HC was used as a screening smoke. It is a mixture of grained aluminum, zinc oxide and hexachloroethane (C2Cl16). It has a total obscuring power (TOP) of 2100. It has no physiological action in exposed personnel.
Old Chemical Weapons Reference Guide (1998)
TM 3-300, Ground Chemical Munitions (1956)
TM 9-1904, Ammunition Inspection Guide (1944)