Phenylguanidine carbonate salt is primarily used in organic synthesis as a reagent or intermediate. It plays a role in the preparation of various pharmaceutical compounds, particularly those involving guanidine derivatives. Its application extends to the development of biologically active molecules, where it acts as a building block for drugs targeting neurological or cardiovascular conditions. Additionally, it is utilized in the synthesis of dyes and pigments, contributing to the production of colorants for industrial purposes. In research, it serves as a useful compound for studying chemical reactions and mechanisms involving guanidine groups.