Chapter 6 Inorganic Analysis 6.1 Notes Pg

Organic vs. Inorganic ¾ of the weight of the Earth ’ s crust is composed of only Oxygen and Silicon 10 elements make up approximately 99% of the Earth’s crust Carbon is less than 0.1 % of the earth ’ s crust Therefore you are going to find non-carbon items at crime scenes

Inorganic Non-carbon containing substances In the lab examiners must compare pieces of physical evidence for trace elements which provide markers that may establish the source of a material

Read pages JFK assassination

Emission Spectrum Display of colors resulting from light passing through a prism Separated into its component colors or frequencies Continuous spectrum = where all colors merge or blend into one another to form a continuous band

Not all light sources produce a spectrum but instead produce a series of colored lines mingled with series of dark bands. Each line represents a definite wavelength or frequency of light called a line spectrum (page 155). must be in vapor state “fingerprint” of element Very practical method of identification

Emission spectrograph Instrument used to obtain and record the line spectra of elements Vaporizes and excites atoms so they emit light Separates light into frequencies Records resultant spectrum

Carbon arc Method of exciting atoms 2 carbon electrodes Direct current arc is passed Arc produces sufficient amount of heat to vaporize & excite

Inductively Coupled Plasma (ICP) Excitation of atoms occurs by placing sample in hot plasma torch ICP used to identify and characterize mutilated bullets and glass fragments

Atomic Absorption Spectrophotometer Technique for the selective absorption of light by atoms Most useful application in providing an accurate determination of an element’s concentration in a sample Sufficiently sensitive in detecting and quantitating elements that are present at trace levels