Germany used chlorine as a chemical weapon in the First World War. They used it at the Second Battle of Ypres in 1915. According to soldiers, which were present at the battle, the chlorine smelled like a mixture of pepper and pineapple. It also tasted metallic and stung the back of the throat and chest. Chlorine reacts with water in the mucosa of the lungs to form hydrochloric acid. Hydrochloric acid will destroy living tissue. It often kills. Gas masks with activated charcoal or other filters can protect the respiratory system. This makes chlorine gas much less deadly than other chemical weapons. German scientist Fritz Haber of the Kaiser Wilhelm Institute in Berlin was the first to use it. Together with IG Farben, he developed methods of how to use chlorine gas against an entrenched enemy. Chlorine is heavier than air, so it will stay in the trenches. On 22nd April, 1915, German forces attacked the French army. With of chlorine, they only killed about 1.200 French soldiers. For this reason, chlorine was soon replaced with the more deadly phosgene and mustard gas.