the process involving the changes in the physical properties and chemical structures of the substances

2. PREPARED BY:
DR ABDUL SAMI
MPHIL EASTERN MEDICINE
THE ISLAMIA UNIVERSITY OF BAHAWALPUR
PAKISTAN

3. Physicochemical processes &
Process of Precipitation and its
applications

4. Physicochemical process:-
“A process involving changes in the physical
properties and chemical structure of
substance.”

5. Examples:-
Crystallization
Catalysis
Desiccation
Precipitation

6. Precipitation

7. Contents
Definition
Precipitate
Precipitant
Supernate
Apparatus
Procedure
Types
Applications
Methods

8. Definition:-
“The process of separating a solid particles from
a previously clear liquid by physical or chemical
changes.”

9. Precipitate:-
“The supermitent solid which is collected at the
surface is called as precipitate.”
OR
“When the reaction occurs, the solid formed is
called precipitate.”

10. Precipitant:-
“The cause of precipitation is called precipitant.”
OR
“Any physical or chemical agent that cause
precipitation is called as precipitant.”

11. Supernate / Supernatant:-
 ”Supernate is the liquid which remains above
the solid (precipitate) formed during the
precipitation reaction.”

13. Apparatus:
It is described for the measurement of the rates of
fast precipitation reactions.
It consists of a T-tube, where reactants are added to
the arms of the T, mixed rapidly at the junction, and
the rates of disappearance of reactants or appearance
of products are measured along the stem of the Tube.
It has been used to investigate the kinetics and
mechanism of iron sulphide precipitation reactions. It
has enabled measurements to be made with relatively
high precision and good accuracy of the first 130 ms
of reaction time.

16. Procedure of precipitation:-
Natural methods of precipitation include
settling or sedimentation, where a solid forms over a
period of time due to ambient forces like gravity
or centrifugation. During chemical reactions,
precipitation may also occur particularly if
an insoluble substance is introduced into a solution and
the density happens to be greater (otherwise the
precipitate would float or form a suspension). With
soluble substances, precipitation is accelerated once the
solution becomes supersaturated.

17. In solids, precipitation occurs if the concentration
of one solid is above the solubility limit in the
host solid, due to e.g. rapid quenching or ion
implantation, and the temperature is high
enough that diffusion can lead to segregation
into precipitates. Precipitation in solids is
routinely used to synthesize nanoclusters.

18. An important stage of the precipitation process
is the onset of nucleation. The creation of a
hypothetical solid particle includes the
formation of an interface, which requires
some energy based on the relative surface
energy of the solid and the solution. If this
energy is not available, and no suitable
nucleation surface is available, supersaturation
occurs.

19. Types:-
1:- Physical Precipitation
2:- Chemical Precipitation

20. Physical precipitation:-
It occur when a hot saturated solution of an
amorphous substance is allowed to cool or when a
liquid in which the dissolve substance is insoluble is
added to solution of that substance. e.g. yogurt and
cheese.
Salting out:-when a liquid in which dissolve
substances are insoluble added to a sol. Of that
substances, the addition of the liquid will produce
precipitation of that substances. This process is
known as salting out.

21. Example:-drug that form mucilage with water like
acacia when alcohol is added in this mucilage then
acacia mucilage is separated.
 Chemical precipitation:-The precipitation in the
bottom of a container of calcium hydroxide solution is
due to the reaction of CaOH with dissolved CO2 which
gives rise to the insoluble CaCO3.
 2NaOH+CO2------->NA2CO3+H2O

22. Conditions Required For Precipitation:-
physical nature of precipitation:-Hot and conc.
solution produce coarse precipitation. And
such precipitates are more readily washed to
remove the contaminating salts.
while the cold conc. sol. produce fine
precipitation which are light in nature.

23. Simple solution chemistry:-all the precipitation
phenomena either chemical or physical are
based on the simple solution chemistry. A solid
has solubility in any given solvent when
concentration is exceeded the super saturation
occurs. This super saturation condition can be
obtained by evaporation by applying thermal
condition.

24. Applications of precipitation:-
It is a convenient method to obtain the desired
solid substances in the form of a fine particles
e.g. precipitation of calcium carbonate.
Precipitation of solid in which impure solids are
usually dissolved in suitable solvents &
One of the important uses of precipitation is
the purification of solids.

25. Purification is also useful to isolate the
products of a reaction during work-up.
Precipitation reactions can be used for making
pigments , removing salts from water in water
treatment, and in classical qualitative inorganic
analysis.
Precipitation reactions are used in the
preparation of salts; in qualitative analysis
reactions; and in the formation of some
sedimentary rocks.

26. Methods Of Precipitation:-
There are three methods.
1) organic solvent precipitation
2) precipitation effected by the change in the PH
of the medium.
3) Double decomposition.

27. 1) Organic solvent precipitation:-
Water insoluble drug cannot be precipitated by
dissolving in water miscible organic solvents
and then adding the organic phase to distilled
water under standard condition.

28. Following are the important factor.
Possible preparation under the sterile
condition.
Subsequent toxicity.
Temperature control
Rate and methods of the phase.
The volume ratio of the organic to the
aqueous phase
Subsequent inherent solvent entrapment

29. 2) Precipitation effected by change in pH
 In this solubility is dependent on pH value
e.g. estradiol suspension can be prepared by
changing the pH of its aqueous solution.

30. 3) Double decomposition:-
It involve only simple chemistry but some of
the physical factors also involved.

31. THANK YOU