For example, in the new application, if you want to add substance A, you don't need to write the preparation method of substance A, because substance A is an existing technology, and if you do, the scope will be narrowed, and it must be completed according to the preparation method of substance A to be considered infringement. What if there are other preparation methods for substance A?
My suggestion is not written in the independent claim, but it can be written in the dependent claim or specification. For example, it is written in the example that this application provides one of the preparation methods for preparing substance A, and the steps are as follows. . . blabla .
When writing in detail, other issues should also be considered: for example, whether substance A is a freely available substance, and whether the preparation method in another application is the only one that can be prepared in the prior art. ..