42

QUANTITATIVE AGRICULTURAL

The apparatus necessary for this class of
work will include accurately standardized
volumetric flasks, burettes and pipettes. The
first are for making solutions of definite con-
centrations and occasionally for measuring;
aliquot parts of such solutions. Pipettes are
for measuring definite portions of Holutionn
and burettes are for measuring the necessary
volume of standard solution as the tit rat ion
is being made. Because of the fact that the*
required volume of standard solution varies in
different tit/rations and that it is
unknown until the experiment is
finished, the burette must bear
graduations for small subdivi-
sions, from zero to full capacity.
Figures 17, 18 and 19 illustrate
the three types of apparatus just
described.

Because of the fact that no
glass apparatus can be made to
deliver all of its contained solu-
tion upon emptying, it is neces-
sary to specify whether a given
piece of apparatus in graduated
"to contain" or "to deliver'1
the stated amount. Also if the
measurement of the delivered
solution is to be at all accurate
the apparatus must be con-
structed scientifically and used
with many precautions. Much
inaccurate work of the chemical
laboratory may be traced to
poorly constructed volumetric*
apparatus or to carelessness
FIG is.-(a) with regard to its use. The

Transfer and t> . c,, . t ,

(6) measuring -Bureau of Standards hat* under-
pipettoa. taken a special study of thin

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