A Short Story of Germanium
A timeline of germanium discovery and isolation
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1
July 1864: A First Hint
John A. R. Newlands (1837-1898) leaves an empty spot in his table of elements published in Chemical News. The spot, between silicon (Si) and tin (Sn), was originally occupied by titanium (Ti). Discrepancies in atomic weight relationships between these three made Newlands rethink titanium's position. However, he does not implicitly predict the existence of hitherto unknown element. [ see note ]
2
1869: Elements are missing...
Dmitrii Mendeleev (1834-1907), at St. Petersburg University, publishes (in Russian) his periodic law and the periodic table of the elements based on the law. He explicitly predicts the existence of unknown elements, including the one between Si and Sn, and leaves empty spots for them in the table. A significantly shorter version of the article appears in German the same year.
3
January 1871: A Full Rationale
Still at St. Petersburg University, Mendeleev publishes a full account of his periodic law, discussing its origins, relationships between the elements, and rationalizes many decisions he made while deriving the law and his table. The text , on over 50 pages in original Russian, also contains detailed predictions on properties of unknown (missing) elements based on the law. The missing element between Si and Sn is named ekasilicon using Sanskrit word for number 1 as a prefix indicating the unknown element is one place below Si. [ see note ]
4
1872: The News Spread
More than a year after original publication, the German version of Mendeleev's 1871 paper appears - this time in full translation - and helps distribute his ideas.
5
September 1885: The mineral
A previously unknown mineral was discovered in the Himmersfürst mine, now abandoned sliver mine in Saxony, east Germany.
6
October 1885: A "Loss of 7%"
Albin Weisbach (1833-1901), a mineralogist and crystallographer, and Hieronymus T. Richter (1824-1898), a chemist, both working at the Mining Academy in Freiberg (near the mine) analyze the new specimen. Richter finds that the mineral contains silver (Ag) and sulfur (S) and some remains. Weisbach gives crystallographic and mineralogical description and names the mineral argyrodite, meaning silver-containing.
The sample is passed to Clemens Winkler (1838-1904), a very gifted analytical chemist working at the same institution. After several consistent analyzes, Winkler reported to the others an "averaged 75% silver and 18% sulphur in numerous experiments, thus a loss of 7%." Winkler correctly assumed that the loss is due to the unknown element. [ see note ]
7
February 1886: The New Element
After four months of detailed work (and by some accounts a bit of luck) Winkler isolates the new element. He names it germanium (Ge), in honour of his homeland, Germany.
Both Weisbach and Winkler publish their research. The former focusing on mineralogy and crystallography of argyrodite , and the latter describing the isolation and basic properties of germanium . At the moment, Winkler is inclined to claim that Ge is ekasilicon and not ekaantimony, another element predicted in Mendeleev's table. [ see note ]
8
February-March 1886: Which one?
Viktor von Richter (1841-1891), form University of Breslau, Germany (today Wrocław in Poland), writes to Winkler stating that his germanium is indeed ekasilicon. Von Richter had significant interest in the topic since he was one of the most influential promoters of the periodic law thanks to his very successful inorganic chemistry textbooks used in Europe and North America.
However, Medeleev disagrees - writing to Winkler from St. Petersbourg, he claims that Winkler's element is ekacadmium. Although ekacadmium was not on the original list of Mendeleev's missing elements, the Russian believed that the list is not exclusive. [ see note ]
9
February 1886: More Support
Lothar Meyer (1830-1895), who discovered periodic law and created his own table of elements virtually identical to, but independently from, Mendeleev, writes to Winkler and also claims that germanium is ekasilicon. [ see note ]
10
Mach 1886-August 1887: It is Ekasilicon
Back at Feiberg, encouraged by the interest in his work and willing to settle the discussion, Winkler works up more than 5 kg of impure argyrodite to obtain about 100 g of his element. He prepared and analyzed many simple compounds of germanium and finally proved using chemical and physical properties of both the element and its compounds that germanium is exasilicon and should be placed under Si in the periodic table. He published his results in two papers, one in July 1886 and the second in August 1887.
11
1940s onward: A Crucial Element
In the decades between 1880s and 1940s, the interest in germanium was more-or-less academic. It all changed in 1940s when the scientists and engineers at then Bell Telephone Laboratories (previously AT&T's Bell Labs, but today Nokia Bell Labs), Murray Hill, New Jersey, constructed first working transistor and revolutionized electronic industry.
Its importance and importance of its compounds only increased in the following decades . Today, germanium is considered technology-critical element (TCE).
