Asubcutaneous injection in the hypodermal or subcutaneous tissue. based on structures found in the hypodermis and not in the epidermis, why is this a preferred area for administering an injection?

Subcutaneous area of the skin is the area called the hypodermis. The hypodermis is the subcutis area where tissues are present but above the muscles. Subcutaneous injection is preferred than injecting through veins when medicines should be absorbed by the body slowly. 

Boyle's law

Boyle's law is named after Robert Boyle, who first stated it in 1662. Boyle's law states that if temperature is held constant, volume and pressure have an inverse relationship; that is, as volume increases, pressure decreases, according to the University of California, Davis' Chem Wiki