Page 125 - The Veterinary Laboratory and Field Manual 3rd Edition

94 Willy Schauwers

Flasks
Two commonly used flasks are the Erlenmeyer
and the volumetric measuring flasks.

• The Erlenmeyer flask (Figure 2.61) has a flat
bottom and sloping sides that gradually nar-
row in diameter so that the top opening is
bottle-like. The opening may be plain, stop-
pered with a bung or it may have threads for
a cap. Erlenmeyer flasks range from 10 ml
capacity to 4000 ml capacity. They may be
used to hold liquids, to mix solutions or to
Figure 2.59 Glass reagent bottles. Photo: Dr Ziay measure non-critical volumes. Markings on
Ghulam, Dr Wahidullah Bahaer, Central Veterinary the side indicate the capacity in millilitres.
Diagnostic and Research Laboratory, Kabul, • The volumetric flask (Figure 2.62) is a
Afghanistan. pear-shaped flask used for making critical mea-
surements that require accuracy. Volumetric
Beakers flasks are manufactured to strict standards and
are guaranteed to contain a specified volume at
Beakers (borosilicate glass, polypropylene a particular temperature. The capacity in mil-
or polymethylpentene) are wide-mouthed, lilitres is marked on the flask. A line is etched
straight-sided containers (Figure 2.60) that in the neck of the flask to indicate the appro-
have a pouring spout formed from the rim. Each priate fill level. Usually a portion of water or
beaker is labelled to indicate the approximate other solvent is added to the flask before add-
capacity in millilitres. Many beakers have addi- ing an exact amount of solute which has been
tional markings to indicate volume increments. weighed. The remaining solvent is then added
Beakers have many functions in a laboratory, to the flask until it approaches the ‘fill’ line.
but they should only be used for non-critical The last portion is added very slowly (use a
measurements or estimated measurements. wash bottle or a pipette) until the lowest point
of meniscus, or curved liquid, is level with the
marking on the neck of the flask when viewed at
eye level. Close the flask and shake upside
down to mix contents. Volumetric flasks are
used to prepare solutions when the accuracy
of the concentration is important.

Graduated cylinders
A graduated (measuring) cylinder (Figure 2.63)
is an upright, straight-sided container with flared
base to provide stability. It is used in the labora-
tory to make non-critical volume measurements
Figure 2.60 Beakers. Photo: Willy Schauwers, and they are available in capacities ranging from
Provincial Institute for Hygiene, Antwerp, Belgium. 5 to 2000 ml.

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