Preparation of potassium ferrocyanide
Those who are good at making potassium ferrocyanide in ancient times, observe their materials and methods, and pay close attention to them.

Those who make this, seek good materials first. Those who take the essence of iron, crushed into crumbs, its quality is pure and free of impurities, which is the basic thing. Also prepare yellow blood salts, choose the color and shape of the whole, in order to ensure its purity.

The method is to put iron filings in the kettle first, slow down the fire and bake it, so that it is dry and sexual. Then throw yellow blood salts into it, and mix it evenly. The firepower needs to be adjusted, and the fire should be softened at the beginning, so that the two will gradually melt. If the fire is slightly fierce, then it should not be too intense, for fear of damaging its quality. Seek changes in the kettle, and wait for it to be uniform and transparent, before you can obtain the method.

During this period, those who are responsible for fire must be careful. Observing the fire, observing the shape of things, and the difference of a millimeter is all about success or failure. When it is completed, it is cold and collected, and placed in a secret vessel to prevent it from changing. It is made of potassium ferrocyanide, which can be used in various karma, and its making techniques, although complex, it cannot be ignored. This wisdom of the ancients has gathered, and future generations should carry it forward.