(h) Let stand for ten (10) minutes to allow red cells to hemolyze.
BLOOD CELL COUNTING CHAMBERS
a. The most common type of hemacytometer consists of two counting chambers
separated by grooves or canals. On the smooth glass surface of the counting
chambers are straight lines etched into glass in a gridwork pattern. The Neubauer
ruling, preferred for hematological work, consists of a gridwork with dimensions of 3 mm
by 3 mm. It is further divided into 9 smaller squares with dimensions of 1 mm by 1 mm;
4 of these squares are used for the white count. The 8 outer squares are further
subdivided into 16 squares 0.25 mm on a side. The central square is divided into 25
squares, 0.20 mm on a side, which are used for the red cell count. Thus the large
squares are 1 square mm, the 16 small squares in the outer large squares are 1/16
square mm and the 25 central squares are 1/25 square mm (see figure 2-4).
Figure 2-4. Rulings on a hemacytometer.
b. The cover glass must be free of visible defects and must be optically plane on
both sides within + 0.002 mm according to the United States (US) Bureau of Standards.
When the cover glass is placed on the platform, the space between it and the ruled
platform should be 0.1 mm.
Glassware can be cleaned in hot, soapy water and thoroughly rinsed in distilled
water. Blood dilution pipets can be washed by flushing water and acetone through
them. Ordinary household bleach can be used to remove blood clots in the bore of
pipets. Dilution pipets are dry when the bead moves freely in the bulb. Glassware to be
used for coagulation studies must be scrupulously clean. This glassware should be