f. All mixing containers, stirring rods, and containers used for storage of
reagents should be chemically cleaned prior to use.
g. During mixing and preparation, as well as in storage, it is good practice to
avoid contact of reagents with metals. Many reagents contain substances that will react
chemically with metals and produce changes that will render than unusable for
h. Do not allow inexperienced personnel to prepare reagents without close
i. Certain reagents are poisonous and adequate precautions should be taken to
prevent accidental poisoning. All highly toxic reagents should be conspicuously labeled
"POISON" and should be stored in a separate cabinet in the laboratory.
j. Commercial reagents should be checked with standards for purity. Record all
lot numbers in case a reagent is not pure.
k. Test all new reagents to assure that proper results are attainable.
Section II. LABORATORY GLASSWARE
a. The blood cell diluting pipet (see figure 2-1) consists of a graduated capillary
tube having an arbitrary volume of one unit and marked in increments of that unit, each
designated as 0.1; note that this unit is not a standard measurement but merely an
arbitrarily selected unit. Above the capillary tube is a mixing bulb containing a color-
coded glass bead, and above the bulb another shorter capillary tube with an engraved
mark. The pipet for performing the white blood cell count has a white bead, the mixing
bulb is smaller than that of the red count pipet, and the marking above the bulb reads
"11." The pipet for performing the red blood cell count has a red bead in the mixing bulb
and the marking above the bulb is "101."
b. These pipets are used to take the specimen directly from a capillary puncture
or, after careful mixing, from a vial of fluid or of blood treated with an anticoagulant,
such as EDTA. The blood or fluid is drawn into the pipet to a predetermined point and
diluted to the correct mark with diluting fluid. After proper mixing, the diluted substance
is placed in the counting chamber and the cells are counted.
c. Usually, the technique for diluting the blood specimen with a pipet calls for
whole blood to be drawn exactly to the 0.5 mark and diluted only to the "11" or "101"
mark with appropriate diluting fluid dependent upon the type of cell count. Since the
volume of fluid in the stem does not enter into the dilution, the dilution is calculated on
the volume in the bulb, thus with the white blood cell count: