August 18 marks the anniversary of the discovery of helium.
French astronomer Pierre Janssen traveled to India in 1868 to watch a total solar eclipse. Among his equipment was a new device to examine emission and absorption lines associated with the Sun’s spectrum. It was the first total solar eclipse since Bunsen and Kirchhoff’s discovery that spectral lines are associated with individual elements. Janssen wanted to view the spectra of the Sun’s chromosphere.
The eclipse occurred on August 18, 1868. Janssen observed a bright yellow line that corresponded to a wavelength of 5874.9 Å. This line did not correspond to any known element and he knew he had found something new. He verified his discovery by constructing a means to create his own eclipse by blocking out the majority of the Sun’s disk and measuring the spectra of the chromosphere. He found his bright yellow line again and verified it was not sodium or any other known element.
British astronomer Norman Lockyer also observed this yellow line and recognized it belonged to a new element. His proposal for the name was ‘helium’ after helios, the Greek word for the Sun. Helium became the first element to be discovered extraterrestrially.
Helium would not be found on Earth for another 33 years. Many chemists believed helium could only exist on the Sun because no one could produce the results on Earth. That didn’t stop William Ramsay from trying to find helium. He finally succeeded in 1895 when he treated the uranium ore cleveite with acid. He was actually looking for argon when he performed these experiments. When he treated the gas to remove oxygen and nitrogen, the remaining gas contained helium’s yellow spectral line. Ramsay had isolated helium on Earth.
1994 – Richard Laurence Millington Synge died.
Synge was an English biochemist who shares the 1952 Nobel Prize in Chemistry with Archer John Porter Martin for the invention of partition chromatography. Partition chromatography is a technique to separate similar substances by repeated extraction by two immiscible liquids. It can separate amino acids to aid in the study of proteins, carbohydrates, and DNA.
1980 – Elizabeth Stern Shankman died.
Shankman (‘nee Stern) was a Canadian pathologist who described the paths where a healthy cell changes to a cancerous cell. Her research changed cervical cancer from a death sentence to an easily diagnosed and treatable condition. She also demonstrated a link between the herpes simplex virus and cervical cancer and a link between cervical cancer and the oral contraceptive pill.