The ironvitriol was used to shorten producing time and the rotten meat was for the tofu's smell.
青矾用于缩短制作时间，而腐烂的肉类则会让豆腐变得更臭。
2
The powdery polyphosphate ferric sulfate was prepared from ironvitriol, the byproduct in titanium pigment production by sulfuric acid process, and complex oxidant.