Andreas Marggraf biography
Date of birth : 1709-03-03
Date of death : 1782-08-07
Birthplace : Berlin, Germany
Nationality : German
Category : Science and Technology
Last modified : 2010-11-29
Credited as : Chemist, pioneer of analytical chemistry,
Andreas Sigismund Marggraf was an important figure in chemistry as it evolved from alchemy in the eighteenth century. He worked on a broad range of subjects, concentrating on problems in the areas of inorganic, organic, and analytical chemistry. He isolated several elements, made an important discovery about sugar, and was one of the first to use a microscope in the field of chemistry.
Marggraf was born on March 3, 1709 in Berlin. His mother was Anne Kellner, about whom little is known. His father was Henning Christian Marggraf, an apothecary to the Royal Court located in Berlin. The elder Marggraf was also an assistant at the medical school (Collegium Medico-Chirurgicum) and did some chemical research. Andreas Marggraf received a well-rounded training in chemistry that began with his father's various connections.
Marggraf was the last important German chemist to believe in the flawed theory of phlogiston, according to Isaac Asimov in his Asimov's Biographical Encyclopedia of Science and Technology. Phlogiston was the theory proposed and popularized by Georg Ernst Stahl that materials were composed of air, water and three earths and that one of these earths escaped from any material during combustion. Perhaps the reason for Marggraf's adherence to this theory, despite the fact that materials often increased in weight when burned, was that one of his first teachers was his father's colleague, Caspar Neumann, an adherent to Stahl's theory. Marggraf studied under Neumann from 1725 through 1730.
According to an entry in the Dictionary of Scientific Biography, by Martin S. Staum, Marggraf further learnt his craft from an apothecary in Frankfort-am-Main, next studied at the University of Strasbourg, and then studied metallurgy in Freiburg. From 1935 through 1953, Marggraf ran his father's apothecary at the court. In 1737, his background and connections helped win him an opportunity he refused, that of a ducal apothecary appointment in Wolfenbuttel, Brunswick.
Instead, Marggraf was admitted in 1738 as a member of the Koniglich Preussischen Societat der Wissenchaften (Prussian Society of Sciences) and remained an unpaid member until 1744. In 1746 the organization was reorganized and renamed Academie Royale Des Sciences et Belles-Lettres. Frederick II named Marggraf director of the chemical laboratory at the Academie in 1753 and Marggraf became director of the physical class in 1760. He remained in these positions until 1782. During this time, he also gave private instruction in chemistry.
Marggraf was a precise and careful chemist, painstaking in his work and in his recording of that work. He was known more for experimenting and describing rather than for postulating and theorizing. Before Marggraf, the alchemists had tried to discover ways to change metals into gold as well as discover the key to perpetual youth. Alchemy was the study of transmutation-the change of a substance into something more desirable.
Marggraf worked with various materials and documented what he found using the balance for weighing exact amounts, both before and after the experimental tests. He was creative in his use of solvents to extract, and then to recrystallize the substance extracted. He also used flame tests to determine differences in substances as the flame burned in different colors depending on the substance burned. This method predates the more modern emission spectroscopy. A metal blowpipe was used for his experiments. This was a tube that heightened the flame by including more air in order to see the colors more vividly. It also allowed one to see the type of debris the substance would leave as it interacted with the metal.
Phosphorus was a rare substance in Marggraf's time, and he found a simple way to prepare it. He evaporated putrefied urine and mixed its salts with "chloride of lead, sand and coal," according to E. O Von Lippmann in the essay on Marggraf he contributed to the book Great Chemists. After heating for four hours and redistilling, it was pure white and clear, and could be poured into glass tubes with the appearance of rods. Marggraf noted that when burned it increased in weight and formed a mass that was feathery. Also, when this phosphorus was dissolved in water it formed phosphoric acid, a substance that was unknown until that time. It could be returned to phosphorus by heating with coal, which was an improvement over previous methods of obtaining phosphorus.
Next, Marggraf tried to produce phosphorus from hydrochloric acid without using urine, as previous scientists had suggested that this was possible. He failed. This led him to suggest that the type of salt contained in urine was necessary in order to produce phosphorus. Staum tells us that Marggraf also substantiated another scientist's statement that phosphorus is contained in vegetable matter and Marggraf figured that "the higher yields of phosphorus from urine in the summer are proportional to increased consumption of vegetable foods."
