Seven Steps of Alchemy

You can share the popular opinion about alchemy as having been the attempt by medieval eccentrics to transmute lead and copper into silver and gold. But it not only about it. The original esoteric study of alchemy involved the idea of spiritual transformation and examined the interrelationships between the natural and supernatural worlds. Alchemy, as a body of secret knowledge, came to be a quest for the secrets of transmuting metals and discovering the Philosopher's Stone - "the physical vehicle for the 'divine spark' necessary to the process of transmutation" (Alchemy 50). Anyway, all that is steeped in mysticism and mystery. You have a choice to considering alchemy as an ancient path of spiritual purification and transformation; and probably you will decipher these mysterious symbols, which can be interpreted simultaneously both at a material and a spiritual level.

From the spiritual point of view, the seven metals of alchemy are said to be one thing at different stages in evolution or the seven steps in the processes of alchemical "transformation". As spiritual process, it can symbolically illustrates the changes and purification processes inside of man. This transformation of matter, in the vessel and the human soul, proceeds in seven stages, which are described in the classical alchemy in a certain order:
1. Calcination
2. Dissolution
3. Separation
4. Conjunction
5. Fermentation
6. Distillation
7. Coagulation

1. Calcination -  represented by Sulfuric Acid, is a destruction of ego and our attachment to material possessions. Calcination is usually a natural humbling process as we are gradually assaulted and overcome by the trials and tribulations of life, though it can be a deliberate surrender of our inherent hubris gained through a variety of spiritual disciplines that ignite the fire of introspection and self-evaluation.
Calcination is working with Fire to burn away mental constructs and reveal a person's true essence.

2. Dissolution  - represented by Iron Oxide or rust, which illustrated the potentially corrosive powers of water on even the hardest of metals. Inwardly this represents a further breaking down of the artificial structures of the psyche and a unifying of the different aspects. Traditionally the approach was such that the initiates conscious minds must let go of control, opening the "floodgates" and generating new energy from the waters held back; again potentially a painful process.
So, Dissolution is working with Water.

3. Separation  - represented by the compound Sodium carbonate, which separates out of water and appears as white soda ash on dry lakebeds. It is the process of the rediscovery of our essence and the reclaiming of dream and visionary "gold" previously rejected by the masculine, rational part of our minds. It is for the most part, a conscious process (that has become conscious through the process of Dissolution), in which we review formerly hidden material and decide what to discard and what to reintegrate into our refined personality. Much of this shadowy material is things we are ashamed of or were taught to hide away from our parents, churches, and schooling. Separation is letting go of the self-inflicted restraints to our true nature, so our true personality can shine through. Working with Air.

4. Conjunction  - symbolized by a Nitrate compound known as cubic-saltpeter or potassium nitrate, or simply salt what was used to separate silver from gold.
It is empowerment of our true selves, the union of both the feminine and masculine sides of our personalities into a new belief system or an intuitive state of consciousness. The Union of opposites can generates the Child, or the alchemical Lesser Stone. After it is achieved, the adept is able to clearly discern what needs to be done to achieve lasting enlightenment, which is union with the Overself.
Working with Earth.

5. Fermentation - represented by Liquor Hepatis (or Balsam of the Soul). The Fermentation phase then begins with the introduction of new life into the product of Conjunction to strengthen it and insure its survival.
Fermentation is the growth of a ferment (bacteria) in organic solutions, such as occurs in the fermenting of milk or wine. During the making of wine, the grapes are "sacrificed" or crushed to release their essences in the juice. Then, putrefaction begins as the juice is allowed to decompose and rot. Next, a white layer of digesting bacteria arises that begins the process of Fermentation. Finally, the new life force “conquers” the original identity of the grape juice and supplants it with a new and higher presence or life. This higher presence is release during the next operation (Distillation), which produces the true Spirit of Wine (its alcohol), which contains the purified essence of grapes.
Figuratively, the Fermentation can be achieved through various activities that include intense prayer, desire for mystical union,or deep meditation etc.
Working with Sulfur.

6. Distillation  - represented by Black Pulvis Solaris. It is marked with the symbol for silver and the Moon.
It is a key process on all levels of alchemy.
In practical terms, this involves heating a substance until it boils, and then condensing the vapors into a purified liquid. It increase its concentration and purity of substance, such as takes place in the distilling of wine to make brandy. In personal level, the agitation and sublimation of psychic forces is necessary to ensure that no impurities from the lower personality are incorporated into the next and final process. Many introspective techniques can be applied to raise the content of the psyche to the highest level possible. It is the purification of the unborn Self. Distillation is described in the Emerald Tablet as: It rises from Earth to Heaven and descends again to Earth, thereby combining within Itself the powers of both the Above and the Below. 
Working with Mercury.

7. Coagulation  - represented by Gold or a compound called Red Pulvis Solaris, which name means "Powder of The Sun". The seventh and final operation in alchemy.
Chemically, Coagulation is the precipitation or sublimation of the purified ferment from Distillation.
It is a higher application of the elements Air and Earth, and it results in a union of spirit with matter. At this stage, it working with the other, resurrected Salt.
Coagulation incarnates and releases the Ultima Materia of the soul, the Astral Body, which the alchemists also referred to it as the Philosopher's Stone. Using this magical Stone, the alchemists believed they could exist on all levels of reality. You can consider it as some supreme value or the living wisdom and knowledge of Truth. The seeker connect here his basic self with the Higher Self and become the Whole Person.

Certainly, it's a very short description. I will not show now the comparison with other methods of transformation (Indian tantra or Chinese taoism, for example) but we can clearly see that Alchemy is a mystical method of self-perfection. And this long quest from ordinary to noble metals we can consider as the another search of the way to liberation and supreme freedom.