3. Water will not mix with usual media in which stained
and sectioned materials may be finally preserved.
The purpose dehydration is therefore, to remove all
traces of water from the cells and tissues before finally
mounting.
Dehydration : treating the material with the series of
solutions containing progressively decreasing
concentration of water and progressively increasing
concentration of the dehydrant.
4. The material should not be allowed to become dry at
any stage .
Long interval in long concentrations make soft tissues
Long interval in high concentrations make materials
brittle.
In the last but one grade of dehydrant,a very small
quantity of eosin powder may be added to colour the
material dehydrated for embedding in paraffin, this
helps in locating materials.
6. DEHYDRATING AGENTS
Ethyl alcohol
Most commonly used.
Isopropyl alcohol is used instead of this
,it is cheap and easily produced
Methyl alcohol rarely used with plant
materials due to high toxicity.
Drastic dehydrating action that damage
structures.
7. Strength of alcohol
60,70,80 percent alcohol by volume ,to be stored in
glass stopper reagent-bottles ,next in this series will be
95 % and absolute alcohol.
Normally the time for which materials are left in each
grade shall be 30 minutes for root tips and small pieces
of leaf ,12 hours for large blocks of wood
Up to 70% and 1 hr and 24hr respectively for 80,95,&
100% .
8. Acetone
The series to be prepared with distilled H2O are 75
,10,15,20,25,30,35,40,50,60,70,80,90,100 %
Intervals can be less than one hour in each grade
The procedure is exactly the same as with ethyl or
isopropyl alcohol.
9. GLYCERINE
It is a thick, colorless, sweet tasting liquid and is an
excellent reagent for dehydrating delicate materials
like filamentous algae and fungi
High boiling point
Water can be removed by evaporation.
Material is washed well and transferred to a large
volume of 5% glycerin take in a wide mouthed jar
Leave this jar open but well protected from dust in a
room until the water evaporates leaving the material
covered by glycerin
10. BUTYL ALCOHOL AND TERTIARY BUTYL
ALCOHOL
Have additional advantage that they can be directly
followed by paraffin impregnation since they are also
solvents of paraffin.
11. Different grades are prepared in combination with
ethyl alcohol and are tabulated below.
SERIES NO ETHYL
ALCOHOL
95% IN ml
NORMAL
BUTYL
ALCOHOL
IN ml
DISTILLED
WATER IN
ml
1 20 10 70
2 25 15 60
3 30 25 45
4 30 40 30
5 25 55 20
6 20 70 10
7 15 85 0
12. SERIES NO ABSOLUTE
ALCOHOL IN
ml
95%ETHYL
ALCOHOL
TERTIARY
BUTYL
ALCOHOL IN
ml
DISTILLED
WATER IN ml
1 0 50 10 40
2 0 50 20 30
3 0 50 35 15
4 0 50 50 0
5 25 0 75 0
The series with tertiary butyl alcohol
13. DIOXANE
DIOXAN (diethylene dioxide)
Does not require any other reagents to be mixed for
dehydration.
No drastic plasmolysing effect
Rapid penetration capacity
Does not make tissue brittle
Reduces the number of separate steps in the process of
dehydration
14. The following series are recommented for materials
washed in water fixing.
Dioxan series 1
SERIES NO DIOXAN IN
ml
DISTILLED
WATER IN
ml
DURATION
IN EACH IN
hr
1 35 65 4-12
2 60 35 4-12
3 100 0 4-12
SERIES NO DIOXANE
IN ml
DISTILLED
WATER IN
ml
DURATION
IN EACH IN
hr
1 50 50 4-12
2 65 35 4-12
3 100 0 4-12
15. Clearing or dealcoholization
Transfer of materials after dehydration in the reagents
that are not solvents of wax
The clearing action is merely incidental to the
function of the reagent to serve as solvent wax.
16. XYLENE (xylol)
a conventional reagent
Used for dealcoholization before materials transferred
to solvents of paraffin
Trichloroethylene is a good substitute for xylene ,it is
non toxic and non-inflammable.
17. Xylene/ trichloroethylene series for large pieces of
tissue
SERIES NO ETHYL
ALCOHOLI
N ml
XYLENE
/TRICHLOR
OETHYLEN
E IN ml
DURATION
IN HOUR
1 75 25 3
2 50 50 3
3 25 75 3
4 0 100 3
18. Xylene/ trichloroethylene for cytological work
SERIES NO ETHYL
ALCOHOL
IN ml
XYLENE/TR
ICHLOROE
THYLENE
IN ML
DURATION
IN min
1 90 10 30
2 80 20 30
3 70 30 30
4 60 40 30
5 50 50 30
6 40 60 30
7 30 70 30
8 20 80 30
9 10 90 30
10 0 100 30
19. CHLOROFORM
Does not make tissue brittle
Chloroform/benzene series.
SERIAL NO ETHYL
ALCOHOL
CHLOROFO
RM IN ml
DURATION
IN Hr
1 65 35 ½-3
2 35 65 ½-3
3 0 100 ½-3
Benzene is a good substitute in this
series
Chloroform and benzene vapors are
inflammable and harmful in inhale too
much.
20. CEDAR OIL
Used like xylol.
Easy to obtain but clearing action is low.
CLOVE OIL
Obtain from syzygium aromaticum.
Eugenol is the major constituent.
Used to clear sections in the slides before mounting.
Give better transparency to tissues & hence visible
clearly .
21. BEECH WOOD CREOSOTE
fragile materials are dehydrated using creosote from
80% alcohol
2 changes are enough to have complete dehydration
Later mounting is done using balsam .
It has method of clearing.
Counter staining can also be done
Fern prothallus ,sections of bryophyte thallus etc…are
double stained properly using creosote method.