T 0990/96 (Erythro-compounds/NOVARTIS) du 12.02.1998

1. It is common practice for a person skilled in the art of preparative organic chemistry to (further) purify a compound obtained in a particular chemical manufacturing process according to the prevailing needs and requirements. Since, as a rule, conventional methods for the purification of low molecular organic compounds are within his common general knowledge, a document disclosing a low molecular chemical compound and its manufacture makes normally available this compound to the public in the sense of Article 54 EPC in all desired grades of purity (no. 7 of the reasons for the decision).

2. If a party alleges that this general rule would not be applicable in a particular case, then the burden of proving the existence of such an exceptional situation, e.g. of a situation where all prior attempts to achieve a particular degree of purity by conventional purification processes have failed, lies with the party who alleges such a situation (no. 8 of the reasons for the decision).