In the event that any property described in paragraph (6) of subdivision (a) of Section 214 shall have been used solely for charitable or hospital purposes for a minimum period of 30 years, the “welfare exemption” granted by Section 214 shall extend to such property irrespective of any reversionary provisions in the title of the property respecting liquidation, dissolution or abandonment, if the ownership, operation, use and dedication of the property are otherwise within the purview of Section 214.