fumes when treated with vinegar. Gahn could not answer, and had promised to ask
Bergman. When Gahn returned and said that not even Bergman new the answer,
Lokk had already got the answer from Scheele. According to a third version of the
story, Bergman, who bought his chemicals from Lokk, had sent Gahn to return a
batch of saltpetre that Bergman claimed was impure as it gave red fumes with acetic
acid after melting. Scheele then explained that nothing was wrong with the saltpetre. According to Sjöstén, Scheele befriended Johan Gottlieb’s brother, physician
Henric Gahn in Stockholm, and he claimed that it was Henric who introduced
Scheele to his brother [8]. During this period Henric was both studying in Uppsala
and practicing in Stockholm; he belonged to the same circles in Stockholm as
Scheele, and was for example acquainted to Daniel Schulzenheim and at some point
he befriended Scheele. Henric Gahn received one of the eight dedication copies of
Scheele’s book on air and fire (Sect. 21.3). Zekert claimed that Scheele and Gahn
collaborated in Stockholm as early as 1768, [9] which seems unlikely. Cassebaum
suggested that Scheele met Gahn in spring 1770, when he visited Uppsala to
discuss his upcoming appointment [10]. It seems unlikely that Scheele would have
made such a trip since he moved to Uppsala in spring 1770. Probably Cassebaum
tried to explain why there are notes by Gahn dated in spring, when Scheele, as far as
Cassebaum knew, moved in the autumn.
13.2 The Collaboration of Scheele and Gahn
As previously indicated, there is a preserved manuscript written by Gahn in the
archive of the Royal Swedish Academy of Sciences containing notes made by Gahn
after his meeting(s) with Scheele in spring 1770 (Fig. 13.4). The subjects include
oxalic acid, tartaric acid, the transformation of water to earth, Prussian blue and
animal earth. The note on animal earth is of special interest. Animal earth was the
ashes left after calcining bones or horns. Scheele had found that the residue
remaining after calcining dear horns consisted of calcium (lime) and a substance
that he could not identify. Gahn has latter added a note reading:
on account of the preceding, J.G.G. immediately undertook to investigate the animal earth
and found soon that it consisted of lime [calcium] with acidum phosphori [phosphoric
acid]. This, Mr Scheele initially refused to believe, even though he saw all the phenomena,
and the identity of the reduced acid to correspond to phosphoric acid in every manner. He
still had some doubts, until he saw phosphorus being prepared from it, which he first
accomplished on a large scale in Uppsala in the summer of 1770, after I, in the spring,
4 with
blow-pipe and in small glass tubes, had only showed him signs.
Previously, the only known source of phosphorus (Fig. 13.5) was urine, and the
price of phosphorus was very high, not least since most workers had hard to stand
the repulsive smell encountered in the extraction process [11]. The discovery by
Gahn and Scheele would eventually greatly reduce the price of phosphorus, never
4
This further proofs that Scheele arrived in Uppsala at the latest in spring.
13.1 Scheele Befriends Johan Gottlieb Gahn
197
Bergman. When Gahn returned and said that not even Bergman new the answer,
Lokk had already got the answer from Scheele. According to a third version of the
story, Bergman, who bought his chemicals from Lokk, had sent Gahn to return a
batch of saltpetre that Bergman claimed was impure as it gave red fumes with acetic
acid after melting. Scheele then explained that nothing was wrong with the saltpetre. According to Sjöstén, Scheele befriended Johan Gottlieb’s brother, physician
Henric Gahn in Stockholm, and he claimed that it was Henric who introduced
Scheele to his brother [8]. During this period Henric was both studying in Uppsala
and practicing in Stockholm; he belonged to the same circles in Stockholm as
Scheele, and was for example acquainted to Daniel Schulzenheim and at some point
he befriended Scheele. Henric Gahn received one of the eight dedication copies of
Scheele’s book on air and fire (Sect. 21.3). Zekert claimed that Scheele and Gahn
collaborated in Stockholm as early as 1768, [9] which seems unlikely. Cassebaum
suggested that Scheele met Gahn in spring 1770, when he visited Uppsala to
discuss his upcoming appointment [10]. It seems unlikely that Scheele would have
made such a trip since he moved to Uppsala in spring 1770. Probably Cassebaum
tried to explain why there are notes by Gahn dated in spring, when Scheele, as far as
Cassebaum knew, moved in the autumn.
13.2 The Collaboration of Scheele and Gahn
As previously indicated, there is a preserved manuscript written by Gahn in the
archive of the Royal Swedish Academy of Sciences containing notes made by Gahn
after his meeting(s) with Scheele in spring 1770 (Fig. 13.4). The subjects include
oxalic acid, tartaric acid, the transformation of water to earth, Prussian blue and
animal earth. The note on animal earth is of special interest. Animal earth was the
ashes left after calcining bones or horns. Scheele had found that the residue
remaining after calcining dear horns consisted of calcium (lime) and a substance
that he could not identify. Gahn has latter added a note reading:
on account of the preceding, J.G.G. immediately undertook to investigate the animal earth
and found soon that it consisted of lime [calcium] with acidum phosphori [phosphoric
acid]. This, Mr Scheele initially refused to believe, even though he saw all the phenomena,
and the identity of the reduced acid to correspond to phosphoric acid in every manner. He
still had some doubts, until he saw phosphorus being prepared from it, which he first
accomplished on a large scale in Uppsala in the summer of 1770, after I, in the spring,
4 with
blow-pipe and in small glass tubes, had only showed him signs.
Previously, the only known source of phosphorus (Fig. 13.5) was urine, and the
price of phosphorus was very high, not least since most workers had hard to stand
the repulsive smell encountered in the extraction process [11]. The discovery by
Gahn and Scheele would eventually greatly reduce the price of phosphorus, never
4
This further proofs that Scheele arrived in Uppsala at the latest in spring.
13.1 Scheele Befriends Johan Gottlieb Gahn
197