Southern symbolism (and hence the phoenix symbolism in alchemy) deals with purity, renewal, strength, health, and the present moment in time.
Fire in alchemy is a symbol of transformation, purification, life, creation/creativity, consumption.
Much like the fire, the sun’s connection to the phoenix in alchemical practice is akin to the cycle of time and cycles of life. It’s also symbolic of clarity, illumination, immortality and expression.
The summer season in alchemy is the same for almost every other cultural wisdom. It equates to growth, rejuvenation of the earth, continuation of life, and the symbolic celebration of the strength of the sun after being weakened through winter.
Alchemy is a practice that incorporates physical, mental, mythical. Red sulfur and phoenix energy would be simultaneously invoked in ceremonies intended to influence the universal principle of life. The element of sulfur in alchemy is synonymous with the animus (the soul), and is a powerful representative of existence.