Charcoal (木炭 mùtàn, traditional 木炭)
Hyper-acidity of the stomach causes heartburn and results from an excess of Yin foods, especially meat and dairy produce. The toxins derived from these make gastric secretions.
A very ancient Chinese remedy for this condition is to mix one teaspoonful of charcoal powder with a cup of green tea, straining the sediment off before drinking it. Another recipe is to mix one teaspoonful of charcoal powder with rice milk or any other grain milk, making sure that you strain it before drinking. In either case, the acidity will be very quickly neutralised.