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A red crystal, it is typically combined with water to create a red liquid that is added to pool water to test pH. When the water is alkaline, the compound colors the water red. When the water is acid, it turns yellow.
To test pH utilizing a test kit: 1. Fill the large comparator with pool water to the 44 mL mark. 2. Add 5 drops Phenol Red (R-0006). Cap and shake to mix. 3. Match the resulting color with the colors on the comparator. Record as pH. 4. If pH is too high, add R-0005, drop by drop. After each drop, count, mix, and compare with color standards until desired pH is matched. See acid demand test treatment tables to continue. 5. If pH is too low, add R-0006, drop by drop. After each drop, count, mix, and compare with color standards until desired pH is matched. See base demand test treatment table to continue.
The pH of human tears, 7.5, is a good goal. Most municipalities allow pH levels between 7.2 and 7.8.