| pH | Constituents |
| 1.9 | CH3COOH (87 ml glacial), HCOOH (25 ml 88%) to 1 L with H2O |
| 2.1 | HCOOH (25 ml 88%) to 1 L with H2O |
| 3.1 | Pyridine (5 ml), CH3COOH (100 ml glacial) to 1 L with H2O |
| 3.5 | Pyridine (5 ml), CH3COOH (50 ml glacial) to 1 L with H2O |
| 4.7 | Pyridine (25 ml), CH3COOH (25 ml glacial) to 1 L with H2O |
| 6.5 | Pyridine (100 ml), CH3COOH (4 ml glacial) to 1 L with H2O |
| 7.9 | 0.03 M NH4HCO3 |
| 8.9 | (NH4)2CO3 (20 g/L solution) |