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Warm up (write questions and answers in you notes)

electronic devices will be confiscated. Warm up (write questions and answers in you notes). Be on time for class and prepared!. Follow all school rules. What is ink made out of? How can inks be separated into their component chemicals?. No food or drinks outside the commons.

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Warm up (write questions and answers in you notes)

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  1. electronic devices will be confiscated Warm up (write questions and answers in you notes) Be on time for class and prepared! Follow all school rules • What is ink made out of? • How can inks be separated into their component chemicals? No food or drinks outside the commons Only supplies needed for class allowed in classroom Do your best work every time

  2. Warm up answers • Ink is made out of a pigment and other chemicals (called “binders) that form a liquid or colloidal solution • Writing Inks • Early 20th century – water-based • 1940’s – oil-based • 1950’s – polyethylene glycol • 1970’s – rare-earth elements

  3. Today’s activities • Pretest • Fix mistakes on IARs from last class • Questioned document analysis part 3 (chromotography)

  4. Pretest – answer each on a separate piece of paper • 1. What do we learn through observation? • 2. How does pattern recognition aid in investigations? • 3. What is the relationship between the legal system and scientific validity?

  5. CSI: Monroe case #3 Someone wrote a note to Dr. Ray in black ink. He was furious because black is not a school color, it is an accent color, and he feels the note should have been written in red or white which are the official school colors. A review of the video surveillance revealed 5 suspects entering the office from the time Dr. Ray left for lunch duty until he returned to his office. The suspects were apprehended and a black pen was confiscated from each. It is your job to determine which of these suspect’s pens match the writing from the note so that Dr. Ray can give this student a red pen to use from now on.

  6. Directions for ink analysis • Select a black pen pen and write the type of pen with a pencil at the top of a piece of chromotography paper • Repeat for each pen • Cut chromotography paper and set up development chamber according to the following diagrams • Place a single dot of ink on the chromotography paper according to the diagram • Repeat for each pen

  7. Directions for ink analysis (cont.) • Put about 0.5 cm of water the development chamber (test tube) • Place one chromotography strip in chamber, allow solvent to move up the paper until it almost reaches the top (you should see color bands appear as they separate) • Remove the chromotography strip from the chamber, mark the location of each color band and the “top” of the solvent with a pencil • Allow to dry • Repeat entire process again using acetone as the solvent • Repeat entire process again using ethanol as the solvent

  8. Directions for ink analysis (cont.) • Obtain the crime scene evidence from Mr. Columbus • Repeat all steps using water, acetone, and ethanol as solvents.

  9. Calculating Rf value • Measure distance from origin to top of solvent front (s) • Measure distance from origin to top of each color (m1, m2, m3, etc.) • Divide m1/ s, m2/s, m3/s, etc.

  10. Cool down • Explain how to separate inks into their component chemicals and how to calculate a Rf value.

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