Notes
Slide 1
This is the only instance in which Newlands questions the position of Ti in his table and leaves an empty space between Si and Sn. All his other tables (before and after) do not have the empty slot.
Newlands table of elements from his July 30, 1864 paper. There is an empty spot between Si and Sn (marked).
Slide 3
As the figure on Slide 3, "January 1871: A Full Rationale" shows, there are quite a few empty spaces in Mendeleev's table, indicated with a dash. At that time, without the knowledge of atomic structure, it would be difficult to confidently predict more than a handful of new elements - only those obviously missing among the known ones. Prudently, Mendeleev focused on these, thus ekaboron, ekaaluminium, ekasilicon, eka-manganese, divmanganese (div means two in Sanskrit) and ekatantalum were born.
Slides 5 and 6
This is not the first time argyrodite was "discovered." German mineralogist Johann F. A. Breithaupt (1791-1873), working at the same institution with Weisbach and Winkler, had a sample of argyrodite but provided such a poor description of the mineral that it was useless for identification. A sample was also found in Bolivia in late 1840s, but the news did not reach Weisbach.
Slide 7
Unfortunately, Weisbach's crystallography was wrong. He described the crystals as monoclinic, when in fact they are orthorhombic. This is not very surprising: the technology at the time did not allow for a precise measurements on Weisbach's argyrodite crystals measuring under 1 mm. The structure of argyrodite was determined in 1977.
Winkler's work also established the chemical formula for argyrodite as Ag 8 GeS 6 . For the actual isolation of germanium, Winkler worked with impure argyrodite, his samples were contaminated with other silver ores, notably those containing arsenic (As) and antimony (Sb). This meant that the samples contained small amount of the new element, but it also told Winkler that the new element could be chemically similar to As and Sb. He employed a method for separation of As and Sb called Freiberg outcrop (or sulfurizing outcrop) in a hope that germanium would separate with them. The method involves heating solid sample with sodium carbonate and sulfur. After cooling, the mixture is added to water. The reaction converts As and Sb compounds into sodium thiosalts Na 3 AsS 4 and Na 3 SbS 4 which dissolved in water. Upon addition of small amount of hydrochloric acid, insoluble As 2 S 5 and Sb 2 S 5 are formed. Winkler followed this method, and separated As and Sb, but could not find the new element. His precipitate had only As and Sb and the leftover solution gave only sulfur (upon further addition of the acid) and sodium chloride (after evaporation). He did the same procedure over and over again for four months. Prof. L. W. McCay (Princeton University) who was Winkler's student at the time, recalls: "Finally, on February 6, 1886, since a moderate amount of free acid, as in all previous cases, caused no change, he added it [the acid] to his filtrate recklessly and in great excess when, suddenly, to his astonishment a white precipitate formed which, on stirring the solution, became flocky and settled rapidly. This precipitate proved to be soluble in ammonia water and could be thrown out of the solution again on the addition of a large excess of the acid. It turned out to be the sulfide of the unknown element. This, oxidized and heated in a current of hydrogen, was transformed into a gray, metallic powder ... —the ekasilicon of Mendeleeff, which Winkler named germanium." (McCay, L. W. (1930) "My Student Days in Germany." J. Chem. Educ. 7(5), 1081; DOI: 10.1021/ed007p1081 .)
The chemistry, starting from pure argyrodite, can be described with following equations:
Slide 8
Ekacadmium was not among new elements proposed by Mendeleev in 1971. But the space after cadmium (Cd) is indeed empty in his table. Today we know that there are no additional elements between cadmium (Cd) and mercury (Hg).
Slide 9
Lothar Meyer independently from Mendeleev established the periodic law and, based on it, created his own periodic table. Initially, Meyer included this work in his 1864 textbook Die modernen Theorien der Chemie und ihre Bedeutung für die chemische Statik (The modern theories of chemistry and their significance for chemical calculations, the table on pg. 137 ). Relatively limited reach of the textbook was one of the reasons only a few were aware of his efforts, although it was circulated five years before Mendeleev's first paper. Meyer however reacted fast upon hearing of Mendeleev's work and published a full paper of his own. In it, he gives full credit to Mendeleev and gives him priority for the discovery. Both Meyer and Mendeleev received the Davy Medal from the Royal Society of London in 1882. Important difference between Meyer's and Mendeleev's work is the fact that Mendeleev paid a lot of attention to the unknown elements, including predicting their physical and chemical properties. Meyer, on the other hand, did not go into such a detail with his predictions.
