Britain used a range of poison gases, originally chlorine and later phosgene, diphosgene and mustard gas. They also used relatively small amounts of the irritant gases chloromethyl chloroformate, chloropicrin, bromacetone and ethyl iodoacetate. Gases were frequently mixed, for example "white star" was the name given to a mixture of equal volumes of chlorine and phosgene, the chlorine helping to spread the denser but more toxic phosgene. Despite the technical developments, chemical weapons suffered from diminishing effectiveness as the war progressed because of the protective equipment and training which the use engendered on both sides. See Use of poison gas in World War I.