Hydrazine dihydrochloride is widely used as a reducing agent in various chemical reactions, particularly in organic synthesis. It is employed in the preparation of pharmaceuticals, where it helps in the reduction of nitro compounds to amines, a crucial step in drug manufacturing. Additionally, it is used in the production of agrochemicals, aiding in the synthesis of herbicides and pesticides.

In analytical chemistry, hydrazine dihydrochloride serves as a reagent for the detection and quantification of carbonyl compounds, such as aldehydes and ketones. It is also utilized in the purification of metals, where it acts as a reducing agent to remove impurities and oxides from metal surfaces.

Furthermore, hydrazine dihydrochloride finds application in the synthesis of polymers and resins, where it contributes to the cross-linking process, enhancing the material's strength and durability. Its role in the preparation of foaming agents for plastics and rubber is also notable, improving the lightweight and insulating properties of these materials.

In the field of biochemistry, it is used in the modification of proteins and peptides, aiding in the study of their structure and function. Overall, hydrazine dihydrochloride is a versatile chemical with significant applications across various industries.