the top left area “15 cm” (Figure 4). 4. Repeat Step 3 for the remaining areas with the labels “30 cm,” “45 cm,” “60 cm,” “75 cm,” and “100 cm.” Materials 3 Cardstock Pieces Masking Tape Permanent Marker Ruler Simulated Blood Tape Measure Transfer Pipette Pair of Disposable Gloves (located in your safety kit) Safety glasses (located in your lab safety kit) *Camera (a camera phone is acceptable) *Paper Towels *Pencil *Adjacent Floor and Wall *You Must Provide Figure 4: Steps 2 - 4 reference. Part 1: Single Drop from Different Distances 60 cm 75 cm 100 cm 15 cm 30 cm 45 cm 55 Fingerprinting Blood 5. Use two pieces of masking tape to secure the tape measure to a wall adjacent to a clear floor space so that the 0 cm mark is touching the ground (Figure 5). 6. Place the cardstock on the floor so that the 15 cm area is directly in front of the tape measure (Figure 5). 7. Remove the cap from the simulated blood sample bottle. Use a transfer pipette to remove several drops of blood from the bottle. 8. Hold the ruler perpendicular to the 15 cm mark in one hand. 9. Holding the transfer pipette vertically, line up the tip of the pipette with the 15 cm mark. Use the ruler as a guide to en-sure the pipette is 15 cm above the cardstock and posi-tioned over the cardstock, so that when it is dropped, it hits the targeted area. 10. Carefully squeeze one drop of simulated blood from the pi-pette onto the cardstock so that it lands on the 15 cm area. 11. Repeat Steps 8 - 10 five more times at the following heights, making sure to adjust the position of the cardstock for each height: 30 cm, 45 cm, 60 cm, 75 cm, and 100 cm. 12. Wait approximately 5 minutes or until the bloodstains have completely dried. You may wish to continue to Part 2 while you wait for the bloodstains to dry. 13. Use the ruler to measure the diameter of each bloodstain. Record the diameters in Table 3. 14. Record observations about the bloodstain patterns for each distance in Table 3. 15. Use a camera to take a photograph of the cardstock after it is dry. Note: You will need to download, scan, or print the photographs to be included with your lab report. 16. Set the Part 1 cardstock aside. You will refer to this card to answer the Post-Lab Questions. Figure 5: Steps 5 and 6 reference. 56 Fingerprinting Blood Part 2: Multiple Drops from One Distance 17. Use a ruler and permanent marker to divide one piece of cardstock into six areas of approximately equal size. Label the center of the cardstock “Part 2: Multiple Drops from One Distance.” 18. Use the permanent marker to label one edge of the top left area “1 Drop.” 19. Repeat Step 18 for the remaining areas with the labels “2 Drops,” “3 Drops,” “4 Drops,” “5 Drops,” and “6 Drops.” See Figure 6 for reference. 20. Place the cardstock on the floor so that the 1 Drop area is directly in front of the tape measure. 21. Hold the ruler perpendicular to the 15 cm mark in one hand. 22. Use the transfer pipette to remove the simulated blood sample from the bottle. Holding the transfer pipette vertically, line up the tip of the pipette with the 15 cm mark. Use the ruler as a guide to ensure the dropper is 15 cm above the cardstock and positioned over the cardstock so that when it is dropped it hits the targeted area (Figure 7). 23. Carefully squeeze one drop of blood from the pipette onto the cardstock so that it lands on the 1 Drop area. Observe the splatter pattern and record your observations about the spatter pattern in Table 4. 24. Repeat Steps 21 - 23 for 2, 3, 4, 5, and 6 drops of simulated blood, making sure to adjust the position of the card stock for each set of drops. Be careful to squeeze the pipette slowly so drops leave the pipette one at a time. Observe how the blood spatter’s pattern changes with each addition-al drop. Note: You may want to wait 1 - 2 minutes between each drop to allow the spatter time to dry. 25. Allow the spatters to dry for approximately 10 minutes. You may wish to continue to Part 3 while you wait for the blood-Figure 6: Steps 17 - 19 reference. Part 2: Multiple Drops from One Distance 4 Drops 5 Drops 6 Drops 1 Drop 2 Drops 3 Drops Figure 7: Step 22 reference. 57 Fingerprinting Blood stains to dry. 26. Use the ruler to measure the diameter of each bloodstain. Record the diameters in Table 4. 27. Record the bloodstain patterns for each distance in Table 4. 28. Use a camera to take a photograph of the cardstock after it is dry. Note: You will need to download, scan, or print the photographs to be included with your lab report. 29. Set the Part 2 cardstock aside. You will refer to this card to answer the Post-Lab Questions. Part 3: Bloodstain with Force 30. Use the permanent marker to label the top of the third piece of cardstock as “Part 3: Bloodstain with Force.” 31. Place the cardstock on the floor so that the center of the cardstock is directly in front of the tape measure. 32. Use a transfer pipette to extract 2 mL of simulated blood from the bottle. 