FORENSIC CHEMISTRY LABORATORY MANUAL

by R.Q. Thompson; Oberlin College

ANALYSIS OF GLASS FRAGMENTS

 

Objective

To compare glass samples based on their refractive index (RI) and their trace magnesium content by atomic absorption spectrophotometry (AA).

 

Sample

Glass fragments (half-inch square) from bottles and from automobiles. Find a junk yard and obtain samples from car headlamps and windshields.

 

Reagents

A set of liquid refractive index standards; magnesium metal; pure lanthanum nitrate; concentrated hydrofluoric acid solution; concentrated hydrochloric acid; concentrated nitric acid

 

Standard Reference Material

 

None
Special equipment

optical microscope; sodium vapor lamp; microscope slides; flame atomic absorption spectrophotometer; ultrasonic bath; plastic centrifuge tubes

 

Procedure

RI: For instructor (detailed) ; For student (brief)

AA: For instructor (detailed) ; For student (brief)

 

Typical results

AA calibration curve for magnesium; magnesium content of typical glass samples; RI of typical glass samples

 

Alternate Method

Inductively Coupled Plasma (ICP) - Emission Spectrophotometry (OES)

 

Procedure

 

(planned for next edition)