a 100 c.c. flask to a beaker, it will be necessary to complete the
transfer by rinsing out the flask and adding the washings; otherwise
there will be a sensible loss. Graduated cylinders (fig. 28) are
convenient for preparing standard solutions.

[Illustration: FIG. 27.]

[Illustration: FIG. 28.]

[Illustration: FIG. 29.]

~Pipettes~ and burettes are graduated to _deliver_ the quantities
specified. The principle of the pipette, and the advantages and
disadvantages of its various forms, may be understood by considering the
first form shown in fig. 29. It is essentially a bulbed tube drawn out
to a jet at its lower end, and having on each side of the bulb a mark so
placed that when the surface of the liquid falls from the upper to the
lower mark the instrument shall deliver exactly 100 c.c. The bore of the
jet should be of such a size as will allow the level of the liquid to
fall at the rate of about one foot in two minutes. If it runs more
quickly than this, an appreciable error arises from the varying amount
of liquid remaining, and damping the sides of the bulb. The flow of
liquid from a pipette must not be hastened by blowing into it. The lower
tube or nose of the pipette should be long enough to reach into the
bottle or flask containing the liquid about to be measured. The pipette
is filled by sucking at the open end with the mouth; this method of
filling renders the use of the instrument dangerous for such liquids as
strong acids, ammonia, and such poisonous solutions as that of potassic
cyanide. One attempt with a fairly strong solution of ammonia will teach
the beginner a very useful lesson. As soon as the liquid rises above the