| Clue | Source | Date |
|---|---|---|
| Obsolete name for nitric acid (4,6) | ||
| An obsolete name for nitric acid (4,6) | ||
| Water on top of castle is nitric acid! (10) | ||
| An old name for nitric acid | The Times Specialist Sunday | 29 Sep 2019 |
| Nitric acid, old-style | Premier Sunday | 07 Apr 2019 |