forensics slideshow class notes (3).pptx

forensics slides

1. Sections Qualitative Analysis (20%) Polymers – Hair, Fiber, Plastics (20%) Chromatography/Mass Spectroscopy (15%) Crime Scene Physical Evidence (15%) Analysis (30%)

2. Qualitative Analysis You will be asked to identify: Sodium Acetate – NaC₂H₃O₂ Sodium Chloride – NaCl Sodium Bicarbonate – NaHCO₃ Sodium Carbonate – Na₂CO₃ Lithium Chloride – LiCl Potassium Chloride – KCl Calcium Nitrate – Ca(NO3)₂ Calcium Sulfate – CaSO Calcium Carbonate – CaCO₃ Cornstarch – C H O Glucose – C₆H O₆ Sucrose – C H₂₂O₁₁ Magnesium Sulfate – MgSO Boric Acid – H₃BO₃ Ammonium Chloride – NH Cl 4 27 48 20 12 12 4 4 You will be given: Iodine reagent (I₂) 2M HCl 2M NaOH Benedict’s solution Hot water bath Bunsen Burner Distilled water

3. How each Reagent is used Flame tests (bunsen burners) Na → golden yellow Li → carmine/red Ca → yellow-red H₃BO₃ → bright green NH Cl → faint green K → light purple Mg → white Iodine reagent Turns black with starch HCl Reacts with carbonates (-CO₃) Benedict’s Solution Turns orange with glucose Turns dark purple with NH Cl NaOH Milky with Ca(NO3)₂ Ca(OH)₂ forms Precipitates with MgSO Mg(OH)₂ forms Ammonia smell with NH₃ forms Distilled water Insoluble: CaSO CaCO₃ starch 4 4 4 4

4. Density test This is very commonly seen in plastics IDs. They’ll tell you whether the plastic floats or sinks in each solution and you need to identify the plastic. Useful to memorize: PETE – 1.37 g/cm³ HDPE – 0.92 g/cm³ PVC – 1.38 g/cm³ LDPE – 0.92 g/cm³ PP – 0.90 g/cm³ PS – 1.05 g/cm³ PC – 1.20 g/cm³ PMMA – 1.16 g/cm³ Water – 1.00 g/cm³ Vegetable oil – 0.91 g/cm³ Isopropyl alcohol – 0.93 g/cm³ 10% NaCl solution – 1.07 g/cm³ Saturated NaCl solution – 1.21 g/cm³