The book explains how scientific principles are applied so that information about the chemical composition of materials can be obtained. It provides a critical guide to the evaluation of the quality of the information that can be obtained about the identity and concentration of chemical compounds present at relatively low concentrations in complex sample materials and how to devise and validate a new analytical method. The book explains why it is difficult to obtain reliable information about the minor and trace chemical constituents of complex materials. As this kind of information underpins many areas of scientific endeavor, and our health and well-being, it is important that everyone concerned is aware of the scope and limitations of chemical measurement technology. Topics include Arsenic Compounds in Food and Drinking Water, The Environmental Chemistry of Arsenic, A Critical Review of Scientific Communication, Analytical Chemistry, Method development and evaluation, The Determination of Arsenic Compounds by Molecular Spectrometry, The Determination of Arsenic Compounds by Atomic Spectrometry, The Determination of Arsenic Compounds by Mass Spectrometry, The Determination of Arsenic Compounds by Electrochemistry, Separation Methods, High Performance Separations, Direct solid analysis, Field and Portable Methods, Problems with the analysis of real samples, especially rice, soil and urine, and Arsenic research projects for students at all stages and citizen scientists.