Joseph Black

Joseph Black ( born April 16, 1728 in Bordeaux, France, † December 6, 1799 in Edinburgh) was a Scottish physicist and chemist. He is the discoverer of carbon dioxide, the element magnesium and the latent heat.

Life

Joseph Black was the son of a native of Ireland, Scotland and later living in Bordeaux wine merchant, John Black. The large family in France had contact with Montesquieu. At age 12, Black was sent to his home in Belfast, at age 18 ( 1746 ), he attended the University of Glasgow and heard lectures from chemical rhetorically gifted William Cullen. In 1751 he moved to the University of Edinburgh to Robert Whytt.

His 1754 doctoral thesis prepared De humore acido a Cibis orto et magnesia alba concerned about studies on the magnesium oxide and magnesium carbonate. 1755 appeared his treatise Experiments upon magnesia alba and other alcaline Substances. Because of this work Black was the successor of William Cullen in Glasgow. Background of Blacks work was a secret recipe on the relief of gallstones by Joanna Stephens. Stephen Hales, who wanted to make publicly available the recipe by a well- rewarded award, promoted the studies on the dissolution of gallstones by lime water with Professors Whytt, Alston. To 1762 Black sought the latent heat, ie, the temperature control of a thermometer at boiling point and freezing point of water. Blacks findings on the latent heat also had influence on the development of the first steam engine. Introduced James Watt, the significant improvements of the steam engine, attended lectures at Black. 1766 Black was appointed professor of chemistry at the University of Edinburgh.

On May 15, 1789, Black Corresponding Member, associé étranger of the French Académie des sciences.

Scientific work

Black is regarded as a pioneer in the development of the atomic theory by Antoine Laurent de Lavoisier. At that time there was neither a knowledge of atoms, molecules, molecular mass, exact causes of mass changes in material transformations. Black could not prove the elements carbon and oxygen in the fixed air ( carbon dioxide ) - that did Lavoisier later - but it has the mass and determines the types of conversion of fixed air, thus making an important contribution to the later clarification of this substance.

Black heated 7.2 g of magnesium oxide (magnesia ) and determined the weight of the residue to about 3.1 g Black guessed that the combustion process air ( phlogiston ) would escape. He solved the converted to magnesium oxide magnesium carbonate in some sulfuric acid ( Vitrolsäure ), the solution was treated with sodium carbonate solution and again received an insoluble solid. After thorough washing and drying, he determined the weight of this substance to 6.6 g under the influence of acids showed up again, evolution of gas ( carbon dioxide ). He again with this transformation, the fixed air in the - introduced magnesia ( magnesium oxide) - formed during the combustion. In the process, however, no air supply development was visible, so that the fixed air probably originated from the carbonate. This thought process was in light of the phlogiston theory is not easily understood, since only gas developments, burns, phlogiston could escape. Black examined on the mass changes during the acid addition to sodium carbonate. Later he found that the magnesium oxide ( magnesia ) more acid until neutralization required as the magnesium carbonate, whereas it was also recognized that the fixed air is present in ordinary air.

Black recognized in 1755 in his De humore acido a Cibis orto et magnesia alba the difference between lime ( calcium carbonate) and magnesia alba ( magnesium carbonate ), which were often confused at this time. He summed Magnesisa alba on as carbonate of a new element. That's why Joseph Black is often referred as the discoverer of magnesium, although he could never represent pure magnesium.

Black studied the change in temperature of the water with a thermometer. With the addition of heat to a water vessel, the mercury of the thermometer scale expanded in ice, however, was evident in the supply of heat long time no temperature change. Even with the formation of water vapor, the temperature of the thermometer did not change. Black concluded that the boiling point and melting still further heat is supplied, although the temperature is not changed. Black realized that a distinction should be between the intensity ( temperature) and the heat amount (quantity ). Furthermore, Black found that different fabrics could also absorb a lot of heat differently.

Black was a discoverer of the heat capacity and specific heat by his theory of latent heat.

Publications

  • Lectures on the elements of chemistry in 2 volumes, edited by Robinson after Black's handwriting, Edinburgh 1803 ( German by Crell, Hamburg from 1804 to 1805 in 4 volumes )
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