December - 20 years ago, 50 years ago, 100 years ago, 120 years ago, 160 years ago

Methyl isocyanate gas leaked from a tank at the Union Carbide India’s Bhopal plant. Thousands of people died and thousands more were permanently injured.

Linus Pauling was awarded the Nobel prize in chemistry for his work into the theoretical nature of chemical bonds. Pauling went on to become the only person to ever receive two sole Nobel prizes when he was awarded the prize for peace in 1962 for his campaigning against nuclear weapons and warfare.

Gerhard Herzberg born in Germany. Herzberg was forced to leave Germany for Canada as a refugee in 1935 and it was here that he undertook his most significant work in atomic and molecular spectroscopy. He was awarded the Nobel prize in chemistry in 1971.

Birth of St Elmo Brady, the first African-American to earn a PhD in chemistry. He received his PhD at the University of Illinois, US, and went on to become professor of chemistry and head of department at Fisk University, Nashville, US.

Horace Wells first demonstrated the use of nitrous oxide (laughing gas) as a dental anaesthetic by having a molar extracted after its administration. Wells successfully used nitrous oxide with patients, but never recovered from an unsuccessful demonstration of the technique where he was booed off stage. He committed suicide under the influence of chloroform just four years later.

Sallie Robins