Strontian method

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With the Strontian process , residual sugar is obtained from molasses . Strontian is a mixture of strontium oxide and strontium hydroxide and is made from the mineral strontianite ( strontium carbonate ).

chemistry

Chemical reactions of the Strontian process : First, SrCO 3 is converted into Sr (OH) 2 . The Sr-sugar complex precipitates out as a disaccharate when heated and goes back into the solution as a monosaccharate when it cools down. In order to obtain the pure sucrose, the strontium is precipitated again as carbonate with an excess of CO 2 .

In a first step, strontium carbonate is burned to form strontium oxide. In contrast to calcium carbonate ( calcination ), simple heating is not sufficient for this, but instead you have to add steam and / or charcoal for burning. The resulting carbon dioxide is needed later.

Strontian reacts with sugar to form poorly soluble strontium saccharate, which can be filtered off. With the help of carbon dioxide (from the burning process), strontium carbonate is precipitated from strontium saccharate. Pure, strontium-free sugar is obtained from the remaining solution by evaporation. The strontium carbonate can be reintroduced into the process as starting material. The strontian process is a cycle in which no strontium is consumed ( catalyst ).

There are two forms of strontium saccharate: the monosaccharate is formed at a low temperature and the disaccharate is formed at a high temperature.

history

Molasses is a residual product in sugar production from sugar beet and itself still consists of more than 50% sugar. The French chemists Hippolyte Leplay and Augustin-Pierre Dubrunfaut developed a process to separate barium saccharates from molasses by reacting barium oxide with sugar. In 1849, they extended their patent to strontium salts. This patent only seems to be about a legal safeguard of the barite process. In practice, Leplay and Dubrunfaut's Strontian method probably did not work.

It was only through the work of Carl Scheibler that the Strontian process became industrially applicable. According to Scheibler, the Strontian process must be carried out at boiling point. Especially in Dessau sugar refinery of Emil Fleischer , the method was used. In Münsterland then a veritable "gold rush" for Gewinning of Strontianit broke out. One of the largest pits near Drensteinfurt was named after Dr. Reichardt, the director of the Dessau sugar refinery. Another place where the Strontian process was used was the Rositz sugar factory .

As early as 1883, the demand for strontianite decreased significantly. For one, it was supplanted by another strontium mineral ( Celestine ) that was imported cheaply from England. On the other hand, the sugar price fell so sharply that it was no longer profitable to extract it from molasses.

literature

  • Martin Börnchen: Strontianite. Exhibition guide of the university library of the Free University of Berlin , 2005. (PDF; 6.5 MB) .
  • THP Heriot: The Manufacture of Sugar from the Cane and Beet. Green and Company, 1920, pp. 341-342. (Archive online) .
  • G. Krause: The arbitration award in the matter of Scheibler's monostrontium saccharate patent. In: Chemiker Zeitung. No. 32, April 19, 1885 (PDF; 4.9 MB) .

Individual evidence

  1. ↑ Reinhard Brauns: The mineral kingdom. Volume 1, Fritz Lehmann Verlag, Stuttgart 1903, pp. 402-403.
  2. ^ About Scheibler's Strontian method. In: Polytechnisches Journal . 248, 1883, pp. 426-428.
  3. ↑ J. Nicklès: Leplay's method for separating the crystallizable sugar from molasses. In: Polytechnisches Journal . 131, 1854, pp. 47-50.
  4. ↑ De Indian opmerker. March 15, 1883. ( Memento of December 12, 2013 in the Internet Archive ) (PDF; 8.1 MB; Dutch).
  5. ^ University of Arizona Bulletin. No. 35, (1916–1917) (PDF; 2.3 MB)
  6. ^ Martin Börnchen: The Strontianite mining in the Münsterland. (PDF; 4.3 MB) .