Joseph Black - Pioneer of Modern Chemistry

Joseph Black was a Scottish doctor of medicine and an influential academic who had wide-ranging interests in science and engineering. At the University of Glasgow in Scotland can be found this memorial to him. Immediately below his name and above a list of positions he occupied at the university it is written Pioneer of Modern Chemistry. In this video we will take a brief look at the life and chemical studies of Joseph Black to see why this qualified doctor played an important role in the development of modern chemistry. Joseph Black was born in 1728 in Bordeaux southwest France. His parents were of Scottish descent but they had settled in Bordeaux where they owned a vineyard. At the age of 12 Joseph was sent to Belfast for his schooling and he duly entered the University of Glasgow in 1746. Eight years later he would qualify as an MD after completing a research study on a substance known as Magnesia Alba at the University of Edinburgh. The results of his study were published in Latin in 1754. Early on in his thesis Black references the celebrated German physician Friedrich Hoffmann for popularizing the medical use of Magnesia Alba as a laxative. The Hoffmann work referred to is an authoritative six-volume set of Hoffmann's complete works published in Latin in 1740 two years before Hoffmann's death. The section on Magnesia Alba is in the fourth volume on page 479. This was the starting point for Black's study. In 1777 Black published a pamphlet which included an English translation of his thesis and the results of further experiments carried out shortly afterwards. For example he noted that on a heating an ounce of Magnesia Alba weight loss occurred such that the residue weighed three drums and a scruple. He attributed the weight loss to the release of a gas he referred to as fixed air. He further noted that other alkaline substances such as calcareous earths also released fixed air on heating. However as Black observed the residue left after heating calcareous earths such as marble or chalk was a quicklime and it was Black's observations with quicklime which were to have the most importance. In particular Black dissolved quicklime in water to obtain limewater. He then noted that when limewater was left exposed to the air a white solid would form at the surface due to the absorption of fixed air from the atmosphere. He further noted that the white solid called the cream or crusts of limewater had the properties of calcareous earths. Thus he showed that this gas which he called fixed air which is released on heating mild alkalis and in which candles would not burn was a constituent of the atmosphere. Although Black was not generally fast to publish his results due to his wide ranging interests he had significant social circles and influential friends such as the engineer James Watt. It was through these connections that Black's discoveries became known and this initiated a search for other gases. This led to many discoveries including those of hydrogen and oxygen. In turn the process of characterization of substances began such that magnesia alba became known as magnesium carbonate and fixed air as carbon dioxide. Thus Black's work marks a turning point for chemistry as it began to become a discipline of its own rather than a sub-discipline of medicine. For this reason Black is correctly known as a pioneer of modern chemistry. Thanks to the online sources shown here and to you for watching to the very end. Hope to see you again sometime soon.