According to T 12/81 (OJ 1982, 296), an end product resulting from the reaction of a specific pair of starting substances may be seen as a novel selection for patent purposes if its preparation requires using entities from two classes of starting substances given in two lists of some length. This criterion has been applied to mixtures of two substances, selected from two lists (T 401/94) and confirmed in subsequent decisions (T 211/93 and T 175/86) (cf. T 806/02).
In T 401/94 the board again adopted one of the criteria for selection inventions laid down in decision T 12/81 (OJ 1982, 296), namely, that if two classes of starting substances were required to prepare the end products, and examples of individual entities in each class were given in two lists of some length, the substance resulting from the reaction of a specific pair from the two lists could be regarded for patent purposes as a selection and, hence, as new. The board applied the above criterion to the case in question and stated that, although T 12/81 concerned the synthesis of a chemical product, and the case in question involved the preparation of a mixture, the claimed subject-matter was defined on the basis of two chemical entities, each of which had been selected from a list of compounds. Hence the criteria defined in T 12/81 were applicable here too. By analogy, the board held that, in this case, the claimed composition had to be viewed as a selection, and therefore as novel, as it corresponded to a specific combination of constituents, each of which had been selected from a relatively long list. The board therefore concluded that there had been no implicit disclosure of the mixture of these constituents.
In T 366/96 the board held that if, when selecting two components of a composition from two known lists of possible ingredients, a skilled person had, as soon as one component was taken from the first list, no choice in selecting the second component from the second list in view of compelling technical necessities which made the particular second component mandatory, then this could not be considered to be a "twofold" selection which could render the resulting combination novel.