Zyklon B - History

History

Even before any of the modern methods of mass producing prussic acid were developed, suggestions were made that it could be used systematically to kill humans. A Berlin pharmacist is credited with the proposal to use rags with prussic acid placed on bayonets to combat the advancing Napoleonic army in 1813. During World War I, the French army reportedly – according to Fritz Haber, the German chemist who helped develop poisonous gas for German Army use (see below) – used 2000 tons of prussic acid as a poison gas agent in artillery ammunition.

Hydrocyanic acid was widely used for the fumigation of valuable tree crops. It was initially applied to citrus fruit in 1887 in California. Use spread to Spain and other countries using either liquid prussic acid, calcium cyanide, or sodium cyanide preparations. During World War I other HCN-based pest control applications were developed, and soon fumigation of ships, stores, factories, and even residential buildings with hydrocyanic acid gas became a popular method of combatting insect and rodent pests in many countries. Thousands of ships, cereal mills, and other food processing factories were fumigated with hydrocyanic acid gas until the mid 1930s in Germany alone.

Degussa ("Deutsche Gold- und Silber-Scheideanstalt") had a leading role in the German research on pest control with hydrocyanic acid gas from 1916/17 on. Degussa's expertise in handling HCN resulted from its use in the extraction of gold from gold ore. Initially, the so-called pot method was used to simply generate HCN gas by treating sodium cyanide or potassium cyanide with diluted sulfuric acid in a pot. Like the utilisation of highly concentrated liquid prussic acid, the pot method has a number of disadvantages. For example, prussic acid is chemically stable only for a limited period of time. This hinders long-term storage. Also, highly explosive air-HCN mixtures form easily when applied.

In March 1919 Deutsche Gesellschaft für Schädlingsbekämpfung mbH (Degesch, lit. "German Limited Company for Pest Control") was founded by a consortium of German chemical companies including Degussa, and initially led by chemistry Nobel laureate Fritz Haber. Haber had World War I experience in the development of poison gas for the German chemical warfare program. At Degesch, Ferdinand Flury developed Zyklon A in 1920. Its development was a major advance over previous methods of delivering hydrocyanic acid for pest control because of its improved chemical stability and the presence of a warning odorant.

Walter Heerdt, Bruno Tesch and Gerhard Peters were all collaborators of Fritz Haber working at the Kaiser Wilhelm Institute for Physical Chemistry and Electrochemistry at Berlin-Dahlem. Out of this group of Haber assistants, Walter Heerdt was named the official inventor of Zyklon B in a Degesch patent application from 20 June 1922 (number DE 438818). Reichspatentamt awarded the patent on 27 December 1926. The main invention in Zyklon B consisted of the absorption of liquid hydrocyanic acid into a highly porous adsorbent. Initially, heated diatomite (diatomaceous earth) was used as an adsorbent. Later, high-porosity gypsum pellets called Erco-dice (described by eye witnesses as "crystals") as well as disks made from wood fibre were also used. The adsorbed hydrocyanic acid was very safe in handling and storage when placed in inexpensive airtight cans of various sizes. Gerhard Peters, manager of Degesch, cites M. Kaiser to the effect that

Heute ist die Zyklon-Blausäure als "das Mittel der Wahl" nicht nur zur Entwanzung und Entlausung, sondern ganz allgemein zur Entwesung großer Räume in allen Erdteilen bekannt. (Today Zyklon-prussic acid is known as the means of choice not only for debugging and delousing but also, in general, for the extermination of large spaces in all quarters of the globe.)

From 1929 onwards the U.S. used Zyklon B to disinfect the freight trains and clothes of Mexican immigrants entering the U.S. Farm Securities Administration photographer Marion Post Wolcott recorded the use of cyanide gas and Zyklon B by the Public Health Service at the New Orleans Quarantine Station during the 1930s.

In early 1942, Zyklon B had emerged as the preferred extermination tool of the Nazi regime for both the Auschwitz-Birkenau and Majdanek extermination camps during the Holocaust. The chemical claimed the lives of roughly 1.2 million people in these camps. Rudolf Höss, commandant of Auschwitz, said that the use of Zyklon-B came about on the initiative of one of his subordinates, Captain Karl Fritzsch, who used the substance to kill some Russian POWs in late August 1941. The experiment was repeated on more Russian POWs, with Höss watching, in September of the same year. The emergence of Zyklon-B as the preferred chemical was a multi-stranded process.