Chemistry, Third edition

(Wang) #1

Forensic Chemistry


Objectives


 Introduces calculations on drugs and alcohol


 Defines the ‘drink driving’ legal limit


 Highlights the importance of analytical measurements in forensic science


 Explains the advantages of analysing hair for drugs.


Pre-requisites


The ideas which form the background to this unit are listed in the following table:


Topic Book page

Half-life 258
Organic chemistry (especially of alcohols) Unit 18, pp. 330–1
IR spectrum of ethanol 382–384
Chromatography 360–4

The scope of forensic chemistry


Forensic chemistry is the application of chemistry to the legal system. It includes the


analysis of unknown substances from the scene of a crime or from samples of body


tissue. Forensic chemistry uses the full range of analytical techniques available to the


chemist, as shown in Table 23.1.


Forensic Chemistry has strong links with forensic toxicology, the ‘science of poi-


sons’. Examples of molecules of interest to the forensic chemist are given in Figure


23.1.


23.2


23.1


Contents


23.1Pre-requisites 422

23.2The scope of
forensic chemistry 422

23.3Variation of the
concentration of a
poison with time 424

23.4Calculations using
first-order kinetics 424

23.5The zeroth-order
kinetics of ethanol
decay 425

23.6Drinking and
driving 426

23.7Analysis of drugs
in hair 428

22.7Revision questions 429

23


UNIT

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