Phenol injections – originally used by the Nazis as part of the Aktion T4 euthanasia program – were used as a means of individual execution by Nazi Germany during the Second World War.

The toxic effect of phenol on the central nervous system, causes sudden collapse and loss of consciousness in both humans and animals; a state of cramping precedes these symptoms because of the motor activity controlled by the central nervous system.^{[“Phenol”. Ullmann’s Encyclopedia of Industrial Chemistry. Vol. 25. Wiley-VCH. 2003. pp. 589–604.]} 

Injections of phenol were used as a means of individual execution by Nazi Germany during the Second World War.^{[ The Experiments by Peter Tyson. NOVA]} 

It was originally used by the Nazis in 1939 as part of the Aktion T4 euthanasia program.^{[The Nazi Doctors Archived 2017-10-22 at the Wayback Machine, Chapter 14, Killing with Syringes: Phenol Injections. By Dr. Robert Jay Lifton]} 

• The term Aktion T4 is a post-war coining; contemporary German terms included Euthanasie (euthanasia) and Gnadentod (merciful death).^{[Miller 2006, p. 160]} 
• The T4 programme stemmed from the Nazi Party policy of “racial hygiene”, a belief that the German people needed to be cleansed of racial enemies, which included anyone confined to a mental health facility and people with simple physical disabilities.^{[Breggin 1993, pp. 133–148]}
• New insulin shock treatments were used by German psychiatrists to find out if patients with schizophrenia were curable.^{[Bangen 1992.]} (Not sure why this is here but it gets its own page as does most everything at Wikipedia’s T4 Aktion page)
• T4 Aktion Background from Wikipedia T4 Aktion page:
  • At the beginning of the twentieth century, the sterilisation of people carrying what were considered to be hereditary defects and in some cases those exhibiting what was thought to be hereditary “antisocial” behaviour, was a respectable field of medicine. Canada, Denmark, Switzerland and the US had passed laws enabling coerced sterilisation. Studies conducted in the 1920s ranked Germany as a country that was unusually reluctant to introduce sterilisation legislation.^{[Hansen & King 2013, p. 141.]} 
  • In his book Mein Kampf (1924), Hitler wrote that one day racial hygiene “will appear as a deed greater than the most victorious wars of our present bourgeois era”.^{[Hitler, p. 447][ Padfield 1990, p. 260.]}
  • In July 1933, the “Law for the Prevention of Hereditarily Diseased Offspring” prescribed compulsory sterilisation for people with conditions thought to be hereditary, such as schizophrenia, epilepsy, Huntington’s chorea and “imbecility”. Sterilisation was also legalised for chronic alcoholism and other forms of social deviance. The law was administered by the Interior Ministry under Wilhelm Frick through special Hereditary Health Courts (Erbgesundheitsgerichte), which examined the inmates of nursing homes, asylums, prisons, aged-care homes and special schools, to select those to be sterilised.^{[ Evans 2005, pp. 507–508]} 
  • It is estimated that 360,000 people were sterilised under this law between 1933 and 1939.^{[“Forced Sterilization”. United States Holocaust Memorial Museum.]}
  • The policy and research agenda of racial hygiene and eugenics were promoted by Emil Kraepelin.^{[ Engstrom, Weber & Burgmair 2006, p. 1710]} 
  • The eugenic sterilisation of persons diagnosed with (and viewed as predisposed to) schizophrenia was advocated by Eugen Bleuler, who presumed racial deterioration because of “mental and physical cripples” in his Textbook of Psychiatry,
    • “The more severely burdened should not propagate themselves… If we do nothing but make mental and physical cripples capable of propagating themselves, and the healthy stocks have to limit the number of their children because so much has to be done for the maintenance of others, if natural selection is generally suppressed, then unless we will get new measures our race must rapidly deteriorate.”^{[Joseph 2004, p. 160][Bleuler 1924, p. 214][Read 2004, p. 36]}

The Germans learned that extermination of smaller groups was more economical by injection of each victim with phenol. Phenol injections were given to thousands of people. Maximilian Kolbe was also killed with a phenol injection after surviving two weeks of dehydration and starvation in Auschwitz when he volunteered to die in place of a stranger. Approximately one gram is sufficient to cause death.^{[ “Killing through phenol injection”. Auschwitz: Final Station Extermination. Linz, Austria: Johannes Kepler University. Archived from the original on 2006-11-12.][The Experiments by Peter Tyson. NOVA]}

From the Wikipedia pages ‘Phenol’ and ‘T4 Aktion’ on August 14, 2022