Page 99 - Vogel's TEXTBOOK OF QUANTITATIVE CHEMICAL ANALYSIS

CHAPTER 3

COMMON APPABATUS AND
BASIC TECHNIQUES

3.1 INTRODUCTION

In this chapter the more important basic techniques and the apparatus
commonly used in analytical operations will be described. It is essential that
the beginner should become familiar with these procedures, and also acquire
dexterity in handling the various pieces of apparatus. The habit of clean, orderly
working must also be cultivated, and observance of the following points will
be helpful in this direction.
1. The bench must be kept clean and a bench-cloth must be available so that
any spillages of solid or liquid chemicals (solutions) can be removed
immediately.
2. Al1 glassware must be scrupulously clean (see Section 3.8), and if it has been
standing for any length of time, must be rinsed with distilled or de-ionised
water before use. The outsides of vessels may be dried with a lint-free
glass-cloth which is reserved exclusively for this purpose, and which is
frequently laundered, but the cloth should not be used on the insides of the
vessels.
3. Under no circumstances should the working surface of the bench become
cluttered with apparatus. Al1 the apparatus associated with some particular
operation should be grouped together on the bench; this is most essential to
avoid confusion when duplicate determinations are in progress. Apparatus
for which no further immediate use is envisaged should be returned to the
locker, but if it will be needed at a later stage, it may be placed at the back
of the bench.
4. If a solution, precipitate, filtrate, etc., is set aside for subsequent treatment,
the container must be labelled so that the contents can be readily identified,
and the vesse1 must be suitably covered to prevent contamination of the
contents by dust: in this context, bark corks are usually unsuitable; they
invariably tend to shed some dust. For temporary labelling, a 'Chinagraph'
pencil or a felt tip pen which will write directly on to glass is preferable to
the gummed labels which are used when more permanent labelling is required.
5. Reagent bottles must never be allowed to accumulate on the bench; they
must be replaced on the reagent shelves immediately after use.
6. It should be regarded as normal practice that al1 determinations are performed
in duplicate.
7. A stiff covered notebook of A4 size must be provided for recording
experimental observations as they are made. A double page should be devoted