A quaternary compound:
  | Oxynitric acid | 24·5 |
| |
A quinquenary compound:
| | ||
| | Nitrous acid | 29·5 |
| |
A sextenary compound:
 | Alcohol | 23·5 |
 |
These symbols are sufficient to give the reader an idea of the notions entertained by Dalton respecting the nature of compounds. Water is a compound of one atom oxygen and one atom hydrogen as is obvious from the symbol
. Its weight 7·5 is that of an atom of oxygen and an atom of hydrogen united together. In the same way carbonic oxide is a compound of one atom oxygen and one atom carbon. Its symbol is