33. Hold the ruler perpendicular to the 15 cm mark in one hand. 34. With your other hand, hold the transfer pipette vertically, such that the tip of the pipette is 15 cm above the cardstock. Use the ruler as a guide to ensure the dropper is 15 cm above the cardstock and posi-tioned over the center of the cardstock so that when it is dropped it hits the targeted area. 35. Quickly squeeze the simulated blood sample onto the center of the card. 36. Record your observations about the bloodstain pattern in Table 5. 37. Allow the cardstock to dry. 38. Use the ruler to measure the diameter of the bloodstain. Record the diameter in Table 5. 39. Use a camera to take a photograph of the cardstock after it is dry. Note: You will need to download, scan, or print the photographs to be included with your lab report. 40. Replace the lid on the bottle of simulated blood. You will need the simulated blood for the next experiment. 58 Fingerprinting Blood Distance from Impact (cm) Bloodstain Diameter (mm) Observations 15 30 45 60 75 100 Table 3: Bloodstain Diameter of a Single Drop at Varying Distances Table 4: Bloodstain Diameter of Varying Drops at the Same Distance Number of Drops Bloodstain Diameter (mm) Observations 1 2 3 4 5 6 59 Fingerprinting Blood Table 5: 2 mL Bloodstain Diameter with Force Height (cm) Bloodstain Diameter (mm) Observations 15 60 Fingerprinting Blood Experiment 2: Bloodstain Analysis Angle of Impact In this experiment, you will simulate and analyze bloodstain patterns caused by different angles of impact. Procedure 1. Use the masking tape to secure a protractor to the edge of a flat surface, such as a table top (Figure 8). To do this, line the origin (the hole on the flat side) up to the top edge of the flat surface. Secure the flat side of the protractor with a piece of masking tape. To keep the protractor from falling towards you, place a second piece of masking tape perpendicular to and over the first piece, through the protractor, and onto the top of the flat surface. 2. Use a permanent marker to label the top of a piece of cardstock “60º angle.” Under the label, write “Trial 1,” “Trial 2,” and “Trial 3” evenly spaced out (Figure 9). Materials 2 Cardstock Pieces Clipboard Masking Tape Permanent Marker Protractor Ruler Simulated Blood Transfer Pipette Pair of Disposable Gloves (located in your safety kit) Safety glasses (located in your lab safety kit) *Camera (a camera phone is acceptable) *Pencil *Flat Surface *You Must Provide Figure 8: Step 1 reference. The red arrow indicates the protractor origin. 61 Fingerprinting Blood 3. Cut the cardstock such that the piece of paper fits within the area of the clipboard (e.g. no edges are over-hanging). 4. Line up the bottom edge of the clipboard (the side opposite the clip) with the origin of the protractor. Use masking tape to secure it to the flat surface. This will create a “hinge” that allows the clipboard to rotate and create different angles with the flat surface. See Figure 10 for reference. 5. Remove the cap from the simulated sample and use a transfer pipette to obtain several drops of simulat-ed blood sample. 60º angle Trial 1 Trial 2 Trial 3 Figure 9: Step 2 reference. The red circles indicate the targeted area to hit with the crime scene blood. Figure 10: Step 3 and 9 reference. The blue, dotted line indicates the angle at which you hold the clipboard to the flat surface. The angle created by the clipboard and drop of blood is the angle of impact, denoted by a red, dotted line. The arrow indicates the protractor origin. The crime scene blood sample is oriented approximately 30 cm above of the clipboard. 62 Fingerprinting Blood 6. Lift up the free edge of the clipboard (edge with the clip) until a 30° angle is created between the clip-board and the flat surface. This creates an angle of impact of 60°. See Figure 10 for reference. 7. While holding the clipboard in place with one hand, orient the transfer pipette containing the simulated blood vertically, approximately 30 cm above the center of the cardstock. 8. Gently squeeze one drop of simulated blood from the transfer pipette onto the cardstock under the Trial 1 label. 9. Repeat Step 8 two more times, dropping the blood under the Trial 2 and Trial 3 labels on the cardstock. Performing three trials helps to visualize the natural variances which occur in bloodstains. 10. Hold the clipboard at a 30° angle (60° angle of impact) until the majority of the simulated blood has been absorbed by the paper. As it dries, examine the three bloodstains. Record observations about the shape and any visible bloodstain components. Record observations in Table 6. 11. Use a ruler to measure the length and width of each bloodstain. Record the lengths and widths in Table 6 12. Calculate the average length and width, and record the average length in Table 6. 13. Repeat Steps 2 - 12, this time creating a 60° between the clipboard and the flat surface (30° angle of im-pact). Record data in Table 7. 14. Use a camera to take a photograph of the cardstock after it is dry. Note: You will need to download, scan or print the photographs to be included with your lab report. 