The time it takes for antacids to dissolve in cold water can vary based on several factors, including the type of antacid, the temperature of the water, the size of the antacid tablets, and how much water is used. Generally, antacids are designed to dissolve relatively quickly, but in cold water, the process may take longer than in warm water.
For most over-the-counter antacid tablets, you might expect them to start dissolving within a few minutes, but complete dissolution could take anywhere from 5 to 15 minutes or more. If you're using powdered forms of antacid, they will typically dissolve more quickly than tablets.
For the best results, refer to the specific instructions on the antacid packaging, as they may provide more detailed guidance on dissolution time and method.