Physical Properties of Physical Properties of Glass & SoilGlass & Soil
Glass BasicsGlass Basics
Glass is a hard, but brittle, amorphous solid Glass is a hard, but brittle, amorphous solid composed of _________________ mixed with composed of _________________ mixed with various compoundsvarious compounds
Types:Types: – – composed of sodium carbonate (Nacomposed of sodium carbonate (Na22COCO33) )
and lime (CaO) and is used in most windows and bottlesand lime (CaO) and is used in most windows and bottles – – (Safety Glass) rapidly heated and cooled (Safety Glass) rapidly heated and cooled
to make it stronger and dice when brokento make it stronger and dice when broken – – composed of boron oxide (Bcomposed of boron oxide (B22OO33) and is ) and is
used in headlights and pyrex glassused in headlights and pyrex glass – – stronger because a layer of plastic is stronger because a layer of plastic is
sandwiched in between 2 layers of glasssandwiched in between 2 layers of glass
Methods for Distinguishing GlassMethods for Distinguishing Glass
Densities of Some Common Densities of Some Common MaterialsMaterials
Methods for Distinguishing GlassMethods for Distinguishing Glass
Refractive IndexRefractive Index
Refractive Index Tutorial
Methods for Determining Methods for Determining Refractive IndexRefractive Index
The FBI has a database The FBI has a database off over 2000 refractive off over 2000 refractive indexes of different types indexes of different types of glass which shows that of glass which shows that glass is very distinctive glass is very distinctive and helps assign an and helps assign an appropriate statistical appropriate statistical probability that the two probability that the two pieces of glass share a pieces of glass share a common source.common source.
Methods for Determining Methods for Determining Refractive IndexRefractive Index
Becke LineBecke Line
Methods for Determining Methods for Determining Refractive IndexRefractive Index
Glass Fracture PatternsGlass Fracture Patterns
Glass Fracture PatternsGlass Fracture Patterns
Glass Fracture PatternsGlass Fracture Patterns
Collection of Glass EvidenceCollection of Glass Evidence
Standard reference glass should be taken Standard reference glass should be taken from the crime scene (1 infrom the crime scene (1 in22))
Package in solid containers to prevent Package in solid containers to prevent breakagebreakage
Preserve garment (shoe, pants, shirt) with Preserve garment (shoe, pants, shirt) with glass on itglass on it
Soil CharacteristicsSoil Characteristics
Mixture of:Mixture of:
Soil AnalysisSoil Analysis
11stst – Gross Analysis – Gross Analysis
Soil AnalysisSoil Analysis
22ndnd – __________ – __________ AnalysisAnalysis Rock and Mineral Rock and Mineral
AnalysisAnalysis Minerals have physical Minerals have physical
properties like color, properties like color, crystal shape, density, crystal shape, density, and refractive indexand refractive index
2,200 minerals 2,200 minerals (40 common)(40 common)
Soil AnalysisSoil Analysis
Microscopic Analysis Microscopic Analysis concon’’tt
Humus
Pollen
Collection of Soil EvidenceCollection of Soil Evidence
Collect samples at various intervals in a Collect samples at various intervals in a 100 yard radius of crime scene100 yard radius of crime scene
Top surface of soil is usually enoughTop surface of soil is usually enough Preserve garment (shoe, pants) with soil Preserve garment (shoe, pants) with soil
on iton it Note layering of soil (as on car tires) when Note layering of soil (as on car tires) when
collecting soil evidencecollecting soil evidence
The EndThe End
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