Editing Chemical weapons in World War I (section)

===1915: More deadly gases===
[[File:American Red Cross and Medical Research Committee, "An Atlas of Gas Poisoning" plate I (square).jpg|thumb|Microscopic section of human lung from phosgene shell poisoning from ''An Atlas of Gas Poisoning'', 1918]]

The deficiencies of chlorine were overcome with the introduction of [[phosgene]], which was prepared by a group of French chemists led by [[Victor Grignard]] and first used by France in 1915.<ref>{{Cite book
 | first=Mary Jo | last=Nye | year=1999 | page=193
 | title=Before big science: the pursuit of modern chemistry and physics, 1800–1940 | publisher=Harvard University Press
 | isbn=0-674-06382-1 }}</ref> Colourless and having an odour likened to "mouldy hay," phosgene was difficult to detect, making it a more effective weapon. Phosgene was sometimes used on its own, but was more often used mixed with an equal volume of chlorine, with the chlorine helping to spread the denser phosgene.<ref name="cbwinfo">{{Cite web | author=Staff | year=2004 | url=http://cbwinfo.com/Chemical/Pulmonary/CG.shtml | title=Choking Agent: CG | publisher=CBWInfo | access-date=30 July 2007 | url-status=dead | archive-url=https://web.archive.org/web/20070814054640/http://cbwinfo.com/Chemical/Pulmonary/CG.shtml | archive-date=14 August 2007 }}</ref> The Allies called this combination ''White Star'' after the marking painted on shells containing the mixture.<ref>{{Cite book
 | author=Kiester, Edwin | title=An Incomplete History of World War I
 | page=74 | volume=1 | publisher=Murdoch Books | year=2007
 | isbn=978-1-74045-970-9 |display-authors=etal}}</ref> German phosgene came in the form of diphosgene, codenamed ''Grün Kreuz'' (Green cross). This was less effective than its allied counterpart, being less toxic and slower to evaporate, but was easier to handle in shell manufacture early in the war.{{sfn|Haber|2002|pp=86-87}}

Phosgene was a potent killing agent, deadlier than chlorine. It had a potential drawback in that some of the symptoms of exposure took 24 hours or more to manifest. This meant that the victims were initially still capable of putting up a fight; this could also mean that apparently fit troops would be incapacitated by the effects of the gas on the following day.<ref>{{Cite web | author=Staff | date=22 February 2006 | url=http://www.bt.cdc.gov/agent/phosgene/basics/facts.asp | title=Facts About Phosgene | publisher=CDC | access-date=23 May 2008 | url-status=dead | archive-url=https://web.archive.org/web/20030417022453/http://www.bt.cdc.gov/agent/phosgene/basics/facts.asp | archive-date=17 April 2003 }}</ref>

In the first combined chlorine–phosgene attack by Germany, against British troops at [[Wieltje]] near Ypres, Belgium on 19 December 1915, 88 tons of the gas were released from cylinders causing 1069 casualties and 69 deaths.<ref name="cbwinfo" /> The British P gas helmet, issued at the time, was impregnated with [[sodium phenolate]] and partially effective against phosgene. The modified [[PH helmet|PH Gas Helmet]], which was impregnated with phenate hexamine and [[hexamethylene tetramine]] (urotropine) to improve the protection against phosgene, was issued in January 1916.<ref name="cbwinfo" /><ref>{{Cite book
 | first=Ludwig Fritz | last=Haber | year=1986
 | title=The poisonous cloud: chemical warfare in the First World War | page=70 | publisher=Oxford University Press
 | isbn=0-19-858142-4 }}</ref><ref>{{Cite book
 | first=Pradyot | last=Patnaik | year=2007
 | title=A comprehensive guide to the hazardous properties of chemical substances | page=85 | edition=3rd
 | publisher=Wiley-Interscience | isbn=978-0-471-71458-3 }}</ref>

Around 36,600 tons of phosgene were manufactured during the war, out of a total of 190,000 tons for all [[chemical weapon]]s, making it second only to chlorine (93,800 tons) in the quantity manufactured:<ref>{{cite web|url=http://www.mitretek.org/mission/envene/chemical/history/ww1.html |title=A Short History of Chemical Warfare During World War I |access-date=18 September 2013 |archive-url=https://web.archive.org/web/19991023051711/http://www.mitretek.org/mission/envene/chemical/history/ww1.html |archive-date=23 October 1999 }}</ref>

* Germany 18,100 tons
* France 15,700 tons
* United Kingdom 1,400 tons (also used French stocks)
* United States 1,400 tons (also used French stocks)