INTRODUCTION
For the most part the operations of analytical chemistry
fall naturally into quantitative lines. This is particularly
true of analysis as applied to agricultural problems because
the qualitative composition of most agricultural materials is
usually fairly accurately known from the nature and proposed
use of the materials themselves.
The qualitative method for the detection of a given element
or compound frequently involves the use of the same reactions
as those that are fundamental to the quantitative determina-
tion of the same materials and in these cases, especially, it is
most convenient to modify the details of the experiment so as to
make a quantitative determination possible in the beginning,
rather than to repeat the work in this manner after the com-
pletion of a qualitative analysis. This is not universally true
and there will be occasional instances in which the complete
qualitative analysis will save the labor of quantitative deter-
mination of elements n,ot present in any significant quantity.
As the name implies, quantitative analysis has for its object
the determination of the quantity (usually, though not always,
expressed as per cent) of the various constituents of a material
under investigation. The constituents determined may be
elements or radicals of a compound, mixture or solution. The
particular method to be used for a given material will be chosen
according to circumstances and, to some extent, according to
individual preference or available equipment. It will necessarily
be modified if interfering substances are present. On this
account it is desirable first to learn a few methods for the quan-
titative determination of some common elements in pure com-
pounds and later to apply these and other methods to a more
extended analysis of more complicated materials.