Chemistry saving lives: using First World War Hypo helmets to avoid chlorine poisoning

A Hypo helmet is a fabric hood soaked with an aqueous solution of two sodium salts for the detoxication of chlorine that was developed during the First World War. Herein, we report on a lecture, developed for non-chemistry majors that used the Hypo helmet to highlight the physical and chemical properties of chlorine. The lecture consisted of the following three components: (1) a brief introduction to the First World War (the Chemists’ War), (2) video demonstrations of the generation of chlorine by mixing bleaching powder and hydrochloric acid and the detoxication of chlorine using a dummy Hypo helmet, and (3) students’ written impressions of the lecture. The students’ written impressions revealed two things: the lecture on chlorine and the Hypo helmet was well received, and most of the students (71 %, N = 82) did not know that chlorine was used as a poisonous gas during the First World War.