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