63 Fingerprinting Blood Bloodstain Dimension Trial 1 Trial 2 Trial 3 Average Observations Length (mm) Width (mm) Table 6: Average Blood Stain Length and Width at 60º Angle of Impact (From a Height of 30 cm) Bloodstain Dimension Trial 1 Trial 2 Trial 3 Average Observations Length (mm) Width (mm) Table 7: Average Blood Stain Length and Width at 30º Angle of Impact (From a Height of 30 cm) Appendix Good Lab Techniques 73 Good Lab Techniques Good Laboratory Techniques Science labs, whether at universities or in your home, are places of adventure and discovery. One of the first things scientists learn is how exciting experi-ments can be. However, they must also realize science can be dangerous without some instruction on good laboratory practices. Read the protocol thoroughly before starting any new experiment. You should be familiar with the action required every step of the way. Keep all work spaces free from clutter and dirty dishes. Read the labels on all chemicals, and note the chemical safety rat-ing on each container. Read all Material Safety Data Sheets (provided on www.eScienceLabs.com). Thoroughly rinse labware (test tubes, beakers, etc.) between experi-ments. To do so, wash with a soap and hot water solution using a bottle brush to scrub. Rinse completely at least four times. Let air dry Use a new pipet for each chemical dispensed. Wipe up any chemical spills immediately. Check MSDSs for special handling instructions (provided on www.eScienceLabs.com). Use test tube caps or stoppers to cover test tubes when shaking or mixing – not your finger! Figure 1: A bench coat or underpad helps prevent any spilled liquids from contami-nating your work surface. A B C Figure 2: Special measuring tools in make experimentation easier and more accu-rate in the lab. A shows a beaker, B graduated cylinders, and C test tubes in a test tube rack. 74 Good Lab Techniques When preparing a solution, refer to a protocol for any specific instructions on preparation. Weigh out the desired amount of chemicals, and transfer to a beaker or graduated cylinder. Add LESS than the required amount of water. Swirl or stir to dissolve the chemical (you can also pour the solution back and forth between two test tubes), and once dissolved, trans-fer to a graduated cylinder and add the required amount of liquid to achieve the final volume. A molar solution is one in which one liter (1L) of solution con-tains the number of grams equal to its molecular weight. For example: 1M = 110 g CaCl x 110 g CaCl/mol CaCl (The formula weight of CaCl is 110 g/mol) A percent solution can be prepared by percentage of weight of chemical to 100ml of solvent (w/v) , or volume of chemical in 100ml of solvent (v/v). For example: 20 g NaCl + 80 mL H2O = 20% w/v NaCl solution Concentrated solutions, such as 10X, or ten times the normal strength, are diluted such that the final concentration of the solution is 1X. For example: To make a 100 mL solution of 1X TBE from a 10X solution: 10 mL 10X TBE + 90 mL water = 100 mL 1X TBE Always read the MSDS before disposing of a chemical to insure it does not require extra measures. (provided on www.eScienceLabs.com) Avoid prolonged exposure of chemicals to direct sunlight and extreme temperatures. Immediately se-cure the lid of a chemical after use. Prepare a dilution using the following equation: Where c1 is the concentration of the original solution, v1 is the volume of the original solution, and c2 and v2 are the corresponding concentration and volume of the final solution. Since you know c1, c2, and v2, you solve for v1 to figure out how much of the original solution is needed to make a cer-tain volume of a diluted concentration. Figure 3: Disposable pipettes aid in ac-curate measuring of small volumes of liquids. It is important to use a new pi-pette for each chemical to avoid con-tamination. 75 Good Lab Techniques If you are ever required to smell a chemical, always waft a gas toward you, as shown in the figure below.. This means to wave your hand over the chemical towards you. Never directly smell a chemical. Never smell a gas that is toxic or otherwise dangerous. Use only the chemicals needed for the activity. Keep lids closed when a chemical is not being used. When diluting an acid, always slowly pour the acid into the water. Never pour water into an acid, as this could cause both splashing and/or an explosion. Never return excess chemical back to the original bottle. This can contaminate the chemical sup-ply. Be careful not to interchange lids between different chemical bottles. When pouring a chemical, always hold the lid of the chemical bottle between your fingers. Never lay the lid down on a surface. This can contaminate the chemical supply. When using knives or blades, always cut away from yourself. Wash your hands after each experiment. 77 Credits Credit Saferstein, R., (2013). Forensic science from the crime scene to the crime lab. (2nd ed.). San Fran-cisco, California: Pearson Education Inc. Technical Working Group on Biological Evidence Preservation. The Biological Evidence Preserva-tion Handbook: Best Practices for Evidence Handlers. U.S. Department of Commerce, National Insti-tute of Standards and Technology. 2013. www.canstockphoto.com © 2016 eScience Labs, LLC All rights reserved
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