Page 31 - Vogel's TEXTBOOK OF QUANTITATIVE CHEMICAL ANALYSIS

CHAPTER 1
INTRODUCTION

1.1 CHEMICAL ANALYSIS
'The resolution of a chemical compound into its proximate or ultimate parts;
the determination of its elements or of the foreign substances it may contain':
thus reads a dictionary definition.
This definition outlines in very broad terms the scope of analytical chemistry.
When a completely unknown sample is presented to an analyst, the first
requirement is usually to ascertain what substances are present in it. This
fundamental problem may sometimes be encountered in the modified form of
deciding what impurities are present in a given sample, or perhaps of confirming
that certain specified impurities are absent. The solution of such problems lies
within the province of qualitative analysis and is outside the scope of the present
volume.
Having ascertained the nature of the constituents of a given sample, the
analyst is then frequently called upon to determine how much of each
component, or of specified components, is present. Such determinations lie
within the realm of quantitative analysis, and to supply the required information
a variety of techniques is available.

1.2 APPLICATIONS OF CHEMICAL ANALYSIS
In a modern industrialised Society the analytical chemist has a very important
role to play. Thus most manufacturing industries rely upon both qualitative
and quantitative chemical analysis to ensure that the raw materials used meet
certain specifications, and also to check the quality of the final product. The
examination of raw materials is carried out to ensure that there are no unusual
substances present which might be deleterious to the manufacturing process or
appear as a harmful impurity in the final product. Further, since the value of
the raw material may be governed by the amount of the required ingredient
which it contains, a quantitative analysis is performed to establish the proportion
of the essential component: this procedure is often referred to as assaying. The
final manufactured product is subject to quality control to ensure that its
essential components are present within a pre-determined range of composition,
whilst impurities do not exceed certain specified limits. The semiconductor
industry is an example of an industry whose very existence is dependent upon
very accurate determination of substances present in extremely minute quantities.
The development of new products (which may be mixtures rather than pure
materials, as for example a polymer composition, or a metallic alloy) also