Dehydrating agents

Ethanol

Dissolves nitrocellulose slowly (unless combined with diethyl ether [1:1 to 1:2] )

Ethanol

Minimal processing time

Ethanol

during prolonged immersion , Tissue to harden excessively and become brittle.

Methanol

Good ethanol substitute but rarely used (volatile, flammable, costly)

Methanol

Does not dissolve nitrocellulose (unless mixed with acetone)

Methanol

µwave processing: hardens tse > ethanol

Isopropanol

Slightly slower in action and not as hydrophobic as ethanol

Isopropanol

Used to dehydrate hard, dense tses

Isopropanol

Shrinks and hardens tse < ethanol

Isopropanol

Can remain in the solvent for extended periods without harm

1:10

Ideal tissue to dehydrating agent ratio is

Glycol-ethers

these reagents do not act as secondary fixatives

Cellosolve

Dissolves nitrocellulose and tends to decompose on exposure to sunlight

Dioxane

It is a cumulatively toxic and a suspected carcinogen.

Dioxane

It has a rapid but gentle action, and is best used in a graded series. It freezes at 12°C.

POLYETHYLENE GLYCOLS

Water-miscible polymers used to dehydrate and embed substances labile to the solvents and heat of the paraffin wax method.

POLYETHYLENE GLYCOLS

They are clear, viscous, slightly hygroscopic liquids or solids of low toxicity.

Acetone

best for processing fatty specimens.

Acetone

Tissues are dehydrated through four changes, last of which should always be fresh.

Acetone

not recommended for microwave processing as it causes excessive nuclear shrinkage.

Tetrahydrofuran

It is less toxic than dioxane for which it can be substituted.

TETRAHYDROFURAN

It dissolves mountants, but not most dyes.