Blisters as Weapons of War: The Vesicants of World War I

A staged exhibition depicting the importance of a soldier carrying and wearing his gas mask. From Frank J. Mackey, Forward—March! A Photographic Record of America in the World War and Post War Social Upheaval (Chicago: Disabled American Veterans of the World War, Department of Rehabilitation, 1937), p. 106

By Joel A. Vilensky and Pandy R. Sinish

In World War I two vesicant (blister-causing) compounds, mustard gas and lewisite, received much notoriety for their toxicity. Lewisite in particular was hailed as what would now be called a “weapon of mass destruction.” Whereas mustard was discovered some 90 years earlier, lewisite, the “dew of death,” was developed primarily during the war. Both the Allies and the Central Powers pursued research on these compounds, and various countries continued to produce them throughout most of the 20th century—and sometimes to use them. But on the Allied side during World War I the United States led the way in producing these vesicant agents in massive quantities.

Resorting to Gas

Although poison agents were used in combat before World War I, that is the war most associated with the use of poisons as weapons. Gas was deployed in response to the stalemate reached by early 1915, as both the Allies and the Central Powers realized that their own high-explosive artillery shells were ineffective at dislodging soldiers from their defensive trenches, and that opposing machine guns effectively prevented offensive actions without devastating losses. The belligerents thus sought a weapon to drive their opponents from the relative safety of their trenches. Poison gas became that weapon.

France had actually initiated plans to use tear gas, but the German forces used chlorine first, on 22 April 1915. The man who designed the chlorine attack was the German chemist Fritz Haber, director of the Kaiser Wilhelm Institute for Physical Chemistry in Dahlem, near Berlin, and head of the German gas program. Haber was then known for the process he had developed with Carl Bosch of BASF in 1910, of fixing nitrogen from the atmosphere for use in fertilizer, for which the two would win the Nobel Prize in 1918.

The German army’s initial use of chlorine succeeded, but the Allies rapidly developed gas masks, rendering chlorine attacks much less effective. They also began using chlorine against German troops. The Germans then retaliated with a more toxic agent, phosgene, on 19 December 1915. But the Allies again quickly developed protective gas masks and retaliated with the same agent. Thus gas was not proving to be the decisive weapon the German High Command had envisioned, and they were on the lookout for a new one. Mustard seemed a promising candidate.

The History of Mustard Gas

Mustard, a liquid that is vaporized to produce a battlefield agent, is chemically 2,2'-dichlorodiethyl sulfide. Probably the first to produce mustard was César-Mansuète Despretz, a Belgium-born chemist and physicist who on combining ethylene and sulfur chloride in 1822 observed the synthesis of a foul-smelling liquid. Similarly, Alfred Riche, a French chemist and colleague of Auguste Cahours, produced it in 1854 by reacting chlorine with ethyl sulfide. Slightly later, in 1860, the British chemist Frederick Guthrie bubbled ethylene through sulfur dichloride to produce a liquid with “a not unpleasant but indescribable smell; its taste is intensely sweet and pungent.” Furthermore, he observed in a footnote, “A drop placed beneath the tongue destroys the epidermis and causes a soreness which lasts for days” (Guthrie, 1860). Also in 1860 the German chemist Albert Niemann, best known for isolating cocaine from the coca plant leaf, described mustard’s vesicant properties: “[T]he minutest trace which may accidentally come in contact with any portion of the skin, though at first it causes no pain, produces in the course of a few hours, a reddening and on the following day, a severe blister which suppurates for a long time and is very difficult to heal” (Niemann, 1860).

The renowned 19th-century German chemist Victor Meyer was the first to characterize the compound definitely, in 1886. Meyer was working in his Göttingen laboratory with ethyl chlorohydrin, which he combined with sodium sulfide to produce the compound thiodiglycol.

Thiodiglycol was then chlorinated with phosphorous dichloride to produce mustard. Meyer’s assistant was seriously injured by the final product. Meyer wondered whether his assistant’s blisters and conjunctivitis might be the result of a mental problem instead, because there was nothing in mustard’s precursors to suggest it would be so toxic. Accordingly, Meyer decided to have the product tested further at a medical school, on rabbits. The rabbits exposed to the vapors developed conjunctivitis and then died. Meyer wrote: “The intended work with this chloride was not continued—on account of the extremely poisonous qualities of the compound. It is very striking that this apparently harmless substance . . . should exert a specific toxic effect. Its chemical properties would never lead one to expect its aggressive properties.”

