The document explains sublimation, a process where a solid transitions directly to vapor without becoming liquid, and deposition, which is the reversal where gas transforms to solid. It discusses the advantages and disadvantages of sublimation, including its effectiveness for purification and potential incomplete recovery. Additionally, it highlights iodine and dry ice as examples, and notes that deposition is used industrially, especially in creating thin coatings.

1. Karwan O. Ali
May 2017

2. Outlines
1- What is Sublimation?
2- How substance undergo sublimation?
4- Advantages and disadvantages of sublimation
5- What is Deposition?
6- uses of deposition
3- Iodine is an example of a substance that undergoes sublimation.

3. What is Sublimation
Sublimation is the process where a solid changes from a solid to a vapor
without passing through the liquid state.

4. Sublimation is an endothermic phase transition that occurs at
temperatures and pressures below a substance's triple point in its
phase diagram.
In thermodynamics, the triple point of a substance is the temperature
and pressure at which the three phases (gas, liquid, and solid) coexist
in thermodynamic equilibrium. A phase transition in which a solid is
converted to a gas, without passing though an intermediate liquid
phase.
How substance undergo sublimation?

5. Dry ice" is actually solid, frozen carbon dioxide, which happens to sublimate, or turn
to gas, at a chilly -78.5 °C (-109.3°F). The fog you see is actually a mixture of cold
carbon dioxide gas and cold, humid air, created as the dry ice "melts" it
mean sublimates.
Sublimation
Deposition

6. Iodine is an example of a substance that undergoes sublimation.
 The iodine crystals at the bottom of the outer test tube change
directly to iodine vapor on heating.
When the vapor reaches the cool surface of the inner test
tube, it goes directly from the gaseous to the solid state.
 The outer test tube contains solid iodine that is being
gently heated.
 The inner test tube contains liquid water and ice.

7. Advantages of sublimation
1- The main advantage of sublimation is for purification process.
2- The minimum amount of product is loss.
3- Solvents are not used.
4- Most traces of any solvent in compound are effectively eliminated.
5- when the substance weighs less than 100mg the best method for purification
is sublimation.

8. Disadvantages of sublimation
1. Recovery may not be complete - the fumes may be blown away.
2. Non-sublimable agent may decompose under heat.

9. Desublimation refers to the process in which a gas changes directly to a
solid without going through the liquid state.
Deposition

10. Deposition as a change of state often occurs in nature. For example,
when warm moist air comes into contact with very cold surfaces—such
as the ground or objects on the ground—ice crystals are deposited on
them.

11. Deposition is used widely to create materials in industry, especially to
apply a thin coating to materials used for cutting or shaping. Much
research is ongoing in the field of chemical vapor deposition, especially
in the area of materials used to cover polymers, and finding materials
that are less harmful to the environment.
Uses of deposition

12. References
3- Mohrig, Jerry R. "Techniques in Organic Chemistry." 2010, W.H. Freeman
and Company
1- Fessenden R. J.; Fessenden J. S (2001). Organic laboratory technique. 3rd ed. USA:
Kristine Waller, pp.111-113.
2- Mayo D. W.; Pike R. M.; Forbes D. C (2010). Micro scale Organic Laboratory: With
Multistep and Multiscale Syntheses. 6th ed. John Wiley & Sons, pp. 112 – 113..