Baking Soda is safe and effective as an antacid to alleviate heartburn, sour stomach and/or acid indigestion. Just mix a teaspoon in a glass of warm water and it will get to work.
One of my packets of Baking Soda (Bicarbonate of Soda) had the following recommendations regarding dosage for oral use as an antacid..
Adults, the elderly and children over the age of 12, dissolve one level 5ml spoonful of powder in warm water. Take up to 4 times a day.
Do not take baking soda internally if you have low calcium levels, reduced stomach acid, congestive heart failure, kidney damage or cirrhosis of the liver, high blood pressure, too alkaline body fluids, if taking any steroid medicine or if pregnant or breast feeding except on a doctors advice. Not recommended for children under the age of 12 years of age.