Tag: history

Today in chemistry history: Germain Hess, Hess’s Law, and enthalpy changes

Today in Chemistry History graphic on Germain Henri Hess, born 7 August 1802. He is known for Hess's Law, published in 1840, which relates to enthalpy changes of reactions and allows for the calculation of unknown enthalpy changes. The graphic shows an example Hess cycle and explains how it can be used to determine enthalpy values.
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On this day back in 1802, Germain Hess was born in Switzerland. Hess would go on to do important work in the field of thermochemistry, the part of chemistry concerned with energy changes in chemical reactions. His work led to the eponymous Hess’s law, explained in the graphic above. Hess also analysed the mineral silver telluride, which was named Hessite in his honour. 

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Today in Chemistry History – Rosalind Franklin and the structure of DNA

Today in Chemistry History graphic on Rosalind Franklin and the structure of DNA. Rosalind Franklin was a chemist and  X-ray crystallographer whose work was instrumental in the discovery of the structure of DNA. She missed out on a Nobel Prize for her work as they are not awarded posthumously. Photograph 51 is an X-ray diffraction image of DNA taken during Franklin’s research. It was crucial in developing a model of DNA and confirming its double helical structure.
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Rosalind Franklin was born on this day in 1920. Her contributions to the discovery of the structure of DNA were key; she took photos of DNA’s structure using X-ray crystallography, and it was these photos that informed the work of Watson and Crick’s model of DNA’s structure. Sadly her contributions were not fully recognised until after her death, and she did not share in the award of the Nobel Prize for the discovery of DNA’s structure as the prize is not awarded posthumously.

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