The reaction of hot phenylhydrazine $ \phi-NH-NH_2 $ with aldoses and ketoses yields osazones, f.i.:
We see that glucosazone and fructosazone are identical! The osazones are yellow solids which crystallize well and which serve to identify the oses
Hydrolysis of osazones provides osones, f.i.:
.. whose cold reduction provides the corresponding ketoses:
Whence the passage Aldose → Osazone → Osone → Ketose
Which substance results from the previous reactions on D-galactose?