No further published work exists for this compound until 1912, when the British-born chemist Hans T. Clarke, then studying under Emil Fischer in Berlin, improved Meyer’s process by substituting hydrochloric acid for phosphorous chloride as the chlorinating agent. When a flask containing mustard broke, Clarke suffered burns on his leg and consequently was hospitalized for nearly two months. He later made a report on his injuries to the German Chemical Society. A letter he wrote in 1947 describes the accident and his suspicion that the report spurred German use of this agent in World War I. (For more on Meyer and Clarke, see Senior [1958].)

The Germans Use Mustard

Two German chemists, W. Lommel at Bayer and Wilhelm Steinkopf, who worked under Haber at the Kaiser Wilhelm Institute, had advocated the use of mustard gas in the war as early as 1916. The German name for mustard, “Lost,” was formed from the first two letters of their last names. Haber also advocated its use—but only if the war could be won in a year, because he presciently feared massive Allied retaliation in kind.

All German production of mustard was based on the process developed by Meyer and modified by Clarke using ethylene chlorohydrin as the precursor compound. German companies had ample facilities to make this compound because it was manufactured on a large scale for use in the German dye industry. The Allies, on the contrary, although they quickly identified mustard’s chemical formula, did not have a strong dye industry and therefore were not ready to manufacture chlorohydrin in large quantities. They did not retaliate with mustard until almost a year after Germany’s first use: the French in June 1918, and the British not until September of that year, shortly before the war ended in November.

During that time massive, similar research and development efforts were undertaken in England, France, and the United States. Here we will discuss the U.S. effort primarily, because by the end of the war the United States was producing 30 tons of mustard per day—more than England, France, and Germany combined.

Scaling Up Mustard in the United States

The U.S. effort to produce mustard gas in large quantities was headed by an unsung hero of American chemical prowess: Frank M. Dorsey. When the war broke out, Dorsey was a chemical engineer at the National Lamps Works Company, a division of the General Electric Company in a suburb of Cleveland, Ohio. Once the United States declared war, Dorsey became involved with engineers from the nearby National Carbon Company in the design and production of gas masks for American soldiers (the National Carbon Company engineers were consulted because of their knowledge of charcoal, the filtering agent used in the masks). This led to the militarization of some of the engineers who worked on this project: Mr. Dorsey became Colonel Dorsey and head of the Development Division of the Chemical Warfare Service (CWS), which was initially organized under the Bureau of Mines but transferred to the U.S. Army in June 1918.

New poison gases were first studied at the CWS Research Division on the grounds of American University—the American University Experimental Station, or AUES—in Washington, D.C., which was set up in July 1917. Gases considered effective for battlefield use were then assigned to Dorsey’s division. Dorsey’s job was to find ways to scale up the small-scale production techniques developed in Washington so as to produce the agents in the thousands of tons necessary for use in war. The job of developing processes to manufacture mustard had actually been given to teams both in England and at the AUES. Sir William Pope, a well-known Cambridge University professor of chemistry, was primarily responsible for the English effort; he sent a cable to the CWS announcing the success of his technique in January 1918. In the United States, James Bryant Conant, a former Harvard University chemist now employed by the CWS, developed the same process virtually simultaneously: Pope’s cable arrived just as Conant was preparing to announce his own success. Both used essentially the same process as those used earlier by the 19th-century chemists; sulfur chloride and ethylene gas were the raw materials.

The project now fell to Dorsey, who established a small experimental mustard plant in Cleveland. In solving the problem of scaling up, he faced three challenges: he had to produce large quantities of ethylene efficiently; to design appropriate equipment to facilitate the absorption of ethylene by sulfur chloride; and to develop purification techniques.

To solve the first problem, Dorsey’s crew developed an ethylene generator—the Dorsey ethylene furnace—that used kaolin (clay) as a catalyst to produce ethylene from alcohol. Once perfected, 40 of these units were installed at Edgewood Arsenal in Maryland, enabling the United States to produce 30 tons of mustard per day by the time the armistice was signed.

To solve the second problem, Dorsey’s unit developed a procedure in which dry ethylene gas was reacted with the sulfur chloride until absorption stopped. This procedure involved introducing steam as well as alcohol into the reaction, facilitating much better temperature control (for efficient ethylene absorption the reaction had to be kept at 131–140°F). A one-ton reactor based on this technique was designed in Cleveland for the mustard operation at Edgewood. For the third problem, Dorsey developed a procedure for flash-still distillation.

In August 1918 Dorsey’s crew worked on an improved mustard process that permitted manufacture at a lower temperature (86°F). This technique facilitated the removal of excess sulfur from the final product but needed refrigeration because the basic reaction was exothermic. Dorsey’s group nevertheless adapted this process for Edgewood, and it was being adopted when the armistice was signed on 11 November 1918. These reactors would have been capable of producing 100 tons per day by December 1918 and 200 tons per day by the following spring.