24
Scheele’s Contribution to Organic
Chemistry
By the time Scheele started his career, very few organic compounds were known in
the pure state, and from this assembly of scattered compounds (e.g. sugar, ethanol,
acetic acid and indigo) it was not possible to develop a field of organic chemistry.
As described in Sect. 10.1, Scheele developed a method to isolate tartaric acid by
precipitating the insoluble calcium salt, which was treated with sulphuric acid to
give sparingly soluble calcium sulphate, which could be filtered off, leaving tartaric
acid in the filtrate. Following the isolation of tartaric acid, Scheele continued to
isolate a number of organic acids and other organic substances. This greatly
enlarged the number of organic compounds known, and other chemists would soon
follow in Scheele’s steps. Related to Scheele’s work on organic chemistry was a
study on the preservation of vinegar (dilute acetic acid), where Scheele found that
heating the acid and keeping it in airtight bottles prevented degradation [1], an early
case of pasteurisation [2].
24.1 Oxalic Acid
After Scheele successfully isolated tartaric acid, probably in Malmö or possibly in
Stockholm, he continued to study other sour vegetable substances, but his success
was initially poor. First, he appears to have turned his attention to a salt known as Sal
acetosellæ (potassium hydrogen oxalate), a sour-tasting salt extracted from wood
sorrel (Oxalis acetosella). In the 1760s, Marggraf had showed that it contained alkali,
and small amounts of acid (oxalic acid, Figs. 24.1 and 24.2) were obtained independently in 1733 by Savary, and by Johan Christian Wiegleb (1732–1800) in 1774,
through pyrolysis of Sal acetosellæ. Scheele’s attempts to isolate the acid by the same
method as tartaric acid, i.e. via its calcium salt, failed, however. Scheele eventually
found that the acid, Acid acetosellæ, had a stronger affinity than sulphuric acid for
calcium (lime), i.e. sulphuric acid would not liberate Acid acetosellæ from its calcium
salt. This is correct in some sense: calcium forms a strong network structure with
© Springer Nature Switzerland AG 2020
A. Lennartson, Carl Wilhelm Scheele and Torbern Bergman, Perspectives on the
History of Chemistry, https://doi.org/10.1007/978-3-030-49194-9_24
331
Scheele’s Contribution to Organic
Chemistry
By the time Scheele started his career, very few organic compounds were known in
the pure state, and from this assembly of scattered compounds (e.g. sugar, ethanol,
acetic acid and indigo) it was not possible to develop a field of organic chemistry.
As described in Sect. 10.1, Scheele developed a method to isolate tartaric acid by
precipitating the insoluble calcium salt, which was treated with sulphuric acid to
give sparingly soluble calcium sulphate, which could be filtered off, leaving tartaric
acid in the filtrate. Following the isolation of tartaric acid, Scheele continued to
isolate a number of organic acids and other organic substances. This greatly
enlarged the number of organic compounds known, and other chemists would soon
follow in Scheele’s steps. Related to Scheele’s work on organic chemistry was a
study on the preservation of vinegar (dilute acetic acid), where Scheele found that
heating the acid and keeping it in airtight bottles prevented degradation [1], an early
case of pasteurisation [2].
24.1 Oxalic Acid
After Scheele successfully isolated tartaric acid, probably in Malmö or possibly in
Stockholm, he continued to study other sour vegetable substances, but his success
was initially poor. First, he appears to have turned his attention to a salt known as Sal
acetosellæ (potassium hydrogen oxalate), a sour-tasting salt extracted from wood
sorrel (Oxalis acetosella). In the 1760s, Marggraf had showed that it contained alkali,
and small amounts of acid (oxalic acid, Figs. 24.1 and 24.2) were obtained independently in 1733 by Savary, and by Johan Christian Wiegleb (1732–1800) in 1774,
through pyrolysis of Sal acetosellæ. Scheele’s attempts to isolate the acid by the same
method as tartaric acid, i.e. via its calcium salt, failed, however. Scheele eventually
found that the acid, Acid acetosellæ, had a stronger affinity than sulphuric acid for
calcium (lime), i.e. sulphuric acid would not liberate Acid acetosellæ from its calcium
salt. This is correct in some sense: calcium forms a strong network structure with
© Springer Nature Switzerland AG 2020
A. Lennartson, Carl Wilhelm Scheele and Torbern Bergman, Perspectives on the
History of Chemistry, https://doi.org/10.1007/978-3-030-49194-9_24
331