This section is from the book "A Treatise On Beverages or The Complete Practical Bottler", by Charles Herman Sulz. Also available from Amazon: A Treatise On Beverages.
1. Sulphuric acid is found by adding a few drops of solution of nitrate of baryta. If sulphuric acid be present the water will show a milky appearance and the clouds remain at the top, or are uniformly diffused. If the clouds sink to the bottom it indicates sulphate of lime. 2. On addition of chlorbaryum a precipitate of sulphate of baryta occurs, if sulphuric acid be present.
In testing for acids generally, dip a piece of blue litmus paper into the water. If it turns red the presence of free acids may be accepted.
In well-water are very frequently traces of phosphoric acid or phosphates. Small traces are without any disadvantage; however, mineral waters containing iron cannot be made with it, and if the phosphoric acid or its phosphates come in contact with lime or magnesia salts, which mineral waters most invariably contain, it causes turbidity. To detect phosphoric acid acidify a sample of water Strongly with nitric acid, add some molybdate of ammonia and bring to a boil in a porcelain vessel. If phosphoric acid be present the water assumes first a yellow color and then forms a yellow precipitate. If the yellowish color of the water looks pale, not distinct yellow, the phosphoric acid is present in but trifling traces.
To make a test for urine in potable water, add a solution of nitrate of silver. A brown color indicates pollution with urine (Leffmann).