Solasodine from Solanum plants is a potential raw material for steroid drug manufacture. Acid hydrolysis of the naturally occuring glycosides of solasodine is a major step in production of the aglycone. As part of a detailed study of the hydrolysis of solasodine glycosides, the hydrolysis procedure has been mathematically modelled. Two models are presented and have been used to obtain kinetic data for the reactions at a number of different reaction conditions. The subsequent conversion of solasodine to solasodiene is considered in Part II of this paper; the combined reactions and guidelines for commercial hydrolysis are presented in Part III.