Essence of Fire

The Chinese also related the Macrocosm of the Universe to the human body in the Microcosm of the world. For example, they identified the heart with the essence of fire, the liver with the essence of wood, the lungs with the essence of metal, the stomach with the essence of earth, and the kidneys with the essence of water. 

Then the heat, having opened up the substance, and animated its hitherto atrophied nature, causes the material parts to be penetrated by a Spiritual Essence. This, itself, is of a fiery nature, and although it may appear to be different under its different forms, it is none the less one and one only. As Hierotheos says, "The Essence of Fire is one and the same everywhere but if thou distribute it in (many) materials, and kindle it (in many flames) it may seem to thee, perhaps, to be as many different (fires) as it has undergone divisions and if it is divided, the division lies (only) in the materials and not in the Essence for the number of the flames Is (exactly) as great as (that of) the divisions of the materials, but in all the divisions thou canst see the self-same Fire." And this penetration or spiritualising is that oft-mentioned volatilising of the Fixed. 

In later years the term sulphureous was synonymous with inflammable. The early alchemists represented fire by an equilateral triangle. Fire, or heat, was known to effect the decomposition of most substances it was supposed to penetrate into them and split them up. An equilateral triangle has the most acute angles of any regular two dimensional figure. So it was chosen to represent fire. As the spiritual sulphur represented the essence of fire or inflammability it, too, was represented by an equilateral triangle, but with the sign of the cross beneath it, thus... 

Under the Greek notion of the four essential elements, a combustible object must contain within itself some essence of fire. When that object burns, it releases that essence. For many years, that essence was believed to be sulfur, but in the 17th century sulfur was replaced by a hypothetical new substance. 

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