Making Military-Banned, But Highly Effective HC Smoke From The 40's

The AN-M8 smoke grenade employs a hexachloroethane (HC) smoke mixture, which consists of:

Hexachloroethane (C₂Cl₆): Approximately 46.7% of the mixture, serving as the primary chlorine source.
Zinc Oxide (ZnO): Approximately 46.7%, acting as a reactant to form zinc chloride.
Granular Aluminum: About 6%, which facilitates the exothermic reaction and aids in ignition.

This mixture is ignited by a pyrotechnic starter composition, typically including materials like silicon, potassium nitrate, charcoal, iron oxide, cellulose nitrate, and acetone to initiate the reaction.
Chemical Reaction
Upon ignition, the mixture undergoes an exothermic, self-sustaining reaction. The primary reaction can be summarized as follows:

Hexachloroethane reacts with zinc oxide and aluminum, producing zinc chloride (ZnCl₂) as the main smoke-generating component.
Additional byproducts include zinc oxychlorides, hydrochloric acid (HCl), and trace amounts of carbon monoxide (CO), phosgene (COCl₂), chlorine (Cl₂), and chlorinated organic compounds like tetrachloromethane, tetrachloroethylene, and hexachlorobenzene.

The zinc chloride forms as a hot vapor, which, upon cooling, nucleates into fine aerosol particles. These particles are highly hygroscopic, absorbing moisture from the air to create a dense, grey-white smoke that scatters light effectively, providing obscuration. The particle sizes typically range from 0.4 to 2.8 µm, with mass-median diameters of 0.77 to 1.05 µm, making a significant portion respirable.
Properties and Effects

Appearance: The smoke is grey-white, composed of tiny zinc chloride particles that create a dense cloud, ideal for concealing troop movements or marking positions.
Toxicity: The smoke is toxic, primarily due to:

Hydrochloric acid: Strongly acidic, it causes irritation and lesions in the mucous membranes of the upper airways.
Zinc chloride: Its thermal reaction with water and fine particle size can damage the lower airways, potentially leading to delayed pulmonary effects.
Trace compounds: Phosgene, carbon monoxide, and chlorinated organics contribute to toxicity, posing risks in high concentrations or prolonged exposure.

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