According to Von Lippmann, the mineral and vegetable alkalies (soda and potash) were thought to be identical, "or the alkali of marine salt (sodium chloride) was held to be analogous to lime." Marggraf demonstrated that these materials were different by one of his painstaking experiments. He observed that potassium chloride when converted to nitrate turned into a needlelike salt and when burned turned the flame blue-violet. However, nitrated marine salt was cubic and turned its flame yellow when burned. The potassium sulfate was barely soluble while the sulfate of the marine salt was much more soluble. After observing all this, Marggraf reasoned that the alkalies were present in the plant before the ashing process began. As Von Lippman states, Marggraf wrote that the plant resource for these salts was that it "attracts them out of the soil, out of water and air."
One of the most significant of Marggraf's findings, at least in terms of its impact on industry, is his discovery that sugar from beets was exactly the same as sugar from cane. Before his time, efforts had been made to extract sugar from many other fruits, vegetables and even nuts. Marggraf postulated that sugar from sweet-tasting plants must contain a sugary substance, so he investigated the white beet, the beet root and the red beet. First he sliced, dried and pulverized the three plant parts just mentioned. Next, with the use of boiling alcohol, he extracted their juice, by filtering and then letting this juice crystallize in corked tubes for several weeks as the liquid evaporated. Once the crystal stage was reached, he examined these crystals under a microscope. This was perhaps the first use of a microscope for chemical identification. The crystals seen under the microscope were identical to those of cane sugar.
Though large-scale production of sugar from beets did not take place in Marggraf's lifetime, he recognized the significance of the discovery. Previous to this time, sugar had been made from cane, which was to be found in the warmer climates such as the West Indies. It was traded to England and other places in Europe and these places experienced high prices and shortages when they were unable to get sugar due to war blockades, especially during the Napoleonic Wars that began at the end of the eighteenth century.
However, Marggraf's discovery and influence made its mark because his student, Achard, tried his experiment on a large-scale, produced a significant amount of sugar, estimated the cost to be six cents per pound, and interested the French Institute in investigating his claims. This was enough to cause King William III of Prussia to finance a sugar beet factory and thus the industry was born. Marggraf's work had reached beyond his time and today sugar is made from beets in many countries all over the world.
Marggraf himself had recognized that this was a boon for the poor farmer when he wrote, as Von Lippmann has it: "There should be no doubt by now that this sweet salt, sugar, can be made from our own plants just as well as from sugar cane." Also, in the book The Story of Alchemy and Early Chemistry, John Maxson Stillman quotes Marggraf: "the poor cultivator could well serve himself with this plant sugar or its syrup instead of the usual costly product, and if by help of inexpensive machines he pressed this juice from these plants, somewhat purified it, and reduced it to the consistency of a syrup." Thus Marggraf realized the real practical implications of his work for the domestic farmer of his time.
Marggraf's other scientific work was important, if not as immediately applicable as his work with beets. He discovered magnesia by decomposing a serpentine mineral; he found another distinct material, alumina; did experiments that isolated zinc by creating an industrially useful distilling process from calamine. He demonstrated that iron was present in limestone and in the ashes of many plants by the fact that these reacted with red prussiate of potash (the equivalent of potassium ferrocyanide). One of his experiments showed that selenite was chemically the same as gypsum.
He worked with cedar wood to isolate cedar oil by steaming it at lower temperatures than its actual boiling point. This process was then used to isolate other oils. He distilled ants into an oil and an acid. He froze and redistilled the acid to purify it. This type of acid forms salts when mixed with alkalies, ammonia, some metals, and reduces mercuric oxide to the metal.
Despite his prolific work in chemistry, Marggraf was never in the best of health. He had a stroke in 1774 and was ill from that time until his death in Berlin on August 7, 1782. However, he left numerous discoveries and observations to the world of chemistry.
Von Lippman tells us that Marggraf's motto was "care and cleanliness in working." He was an introvert who kept out of politics and dedicated his life to his work in chemistry. His methods of careful weighing and measuring both before and after reactions yielded much quantitative information for future scientists. His patience when waiting for crystallization, poisoning, and other reactions lent credence to the importance of time in chemical reactions. He laid much groundwork for future chemists, not to mention the practical implications of his work for industrialists.