Parameters:
(1) specific gravity of the organ
(2) specific gravity of the fixative solution (may be determined with a hydrometer)
(3) solute to raise the specific gravity of the fixative, such as sodium chloride
(4) volume of the fixative to be used in mL
difference in specific gravity =
= (specific gravity of organ) – (specific gravity of fixative solution)
amount of solute needed in grams =
= (difference in specific gravity) * (mL of fixative needed)
Considerations:
(1) Making a solution hypertonic will cause water to leave the cells, causing them to shrink. However, a tissue fixative should reduce this tendency.
(2) This method assumes that all of the solute dissolves.
(3) The temperature of storage will determine the solubility of the solute used to raise the specific gravity of the fixative solution. More solute may be required if the specimen will be refrigerated.
