Mannonic acid sodium salt

An unusual classification of hexonic acids described by Levene21 was based on the differences in optical rotation between the free acid and its sodium salt. For example, in the D-gluconic acid series the sodium salt has the more positive rotation whereas in the D-mannonic acid group the reverse is the case and the acid has the more positive rotation. In comparison with these results glucosaminic acid was found to have a rotation of —15° (and its sodium salt +1.3°) and therefore these derivatives were in conformity with the D-gluconic acid series. 

---