Phthalhydrazide is primarily used in the synthesis of various organic compounds, particularly in the production of dyes and pigments. It serves as a key intermediate in the creation of colorants for textiles, plastics, and inks, contributing to vibrant and stable colors. Additionally, it is utilized in the preparation of pharmaceuticals, where it acts as a building block for certain active ingredients. In analytical chemistry, phthalhydrazide is employed as a reagent for the detection and quantification of specific substances, leveraging its reactive properties. Its role in these applications underscores its importance in both industrial and scientific contexts.