Vitriol method

The vitriol process is the oldest process for the production of sulfuric acid . The process is based on the thermal decomposition of naturally occurring sulfates , the so-called vitriols . Due to the high temperatures required, the process was costly and was quickly replaced by alternatives after the development of alternatives. It was first mentioned in the writings of the alchemist Jabir ibn Hayyan from the 8th century and was used for the production of oleum until the development of the contact process in 1870.

history

Galley stove as it was used for the vitriol process

After the first mention by Jabir ibn Hayyan, the procedure is described in more detail by the alchemists Albertus Magnus and Basilius Valentinus . They name alum and chalcanthite (copper vitriol) as raw materials. From the 16th century onwards , due to the greater demand for sulfuric acid, the vitriol process was used on an industrial scale. After the focus of production in Nordhausen , the product was also called Nordhäuser Vitriol . Here, iron (II) sulfate (iron vitriol, FeSO ₄ · 7 H ₂ O) was used as the raw material. This was heated in retorts and converted into sulfur trioxide , from which sulfuric acid was then obtained with water , which was known as vitriol oil . Several retorts were connected in parallel in galley stoves, some of which were multi-story, in order to obtain larger quantities of vitriol oil. In the middle of the 19th century, the Vitriol huts of the Starck company, founded by Johann David von Starck , were the most important in the Bohemian Forest. Here in 1873 up to 120 galley stoves were used in 12 huts, with one galley stove having around 300 retorts. The total production of vitriol oil in Bohemia was around 50,000 quintals in 1845 (equivalent to 2,800 t).

Since the process was expensive and cumbersome, an alternative was sought for the increased demand caused by the Leblanc process and the lead chamber process was also developed in the 18th century . However, since a maximum acid concentration of 78% could be achieved with this, the vitriol process was still used for the production of concentrated acid and oleum . It was only with the contact process from 1870 that a process was available with which the concentrated acid could also be obtained in a significantly cheaper way.

Procedure

The process is based on the decomposition of sulfates at high temperatures and the conversion of the resulting sulfur trioxide with water to form sulfuric acid. In a first step, the water of crystallization was split off by high temperatures and the divalent iron was oxidized to trivalent iron with oxygen . Then the iron (III) sulfate decomposes to iron (III) oxide and sulfur trioxide.

${\displaystyle \mathrm {6\ FeSO_{4}\cdot 7\ H_{2}O+O_{2}\longrightarrow 2\ Fe_{2}(SO_{4})_{3}+2\ FeO+42\ H_{2}O} }$

Oxidation of iron (II) sulphate

${\displaystyle \mathrm {Fe_{2}(SO_{4})_{3}\longrightarrow Fe_{2}O_{3}+3\ SO_{3}} }$

Decomposition of iron (III) sulfate

The resulting sulfur trioxide is then converted into sulfuric acid with water.

${\displaystyle \mathrm {SO_{3}+H_{2}O\longrightarrow H_{2}SO_{4}} }$

Individual evidence

1. ^ NN Greenwood, A. Earnshaw: Chemistry of the elements . 1st edition. VCH Verlagsgesellschaft, 1988, p. 928, ISBN 3-527-26169-9 .

literature

• Claus Priesner: Johann Christian Bernhardt and the vitriolic acid , in: Chemistry in our time , 1982, 16, 5, pp. 149–159.

Web links

• Heinrich Schönemann: From the history of chemistry: From vitriols to sulfuric acid