Why the shape of pycnometer cap is conical?

The conical shape of a pycnometer cap is designed to minimize the amount of air trapped within the cap when it is placed on the pycnometer. This helps ensure accurate measurements of the liquid or solid substance being measured, as any trapped air could affect the density readings. The conical shape also allows for a secure and tight seal on the pycnometer, preventing any leakage or evaporation of the substance inside. Additionally, the conical shape facilitates easy handling and placement of the cap on the pycnometer, making it more user-friendly in laboratory settings.