What Magnesium Sulfate, Sodium Bicarbonate and Tartaric Acid is used for: It is used for treating acid indigestion, heartburn, sour stomach, and constipation. Magnesium Hydroxide is an antacid. It works by neutralizing the acid in the stomach and by stimulating the bowels to move. How to take Magnesium Sulfate, Sodium Bicarbonate and Tartaric Acid: Adults: For upset stomach, heartburn, indigestion, feeling sick: One or two teaspoonfuls. For constipation: Take two teaspoonfuls before breakfast or at bedtime Children of 3 years and over: Reduce the amount above according to size and age. Check the inner seal is not broken before first use. If it is, do not use the powder. Use a dry spoon to measure. Mix the amount recommended below with a glass of water and drink the solution, before it stops fizzing.