From The Peoples’ Pharmacy site, quoting a Gastroenterology article:
“Some people selected doses of bicarbonate that would result in several hundred milliliters of gas release within 3 min; it seems likely that such injudicious ingestion of sodium bicarbonate, if taken when the stomach was distended with air, food, and liquid, could be an important factor in spontaneous gastric rupture.”
One study I posted described 1/8 of a teaspoon, taken three times a day, with meals.