Question

Why is formalin citrate used to dilute blood for counting rbc's?

Answer 1

The counting of blood cells, manually with the help of microscope, is not possible. Therefore, to count the cells, blood is diluted and placed in a special type of counting chamber. This technique is called haemocytometeric counting. The cells often counted by this method are red cells, white cells, platelets, and eosinophills.For total red cell counts following equipment are required:

1. RBC diluting fluid

2. RBC pipette

3. Haemocytometer

4. Blood sample.

1. RBC Diluting Fluid:

RBCs are about 5 millions/cu mm of blood. Counting this much number is highly impossible. Therefore, the blood sample is diluted with the help of RBC diluting fluid. It fixes and preserves RBC. It is isotonic to red cells.

Following two types of RBC diluting fluid are commonly used:

Formalin Citrate Diluting Fluid:

Composition:

i. Trisodium citrate – 3 gm.

ii. Formalin – 1 ml.

iii. Distill water – 99 ml.

This diluting fluid is cheap and commonly used.

Haym’s Diluting Fluid:

Composition:

a. Sodium chloride -0.5 gm

b. Sodium sulfate -2.5 gm

c. Mercuric chloride -0.25 gm

d. Distilled water – 100 ml.

The RBC diluting fluid prevents haemolysis and removes unwanted blood cells.

Answer 2

RBCs are about 5 millions/cu mm of blood. Counting this much number is highly impossible. Therefore, the blood sample is diluted with the help of RBC diluting fluid. It fixes and preserves RBC.

this is what uh asked for.

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