Here is a list of fixatives for microscopic study with its preparation.
1. Bouin’s Fluid (aqueous):
Reagents:
Distilled water ………. 75 ml
Picric acid Formaldehyde
(Reagent grade) 40% ………… 25 ml
Glacial acetic acid ……………. 5 ml
Preparation:
Prepare a saturated solution of picric acid in distilled water. Add 25 ml formaldehyde to 75 ml saturated solution of picric acid and 5 ml glacial acetic acid. Mix thoroughly.
2. Bouin’s Fluid (Alcoholic; Duboscq):
Reagents:
Alcohol ……….. 80%
Picric acid ……………. 1 g
Glacial acetic acid ….. 15 ml
Formaldehyde
(Reagent grade) 40% ………… 60 ml
Preparation:
To 150 ml 80% alcohol add 1g picric acid and 60 ml formaldehyde. Dissolve and stock. Add 15 ml glacial acetic acid before use.
3. Mayer’s Albumen:
Reagents:
White of egg …… 20 ml
Glycerine ….. 50 ml
Sodium salicylate ….. 1 g
Preparation:
Make a small hole at the narrow end of an egg and hold it with the hole downwards on a beaker. The albumen will slowly flow out and collected in the beaker. Put the reagents and albumen in a glass-stoppered vial. Shake thoroughly till the ingredients mix completely. Filter, add a few crystals of thymol as preservative and store in a glass-stoppered bottle.
4. Schaudinn’s Fluid:
Reagents:
Saturated aqueous
mercuric chloride ….. 2 parts
Absolute alcohol ….. 1 part
Preparation:
Mix the two.
Use:
1. It is a good fixative for small specimens, particularly protozoans. Put the specimens on a slide and cover those with a layer of Schaudinn’s fluid. Wait for about 15 to 20 minutes. The specimens are fixed on the slide. Drain out the extra fluid.
or
2. Put two pieces of glass rods, about 3 mm diameter, at a distance of 5 cm in a 10 cm petridish. Pour Schaudinn’s fluid in the dish to just cover the rods. Place the slide with the objects, face downwards, on the rods. The materials on the lower surface of the slide are in contact with the fixative. Cover the petri dish with a glass plate or another petri dish. Wait for about 15 minutes and follow routine procedure.
In this method, the heavier and larger objects fall to the bottom of the dish, while small and lighter objects like protozoans and minute animals remain attached to the slide by the upward thrust of the fluid. The fixative may be used for several times.
5. Aceto Alcohol:
Reagents:
Absolute alcohol ….. 3 parts
Glacial acetic acid ……………. 1 part
Preparation:
Mix the two thoroughly and use.
6. Carnoy’s Fluid:
Reagents:
Absolute alcohol ….. 6 parts
Chloroform ….. 3 parts
Glacial acetic acid …… 1 part
Preparation:
Mix the reagents; put in a well-fitted screw capped bottle to prevent evaporation.
Use:
Carnoy’s fluid is a rapid nuclear fixative; preserves glycogen, and also a good fixative for cytology of virus-infected monolayer cell culture.
7. FAA (Formalin Acetic Acid Alcohol):
Reagents:
Formalin 40% ……… 10 ml
Glacial acetic acid ……….. 5 ml
Ethyl alcohol 70% …………… 85 ml
Preparation:
Mix the reagents.
8. Zenker‘s Formal or Helly’s Fluid:
Reagents:
Potassium dichromate (K2Cr2O7) ….5 g
Mercuric chloride (HgCI2) ….. 10 g
Sodium sulphate crystal …. 2 g
Neutral formalin (40%) …… 10 ml
Distilled water …… 200 ml
Preparation:
Mix the reagents in a stoppered bottle and shake well.
Use:
Add 5 ml acetic acid just before use.
The fixative is recommended for animal tissues in general but particularly for blood forming organs.
9. Formol Sublimate:
Reagents:
Saturated solution of mercuric
chloride …. 9 parts
Formalin (commercial 40%) …. 1 part
Preparation:
Mix the reagents.
10. Neutral Formalin:
Reagent:
Formalin … 1 part
Tap water … 9 parts
MgCO3 … excess
Preparation:
Shake well and allow to stand.
Use:
It is a good fixative. Fix tissue for 24 hrs.