Gu Ji's first reaction upon seeing it was to think of chlorine gas!
Chlorine gas is a yellow-green gas at room temperature and pressure, with a strong pungent odor and is extremely toxic. It is suffocating and denser than air.
In modern industry, it is a very common chemical raw material, mainly used in the production of plastics, synthetic fibers, dyes, pesticides, disinfectants, bleaches, and various chlorides.
But in the early 19th century, besides the chemical field, it was also used on the battlefield.
This is the reason why the security personnel reacted so violently upon hearing the word "chlorine gas".
The first appearance of chlorine gas on the battlefield was during the First World War.
