Fang Ling began to try to concentrate the sun's fire energy between his palms, slowly releasing it, and the fire energy floated on the palms, forming an internal fire force.

Fang Ling secretly rejoiced, he didn't expect that this internal fire could really release heat, and if it was combined with the firewood below, it would definitely be able to greatly advance the time for alchemy.

However, he was suddenly stunned again, and realized that this idea was wrong, that is, fire.

Xiao Xue said that in the art of alchemy, heat is an extremely important part, and if the temperature is too high or too low, it will lead to the failure of alchemy, so it is necessary to open the lid to dissipate heat and stir when the temperature is too high, and increase the heat when the temperature is too low, and use a pair of hands to perceive the change in temperature, so as to control it.

However, once an internal fire is added, it becomes difficult to grasp the temperature, and it can even be said that it is impossible to accurately control the temperature at all. If you use only one hand to release the internal fire, the temperature will also become unbalanced.

However, Fang Ling felt a little strange, it stands to reason that the addition of this internal fire can greatly increase the speed and effectiveness of alchemy, then, this internal fire is probably not so simple to join.

Fang Ling's eyebrows were deeply locked, he had been wise since he was a child, and no problem could be stumped, although this alchemy technique was just getting started, but the words he heard from Xiao Xue and the alchemy in the past few months had given him a lot of understanding.

So, without any guidance, Fang Ling studied and groped at the same time, and gradually found a clue.

The so-called internal fire refining is not simply to release the qi of heaven and earth to increase the temperature, but to cross the qi of heaven and earth into the ding, so that it forms another space in the ding, which is the real mystery of the internal fire. Therefore, the fire of the inner fire is not the real temperature, but the transmission of energy.

Fang Ling had no master, and after comprehending this, he suddenly had an epiphany, if Xiao Xue was here at this time, I am afraid that he would regret passing on this alchemy to him, just such a comprehension made Fang Ling surpass the alchemy of the disciples of the Qi Storage Realm Immortal Sect to a certain extent, and it can even be said that it has reached an unmatchable level.

As a result, the internal fire rushes into the tripod along the wall of the medicine tripod, forming a layer of space in the tripod, and through the continuous heating of the external fire, the medicinal materials absorb the qi of heaven and earth.

And in the place where Fang Ling couldn't see, inside the medicine tripod, with the influx of heaven and earth qi in waves, the strange lines on the tripod wall also flashed with circles of light, sometimes bright and sometimes dark.

Time passed minute by minute, Fang Ling concentrated on refining the elixir, without a little distraction, the qi of heaven and earth in the body gushed out along the breath, and at the same time, the technique of melting the sun and the moon was running in the body, constantly releasing the absorbed qi of heaven and earth, this alchemy was like practicing.

By the next morning, after about 6 hours, Fang Ling had finally refined the Hun Tie Dan, which was half the time written on the Dan Fang.

This Hun Tie Pill is like iron, extremely dark, but there is a layer of light on the surface, although it is still a little rough, but this pill containing the qi of heaven and earth is very different from Peiyuan Dan.

In fact, the fifth-level Dan Fang and the first-two, three-and-four-level Dan Fang refined by the internal fire are very different in terms of efficacy, because they absorb the cultivator's Heaven and Earth Qi, and these Heaven and Earth Qi are constantly refined under the tempering of the external fire, forming the refined Heaven and Earth Qi.