The directions are on the box.
https://www.armandhammer.com/en/for-everything-soda/antacid-soda
Directions
Add ½ teaspoon to ½ (4 oz.) glass of water. (Accurately measure ½ teaspoon.*)
Dissolve completely in water.
Drink mixture every 2 hours, or as directed by a physician.
Refer to ARM & HAMMER Baking Soda package for more detailed instructions before using.
Warnings – See package for complete warnings
Do not administer to children under age 5.
*Do not take more than the following amounts in 24 hours:
Seven ½ teaspoons or three ½ teaspoons if you are over the age of 60.
Do not use the maximum dosage for more than 2 weeks.
Stop and consult a doctor if symptoms last more than 2 weeks.
Stomach Warning:
To avoid serious injury, do not take until powder is completely dissolved. It is very important not to take this product when overfull from food or drink. Consult a doctor if severe stomach pain occurs after taking this product. Stop use and ask a doctor if symptoms last more than 2 weeks.