In 1941 he retired from teaching, but continued his researches. Hans von Euler-Chelpin married twice. His first wife was Astrid Cleve, who was the first Swedish woman to obtain a doctoral degree of science. In 1913 he married again to his second wife, Elisabeth Baroness af Ugglas (1887-1973), whose participated in collaborations with Euler-Chelpin. His son, Ulf von Euler (1905 - 1983), was a well-known physiologist and in 1970 he received a Nobel Prize for his research on the chemical nature of norepinephrine on the synapses. In 1931, his daughter Karin von Euler-Chelpin married the writer Sven Stolpe. During his life, Euler-Chelpin created a series of monographs such as "Biochemistry of Tumours", written in collaboration with Boleslaw Skarzynski, published in 1942 and the other entitled "The Chemotherapy and Prophylaxis of Cancer", published in 1962. Euler-Chelpin died in Stockholm on 6 November 1964, at the age of 91. In 1929, Euler-Chelpin and Arthur Harden received the Nobel Prize in chemistry for research on alcoholic fermentation of carbohydrates and the role of enzymes. Arthur Harden dealt only with the chemical effects of bacteria from 1903 with alcoholic fermentation. Harden discovered that the enzyme zymase, discovered by Eduard Buchner, only produces fermentation in interaction with the coenzyme cozymase. Euler-Chelpin, in turn, convincingly described what happens in sugar fermentation and the action of fermentation enzymes using physical chemistry. This explanation led to the understanding of the important processes taking place in the muscles for the supply of energy.